Manual of Multistorey Timber Construction: Principles – Constructions – Examples [2nd edition 2022 (revised and extended reprint)] 9783955535827, 9783955535810

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Manual of Multi-Storey Timber Construction Principles – Structures – Examples

Hermann Kaufmann Stefan Krötsch Stefan Winter

Edition ∂

2

Imprint

Authors Hermann Kaufmann Stefan Krötsch Stefan Winter Co-authors Sonja Geier, Annette Hafner, Wolfgang Huß, Holger König, Maren Kohaus, Frank Lattke, Klaus Mindrup, Lutz ­­ Müller, Anne Niemann, Daniel Rüdisser, Christian Schühle, Sandra Schuster, Manfred Stieglmeier, Martin Teibinger, Gerd Wegener Research assistants: Ruth Klingelhöfer-Krötsch Claudia Köhler, David Wolfertstetter Student assistants: Sandra Gressung, Tobias Müller, Maren Richter, Moritz Rieke, Sascha Ritschel, Konstanze Spatzenegger, Fabia ­Stieglmeier

Editorial services Steffi Lenzen (project manager) Jana Rackwitz (editorial services and layout), Cosima Frohnmaier, Sophie Karst, Sonja Ratz, Daniel Reisch, Eva ­Schönbrunner Charlotte Petereit (editorial assistant) Carola Jacob-Ritz (proofreading German edition) Drawings: Ralph Donhauser Marion Griese, Martin Hämmel, Simon Kramer, Dilara Orujzade, Janele Suntinger Translation into English: Mark Kammerbauer, Landshut (DE) Translation of the first edition 2018: Christina McKenna, Douglas Fox, Meriel Clemett for keiki communication, Berlin (DE) Copy editing (English edition): Stefan Widdess, Berlin (DE) Proofreading (English edition): Meriel Clemett, Bromborough (GB) Cover design based on a concept by: Wiegand von Hartmann, Munich (DE) Production and DTP: Simone Soesters Reproduction: ludwig:media, Zell am See (AT) Printing and binding: Grafisches Centrum Cuno, Calbe (DE)

© 2022 second edition English translation of the third, revised and expanded ­German edition 2021 “Atlas Mehrgeschossiger Holzbau” (ISBN: 978-3-95553-556-8) 2018 first edition English translation of the first German edition 2017 Paper: environment Grocer Kraft (cover), Magno Volume (content) Publisher: Detail Business Information GmbH, Munich detail.de ISBN: 978-3-95553-581-0 (printed edition) ISBN: 978-3-95553-582-7 (e-book) Bibliographic information published by the German National ­Library. The German National Library lists this publication in the German National Bibliography (Deutsche National­ bibliografie); detailed bibliographic data is available on the Internet at http://dnb.d-nb.de. This work is subject to copyright. All rights reserved. These rights specifically include the rights of translation, reprinting, and presentation, the reuse of illustrations and tables, broadcasting, reproduction on microfilm or on any other media and storage in data processing systems. Furthermore, these rights pertain to any and all parts of the material. Any reproduction of this work, whether in whole or in part, even in ­individual cases, is only permitted within the scope specified by the ap­plicable copyright law. Any reproduction is subject to charges. Any infringement will be subject to the penalty clauses of copyright law. This textbook uses terms applicable at the time of writing and is based on the current state of the art, to the best of the authors’ and editors’ knowledge and belief. All drawings in this book were made specifically by the publisher. No legal claims can be derived from the contents of this book.

3

Contents

Foreword

  5

Part A  Introduction 1  2  3  4  5 

The Evolution of Multi-storey Timber Construction Wood as a Resource Solid Wood and Wood-based Products Life Cycle Analysis Indoor Air Quality – The Influence of Timber Construction

  8  14  18  24  32

Part B  Structural Systems 1  Structures and Load-bearing Systems 2  Construction Components and Elements

 42  56

Part C  Construction 1  Protective Functions 2  Thermal Insulation in Summer – A Question of Planning 3  The Layer Structure of Building Envelopes 4  The Layer Structure of Interior Construction Components 5 Building Services Technology – Particularities of Timber Construction

 78  94  98 126 136

Part D  Process 1 Planning 2  Digitalisation in Timber Construction 3  Timber Production 4 Prefabrication 5  Solutions for Modernising and Expanding Existing Buildings

146 154 158 162 172

Part E  Examples of Buildings in Detail Joinery in Detail Project Examples

184 190

Appendix Authors Bibliography Glossary DIN Standards Image Credits Project Participants Index Supporters / Sponsors

298 300 302 306 308 310 311 312

5

Foreword Timber construction has experienced profound advancements in recent years. The newest quantum leap is demonstrated by the fact that a growing number of ever taller buildings feature timber construction. This classic building material, all but forgotten in the modern era, is undergoing a renaissance for various reasons. Climate change has led to an increasing interest in the public sphere and among architects and their ­clients in resource-efficient, sustainable construction solutions rooted in biological processes. Timber construction offers better answers to related questions than other construction methods. The special tactile, visual and olfactory qualities of wood as a natural building material and its outstanding strength-to-weight ratio make timber construction increasingly attractive for modern building projects. However, the primary costs, compared to common standard solutions, can be somewhat higher than those for conventional structures – depending on the type of project. Yet, in terms of overall economic efficiency, modern timber construction is already and by all means competitive. While timber construction for single-family homes and for agricultural structures has, for a long time, seen ongoing growth, it had all but vanished from cities. This is now changing. Initiated by dedicated housing development associations, cooperatives and groups with an increasing environmental awareness, new multi-storey timber constructions are being built that allow many people to directly experience humankind’s oldest natural building material. Its return to the cities is also due to the fact that timber construction is highly suit­able for purposes of converting existing structures and increasing densities in metropolitan centres, such as in the case of rooftop additions, expansions and remodelling. Wood is light, easily workable, permits efficient transport. Prefabrication enables building quickly and with a low degree of disruption. The many interesting examples of timber buildings in this manual clearly demonstrate the ways in which they enrich architecture in an urban context. Many of them are, in fact, hybrid structures, which is by no means a step backward for timber construction. On the contrary, it is logical and sensible to skilfully combine the tried and tested building materials and construction methods available on the market in relation to their performance, availability, price and design potential, in order to build efficient

and economically viable buildings. This approach has long been typical to building in an urban context. Consider how ­construction methods were blended in the Middle Ages, when combinations of ­timber and stone made it possible to build impressive half-timbered structures, or ­Wilhelmian buildings, which seemingly consist of solid masonry on their exterior, while their horizontal construction elements such as slabs and roofs actually contain a large proportion of timber. The opportunities offered by modern means of construction motivate us to question the conventional and very narrow categorisation of timber structures into frame, panel and solid timber-based construction types and, as a result, expand upon them. Based on the possibilities of combining horizontal and vertical elements already in practice today, timber construction constitutes a ­fascinating and creative process. In conjunction with modern building envelope construction types, the range of applications for this renewable raw material is nearly boundless and ever-expanding. The continuous use of wood as a construction material and the resulting long-term carbon storage capacity and creation of carbon sinks are positive contributions to the struggle against global warming. Nevertheless, climate change will impact and transform the supply of timber. In future, wood as a natural building material will be available to us in a different supply mix than today. The availability of hardwood will likely grow, while softwood stock will simultaneously decline. This will necessarily result in new and further developments in wood-based materials and a much larger share of hardwood-based materials in ­multi-storey timber buildings than is the case thus far, with positive consequences. Many hardwood species feature much ­better strength and stiffness characteristics, allowing the production of very thin and lightweight ­construction components that open up entirely new design opportunities in the realm of multi-storey timber construction. The forestry industry in Europe has been a sus­tainable practice for centuries and demonstrates that thriving forests can be maintained while sustaining other functions, ranging from air puri­fication and water storage to serving as a recreational space – despite the intensive harvesting of this raw material. Europe currently grows more wood than it uses. Germany, Austria and Switzerland could theoretically realise all

new timber buildings by using about half of their annual wood supply. Particularly for interested planners and ­clients with little or no experience in building with timber, this manual will help combat scepticism, misconceptions and bias regarding a material that is possibly largely unknown to them. Based on a new, practical approach to the systematisation of construction methods, potential design options are introduced and explained that show how planning with timber isn’t any more difficult than with any other building material. It is high time to employ this readily available natural resource as a construction material and integrate it into the residential and work environments of people to a stronger degree than ever before. Following the publication of the first edition in 2017, some areas experienced innovations that resulted in the need for a revision. In addition, very interesting examples have been realised that document said innovations. The topic of building simply, the use of hardwood in construction, planning and digitalisation processes adapted to timber, which were still in research and development stages at the time of the original version of this book, have now been implemented within pilot projects. These interesting developments are featured here. We would like to thank everyone who contributed to the creation of this book: the publishers for their excellent cooperation, the authors for their knowledgeable contributions, the sponsors for their generous support, our project manager of the ori­ ginal edition, Anne Niemann, and the project manager of this new edition, Manfred Stieglmeier, for their tireless commitment. Munich, July 2021

Hermann Kaufmann Stefan Krötsch Stefan Winter

Agricultural Centre, Salez (CH) 2019, Andy Senn ­Architekt

7

Part A  Introduction

1

Office building, Vandans (AT) 2013, Architekten ­Hermann Kaufmann

The Evolution of Multi-storey Timber Construction Antiquity and the Middle Ages in Eastern Asia The Middle Ages in Europe The Modern Era Urban Timber Construction

8 8 9 10 12

2 Wood as a Resource A Look Back Quantifying Forests and Timber Forestry and Wood: Partners in Timber Construction The Timber Resource Situation and its Prospects Hardwood: Alternatives in Timber Construction Conclusion

14 14 14 15 16 17 17

3 Solid Wood and Wood-based Products

18

4 Life Cycle Analysis Environmental Protection Impact of Timber Buildings Carbon Sequestration and Substitution Carbon Sequestration vs. Resource Efficiency in Construction CO2-efficient Timber Construction Comparative Life Cycle Assessment: Conventional vs. Timber Construction Conclusion

24 25 25 27 27 29 30

5 Indoor Air Quality – The Influence of Timber Construction Healthy Indoor Climate Emissions in Indoor Air Impact of Untreated Wood Impact of Glued Structural Timber Products Impact of Wood-based Materials Strategies for Managing Emissions Conclusion

32 32 33 36 37 37 38 39

8

The Evolution of Multi-storey Timber Construction Stefan Krötsch, Lutz Müller

A 1.1

Since the emergence of fortified towns and villages, developments in construction have focused on erecting tall, multi-­ storey buildings, sometimes due to a lack of available space within fortified areas, but also for reasons of prestige. In regions where wood was the predominant building material, the knowledge and craftsmanship for erecting durable, multi-storey timber buildings have been established since antiquity. Even log construction, one of the oldest methods of timber construction and one practised since the Neolithic Age, made it possible to erect buildings of ­remarkable height. This method was ­common in the densely forested parts of Asia and Europe well into the modern era and is still in use in some regions. Closed, windproof and insulated walls are created by stacking blocks or logs, ­stiffened by dovetail, lap or box joints ­applied to corners and interior walls. ­Although tall buildings made of horizontally stacked logs can be subject to ­significant settlement, buildings of no­ table height were built in areas with long ­traditions of craftsmanship, such as the ­five-storey house in the Swiss canton of ­Valais (Fig. A 1.2).

Antiquity and the Middle Ages in Eastern Asia With the advent of Buddhism, highly-­ developed woodworking techniques emerged in 6th-century Japan, based on the influence of Chinese architecture. Their pro­tagonists were referred to as ­“master builders” and “great craftsmen” and were held in high regard. During the Asuka and Nara periods, a type of frame construction developed that was ­considered characteristic of Japanese architecture well into the modern era. A roof structure secured against the effects of wind by use of heavy loads is ­supported by pillars tied into a frame structure through beams with mortise and tenon-like joints. The entire structure is placed on top of stone plinths without ­further connection. Its solid, continuous ­pillars can bear heavy loads, while the ­ductility (i.e. the ability to deform without ­failure) of the frame connections and plinth placement ensures very good pro­ tection from earthquakes. As long ago as 725, in the capital city of Japan at the time, Nara, the pagoda of the Buddhist Kōfuku-ji Temple, was ­constructed, featuring five storeys and at a height of more than 50 metres. The

A 1.1 Competition design for the Langelinie Pavilion, Copenhagen (DK) 1953, Jørn Utzon A 1.2 Five-storey residential building in Evolène, Valais (CH) 1958, Follonier brothers A 1.3 Tō-ji Temple, Kyoto (JP) 9th century (the pagoda was rebuilt after being destroyed in 1644) A 1.4 Pura Besakih Temple, Bali (ID) 11th century A 1.5 Himeji Castle, Himeji (JP) 17th century A 1.6 “Alter Bau” granary, Geislingen an der Steige (DE) 1445 A 1.2

A 1.3

T H E E V O L U T I O N O F M U L T I - S T O R E Y T I M B E R CONSTR UCTION

main hall of the world’s largest building erected entirely of wood, the Buddhist ­temple of Tōdai-ji, is also located in Nara. Built in 745, it is 57.01 metres wide, 50.48 metres deep and 48.74 metres tall. The ­five-storey, 57-metres tall pagoda of the Tō-ji Temple in Kyoto, built in the 9th century, was Japan’s tallest building at the time (Fig. A 1.3). The buildings of the 11th-century Pura Besakih Temple on the island of Bali reach a height of up to 44 metres (Fig. A 1.4). Each of the eleven storeys comprises a ­single room that is used as a shrine for ­religious rituals. The slender towers are ­stiffened by elaborate framework connections between the pillars and beams, using a technique similar to that employed in the Japanese structures described above. The palaces of Beijing’s Forbidden City were built in less than two decades in the early 15th century. With a height of 35 metres and a floor area of 2,400 m2, the “Hall of Supreme Harmony” is the ceremonial centre of this gigantic building complex. The 17th-century Himeji Castle in Japan, six storeys and 31.50 metres tall, was one of the largest multi-storey timber buildings of its day (Fig. A 1.5). Frame construction and the accompanying openness in terms of functional and spatial

A 1.4

system remained unchanged in China and Japan for a long time. It was not until the early modern era that this millennia-old ­tradition ended abruptly. As a material for the primary structure of buildings with more than two storeys, timber was replaced completely by new building materials such as steel and concrete.

The Middle Ages in Europe Half-timbered construction was the pre­ dominant method used to erect buildings in central European cities from the Middle Ages until well into the 19th century. However, it follows a fundamentally different construction approach than Asian frame construction. Despite their frame-like appearance, posts and braces, together with bottom and top plates, function as stiff wall panels rather than frames. These wall panels, in the form of interior and ­exterior walls, stiffen the building without having to rely on the ceiling slab in structural terms. Ceiling joists are set on top of the walls, often following their own rhythm without regard to the spacing of posts. In contrast to Asian frame construction, ­supporting pillars are not continuous from one storey to the next, but are interrupted

A 1.5

9

by the bottom plate, ceiling joists and wall plates and are sometimes even offset between storeys. Ceiling joists are ­tension-tied between the wall panels. This enables greater ceiling spans and keeps down vibrations. An overhang or “jetty” ­protects the facade beneath from the weather. Post-in-ground and post-and-beam ­structures were the precursors of half-­ timbered buildings. Post-in-ground or pole framing is a framed construction method. Here, posts are driven metres deep into the earth and dug in, serving as supports that stiffen the building. The base of a ­pillar would usually rot away completely within 20 to 30 years, which required re­­ placing the entire building. Post-and-beam buildings offered a solution to this problem. Instead of poles buried in the ground, it made use of building-height posts placed dry on top of a horizontal bottom plate, which greatly prolonged the lifespan of buildings. This technique permitted the ­construction of multiple storeys, while the height of individual buildings was limited by the length of available logs. Load-bearing pillars could only be replaced at great expense. The introduction of half-timbered construction equalled a revolution in terms of build-

A 1.6

10

Tō-ji Temple Japan, 888 57 metres 5 storeys

Pura Besakih Temple Bali, 11th century 44 metres 11 storeys

Hopperstad stave church Norway, 1130 27 metres 4 storeys

Qigu Tan China, 1420 25 metres 3 storeys

Historic granary Germany, 1445 21 metres 7 storeys

90 m 80 m 70 m 60 m 50 m 40 m 30 m 20 m 10 m

Medieval

ing: it was now possible to build timber structures that would remain intact for ­hundreds of years. Their load-bearing ­components permitted easy replacement without having to disassemble the entire load-bearing structure. Half-timbered construction also resulted in establishing a great deal of knowledge and skill involving construction-based timber preservation that is still in use today. Prolonging the lifespans of buildings and structures by introducing post-andbeam construction or the timber framing method comprising stacked and appro­ priately ­stiffened storeys facilitated the ­construction of multi-storey buildings made of wood. The former granary (Alter Bau) in Geislingen an der Steige, dating from 1445, comprises a seven-storey timber structure set on top of a first floor plinth made of masonry brick. The building is proof of the performance and permanence of this construction method (Fig. A 1.6, p. 9).

A 1.7

The Modern Era Concrete and steel dominated the material canon of classic modernism. Here, timber as a material for load-bearing structures no longer played a significant role. Competition from suddenly widely available, nondegradable and non-combustible materials relegated timber to the role of building material for lower-height and sometimes temporary buildings. Only following the turn of the millennium has timber construction experienced a fundamental reframing based on a series of technical innovations. In the context of a worldwide political process of reassessment in the face of global environmental change and especially global warming, timber construction has received renewed appreciation in central and northern Europe. A broadly conceived model project in Bavaria and new developments in Austria had led to the building of a number of threestorey timber apartment houses (Fig. A 1.7).

Accordingly, the first issue of the professional magazine zuschnitt summed up an analysis of new timber construction in 2001 in their subtitle: “[...] the first gener­ ation of multi-storey buildings has passed the test.” Technical advances and a continuously adapting legislative context have since resulted in new height records for timber buildings in increasingly short intervals. The seven-storey e 3 apartment building erected in Berlin in 2008 features elements such as timber-concrete composite slabs and an exterior reinforced concrete staircase in order to adhere to fire safety requirements (Fig. A 1.8). Eight-storey buildings that nearly qualify as high-rise structures, such as the H8 in Bad Aibling (Fig. A 1.9) and the LifeCycle Tower One in Dornbirn, followed in 2011 and 2012. The first timber building considered a high-rise, the tenstorey Murray Grove Tower, was built in London in 2009 (Fig. A 1.11). Another tenstorey apartment building, Forté Tower, was

A 1.8

A 1.9

T H E E V O L U T I O N O F M U L T I - S T O R E Y T I M B E R CONSTR UCTION

Damaschke housing estate Germany, 1996 9 metres 3 storeys Architects: Fink + Jocher

H8 Germany, 2012 25 metres 8 storeys Architects: Schankula Architekten

Forté Tower Australia, 2012 32 metres 10 storeys Architects: Lendlease

Student residence Canada, 2017 63 metres 18 storeys Architects: Acton Ostry Architects

11

Cultural centre and hotel Sweden, 2021 82 metres 20 storeys Architects: White Arkitekter 90 m 80 m 70 m 60 m 50 m 40 m 30 m 20 m 10 m Time

Moderne

completed in Melbourne in 2012. While the building complex along the Via Cenni in Milan, completed in 2013, is only nine storeys tall, it consists of four residential towers connected by a platform building that covers an entire city block. In the United Kingdom, Australia and Italy, as in many other countries, there exist no requirements concerning the combustibility of load-bearing structures, even for high-rise buildings – as long as a degree of fire resistance is ensured for a sufficient amount of time. For this purpose, buildings can comprise encapsulated cross-laminated timber panels. A 14-storey building with a glued-laminated timber frame and prefabricated modular rooms set into its structure was built in Bergen in Norway in 2015 (Fig. A 1.12). In 2016 a student housing project with 18 storeys and a height of 53 m was completed in Vancouver in ­Canada, comprising a frame construction with glued-laminated timber columns and cross-laminated timber ceilings. The completion of the HoHo in Vienna and of the

Mjøstårnet in Brumunddal in Norway constitute the current apex in the quest for reaching ever new record-breaking heights. The HoHo is an 80-metre tall timber-concrete hybrid high-rise building with 23 storeys (Fig. A 1.13). The Mjøstårnet consists of glued-laminated timber posts and crosslaminated timber ceilings as well as a limited number of concrete ceilings on the upper floors of the 18-storey, 84-metre tall structure. The hotel tower of the Cultural Centre in Skellefteå in Sweden reaches a height of 82 m (see project example p. 198ff.). There seems to be no end in sight for these constantly accelerating height developments, raising the question of whether the increasing effort involved justifies pushing these limits further. It proves, however, that timber meets each and every requirement placed on modern building materials. The examples from recent years outlined above show that the combustibility of timber has long been overstated and is by no means an obstacle to the construction of multi-­

A 1.11

A 1.12

A 1.10

A 1.7  Apartment building – Bavarian model project, Regensburg (DE) 1996, Fink + Jocher A 1.8  e 3 high-rise apartment building, Berlin (DE) 2008, Kaden Klingbeil Architekten A 1.9  H8 high-rise apartment building, Bad Aibling (DE) 2011, Schankula Architekten A 1.10 Overview of multi-storey timber buildings ­according to height A 1.11 Murray Grove Tower, London (GB) 2009, Waugh Thistleton Architects A 1.12 High-rise apartment building, Bergen (NO) 2015, Artec Arkitekter / Ingeniører A 1.13 HoHo timber high-rise building, Vienna (AT) 2019, RLP Rüdiger Lainer + Partner

A 1.13

12

storey buildings. This finding is slowly yet steadily reflected within legislation. Even in a country such as Germany, strongly regulated by building codes, standards are becoming less and less an impediment to timber construction. Here, the state of Baden-Württemberg has taken on a pioneering role in Germany. The realisation of Building Class 5 structures, for example, is no longer tied to the non-combustibility of building materials used for primary structural components and partitions between spaces. Instead, it is solely related to fire resistance time. In 2019, the first German timber high-rise building, the 34-metre tall Skaio, was erected in Heilbronn. In other countries, legislation often supports a sig­ nificantly more extensive use of wood.

Urban Timber Construction A 1.14

A 1.15

The result of recent technological and ­societal developments is that everyday building typologies, such as blocks of flats, commercial or educational buildings are becoming increasingly common as timber structures on an urban scale. In 2008 more than half of the global population lived in ­cities. In 1950, 70 % still lived in rural areas. According to UN estimates, the global share of urban dwellers will increase to more than 60 % by 2030 and reach 70 % in 2070 [1]. If timber construction, based on its ecological advantages, finds use in the construction sector at relevant scales, it will also return to the cities. In the meantime, entire urban sites with a focus on timber construction are under development. This is typically motivated by ecological aspirations of regional polit­ ical actors aimed at decarbonising the building industry. In Munich, the tendering process for building plots on a section of the former Prinz-Eugen Barracks was contingent on adhering to an ambitious list of ecological criteria and using renewable

raw materials to the highest possible degree (Fig. A 1.16; see project example p. 216ff.). As a result, construction began on eight plots in 2019 for an ecological model settlement with a total of 566 apartment units, in the form of high-density urban development with two to seven-storey buildings (Fig. A 1.16 b). The exterior walls of nearly all buildings consist of wall framing. Ceilings and interior walls of most buildings are made of cross-laminated timber. Concrete staircase cores predominantly serve as emergency exits. The majority of facades, despite strict fire safety requirements, ­feature back-ventilated wood facades with designs highly adequate to the urban context. Frame wall construction is less thick than ­mineral-based construction, while providing the same degree of thermal insulation. The resulting increase in area efficiency contributes to the economic efficiency of the building, despite higher construction costs in an urban context with high property values. Often, the result is hybrid buildings with reinforced concrete ceilings, columns, staircase cores and wood building envelopes. Based on the light weight of wood as a ­construction material and its suitability for ­prefabrication tasks, wood buildings are ideal for adding additional floors to existing structures, offering significant potential for increasing density in European cities. Due to the possibilities of extensive prefabrication and corresponding short construction time, timber buildings constitute an inter­ esting option for urban spaces, also by reducing the impact of construction sites on intensively frequented infrastructure and neighbourhoods to a minimum. In the last two decades timber construction has occupied an ever-growing field of applications: residential buildings as well as offices, production facilities and other commercial buildings, in addition to kindergartens, schools, sports facilities, sacred and

T H E E V O L U T I O N O F M U L T I - S T O R E Y T I M B E R CONSTR UCTION

13

A 1.14 Kammerzell House Strasbourg (FR) 1427 A 1.15 Cultural Centre with hotel, Skellefteå (SE) 2021, White Arkitekter A 1.16 Residential development Prinz-Eugen-Park, ­Munich (DE) a Construction phase WA 14 West, 2019, Rapp Architekten b Site plan, scale 1:7,000, GSP Architekten and Rainer Schmidt Landschaftsarchitekten c Construction phase WA 14 Ost, 2020, ARGE ArchitekturWerkstatt Vallentin, Johannes Kaufmann Architektur a

cultural buildings are all made of wood. The impressive apex of this development is the Cultural Centre in the Swedish city of Skellefteå, which houses a library, an art museum, an art gallery, a concert hall, the­ atre stages, a conference centre and a hotel within a single wood structure (Fig. A 1.15; see project example p. 198ff.). Wood is often considered a rural building material. An urban context, on the other hand, is associated in historical terms either with masonry brick and rendered facades or with the steel, glass and concrete of the modern era. Specifically in central and northern Europe, timber buildings defined the image of cities well into the 19th century. The rich heritage of building culture can still be experienced to this day, for instance in the old town of Strasbourg (Fig. A 1.14). Characterised by its medieval half-timbered buildings, it is also a UNESCO World Heritage Site. The Kammerzell House, built in 1427 and located on the Münsterplatz, is a four-storey half-timbered building set on a one-storey masonry plinth. The rich ornamentation of its hand-carved facade is fascinating – its urban surroundings are inconceivable without it. It is a fitting ex­­ ample for the fact that not only the material as such, but rather its architectural treatment is decisive for the successful integration in the urban context. Wood seems to have arrived within the canonical material selection of the modern era – well on its way towards reconnecting with its extensive history as a building ­material for tall and urban buildings.

5 5 2 6

3 1

5

4 7

7

8

5

7 7 7

1 Neighbourhood square 2 Primary school 3 Culture meeting point for residents (planned) 4 Community centre with ­mobility station, neighbourhood café and bicycle store 5 Daycare facility 6 Retail, doctor's offices 7 Ecological model settlement 8 Senior citizen centre (under construction)

b

Notes: [1] United Nations, Department of Economic and Social Affairs, Population Division: World Urbanization Prospects: The 2018 Revision. https://esa.un.org/unpd/ wup/Publications c

A 1.16

14

Wood as a Resource Gerd Wegener

A Look Back

A 2.1 Mixed forest A 2.2 Medieval half-timbered buildings in Einbeck (DE) A 2.3 Platform hall, Munich central railway station (DE) ca. 1850 (demolished in the 1870s) A 2.4 Broadcasting tower in Ismaning near Munich (DE) 1932 (demolished in 1983) A 2.5 Global annual consumption of important con­ struction materials A 2.6 EU-wide timber stock by country

Throughout human history and well into the 19th century, wood was indispensable as a raw material, as a building material and as a part of our cultural heritage. It has been in use for the construction of build­ ings, wagons and ships and has served as a mater­ial for making tools, weapons, furni­ ture and works of art, to name just a few ex­­ amples. Wood was the most important fuel, was used to produce a wide range of basic chemical materials such as alcohol and ­tanning agents and was the main raw mate­ rial for making charcoal and potash for the production of iron and glass. The diversity of its application meant that wood was more familiar to people than any other material. Aside from wood, forests additionally pro­ vided a large number of further raw mate­ rials and products (game, berries, mush­ rooms, medicinal remedies, etc.). The overuse of timber resources in Europe, most of all in the 17th and 18th centuries, led to a shortage of wood and to deforesta­ tion [1]. In response to these grievances, in 1713 Hans Carl von Carlowitz formulated his ­guiding principle on sustainable forest use: “Do not cut more wood than will regrow” [2]. By the late 19th and into the 20th century, wood was supplemented to large degrees by other materials (steel, concrete, rein­ forced concrete, plastic) and new sources of energy (coal, oil, gas, nuclear energy) and replaced entirely in many areas. Looking back at the highlights of various cultural epochs in the context of building with timber, the millennia-old significance of wood as a construction material becomes obvious: dwellings of the Stone Age, of the Celts and later of the Vikings, stave churches and medieval half-timbered buildings (Fig. A 2.2) demonstrate this significance, as do the ­mid-19th century platform hall of Munich’s central railway station (Fig. A 2.3) and the 163-metre tall, early 20th-century Ismaning radio transmission tower (Fig. A 2.4).

A 2.1

Timber became less important as a con­ struction material in the early decades fol­ lowing World War II, with the exception of its typical application for roof structures, stair­ cases and flooring. In the last 20 to 30 years, however, timber construction has enjoyed renewed popu­ larity. We may even speak of the dawn of a new era in building with timber. This development is, on the one hand, due to the many ecological advantages of this renewa­ ble building material and is enabled, on the other hand, by the enormous diversity of new, high-performance wood-based and composite materials, innovative joinery and powerful adhesives. Specialised engi­ neering services, computer-based plan­ ning and industrial prefabrication have also decisively contributed to architecturally sophisticated construction with timber in urban and rural areas reaching new qual­ities and heights. This type of construction can be fast, dry and competitive while ­demonstrating high quality. This applies to renovating existing structures and to ­creating new residential buildings, kinder­ gartens, schools, as well as office and ­commercial buildings, below the high-rise threshold and above.

Quantifying Forests and Timber Issues of resource availability in a glo­ balised world require us to take a local, regional and global look at forests and wood. About 30 % of the Earth’s land sur­ face, 4 billion hectares, are currently cov­ ered by forests. The global forest cover has, however, been shrinking for decades, mostly due to slash-and-burn farming, ­conversion into agricultural land and illegal logging, predominantly in tropical and ­subtropical forest regions. Yet, from 2015 to 2020 deforestation has declined from 15 to 10 million ha per year. Reforestation

15

W O O D A S A R ESOUR CE

A 2.3

struction timber, or for energy generation. The Earth’s forests provide 4 billion m3 (= 2.4 billion t) of logs annually, of which 1.5 billion m3 are softwood and 2.5 billion m3 are hardwood. 51 % of logs are used to generate energy, while 49 % are turned into products [4]. Thus, wood continues to be the most important renewable raw material and energy source on Earth and one of the three most commonly used materials. Figure A 2.5 strikingly shows that a world without wood as a raw and construc­ tion material or energy source would be inconceivable [5]. The nearly 2 billion m3 of timber are processed into 440 million m3 of sawn lumber and 390 million m3 of woodbased products for construction and resi­ dential uses (building, interiors, furniture) as well as 400 million t into paper and paperbased products [6]. Byproducts and waste materials from processing are subject to efficient value creation in material form (basic material) or used for power gener­ ation (e.g. pellets).

[billion m3]

A 2.2

and the creation of plantations on currently 7 % of the total global forest cover result in an average annual net loss of 4.7 million ha [3]. Still, the annual losses can vary between individual countries and regions, for instance, due to influences based on ­climate or policy or an increase in illegal fires, such as in the Amazon region in 2020. Tropical, subtropical, boreal and temperatezone forests are the most important forest types for producing timber. The cultivation of forests of the type almost exclusively found in Europe indicates a focus on multifunctional, sustainable forest management. In addition to supplying timber, this includes a wide range of functions, from protection, production and recreation to maintaining biodiversity. In contrast, the global planta­ tion industry mainly grows eucalyptus and fast-growing pine species in monocultures for the production of timber and biomass for specific purposes, such as the manu­ facture of cellulose, paper, wood-based materials and lower-quality types of con­ 7

7

6

5

4

4

3

2

2

1 0.23

0.24

Steel

Plastic

0 Concrete

Logs, of which lumber

0.06 Aluminium

A 2.5

A 2.4

Forestry and Wood: Partners in Timber Construction

In Europe, timber construction is part of the economic sector of forestry and wood that forms a complex value chain extending from forestry, the wood industry and timber construction to the paper, print and publish­ ing industries. This sector reports nearly EUR 500 billion in sales and 3.5 million employees. In Germany, with a turnover of EUR 180 billion and 1.1 million employees, the sector is highly relevant with regards to social policy, resources and the environ­ ment. Its importance is equal to that of ­engineering and the automotive industry, especially in rural regions. The timber industry comprises the wood industry, the paper industry, the woodwork­ ing trades and the lumber trade. Further partners in timber construction (prefabri­ cated timber construction, industrial timber construction and trades such as carpenters and cabinet makers) include forestry, the

Germany 3.70

33

Sweden 3.00

68

France 2.60

31

Poland 2.54

31

Finland 2.33

73

Romania 1.94

30

Italy 1.45

32

Spain 1.21

38

Austria 1.16

47

Norway 1.16

33

Czech Republic 0.79

34

Slovakia 0.53

40

Switzerland 0.44

32

Slovenia 0.43

62

Croatia 0.42

34 Timber stock in billion [m ] 3

Forest cover share of land area [%] A 2.6

16

A 2.7

sawmill industry and the sawn lumber, wood-based product and wood component trade industries [7].

The Timber Resource Situation and its Prospects In summary, the statement can be made that Europe’s forests are forests of cultural and commercial importance that have expe­ rienced centuries of human influence while providing the domestic raw material wood for the timber industry and for timber con­

A 2.8

struction. In 2020 the EU Member States had access to more than 180 million ha of forests with a large variety of tree ­species. This equals 41 % of the total EU area. It is remarkable that the forest cover has steadily grown in the last 40 years. In ­Germany alone, its figure has increased by an annual average of 5,000 ha in the last 10 years. In recent years, however, large areas of commercial (especially coniferous) forests have been lost or limited in their effi­ ciency due to windthrow, extreme drought and related forest fires, aridity and other calam­ities (most of all, bark beetle infesta­

German timber stock: 3.7 billion m3 The annual wood growth in Germany comprises approx. 80 million m3. Approx 70 million m3 are harvested as logs which theoretically yield 45 million m3 of timber construction products.

Approx. 150 million m3 of residential space (31 million m2 liveable area) and 190 million m3 of new non-residential space are built annually in Germany (Statistisches Bundesamt: Baufertigstellungen 2020). Per m3 enclosed space approx. 0.08 m3 of wood in the form of timber construction products are required for residential construction and approx. 0.05 m3 for non-residential construction.

Less than half of the annual German wood harvest would be sufficient to build the entire annual national construction volume with timber.

A 2.9

tion). Future-proof reforestation will need to compensate these losses. At about 27 ­billion m3 the stock of available wood in European ­forests is, however, still large. Germany ranks at the top with 3.7 billion m3 (Fig. A 2.6, p. 15). With an average of 340 m3/ha, it has the second-largest stock per hectare, behind Austria. The stock of raw material is, therefore, sustainably large and even increasing. In Germany 120 mil­ lion m3 of surface biomass regrow annually, about 80 million m3 of which are used in the form of rough lumber [8]. A model calcula­ tion came to the surprising conclusion that all new buildings erected in Germany could be built by using slightly less than half of the country’s average sustainable timber harvest (Fig. A 2.9) [9]. Sustainable timber use is, thus, imperative to maintaining and rejuvenating forests. Combined with concepts for climate-proof mixed forests adapted to their specific location, it can contribute to near-natural, stable forests characterised by biodiversity, a diversity of tree species (in Germany, more than 50) and increasing shares of dead and decaying wood. In its basic sce­ nario, the Sustainability Assessment of ­Alternative Forest Management and Timber Use Scenarios (Nachhaltigkeitsbewertung alternativer Waldbehandlungs- und Holz­ verwendungsszenarien, WEHAM) predicts a figure of about 80 million m3 for the poten­ tial supply of raw lumber per year over the next 40 years [10]. This would increase the timber stock to 3.9 billion m3. The raw lumber potential of the most import­ant wood species, spruce, currently comprises 44 % of available raw lumber. This figure will likely decrease to roughly 35 % by 2027. Alternative softwood species include pine, Douglas fir and fir, shares of which will increase significantly. Major increases are also expected to take place for wood species such as beech (+59 %) and oak (+97 %), yet also other wood species, including ash, maple, birch, alder and

W O O D A S A R ESOUR CE

­ oplar [11]. Coinciding with advan­cing p ­climate change, this will lead to a ­significant increase in deciduous and mixed forests.

Hardwood: Alternatives in ­Timber Construction Following the severe windthrow caused by storms “Vivian” and “Wiebke” in 1990 and the forestry policy goal set at the time of converting forests from purely conifer­ ous forests to near-natural mixed forests adapted to their specific location, the mixed forest cover has increased to 77 % and the deciduous forest cover in both mixed and deciduous forests to 44 % in Germany [12]. All across Europe, the share of deciduous forests has grown significantly. In addition to preserving ecological diversity, this is aimed at mitigating risks related to storms, drought and climate change. Beech makes up 45 % of total deciduous timber stock in Germany and is, thus, a specific focus in the use of hardwood for timber construc­ tion [13]. Beech was long considered a classic firewood and has been used for wood-based materials, veneers, parquetry, stairs and various forms of interior fittings, as well as furniture. Despite its good strength and rigidity values, it has been irrelevant thus far as construction timber. Thanks to the resource scenario described here and the dynamic developments in timber con­ struction, for a number of years, the scien­ tific debate and technological deliberation on new, construction-related opportunities of using hardwood – aside from beech, most of all oak, ash, maple and acacia – have pro­ duced a series of hardwood products and led to their innovative use in timber con­ struction. Due to the strength properties of hardwood, demonstrating 1.5 to 3 times higher values than spruce products, engi­ neers and architects can plan structural components with significantly smaller cross

sections or capable of bearing greater loads. Innovative hardwood building prod­ ucts include laminated veneer lumber (LVL; Fig. A 2.8), as well as cross-laminated ­timber (CLT; Fig. A 2.7), also in hybrid form (beech / spruce). Currently various hardwood building prod­ ucts are available. Corresponding publica­ tions provide information on building with hardwood [14].

Conclusion People have tended to and shaped our ­cultivated and commercial forests for cen­ turies, turning them into cultivated eco­ systems. Given the challenges of sustain­ ability, ecological diversity, climate protec­ tion and the transition to environmentally friendly energy, resources and materials, forests will become increasingly important as a habitat, as economic spaces and also as repositories and suppliers of raw mate­ rials, energy and carbon. By employing resource and energy efficiency and closed loops, the value chain from forests to ­wood-based products and timber buildings comprises a unique symbiosis of nature, technology and culture. When society and policymakers take the transition to a decarbonised economy based on sustainable and renewable resources seriously, wood will play a major role in it, as a raw material and a building material. For this purpose, forests as well as sustainable and nature-oriented forestry worldwide require high degrees of societal appreciation. Yet, this aim is not compatible with conventional softwood economy, largescale deforestation and exclusively econom­ ically oriented methods of harvest that are still practiced in large parts of Europe to this day. Only forest management and related wood use as well as making forests climate and future-proof can guarantee, in

17

the long term, that the various societally important ­functions of forests, and eventu­ ally, ­timber construction are acknowledged as a contribution to the task of climate ­protection. Notes:   [1] Radkau, Joachim: Holz. Wie ein Naturstoff ­Geschichte schreibt. Munich, 2012   [2] von Carlowitz, Hans Carl: Sylvicultura oeconomica (Leipzig 1713). Munich, 2013   [3] FAO (ed.): Global Forest Resources Assessment 2020. Rome 2020   [4] FAO (ed.): Yearbook Forest Products 2018. Rome 2020   [5] FAO (ed.): Yearbook Forest Products 2018. Rome 2020 Wegener, Gerd: Wald und Holz: Unverzichtbare Ressourcen. In: Boden, Wald und Holz als unver­ zichtbare Ressourcen. MUTation Vol. 5. Freising 2018 EAU – The European Cement Association. Activity Report 2020 World Steel Association: Steel Statistical Yearbook 2019 World and EU plastics production data 2019. In: Plastics Europe (ed.): Plastics – the Facts 2020 The International Aluminium Institute: World. ­Aluminium 2017 Anode Effect Survey 2019   [6] cf. note 4   [7] Becher, Gerhard: Clusterstatistik Forst und Holz. Thünen Working Paper 32, November 2014   [8] EUROSTAT: Forstwirtschaftliche Statistik 2019   [9] Bundesministerium für Ernährung und Land­ wirtschaft (ed.): Der Wald in Deutschland. Berlin 2018 [10] Thünen-Institut: press release 29.06.2015. www.thuenen.de/de/infothek/presse/pressearchiv/ pressemitteilungen-2015/thuenen-wissenschaftler­ berechnen-das-holzangebot-der-waelder-in-denkommenden-vierzig-jahren/ (accessed: 20.09.2021) [11] ibid. [12] cf. note 9 [13] cf. note 9 [14] e.g. Merz, Konrad; Niemann, Anne; Torno, Stefan: Bauen mit Holz. Laubholz in der Tragkonstruktion. Munich 2020 [15] Churkina. Galina et al.: Buildings as a Global ­Carbon Sink. Nature Sustainability 3/2020

A 2.7 Beech glued laminated timber left: no heartwood colouring, right: with heartwood colouring A 2.8 Laminated veneer lumber, left: parallel grain ­layers, right: crossed grain layers A 2.9 Timber stock in Germany

18

Solid Wood and Wood-based Products Anne Niemann

Many new solid wood products and woodbased materials have been developed as a result of the industrialisation of timber processing. This chapter offers an overview of the most important characteristics of the timber products currently most commonly used. Solid wood products Using wood as a building material is a ­centuries-old tradition. By finger jointing and gluing together cross sections, they can span greater lengths and bear greater loads. Drying timber reduces shrinkage and the risk of fungal decay. Wood-based materials Wood-based materials are made by bonding wood components (boards, panels, chips or fibres) in a wet or dry process, often by use of adhesives. By doing so, the advantageous properties of wood can be enhanced in a targeted way. The development of high performance products has contributed to the construction of modern multi-storey timber buildings in a significant way. Technical regulations The EU Construction Products Regulation (CPR) only gives its approval to products that have demonstrated their usability. This is especially significant in the domain of wood-based materials, because their usability is difficult to determine due to the wide range of products available. Product properties are described in EN product standards, while more detailed requirements are specified by the ETA (European Technical Assessments). Products that are not yet approved require proof of usability. Types of wood Softwood and hardwood have very different structures and are therefore used for different purposes. Climate change has led to an increased use of alternative types of wood

and, in particular, hardwood from decidu­ ous trees for timber construction (see “Wood as a Resource”, p. 14ff.). Adhesives, bonding agents, additives Bonding agents can be used to process panels, chips or fibres into wood-based materials. Additives can influence material performance in terms of resistance to fire or moisture and load-bearing capacity. Bonding agents made of renewable raw materials are currently under development. They do not yet play any significant role in the wood-based materials industry (see “Indoor Air Quality – The Influence of Timber Construction”, p. 32ff.). Bulk density / specific weight [kg/m ] The bulk density of timber is related to ­significant technological characteristics, such as strength, thermal conductivity or hardness. Determining the bulk density of wood takes its moisture content (changes to mass and volume due to swelling and shrinkage) into account as well as its orig­ inal position within the log. 3

Fire behaviour A European Commission decision defining the fire classification of ­particular ­construction products has resulted in ­uniform requirements for fire protection across Europe (DIN EN 13 501, Euro­ klassen A – F). Burn rates are specified by DIN EN 1995-1-2. Bending or flexural strength fm, k [N/mm2] The bending strength of wood is a measure of its resistance to a force that results in bending. Wood with higher bulk density will have greater bending strength, while wood with higher moisture content will display less bending strength. Water vapour diffusion resistance – μ Porous materials usually have a lower μ-value than dense materials. The lower

the μ-value, the lower the water vapour ­diffusion resistance of a building material. The higher the μ-value, the more resistant to vapour the material will be. Wood-based materials containing a high degree of ­adhesives can be used to create vapour ­diffusion-retardant layers for construction purposes (Fig. C 3.3, p. 99). Thermal conductivity [W/mK] The thermal conductivity of wood depends mainly on its bulk density, moisture content and grain direction. Simplified calculations according to DIN 4108 are required to verify thermal insulation rates in practice. Carbon content [kg/m3] The amount of carbon stored in timber products is converted into a CO2 content figure as per DIN EN 16 449. The higher the figure, the more carbon is stored in the building component, which helps mitigate its impact on the global climate. However, the carbon is released when the building component is used to produce energy. Cascading or multiple use of wood in several steps delays this process (see “Carbon Sequestration and Substitution”, p. 25ff.). Global warming potential (GWP) [kg CO2 eq.] Greenhouse gas emissions are currently the most important indicator for climate change within related debates. The global warming potential category describes the potential contribution of a material to the temperature increase of air layers near the ground, i.e. its impact on the greenhouse effect. The figure is specified relative to the global warming potential of carbon dioxide (CO2). The lower the CO2-equivalent figure is, the lower its potential effect on global warming and the lower related environmental effects will be. The figure shown here refers to the creation of a ­timber product (see “Life Cycle Analysis”, p. 24ff.).

S O L I D W O O D A N D W O O D - B A SED PR ODUCTS

a

b

19

A 3.1 Common solid wood products and wood-based materials a Solid wood, sawn softwood /sawn hardwood b Finger-jointed solid timber /solid construction timber c Double and triple-laminated beams d Glued laminated timber e Lightweight timber beams /posts /columns f Cross-laminated timber g Three-ply panel h Single-ply panel i Veneer plywood

j Beech veneer plywood k Laminated veneer lumber (LVL) l Medium-density fibreboard (MDF) m Porous wood fibreboard n Cement-bonded particle board o Particle board p OSB (oriented strand board) q Long span lumber (LSL) r Lightweight wood wool panel (WW) A 3.2 Comparison of common solid wood products and wood-based materials according to aspects relevant to use

c

e

d

g

h

i

j

k

l

m

n

o

p

q

r

f

A 3.1

20

Vollholz (VH) aus Vollholz - stabförVollholz Vollholz - stabför1) (VH) aus Basic Components Name  Wood type Nadelschnittholz (NH) Technical regulations mige Werkstoffe Nadelschnittholz (NH) mige Werkstoffe Vollholz (VH) aus Vollholz stabförmaterial Nadelschnittholz (NH) mige Werkstoffe Vollholz (VH) aus Vollholz - stabförVollholz (VH) aus Vollholz - stabförVollholz (VH) aus (VH) aus Vollholz - stabförVollholz Vollholz - stabförNadelschnittholz mige Werkstoffe Nadelschnittholz (NH) (NH) mige Werkstoffe Nadelschnittholz (NH) mige Werkstoffe Nadelschnittholz (NH)DIN EN 14 081-1, strength grading spruce, fir, pine, Werkstoffe Solid softwood timber Solid wood –mige Solid wood bar-shaped Vollholz (VH)Vollholz aus (VH) aus of wood as per DIN 4074-1 in con- larch, Douglas fir Vollholz - stabförVollholz - stabförjunction with DIN EN 1912, strength materials Nadelschnittholz (NH) mige Werkstoffe Nadelschnittholz (NH) mige Werkstoffe classes as per DIN EN 338, ­grading by appearance as per DIN EN 1611-1

Solid wood products

Vollholz - stabförmige Werkstoffe

Fingerjointed solid wood

Laminated beams

Main field of application

Other fields of application

load-bearing structures, formwork, cladding, ­ceilings, walls, roofs, wood panel construction

civil engineering, timber structural engineering

beech, oak seldom: poplar, maple, alder, birch, chestnut, ash, eucalyptus

structural reinforcement for interiors, increasingly in quality suitable for ­exposed application

timber structural engineering

spruce, fir, pine, larch, Douglas fir

load-bearing cross ­sections for ceilings, walls, roofs and wood panel construction

stacked element

spruce, fir, pine, larch, Douglas fir, poplar

exposed wall, ceiling and roof construction with large cross sections

–

spruce, fir, pine, larch, Douglas fir, western hemlock, cedar, poplar; hardwood: beech, meranti, European chestnut, oak

universal application for all bar-shaped components, ceiling elements, structural components for heavy loads and long spans

straight and curved beams with very stable forms and high visual quality; softwood glulam: only straight beams permitted

flanges: mostly ­construction timber sorted according to strength, glued laminated timber or lami­ n­ated veneer lumber; webs: mostly OSB or wood fibreboard

wall posts, ceiling and roof beams, framing with high thermal insulation ­requirements

supports for ­concrete formwork

softwood, mostly spruce, fir; seldom pine, larch, Douglas fir

non-load-bearing and load bearing elements, panels, walls, ceilings and roofs

non-load-bearing walls

DIN EN 13 353 DIN EN 13 986 as per approval

softwood, mostly spruce, Douglas fir

non-load-bearing, load bearing and stiffening panels for walls, ceilings, roofs, box elements and facade cladding

formwork, interiors, furniture

DIN EN 13 353 DIN EN 13 986 as per approval

softwood, mostly spruce, Douglas fir; seldom hardwood: maple, beech, oak, alder

furniture and interiors, ­exposed surfaces

–

Vollholz (VH) aus Vollholz (VH) aus Laubschnittholz (NH) DIN EN 14 081-1, strength grading Solid hardwood timber Laubschnittholz (NH) Vollholz (VH) aus as per DIN 4074-5 in conjunction Laubschnittholz Vollholz (VH) Vollholz (VH) aus aus(NH) Vollholz (VH) aus Vollholz (VH) aus (VH) aus Vollholz with DIN EN 1912, strength classes Laubschnittholz (NH) Nadelschnittholz (NH) Laubschnittholz (NH) Laubschnittholz (NH) Laubschnittholz (NH)as per DIN EN 338, visual grading Vollholz (VH)Vollholz aus (VH) aus as per DIN EN 975-1 Laubschnittholz (NH) Laubschnittholz (NH)

Konstruktionsvollholz Konstruktionsvollholz (KVH) (KVH) Konstruktionsvollholz Construction timber DIN EN 15 497 and application standard DIN 20 000-7; (KVH) Konstruktionsvollholz Vollholz (VH) aus Konstruktionsvollholz Konstruktionsvollholz Konstruktionsvollholzmaximum moisture content (KVH) Laubschnittholz (NH) (KVH) (KVH) (KVH) 18 %, dimensional accuracy and stability, appearance, Konstruktionsvollholz Konstruktionsvollholz surface qualities, preferred (KVH) (KVH) cross sections and lengths Triobalken Duo-/ Duo-/ Triobalken accounted for Duo-/ Triobalken Two-ply / three-ply strength grading as for sawn Triobalken Duo-/ Duo-/ Triobalken Duo-/ Triobalken laminated beams ­lumber, DIN EN 14 080 Duo-/ Triobalken or proof of usability according Duo-/ Triobalken Duo-/ Triobalken to approval Z-9.1-440

Konstruktionsvollholz Glued laminated timber (KVH)

strength grading as for sawn lumber, DIN EN 14 080 and application standard Brettschichtholz (BSH) DIN 20 000-3 softwood glued laminated timber according to ETA /abZ

Mixed product

Composite beams

Duo-/ Triobalken Lightweight timber beams / posts

as per ETAG 011

leichte Holzbauträger/ -stützen

Wood-based materials

BretterBretter Bretter BretterBretter Bretter Bretter Laminated Boards materials Bretter Bretter

Cross-laminated timber

as per approval

Brettsperrholz (BSP)

Three-ply panel

Dreischichtplatte (3 S SWP) Single-ply panel Bretter Einschichtplatte (1 S SWP)

S O L I D W O O D A N D W O O D - B A SED PR ODUCTS

21

Share of additives [kg/m3]

Adhesive, bonding agent, aggregate

Bulk density / specific weight [kg/m3]

Fire behaviour

Bending strength fm, k [N/mm2]

Water vapour diffusion resistance μ (dry / moist) 2)

Thermal conductivity λ [W/mK] 3)

Carbon content [kg/m3]

GWP [kg CO2eq/m3] A1 to A3 4)

–

none

as per DIN EN 350: spruce 440 – 470 fir 440 – 480 pine 500 – 540 larch 470 – 650 Douglas fir 470 – 550 cedar 450 – 600 calculated bulk density as per DIN EN 338 for dimensioning and ­design and as per DIN EN 1991 for design load

D-s2, d0

strength and stiffness values as per DIN EN 14 081-1 and strength class C 14 – C 50 as per DIN EN 338

50/20

spruce 0.09 – 0.12 fir 0.10 – 0.13 pine 0.12 – 0.14 larch 0.11– 0.13 Douglas fir 0.12 cedar 0.09 λ

216.3

-735

–

none

as per DIN EN 350: beech 690 –750 oak 650 –760 poplar 420 – 480 maple 610 – 680 alder 500 – 550 birch 550 –740 ash 680 –750 eucalyptus 540 – 900 chestnut 500 – 590 calculated bulk density as per DIN EN 338 for dimensioning, as per DIN EN 1991 for design load

D-s2, d0

strength and stiffness values as per DIN EN 14 081-1 and strength class D 18 – D 80 as per DIN EN 338

50/20

beech 0.15 – 0.17 oak 0.13 – 0.17 poplar 0.12 – 0.13 maple 0.15 alder 0.15 – 0.17 birch 0.14 ash 0.15 – 0.17 eucalyptus 0.13 – 0.24 chestnut 0.13 – 0.15

340

-1,120 5)

0.5

polyurethane adhesive (PUR) or melamineurea-formaldehyde (MUF) resin + curing agent; ­seldom: phenol-­ resorcinol-formaldehyde (PRF) adhesives

related to wood type

D-s2, d0

strength and rigidity values as per DIN EN 14 081-1 and strength class C 14 – C  50 as per DIN EN 338

50/20

0.13 (average) related to wood type and bulk density

219.83

-712

5

melamine-urea-formaldehyde (MUF) resin + ­curing agent or poly­ urethane (PUR); seldom: phenol-resorcinol-­ formaldehyde (PRF) resin or emulsion-polymer-­ isocyanates (EPI)

related to wood type

D-s2, d0

characteristic ­bending strengths parallel to grain as per DIN EN 14 080 between 20 and 32 N/mm2

50/20

0.13 (average) related to wood type and bulk density

221.14

-674

8.8

melamine-urea-formaldehyde (MUF) resin + curing agent or polyurethane (PUR); seldom: phenolresorcinol-formaldehyde (PRF) or emulsion-­ polymer-isocyanates (EPI)

related to wood type

D-s2, d0

characteristic ­bending strengths parallel to grain as per DIN EN 14 080 between 20 and 32 N/mm2

50/20

0.13 (average) related to wood type and bulk density

222.46

-650

–

adhesive as per DIN EN 301 or DIN EN 15 425

related to wood type of components

related to existing materials, mostly D-s2, d0

as per approval

50/20

as per EN 13 986 0.13

n. f. i.

n. f. i.

7.5

polyurethane (PUR) or melamine-urea-­ formaldehyde (MUF) resin + ­curing agent; seldom: emulsion-polymer-­ isocyanates (EPI)

related to wood type

D-s2, d0

as per approval

50/20

0.13 (average) related to wood type and bulk density

215.12

-632

17.8

melamine-urea-­ formaldehyde (MUF) resin

400 – 500

D-s2, d0

parallel to top layer grain 12 – 35, ­perpendicular to top layer grain 5 – 9

50/20

0.09 – 0.13 related to bulk density

221.9

-642

1.5

melamine-ureaformaldehyde (MUF) resin

400 – 500 (figures for hardwood vary)

D-s2, d0

as per DIN EN 13 353: parallel to grain 40 (figures for hardwood vary)

50/20 (figures for hardwood vary)

0.09 – 0.13 related to bulk density (figures for hardwood vary)

220 (figures for hardwood vary)

-712 (figures for hardwood vary)

A 3.2

22

Furniere Furniere Furniere Furniere Furniere Furniere Furniere Furniere Furniere Furniere Basic Furniere Components material Furniere Furniere

Veneer

Spanwerkstoffe Spanwerkstoffe Spanwerkstoffe Spanwerkstoffe Spanwerkstoffe Spanwerkstoffe Spanwerkstoffe Spanwerkstoffe Spanwerkstoffe Chips Strand, chip andSpanwerkstoffe fibre based Spanwerkstoffe materials

Baufuniersperrholz Baufuniersperrholz Nadelholz (BFU) Baufuniersperrholz Nadelholz (BFU) Baufuniersperrholz Nadelholz (BFU) Baufuniersperrholz Baufuniersperrholz Baufuniersperrholz Nadelholz (BFU) Nadelholz (BFU) Nadelholz (BFU) Nadelholz (BFU) Baufuniersperrholz Baufuniersperrholz Nadelholz (BFU) Nadelholz (BFU) Baufuniersperrholz 1) Name  Nadelholz (BFU) Baufuniersperrholz Nadelholz (BFU) Baufuniersperrholz Baufuniersperrholz Baufuniersperrholz Baufuniersperrholz Buch (BFU-BU) Baufuniersperrholz Buch (BFU-BU) Baufuniersperrholz Nadelholz (BFU)(BFU) Nadelholz (BFU-BU) Baufuniersperrholz Baufuniersperrholz VeneerBuch plywood Baufuniersperrholz Buch (BFU-BU) Buch (BFU-BU) Buch (BFU-BU) Buch (BFU-BU) Baufuniersperrholz Baufuniersperrholz Buch (BFU-BU) Buch (BFU-BU) Baufuniersperrholz Buch (BFU-BU) Baufuniersperrholz Buch (BFU-BU) Funierschichtholz Funierschichtholz Beech veneer plywood Baufuniersperrholz Baufuniersperrholz (FSH) Funierschichtholz (FSH) Funierschichtholz Buch (BFU-BU) Buch (BFU-BU) (FSH) Funierschichtholz Funierschichtholz Funierschichtholz (FSH) (FSH) (FSH) (FSH) Funierschichtholz Funierschichtholz (FSH) (FSH) Funierschichtholz (FSH) Funierschichtholz Laminated veneer lumber (FSH) (LSL) (LVL) Langspanholz Langspanholz (LSL) Funierschichtholz Funierschichtholz Langspanholz (LSL) Langspanholz (LSL) (FSH)(FSH) Langspanholz (LSL) Langspanholz (LSL) Langspanholz (LSL) Langspanholz (LSL) Langspanholz (LSL) Laminated strand lumber (LSL) Langspanholz (LSL) Langspanholz (LSL)

Technical regulations

Wood type

Main field of application

Other fields of application

DIN EN 636 DIN EN 13 986 as per approval DIN EN 635-3

spruce, pine, ­Aleppo pine, ­Douglas fir, ­hemlock, ­mahogany, makore

load-bearing ceilings and walls, load-bearing and stiffening panels for walls, ceilings and roofs

weatherproof cladding, ­formwork, ­scaffolding, interiors, furniture

DIN EN 636 DIN EN 13 986 as per approval DIN EN 635-2

beech

load-bearing ceilings and walls, load-bearing and stiffening panels for walls, ceilings and roofs, very high strength

weatherproof cladding, ­formwork, scaffolding, interiors, furniture

DIN EN 14 279 DIN EN 14 374 as per approval

spruce, beech, pine, Douglas fir

interiors, ­ load-bearing structures, beams, posts, struts and furniture bracing of truss beams and lattice girders, load-bearing structures for large halls

as per approval

poplar, Douglas fir, pine

applications with extreme structural requirements, e.g. bottom wall plates, rim joists or lintels, wall, roof and ceiling panels, posts and beams

floor and ceiling panels

Oriented Strand Board Oriented Strand(LSL) Board Langspanholz Langspanholz (LSL) (OSB) Oriented Strand Board (OSB) Oriented Strand Board (OSB) Oriented Strand Board Oriented Strand Board Oriented Strand Board (OSB) (OSB) (OSB)Strand Board (OSB) Oriented Oriented Strand Board pine, Aleppo load-bearing walls, Oriented strand board (OSB) DIN EN 13 986 subfloor panels (OSB) (OSB) for flooring, DIN EN 300 pine, Douglas fir, load-bearing and Oriented Strand Board DIN EN 12 369-1 ­concrete formalder, poplar stiffening panels (OSB) Oriented Strand Board as per approval for floors, walls, work, interiors, (OSB) furniture ceilings, box elements Spanplatte Spanplatte Oriented Strand Board Oriented Strand Board and roofs (weatherSpanplatte Spanplatte (OSB) (OSB) proof exterior), I-joist Spanplatte Spanplatte Spanplatte webs Spanplatte Spanplatte pine, spruce, interiors, universally usable for Particle board DIN EN 13 986 beech, birch, DIN EN 312 non-load-bearing, loadfurniture Spanplatte DIN EN 12 369-1 bearing and stiffening alder, ash, Spanplatte as per approval ­panels and as sheathing oak, poplar zementgebundene for timber panel con­ zementgebundene Spanplatte Spanplatte Spanplatte zementgebundene struction Spanplatte zementgebundene Spanplatte zementgebundene zementgebundene zementgebundene Spanplatte Spanplatte Spanplatte Spanplatte zementgebundene zementgebundene Spanplatte spruce, fir, fire-retardant panels, non-load-bearing Cement-bonded DIN EN 13 986 Spanplatte particlezementgebundene board DIN EN 634 cement-bonded load-bearing and stiffening interior walls, Spanplatte sound and as per approval softwood chips panels for interiors and zementgebundene ­thermal insula­exteriors, facade cladding Spanplatte FaserwerkstoffeMitteldichte Faserplatte FaserwerkstoffeMitteldichte Faserplatte tion zementgebundene zementgebundene Fasern (MDF) FaserwerkstoffeMitteldichte Faserplatte Fasern (MDF) FaserwerkstoffeMitteldichte Faserplatte Spanplatte Spanplatte Fasern (MDF) FaserwerkstoffeMitteldichte Faserplatte FaserwerkstoffeMitteldichte Faserplatte FaserwerkstoffeMitteldichte Faserplatte spruce, pine, Fibres Medium density fibreboard DIN EN 622-5 interiors, acoustic Fibre-based limited use as Fasern (MDF) Fasern (MDF) (MDF) Faserplatte Fasern (MDF) (MDF) Mitteldichte DIN EN 13 986 materialsFaserwerkstoffe– Fasern fir, beech, birch, panels, furniture load-bearing and FaserwerkstoffeMitteldichte Faserplatte DIN EN 316 ­fibres Fasern poplar, eucalyptus stiffening panels, (MDF) Fasern (MDF) as per approval for production of FaserwerkstoffeMitteldichte Faserplatte wall, ceiling and Fasern (MDF) FaserwerkstoffeMitteldichte Faserplatte roof panels Fasern (MDF) poröse Platte poröse Platte FaserwerkstoffeMitteldichte Faserplatte FaserwerkstoffeMitteldichte Faserplatte (SB (soft board) HFD) poröse Platte (SB (soft board) poröse PlatteHFD) Fasern (MDF) Fasern (MDF) (SB (soft board) HFD) poröse Platte poröse Platte poröse Platte (SB (soft board) HFD) DIN EN 13 171 interior, exterior and spruce, fir, pine, sheathing for Porous (SB panels (softPlatte board) HFD) (SB (soft board) HFD) (SB (soft board) HFD) poröse beech, birch, roofs or for DIN EN 622-4 infill insulation between poröse Platte (SB (soft board) HFD) ­poplar, eucalyptus posts and rafters of walls wind protection (SB (soft board) HFD) DIN EN 13 986 DIN EN 316 and roofs, insulation for for building poröse Platte as per approval partition walls, impact ­envelopes (SB (softPlatte board) HFD) poröse sound insulation (SB (soft board) HFD) Holzwolle Holzwolle-LeichtbauHolzwolle Holzwolle-Leichtbauporöse Platte poröse Platteboard platte (WW) HolzwolleWood wool Holzwolle-Leichtbauinterior and Wood wool Lightweight wood wool DIN EN 13 168 spruce, pine, render base for ceilings platte (WW) Holzwolle (SBHolzwolle-Leichtbau(soft board) HFD)HFD) (SB (soft board) (WW) Holzwolle Holzwolle-Leichtbau(WW) platte ­mostly softwood and soffits, acoustic panels ­exterior panelHolzwolle Holzwolle-LeichtbauHolzwolle Holzwolle-Leichtbauplatte (WW) platte (WW) for soundproofing ling, thermal platte (WW) platte (WW) Holzwolle Holzwolle-LeichtbauHolzwolle Holzwolle-Leichtbau­insulation in platte (WW) platte (WW) summer Holzwolle Holzwolle-Leichtbau1)  platte (WW) Acronyms differ in relation to language or region Holzwolle Holzwolle-Leichtbau2)  Figures according to DIN EN ISO 10 456 platte (WW) 3)  For a 15 % moisture content, perpendicular toHolzwolle-Leichtbaugrain direction Holzwolle Holzwolle Holzwolle-Leichtbau4)  The biogenic carbon stored in the product is featured in(WW) Module A1– A3. The amount of stored carbon exits the system after disposal of a product in Module C3, either as CO2 platteplatte (WW) (used for energy generation) or embedded in waste wood. All modules require consideration within life cycle assessments. 5)  1 m3 of hardwood contains about 1.5 times as much biogenic carbon as softwood. The GWP (A1– A3) figure for hardwood is, thus, much higher than for softwood. Observations across the entire life cycle put this into perspective: hardwood processing requires increased primary energy, resulting in higher greenhouse gas emissions.

Wood-based materials

Spanwerkstoffe Spanwerkstoffe

S O L I D W O O D A N D W O O D - B A SED PR ODUCTS

23

Share of additives [kg/m3]

Adhesive, bonding agent, aggregate

Bulk density / specific weight [kg/m3]

Fire behaviour

Bending strength fm, k [N/mm2]

Water vapour diffusion resistance μ (dry / moist) 2)

Thermal conductivity λ [W/mK] 3)

Carbon content [kg/m3]

GWP [kg CO2eq/m3] A1 to A3 4)

89.5

melamine-ureaformaldehyde (MUF) resin or phenolformaldehyde (PF) resin

450 – 580

D-s2, d0

related to class 5 –120

200/70

0.11– 0.15 related to bulk density

340

-350.9

89.5

melamine-urea-­ formaldehyde (MUF) resin or phenol-­ formaldehyde (PF) resin

720 –780

D-s2, d0

related to class 5 –120

220/90

0.14 – 0.18 related to bulk density

340

-350.9

56.8

melamine-ureaformaldehyde (MUF) resin or phenolformaldehyde (PF) resin

480 – 580

D-s2, d0

as per DIN EN 14 374 or as per approval

200/70

as per DIN EN 13 986 0.09 – 0.17 related to bulk density

180

-350.9

58

polymeric diphenylmethane diisocyanate (PMDI)

600 –700

D-s2, d0

as per approval

50/15

0.13

268.83

-768

42.1

phenol-formaldehyde (PF) or melamine-ureaformaldehyde (MUF) resin or polymeric diphenylmethane diisocyanate (PMDI)

550 – 650

D-s2, d0

related to application and thickness range as per DIN EN 300 related to board types 1– 4, major axes 14 – 30, minor axes 7–16

50 / 30

as per DIN EN 13 986 0.13

265.43

-565

58

urea-formaldehyde (UF), phenol-formaldehyde (PF) or melamine-ureaformaldehyde (MUF) resin or polymeric diphenylmethane diisocyanate (PMDI), as required paraffin wax

as per DIN EN 13 986 300 – 900

D-s2, d0 D-s2, d2

5.8 –18.3 as per DIN EN 12 369-1 related to application and thickness as per DIN EN 312

50/10-20

as per DIN EN 13 986 0.07– 0.18, related to bulk density

268.83

-768

862

portland cement, as ­required foamed clay granulate, foamed glass granulate, alkali resistant glass fibre mesh

1,000 –1,500

B-s1, d0

9 (for all thicknesses) as per DIN EN 634-2

50 / 30

as per DIN EN 13 986 0.23

298.75

357

100.3

urea-formaldehyde (UF) or melamineurea-formaldehyde (MUF) resin, phenolformaldehyde (PF) or polymeric diphenylmethane diisocyanate (PMDI)

760 –790

E to D-s2, d0

5.1– 20 as per DIN EN 622-5 related to application and thickness range

30/20

as per DIN EN 13 986 0.08 – 0.14, depending on bulk density 8)

295.3

-668.6

1.5

natural tree resin, alum or hydrophobic materials such as bitumen, paraffin wax, latex or polyurethane (PUR), as required fire ­retardants

40 – 230 6)

E

0.8 –1.3 as per DIN EN 622-4 related to application and thickness range

5/3

0.039 – 0.045 8)

88.5 6)

-164

54

portland cement or ­magnesite bonded

350 – 570

A2 – s1, d0 to B-s1, d0

related to application and thickness range as per DIN EN 13 168

5/3

0.08 – 0.11 7)

133.74 7)

136.3

dataholz.com – catalogue of ecologically certified timber building components, partly converted Manufacturer EPD; partly converted Informationsdienst Holz, Faserdämmstoffe (fibre insulating materials) Source: Rüter, Sebastian; Diederichs, Stefan: Ökobilanz-Basisdaten für Bauprodukte aus Holz. Arbeitsbericht aus dem Institut für Holztechnologie, No. 2012/1; Johann Heinrich von Thünen-Institut (ed.). Hamburg 2012 6)  7) 

8) 

A 3.2

24

Life Cycle Analysis Annette Hafner, Holger König

A 4.1

A 4.1 Passive house timber residential development Samer Mösl, Salzburg (AT) 2006, sps-architekten A 4.2 Amount of carbon (C) and its conversion into CO2-equivalent, specific building examples

The construction sector is responsible for a major share of global resource consumption and related greenhouse gas emissions, accounting for 40 % of total energy and material consumption in Europe. The sector also produces 36 % of all greenhouse gases and 33 % of all waste [1]. There is a resulting and increasing need to focus on environmental aspects in the planning and design of buildings. Increasing efficiency in building operation will not be sufficient to achieve the targets for reducing emissions as required by climate protection agreements. In this regard, the selection of building materials plays an increasingly import­ant role. The growing use of wood and wood-based materials can contribute significantly to the long-term reduction of construction sectorrelated carbon (CO2) emissions. Two methods exist for reducing the amount of CO2 in the atmosphere: either by reducing CO2 emissions or by extracting CO2 from the atmosphere and storing carbon by use of a so-called carbon sink. Wood has the unique capacity to support both methods. A life cycle assessment (LCA) is an established method of quantifying the environmental impact of a product. It also facilitates comparison of the environmental impacts of ­different products. In the building sector in particular, it supports analysing the environmental parameters of buildings based on different construction types. The information gained this way is key to demonstrating wood-related positive climate effects and can inform decision making on whether to use – or not to use – a specific building material. A life cycle assessment of a building consists of two parts: first, a material flow and energy balance plus verification of the resources (including lists of materials) and renewable and non-renewable primary energy used and, second, an impact assessment based on various indicators, such as the potential for greenhouse gas emissions, ozone depletion and summer

smog, as well as potential for acidification and over-fertilisation. Based on the quantification of building products used, the share of renewable raw materials in the building product is identified and the related amount of carbon (C) stored is calculated and, thus, the extent of temporary CO2 sequestration. Correlating the building product quantities to the life cycle assessment data can contribute to an impact assessment. For the calculation and comparison of life cycle assessment data for buildings across the entire life cycle, system boundaries, functional equivalent and data sources of the building products that calculations are based on are highly relevant. DIN EN 15 978 (Assessment of environmental performance of buildings) and, at the product level, DIN EN 15 804 (Environmental product declarations) currently provide a uniform basis for evaluating building life cycle assessments. The stan­ dards offer clear rules for adequately ­illustrating the particular characteristics of timber construction. Up-to-date data sets on wood construction products are already available for timber construction (especially those issued by the Thünen Institute of Wood Research) [2]. The global warming potential (GWP) impact category is also often referred to as an ecological or carbon “footprint”. It describes the anthropogenic share of global warming and is specified as CO2-equivalent. To ensure that calculations include the retention period of greenhouse gases in the atmosphere, a carbon footprint always features an integration period, usually GWP 100, i.e. a period of 100 years. The greenhouse gas indicator itself is not suitable for making a statement on the quantity of CO2 sequestered by use of renewable resources within a building during the use stage, if this carbon storage is used for heat generation at the end of the life cycle and, hence, is lost. For building materials consisting of renewable raw materials, the current DIN EN 15 804 calls for a distinction between biogenic and fossil

L I F E C Y CLE A SSESSM ENT

25

0 200 400 600 800 1,000 1,200 Absolute figures for carbon and CO2 sequestration in buildings [t C /CO2] C

1,400 CO2

Holztechnikum Kuchl college Samer Mösl housing development Ludesch community centre Garmisch-Partenkirchen tax office Lebenshilfe workshops, Lindenberg New replacement building, Fernpaßstraße housing development, Munich Housing complex in Erlangen Munich-Hadern youth centre Modernisation of Fernpaßstraße housing development, Munich Modernisation of Grüntenstraße housing development, Augsburg Modernisation of Gundelfingen primary school

GWP with regards to the greenhouse gas potential indicator. This facilitates separation of the captured carbon from the emissions that are required to create building products, even during the building construction phase.

Environmental Protection ­Impact of Timber Buildings Wood components integrated into buildings store carbon and delay its release until the component is disposed of. Disposal results in the release of carbon if wood is incinerated in order to generate energy. The longer timber is used as a material, the longer the storage effect is maintained. Therefore, a timber building is considered a form of temporary carbon storage. Carbon sequestration can play an important role in improving the effectiveness of forests as carbon sinks. In the 1997 Kyoto Protocol the delayed emissions from wood products that sequester carbon were not taken into account in the inventory rules of the first commitment period. After negotiations at the Durban Climate Change Conference in 2011 the agreements reached under the Kyoto Protocol were amended and some of the rules on the forest and timber industry’s inventorying and quantifying were revised. Since then, the reporting on and inclusion of forest management has become obligatory and any temporary, dynamic changes in the carbon pool of wood harvested and used must be explicitly taken into account [3]. Under the Kyoto Protocol and agreements reached at the Durban Climate Change Conference, from early 2013 onward the use of wood products as material was credited in the second commitment period until 2020, although the credits were provided only at the national level and only for domestic timber. Following 2020 the specifications of the 2015 Paris Agreement continue to be valid for calcula-

tions intended for balancing in the land use sector. Every increase in the use of wood as a material – and especially the increased use of domestic timber in construction – has a positive effect on the results of the CO2 balance. For the German case, it was established at the end of the commitment period in relation to a predetermined reference ­(reference level for forestry management). Quantifying the expected climate impact of the increased use of wood as a material is highly important at the national level and can support enhancing the sink effect of ­forests. The amount of carbon captured within wood used for construction is estimated on the basis of sawn lumber, the quantity of applied wood-based products, as well as paper consumption. This includes the wood used by the construction industry to a comprehensive degree [4]. To demonstrate the effects of the climate neutrality of wood in relation to the CO2 ­balance of forests, only wood sourced from domestic forests, inventoried in advance according to Kyoto Protocol Article 3.4, is used for calculating its contribution to woodbased product carbon sequestration. This means that wood sourced from deforestation is excluded from the balance. For this reason, certification systems in Germany require that the wood used has an FSC (Forest Stewardship Council) or PEFC (Programme for the Endorsement of Forest Certification Schemes) certificate. These certificates, however, provide no information on whether, in the context of the respective nation, quantitative sustainability in the context of forest management is ensured and, therefore, the carbon neutrality of forests. To assess the impact of timber buildings on the environment, the carbon sequestered must be determined separately according to material groups. Potential substitution factors for buildings can also be specified if they are built with timber instead of mineral building materials. Life cycle assessments support the required evaluation.

Carbon Sequestration and Substitution

A 4.2

Two aspects are of particular interest regarding the environmental impact of wood and wood products in construction: •  The building as a carbon sink •  Substituting finite raw materials Renewable raw materials and carbon ­sequestration CO2 balancing of forestry management was also included in the amended Kyoto Protocol rules for the second commitment period. This creates a basis for including the effects of the carbon sequestration of wood products on the environmental impact assessment of a building. For this purpose, the amount of carbon stored by a building is established and subtracted within the life cycle assessment. When demolition of the building or parts of it takes place, the carbon is released and the greenhouse gas emissions for inciner­ ation are added as part of disposal. As a result, the negative numbers for production and the positive numbers for greenhouse gas emissions in the disposal stage cancel each other out. This is often referred to in simple terms as the climate neutrality of renewable raw materials. The Intergovernmental Panel on Climate Change (IPCC) has published lists of the quantities of ­carbon stored in various timber products. The assumption is that there are 225 kg of carbon in each m3 of timber (with a bulk density of 450 kg in absolutely dry condition). DIN EN 16 449 determines the conversion of stored carbon into CO2. Based on this approach to the balance, the carbon sequestration effects of various material-specific structures in the ­building sector can be researched, calculated, evaluated and compared. Figure A 4.2 shows different building ex­­amples ­and the absolute amounts of carbon resulting from the use of products made

26

A 4.3 Analysis of a life cycle assessment for a multifamily residential building (based on gross floor area – GFA) without operating energy during use phases for A (production), B (maintenance), C (disposal) A 4.4 Quantities of renewable raw materials in kg/m2 usable residential area for different multi-family residential buildings featuring hybrid or timber construction types

of renewable raw materials within these buildings and their conversion into CO2, in tons [5]. Potential substitution savings Beyond the temporary storage effects of biogenic carbon, the use of building products made of renewable raw mate­ rials can serve to replace materials made of finite resources, such as plastics or ­metals, yet also mineral-based components. This process is defined as substi­ tution. One basic requirement for estimating the potential savings resulting from the use of construction products made of renewable materials is the application of the matching functional equivalent. This precondition is fulfilled by conducting analyses according to cubic metres of a particular building component or of matching parts of a building displaying matching energy consumption. The substi­ tution potential varies for each environmental indicator. The potential related to the greenhouse gas indicator (carbon dioxide equivalent or CO2eq) is presented here as an example.

The substitution effect that can be achieved by using products made of renewable raw materials can be managed by selecting specific materials for the primary ­structure, yet also for fittings (windows, doors, flooring and facade cladding). The related literature currently refers to the meta-study by Sathre and O’Connor, which summarily identified an average ­substitution factor of 3.9 t CO2eq per tonne of timber used [6]. However, figures calculated in this study do not take ­current standards into account and contain possible credits. For the research ­projects THG-Holzbau [7] and HolzIm­ BauDat [8] the potential for standards-­ compliant substitution was investigated at the building scale for new residential and non-residential building construction. The substitution potential compares functionally equivalent buildings related to various construction types, in particular solid wood and wall framing on the one hand and different mineral-based construction types on the other, calculated according to DIN EN 15 978 across the entire life cycle and based on their global warming

Global warming potential [kg/CO2eq/m2 GFA]

solid wood, mineral wool aerated concrete

brick, thermal render (exterior wall insulation) brick, mineral wool

fossil GWP biogenic GWP

300 200

substitution potential

100 0

-100 -200

Module A production

Module B maintenance

Module C disposal

Module A + C production + disposal A 4.3

potential. All researched buildings dem­ onstrated positive substitution effects in terms of climate protection. Potential credits beyond the system borders were not included. For the production of the related materials, the share of ­biogenic ­carbon originating in trees is ­transferred to the building production ­system. At the end of the building life cycle, this share exits the defined system, which constitutes a zero-sum game (which is why it is described as temporary carbon storage). The results from the THG-Holzbau and ­HolzImBauDat research projects indicate: by replacing mineral-based construction with timber construction, new development of single family or duplex homes allows greenhouse gas emissions savings of 9 to 56 % in relation to the construction type. The savings for non-residential development and related construction types range, on average, from 5 to 48 %. In principle, the amount of each respective substitution potential at the building scale is, aside from the construction materials used, dependent on the design and type of ­building as well as the building class, which in return determines fire safety requirements. The more similar the compared buildings are in terms of materials used, i.e. the higher the share of mineral building materials, also in wood structures, the lower the greenhouse gas reduction potential compared to the mineral alternative. Vice versa: the higher the share of wood components used in mineral-based construction (e.g. roof structure), the lower the substitution potential. Fig. A 4.3 shows the standards-compliant analysis of a life cycle assessment according to modules. Biogenic GWP represents carbon storage, the colour-coded difference indicates the substitution potential.

27

renewable raw materials [kg/m2WF]

L I F E C Y CLE A SSESSM ENT

250

Timber construction

Hybrid

200

189

150 91

100 50 0

170

188 163

141

136

128

119

204 186

118 98

96

43

ground floor + ground floor + ground floor 4 full storeys 4/6 full storeys + 5 full storeys exterior wall: wood panel construction

exterior wall: wood panel construction, solid wood

exterior wall: wood panel construction

ceilings: ceilings: wood ceilings: reinforced concrete wood concrete concrete hollow composite composite core slabs construction construction

ground floor ground floor ground floor + 3 full storeys + 3 full storeys + 3 full storeys (variant 2) (variant 1) exterior wall: exterior wall: exterior wall: wood panel wood panel wood panel construction construction construction

ground floor ground floor ground floor + 3 full storeys + 3 full storeys + 3 full storeys (variant 5) (variant 4) (variant 3) exterior wall: wood panel construction

exterior wall: wood panel construction

exterior wall: wood panel construction

ground floor + ground floor + ground floor two full storeys 7 full storeys + 7 full storeys (variant 1) exterior wall: exterior wall: exterior wall: wood panel wood panel solid wood construction construction

ground floor ground floor ground floor + 5 full storeys + 3 full storeys + 3 full storeys exterior wall: wood panel construction, solid wood

exterior wall: wood panel construction

exterior wall: solid wood

ceilings: wood beams

ceilings: wood concrete composite construction

ceilings: wood beams

ceilings: solid wood

ceilings: Å-joists

ceilings: wood beams

ceilings: solid wood

ceilings: solid wood

ceilings: solid wood

ceilings: solid wood

ceilings: solid wood

ceilings: solid wood

interior walls: reinforced concrete

interior walls: reinforced concrete (ground floor) solid wood (upper floors)

interior walls: reinforced concrete, wood posts

interior walls: wood posts

interior walls: wood posts

interior walls: wood posts

interior walls: wood posts

interior walls: wood posts

interior walls: solid wood

interior walls: wood posts, reinforced concrete

interior walls: solid wood

interior walls: solid wood

interior walls: solid wood

interior walls: solid wood

interior walls: wood posts

roof: reinforced concrete hollow core slabs

roof: solid wood

roof: wood beams

roof: wood beams

roof: Å-joists

roof: Å-joists

roof: Å-joists

roof: Å-joists

roof: wood beams

roof: solid wood

roof: solid wood

roof: solid wood

roof: wood beams

roof: solid wood

roof: Å-joists

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: reinforced concrete

staircase: steel

staircase: staircase: reinforced reinforced concrete, steel concrete, steel

A 4.4

Carbon Sequestration vs. ­Resource Efficiency in Construction If extensive carbon sequestration contributes to achieving climate protection goals, it would seem to be advisable to use wood as a building material as much as possible. Yet, if we want to use material resources efficiently and employ timber structures appropriately, we should not leap to this conclusion too quickly. Aims of using more wood as a material, especially in competition with the use of wood for power gener­ ation, must also ensure that enough renew­ able raw material remains available. For each construction task, comprehensive ­carbon storage on the one hand and the efficient use of wood in terms of resources and material on the other need to be weighed up. Optimising a building in terms of criteria of structural engineering, fire safety, energy consumption, ecology and indoor climate will always constitute a compromise. Every type of construction will result in a different optimum. In principle, a load-bearing structure functions well as carbon storage, since it requires large quantities of building materials. This is less the case for facades, which need to provide maximum thermal insulation with components of minimum thickness. As a result, their share of wood is low compared to the high share of insulation materials. Visible interior walls and solid timber ceilings offer potential for extensive carbon sequestration, but it may be preferable to build these

according to other construction types, due to soundproofing or fire safety reasons. Each case requires consideration of specifically relevant aspects. A German Federal Environmental Foundation (Deutsche Bundes­ stiftung Umwelt – DBU) research project compared various timber buildings and analysed their differences in terms of quantity of renewable raw materials used, carbon sequestration and greenhouse gas emissions [9]. Fig. A 4.4 shows the amount of renewable raw materials in timber multi-­ family residential buildings classified either as hybrid buildings (share of timber used in exterior walls), timber frame / timber panel buildings and solid timber buildings (with cross-laminated timber load-bearing structures). The table also features the related construction components. Grant programmes and funding oppor­ tunities provided by political actors are import­ant to promote timber construction. In the City of Munich, for example, a supplemental funding programme is in place that ­supports the environmentally friendly construction of timber buildings. Here, the city offers subsidies for every kilogram of carbon stored, as long as timber sourced from sustainable forestry is used. Debates on resource efficiency in the building sector show that wood buildings demonstrate a material intensity equalling less than half of mineral-based buildings [10]. Further, comparisons of existing examples show that foundation slabs for timber structures can be built significantly less thick, due to lower building loads.

CO2-efficient Timber Con­ struction For building construction to be as CO2-­ efficient as possible, clients are required to make appropriate decisions in the early ­planning phases and define precise goals. Planning a CO2-efficient building During the preliminary design phase target values should be determined in relation to the following premises: • use timber for the primary structure – this can significantly influence the results of the life cycle assessment • keep energy consumption to a minimum during the use stage • define maintenance cycles for individual building components – this can influence construction and create specifications for construction quality • formulate disposal scenarios for the entire building and for dismantling the building into separate parts, including options for the reuse of timber elements Example: a wood-based residential development The ecological model settlement PrinzEugen-Park in Munich is currently the ­lar­gest coherent wood-based residential development in Germany (see project example p. 216ff.). Here, nearly 570 apartment units on eight distinct plots were ­realised as modern timber structures for a multi-storey residential development. It is

28

Multi-family residential EnEV 2009 standard (70 kWh/m2a)

Multi-family residential Passive house standard (15 kWh/m2a) 25 % 36 %

69%

6%

construction maintenance building services across 50 years

47%

17%

A 4.5

interesting to note that about two-thirds of the apartments belong to subsidised housing categories, with the remainder implemented by building cooperatives and associations. For the first time, an ecological set of criteria guided the allocation of plots while offering plots for sale within concept tendering processes. Timber construction was an important element that was included in the tendering process according to ­specified quantities of renewable resources per m2 residential area. Additionally, the City of Munich instituted an advisory board in the early planning phases in order to ­enable quality control during implementation. Further, a grant programme was ­developed in order to subsidise timber ­construction based on the quantity of carbon captured by buildings in kg (based on residential floor area) [11]. In order to ­demonstrate the impact of selecting wood as a construction material on climate protection efforts, the life cycle assessment was calculated for all buildings of the ecological model settlement. The results show that very good energy e ­ fficiency standards and the selection of building materials are decisive across the entire life cycle. All buildings are based on different designs, energy characteristics and construction types. For each plot, the best compromise was sought to balance requirements, design and economic feasibility, each according to different approaches. Altogether the wood used for construction in the entire development corresponds to a long-term built-in carbon storage of more than 12,500 t of CO2. Results were published in detail and in-depth [12]. To subsidise wood as a building material, a certification of sustainable forestry was required (certification according to PEFC, FSC, Naturland or regional sources in the vicinity of Munich). Finally, all buildings of the Prinz-Eugen-Park development demonstrated that it was possible to certify sustainable forestry for nearly all mass construc-

tion components comprised of renewable materials. This certification is necessary in order to guarantee, on the building scale, that the wood used was not sourced from illegal logging. This timber residential development shows that selling plots by tender can be based on specific guidelines (minimum quantity of wood and/or carbon storage) when aiming at sustainable construction types. The connection between construction and use stages Efforts to optimise buildings have so far concentrated on the lowest possible energy demands and, as a result, keeping CO2 emissions low during the use stage. With the introduction of the passive house standard, near-zero energy and plus-energy buildings, there is an increasing focus on the potential savings that the construction and maintenance of buildings can offer. Figure A 4.5 shows a comparison of the ­primary energy requirements of multi-­ storey buildings according to the EnEV 2009 standard (70 kWh/m2a) and those built according to the passive house standard (15 kWh/m2a), displaying the energy required for construction, maintenance and power supply for a period of 50 years. This demonstrates that the overall energy demand of buildings with highly efficient energy standards is lower across the building life cycle. At the same time, the percentage distribution of buildings (construction) on the one hand and energy supply on the other changes in the use stage. The conclusion is that primary energy consumption is of particular significance in buildings with high energy efficiency standards. More than 50 % of primary energy consumption and greenhouse gas emissions of passive house buildings are related to building ­construction and maintenance. Therefore, the selection of materials and, as a result, specific building products are increasingly becoming a focus of attention. The better

a building’s energy efficiency standard is and the lower its energy demands are, the greater the influence its construction will have on its life cycle assessment. Demolition and disposal The EU Waste Framework Directive establishes a waste hierarchy according to which as much material as possible should be reused or recycled in Europe [13]. Material itself is regarded as an energy resource only in a second step. In order to reuse wood as a material, it is necessary to introduce classifications of waste wood [14]. Only timber that is not contaminated with hazardous substances can be reused. Correspondingly, timber that has been treated with wood preservative chemicals cannot be reused, but must serve to generate energy. Better reuse of untreated, reclaimed waste wood can, first, help stabilise the long-term availability of wood at a reason­ able cost. Second, solid wood should generally first be used as construction timber, in addition to using weak wood and wood cut during thinning in wood-based materials. The third and final option is to use wood in thermal energy recovery. This approach greatly extends and expands the extent of carbon sequestration. Long transport routes have a negative effect on environmental assessments since the required fossil fuel reduces primary energy efficiency. Thus, the wood used for buildings should be sourced from the region in which it is processed, applied and then reused in thermal energy recovery as far as possible. Cascading use of raw materials A targeted extension of the material life cycle especially of solid wood products and the consistent application of so-called cascading use (the multiple reuse of a raw material) can offer greater access to sources of raw material for new products. Avoiding contaminants and employing intel-

L I F E C Y CLE A SSESSM ENT

ligent concepts for disassembly and dismantling (reuse or recycling of valuable materials) enable the amounts of residual materials used for thermal energy recovery to be reduced. In the wood-processing ­sector, the potential of efficient cascading use currently plays a role only in horizontal reprocessing and recovery (simultaneous use of wood, bark and shavings) and remains other­wise largely unused. Vertical integration of this kind of use across the entire material life cycle offers potential for growth. Every construction is comprised of layers. The ­layers and their sequences are closely related to the total service life of the building element and must be conceptualised and optimised during planning with regards to maintenance, dismantling and recycling scenarios. The interaction of layers allows for the better delineation of building elements and components and, therefore, enables their joints to be planned with a view to their later disassembly. Detachable connection types (e.g. screws and bolts instead of adhesives) are in focus of attention.

• The extent of carbon sequestration in­­ creases with the amount of wood or woodbased materials used. Load-bearing structures require large amounts of different materials. Another factor that may increase carbon sequestration is the use of panel-shaped solid wood components for walls, ceilings and roofs. • The amount of timber used must be related to a resource-saving use of timber stock. A balance needs to be established between the advantages of maximum ­carbon sequestration and the economical use of timber. • Local government authorities should establish sustainable tendering practices by prescribing maximum carbon footprint specifications for the construction phase of different types of buildings. These could be embedded in development plans. Wood connectors such as digitally produced woodworking joints comprise a further developmental step towards monomaterial-based separation and reuse.

The timber carbon footprint in buildings Some general provisions need to be taken into account when using timber for carbon sequestration in buildings: • To erect carbon-efficient buildings, ­specifications with regards to the carbon footprint of the structure, primary energy consumption (in terms of material and energy) and the amount of renewable raw materials used must be determined during planning. • The intensive use of energy required for mineral building materials means that parts of a structure such as basements and foundations have a major impact on the building carbon footprint. Their share depends on the size of basement and type of foundation. The taller a building is, the lower the share will be. • The wood used must originate from sustain­able forest management.

Comparative Life Cycle ­Assessment: Conventional vs. Timber Construction Comparisons between buildings based on conventional (mineral) construction ­methods that include building products made of finite resources on the one hand and buildings with a high degree of ­building products based on renewable raw materials on the other indicate the ­significant potential that timber construction offers to the protection of the ecosystem. For the study “Life Cycle Analysis of ­Residential Buildings” (Lebenszyklus­ analyse von Wohn­gebäuden) [15] a comprehensive life cycle assessment was ­conducted for a representative model house. The study focused on a single-family home without basement and a net floor area of 150 m2, of which 135 m2 are usable area.

29

This building was modelled according to 72 variants: • six different construction types (brick, calcium silicate /sand lime brick, autoclaved aerated concrete, hybrid, timber frame construction, solid wood construction) • three different energy levels (EnEV 2016, 30 kWh/m2, 15 kWh/m2) • four different heating types (gas condensing technology, wood pellets, air to water heat pumps, water to water heat pumps) The evaluation criteria included quantifiable ecological and economic aspects, yet also qualitative aspects, such as thermal comfort, acoustics, as well as fire behaviour. In ecological terms, the environmental impact related to resource consumption (renew­ able or non-renewable primary energy) and impact balance (greenhouse gas, acid­ ification, eutrophication potential) were researched. The analysis of the life cycle assessment followed three steps: • buildings according to phases of production, use, disposal (modules A– C according to DIN EN 15 978) • building operation, including heating, hot water and auxiliary units •  building and operation combined This approach separates the two spheres of building /construction / material and mechanical services / heating /energy sources. This separation permits identifying specific fields of action and developing separate strategies for an optimised result. The observation period both for the calculation of the life cycle assessment and the life cycle costs is set at 50 years. This avoids the operations phase including energy supply gaining priority over the construction phase, maintenance /replacement and d ­ isposal. A 4.5 Interrelation between primary energy demand for building construction and primary energy ­demand of the building during a 50-year period according to different energy standards

30

solid solid brick brick construction construction

timber timber frame frame

aerated aerated concrete concrete

hybrid hybrid construction construction

solid solid brick brick construction construction

timber timber frame frame

hybrid hybrid construction construction

sand-lime sand-lime brick brick

brick brick

solid solid brick brick construction construction

Global warming potential – building Global warming potential – building

aerated aerated concrete concrete

30 kWh – building 30 kWh – building

sand-lime sand-lime brick brick

15 kWh – building 15 kWh – building

timber timber frame frame

hybrid hybrid construction construction

aerated aerated concrete concrete

sand-lime sand-lime brick brick

brick brick

solid solid brick brick construction construction

timber timber frame frame

hybrid hybrid construction construction

aerated aerated concrete concrete

sand-lime sand-lime brick brick

brick brick

solid solid brick brick construction construction

timber timber frame frame

hybrid hybrid construction construction

aerated aerated concrete concrete

sand-lime sand-lime brick brick

brick brick

solid solid brick brick construction construction

30 kWh – building 30 kWh – building Global warming potential – operation Global warming potential – operation -22 to -3 -22 to -34 % 4%

EnEV – building EnEV – building b

timber timber frame frame

hybrid hybrid construction construction

EnEV – building EnEV – building

brick brick

Global Global warming warming potential potential 2 2 [kg/CO [kg/CO eq/m eq/m usable usable area area per per year] year] 2 2

aerated aerated concrete concrete

-37 to -4 -37 to -48 % 8%

a 35 35 30 30 25 25 20 20 15 15 10 10 5 5 0 0

however, easily balanced across a period of 50 years of operation (Fig. A 4.6 b). The life cycle assessment for the observation period of 50 years for the six construction types that feature specific mechanical services technology (heating via gas condensing boilers and solar thermal energy for hot water) indicates an overall reduction potential of 22 to 34 % for the most energy-efficient buildings, in relation to construction type. The difference between the buildings with the highest emissions and the building with the lowest emissions (solid wood building, 15 kWh level) amounts to nearly 50 %. Global warming potential – building Global warming potential – building

sand-lime sand-lime brick brick

35 35 30 30 25 25 20 20 15 15 10 10 5 5 0 0

brick brick

Global Global warming warming potential potential 2 2 [kg/CO [kg/CO eq/m eq/m usable usable area area per per year] year] 2 2

The global warming potential (grey emissions) is significantly lower for buildings comprised of renewable raw materials than for solid (mineral) construction. The reduction potential ranges from 37 to 48 % depending on energy level (Fig. A 4.6 a). The evaluation of building variants also indicates that higher expenditure is required to produce energy-efficient buildings. In return, this leads to greater greenhouse gas emissions. This additional expenditure can comprise 5 to 15 % of the entire building expenditure. The additional greenhouse gas emissions for the production of buildings is,

15 kWh – building 15 kWh – building A 4.6

Conclusion The construction sector offers considerable opportunities for the significant reduction of greenhouse gas emissions. The operation of new buildings is becoming increasingly energy-efficient and, as a result, the carbon footprint of building materials is increasingly becoming a focus of interest. The advantages of using timber from an ecological point of view Timber products offer a number of significant advantages in terms of climate pro­ tection: • Wood used as a building product can be doubly effective in terms of climate protection. Compared with other building materials, it produces only low CO2 emissions from fossil sources and possesses the capacity to store CO2 and remove it from the atmosphere temporarily. • The best ways to take advantage of the potential savings of CO2 that wood offers for the building sector are to use timber products extensively, thereby replacing energy-intensive materials with wood and wood products, as well as selecting wood products with the longest possible service life. • Specific national factors decisively influence the carbon footprint of construction products and buildings, because the different energy sources in the electricity mix of various countries can mean that similar production processes may have different carbon footprints. These factors must be properly taken into account when evaluating products. • To avoid negative effects on the carbon sink function of forests, wood must be sourced from sustainably managed forests. • After demolition and disassembly, wood and wood-based building materials en­­ able cascading use, reuse, recycling as a material and, eventually, use for energy

L I F E C Y CLE A SSESSM ENT

generation. This can extend the duration of atmospheric carbon storage many times over. The cascading use of wood makes it possible to employ this resource efficiently and also allows for multiple substitution effects, since wood can serve to replace more energy-intensive materials and/or fossil energy sources in energy recovery. The carbon footprint of construction components in timber buildings As a means of temporary carbon storage, timber construction can contribute greatly to achieving climate protection goals based on its substitution potential. However, the precondition is that wood is sourced from sustainable forest management. Beyond that, the following factors should be taken into account: • Foundations and basements have the greatest impact on the carbon footprint of buildings. Their influence depends on the size of basement and the type of foundation. The taller the building, the lower their degree of influence will be. • The extent of carbon sequestration increases with the amount of timber from sustainable forestry used in a ­building. • The major share of carbon is stored in load-bearing structures because they consist of the largest amount of timber. Solid wood structures require a great deal of timber and, thus, can store a large quantity of carbon. The amount of timber used must, however, correspond proportionally to a resource conservation oriented practice of using timber stock. For this reason, it is imperative to maintain a balance between the greatest possible carbon sequestration and the economical use of wood. • Interior design and fittings (flooring, windows, doors and possible wood facade cladding), regardless of the material used

for the load-bearing structure, can ­influence long-term carbon sequestration, particularly since fittings may be replaced several times within a building life cycle [15]. • The carbon footprint of the assembly on site is low compared to that resulting from the manufacture of building materials. • Maintenance of structural components (e.g. through construction-based wood preservation) is essential for optimising the service life of building products beyond the building life cycle, and thus, their carbon footprint. Notes: [1] Commission of the European Communities, COM (2007) 860 final: A lead market initiative for Europe. Brussels, 21.12.2007 https://eur-lex.europa.eu/LexUriServ/LexUriServ.do? uri=COM:2007:0860:FIN:en:PDF, (accessed 20.09.2021) [2] Rüter, Sebastian; Diederichs, Stefan: Ökobilanz-­ Basisdaten für Bauprodukte aus Holz. Arbeitsbericht 2012/1. Thünen-Institut https://literatur.thuenen.de/digbib_extern/dn050490. pdf (accessed 20.09.2021) [3] Berichterstattung unter der Klimarahmenkonvention der Vereinten Nationen und dem Kyoto-Protokoll 2012 – Nationaler Inventarbericht zum Deutschen Treibhausgasinventar 1990 – 2010. Umweltbundes­ amt (ed.), 08/2012 [4] Rüter, Sebastian; Matthews, Robert William; Lundblad, Mattias; Sato, Atsushi; Hassan, Rehab Ahmed: Chapter 12: Harvested wood products. 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories 4, p. 1– 49. Geneva 2019 Rüter, Sebastian: Chapter 6.10: Harvested wood products (4.G). Climate Change 2019/24, Geneva 2019, p. 661– 665 [5] Kaufmann, Hermann; Nerdinger, Winfried et al.: Bauen mit Holz: Wege in die Zukunft. Munich 2011 [6] Sathre, Roger; O’Connor, Jennifer: Meta-analysis of greenhouse gas displacement factors of wood product substitution. In: Environmental Science & Policy 13, 2010, p. 104 –114 [7] Hafner, Annette et. al.: Treibhausgasbilanzierung von Holzgebäuden – Umsetzung neuer Anforde­ rungen an Ökobilanzen und Ermittlung empirischer Substitutionsfaktoren (THG-Holzbau). Ruhr University Bochum, 4/2017 [8] Rüter, Sebastian; Hafner, Annette, et al.: Daten­ basis zur Bewertung einer nachhaltigen und effizienten Holzverwendung im deutschen Bausektor –

31

 HolzImBauDat. Forschungsprojekt: FK 22028516 – BMEL /FNR. Braunschweig / Bochum 2020   [9] Methodenentwicklung zur Beschreibung von Ziel­ werten zum Primärenergieaufwand und CO2-Äqui­ valent von Baukonstruktionen zur Verknüpfung mit Grundstücksvergaben und Qualitätssicherung bis zur Entwurfsplanung. Deutsche Bundesstiftung Umwelt, file number: 31943/01 [10] Krause, Karina: Strategische Erfassung der Sekundärressourcen basierend auf Ökobilanzen und einem Geoinformationsystem am Beispiel von drei Wohngebieten. Dissertation, Ruhr University Bochum 2020 [11] cf. note 9, also: Förderrichtlinien für das Zuschuss­ programm in der Ökologischen Mustersiedlung im Prinz-Eugen-Park. Landeshauptstadt München, Referat für Stadtplanung und Bauordnung (ed.) 2017 [12] Djahanschah, Sabine; Hafner, Annette; Seidel, Arnim (eds.): Wohnquartier in Holz – Mustersiedlung in München. DBU Bauband 4. Munich 2020 [13] Waste Framework Directive 2008/98/EC of the ­European Parliament and Council, 19 November 2008 on waste and on the discontinuation of specific guidelines https://eur-lex.europa.eu/legal-content/DE/TXT/PD F/?uri=CELEX:32008L0098&from=DE (accessed 20.09.2021) [14] In Germany, this occurs according to the Deadwood Provision or “Altholzverordnung. Verordnung über Anforderungen an die Verwertung und Besei­ tigung von Altholz” (Altholzverordnung – AltholzV), 2012 [15] König, Holger: Lebenszyklusanalyse von Wohn­ gebäuden. Final report. Bayerisches Landesamt für Umwelt (ed.). Munich 2018 [16] König, Holger: Ökobilanz-Vergleich von Gebäuden in Holzbauweise im Vergleich zu Standard-Bauweisen bei Neubauten und bei Gebäude­moderni­ sie­rung. In: Kaufmann, Hermann; Nerdinger, ­Winfried (eds.): Bauen mit Holz – Wege in die ­Zukunft. Ergänzung zum gleichnamigen Ausstellungskatalog. Munich 2015

A 4.6 Global warming potential (GWP) of the different construction types in relation to net floor area a for the building (without operation), three different energy levels b for the building and operation during a 50-year period, three different energy levels (gas ­condensing boiler with solar thermal energy in operation)

32

Indoor Air Quality – The Influence of ­Timber Construction Maren Kohaus, Holger König

A 5.1

A 5.1 Wood interiors, kindergarten, Bludenz (AT) 2013, Bernardo Bader, Monika Heiss – Farbe & Design A 5.2 Recommended TVOC levels and resulting ­recommendation for action A 5.3 Thermal effusivity coefficients of select building materials A 5.4 Classification of chemical compounds by boiling point

Wood has been in use as a construction material for human dwellings for centuries. Contemporary building continues to use wood and wood-based materials in a wide range of ways – as a construction material, for flooring, wall and ceiling cladding and for fittings and furnishings. The material is highly valued now as ever for its natural character and authenticity. Wood surfaces in particular, due to the ­specific character, colour, grain, texture and structure of the material, are generally regarded as appealing to the senses, as Maximilian Moser’s study “Interaktion Mensch und Holz” confirms [1]. Characteristics of wood specific to the material and related to building physics, such as low thermal conductivity (Å-value = 0.11– 0.17 W/mK) and low thermal effusivity coefficient or b-value (Fig. A 5.3) mean that wood surfaces are perceived as warm. Untreated wood surfaces also support the control of indoor ­climates, because wood enables the ab­­ sorption of indoor air moisture and its timedelayed release. The scent of wood, which is made up of emissions of volatile substances, has a pleasantly calming effect on some people. A 2003 study by the Joanneum Research Forschungsgesellschaft on the potential effects of stone pine wood in the immediate environment on people’s circulation and sleep found that it improved their perform­ ance and general well-being [2]. Maximilian Moser’s 2007 study “Schule ohne Stress” (School without Stress) anal­ ysed the effect of solid wood fittings and furnishing in classrooms. The study states that the calming effect of wood, estimated by measuring the students’ heart rates and vagal tone, might yield positive health effects [3]. The 2017 metastudy HOMERA presents an analysis of 44 research projects regarding the interrelation between emissions and wood and /or engineered wood on the one hand and indoor air quality on the other,

as well as the possible effects on humans. Analyses of current testing and measuring methods that serve as basis for legal boundary values show how complex this topic is and also indicate the need for ­further research projects in order to synthesise results [4]. Until further findings become available, ­discussions on the extent to which emissions from wood and wood-based materials in contemporary timber buildings can be regarded as either harmful to health or as inherent to wood and, therefore, natural, harmless or even promoting health, are ongoing. To offer clients, users and planners a degree of security and bring clarity to the discussion, relevant aspects will be examined in detail below.

A Healthy Indoor Climate Regardless of construction type, a building must provide an indoor climate that users perceive as pleasant and must accommodate the activities it was planned for. Comfort criteria (as specified in DIN EN 15 251) offer guidance on the factors that need to be taken into account: • protection from weather-related low /high temperatures and moisture /dampness • protection from high levels of use-related moisture, resulting condensation and mould risk • protection from interior and exterior noise exposure • optimum lighting and adequate daylight intake, as well as protection from excessive sunlight (heat /overheating risk) • sufficient ventilation for the particular use and resulting reduction of CO2 levels in the air • protection from ionising (e.g. radon) and non-ionising radiation (e.g. electric smog) • poor indoor air quality due to building materials, equipment and devices

I N D O O R A I R Q U A L I T Y – T H E I N F L U E N C E O F T I M B E R CONSTR UCTION

33

Recommended TVOC levels (indoor air)

Hygiene assessment and recommendations for action

Level 1: TVOC

< 0.3 mg/m3 (< 300 μg/m3)

• hygienically acceptable as long as levels for individual substances are not exceeded • “target level” (= hygienic prevention range; recommended)

Level 2: TVOC

> 0.3 mg/m3 (> 300 μg/m3

Level 3: TVOC

> 1.0 mg/m3 and < 3.0 mg/m3 (> 1,000 μg/m3 and < 3,000 μg/m3)

Level 4: TVOC

> 3.0 mg/m3 and < 10.0 mg/m3 • hygienically unsound, occupation only for limited time (> 3,000 μg/m3 and < 10,000 μg/m3) ­periods •  individual toxicological evaluation recommended

Level 5: TVOC

> 10 mg/m3 and < 25.0 mg/m3 •  hygienically unacceptable, occupation to be avoided (> 10,000 μg/m3 and < 25,000 μg/m3) •  individual toxicological evaluation recommended

and < 1.0 mg/m3 and < 1,000 μg/m3)

• hygienically acceptable as long as levels for individual substances are not exceeded •  increased ventilation necessary • hygienically questionable, occupation only for limited time periods • health impact of substances exceeding recommended levels must be tested; individual toxicological evaluation recommended

A TVOC concentration of more than 3,000 μg/m3 is regarded as hygienically unsound. BNB/DGNB certification only to be issued if TVOC levels are in the range of 300 μg/m3 (non-defined measurements) to 500 μg/m3 (defined measurements). A 5.2

Adequate air exchange provided by manual or mechanical ventilation ensures that emissions produced by building products, electronic devices and by occupants are removed. However, the use of toxin-free building materials wherever possible is advised.

•  VVOC: very volatile organic compounds •  VOC: volatile organic compounds •  SVOC: semi-volatile organic compounds

allergenic, but are not harmful to health in the concentrations usually present in timber buildings.

VOCs In both construction practice and the ana­l­ ysis of interiors, VOC gases are classified according to their boiling point (Fig. A 5.4):

During construction, many different VOCs are temporarily discharged into indoor air. These higher-than-usual concentrations can usually be greatly reduced by heavy ventilation during and after work. VOCs are considered a single group of substances, albeit a very diverse one. They can be harmless, become a nuisance due to their smell or even be harmful to health. The most familiar VOCs are alkane /alkene, aromatic compounds, terpenes, halogenated hydrocarbons, esters, aldehydes and ketones. Wood exudes small amounts of terpenes and aldehydes that are perceived as typical wood scent. They are termed nVOC (natural Volatile Organic Compounds) due to their origin in natural raw materials. The toxicity of different types of VOCs ­varies significantly. Carcinogenic benzene is a particularly harmful indoor air pollutant, while numerous VOCs, such as terpene originating in natural oils, natural colours or natural wood resin are considered comparatively harmless. In high concentrations (e.g. perceivable smell of turpentine oil), they may impair people’s well-being and be

VOC emissions from building products There are no Europe-wide statutory limits or prohibitions imposed on VOC emissions from building products. Since 2004 the AgBB evaluation scheme of the DIBt approval process, introduced by the Committee for Health-related Evaluation of Building Products (Ausschuss zur gesundheitlichen Bewertung von Bauprodukten), has served as the basis for the healthrelated evaluation of building product emissions. Updated in 2018 and adopted by the Model Administrative Provisions – Technical Building Rules (Musterverwaltungsvorschrift Technische Baubestimmungen, MVV TB) in 2019, it sets maximum emission values for building products and determines exclusion criteria according to which building products are not permitted for use. However, emissions tests of individual products should not serve to conclude what the expected indoor air concentration might be [6]. This is due to the fact that it is dependent on the influence of other factors. These factors include e.g. the situa-

Material

Abbreviation

Name

Boiling point [°C]

Examples

VVOC

very volatile organic compounds

0 to 50 (-100)

formaldehyde, acetone, acetaldehyde

VOC

volatile organic compounds

50 (-100) to 240 (-260)

many solvents, such as styrene and xylene

SVOC

semi volatile organic compounds

240 (-260) to 380 (-400)

plasticisers, biocides, flame retardants, PCBs

POM

particulate organic matter

> 380

PAH in bituminous building materials

MVOC

microbial volatile organic compounds ­(produced by mould and ­bacteria)

within VOC range

wide range of different substances and s­ ubstance classes

Emissions in Indoor Air Materials used in building interiors can impact indoor air by discharging particles in the form of particulate matter and fibre or by emitting gases. User behaviour and indoor climate conditions (indoor humidity, temperature, etc.), as well as the situation and integration of construction materials into building components and their contribution to diffusion processes are relevant for levels of indoor air pollutants [5]. When discussing emissions in indoor air and wood-based materials, two terms are highly relevant: VOCs (volatile organic compounds) and formaldehyde.

insulation (mineral fibre)

Thermal effusivity coefficient b value [KJ/Km2√s] 0.06

cork

0.10

wood

0.4 ... 0.5

human skin

1.0 ...1.3

glass

1.3 ...1.5

water

1.6

concrete

1.8 ... 2.2

steel

14

copper

36

Materials with high thermal effusivity coefficients such as metals are perceived as cold when their temperature is lower than that of human skin. In contrast, materials with low thermal effusivity coefficients such as wood or insulation are perceived as warmer at the same temperature. A 5.3

A gas /substance with a high boiling point is less volatile and is discharged into the surrounding atmosphere at slower rates. A gas /substance with a low boiling point is highly volatile and is therefore discharged at faster rates. Values analogous to WHO classification. A 5.4

34

Substance / substance class

Recommended level

Note

bicyclic monoterpene 1)

RL I = 0.2 mg/m3 RL II = 2 mg/m3

Ad-hoc Working Group (2003) 5)

monocyclic monoterpene 2)

RL I = 1 mg/m3 RL II = 10 mg/m3

Ad-hoc Working Group (2010) 5)

saturated acyclic aliphatic C4 to C11 aldehyde

RL I = 0.1 mg/m3 RL II = 2 mg/m3

Ad-hoc Working Group (2009) 5)

2-furaldehyde (furfural)

RL I = 0.01 mg/m3 RL II = 0.1 mg/m3

Ad-hoc Working Group (2011) 5)

benzaldehyde

RL I = 0.02 mg/m3 RL II = 0.2 mg/m3

Ad-hoc Working Group (2010) 5)

formaldehyde

0.1 ppm 3) / 0.124 mg/m3 0.08 ppm 4) / 0.1 mg/m3 0.08 ppm / 0.1 mg/m3

Bundesgesundheitsamt (German Federal Health Agency) 1977 WHO (2010) AIR confirms the level recommended by the WHO in 2010 for formaldehyde (2016)

lead compound α pinene lead compound D-limonene 3)  confirmed in 2006 by the Ad-hoc Working Group 4)  defined for short-term and long-term exposure 5)  In March 2015 Ad-hoc Working Group was renamed “Ausschuss für Innenraumrichtwerte” (AIR).    • RL II = recommended level II (hazard reference level) refers to the concentration of a substance in indoor air requiring immediate action if levels are exceeded. •  RL I = recommended level I (prevention reference level) refers to the concentration of a substance /group of substances in indoor air identified within individual substance assessments not leading to projected health hazards based on current knowledge. RL I should be the goal in renovations and not be exceeded. Levels in the I – II range require action. •  Recommended levels do not offer information on possible effects of substance combinations. A 5.5 1)  2) 

Type of wood

Formaldehyde concentrations 1 ppb = 0.001 ppm = 1.25 μg/m3 at 20 °C and 1,013 hPa

Beech

2 – 3 ppb

= 0.002 – 0.003 ppm

Oak

4 – 9 ppb

= 0.004 – 0.009 ppm

Douglas pine

4 – 5 ppb

= 0.004 – 0.005 ppm

Spruce

3 – 4 ppb

= 0.003 – 0.004 ppm

Pine

3 – 5 ppb

= 0.003 – 0.005 ppm

Comparison: limit value for E1 “building product” = 0.1 ppmA

The following glues contain formaldehyde: •  urea-formaldehyde (UF) •  melamine-formaldehyde (MF) •  melamine-urea-formaldehyde (MUF) •  melamine-urea-phenol-formaldehyde (MUPF) •  phenol-formaldehyde (PF) Wood-based materials containing aminoplast adhesives (UF, MF, MUF) tend most towards releasing formaldehyde. Emissions often persist for decades and fluctuate depending on indoor climate. The warmer and damper it is, the more formaldehyde is released. Alternative glues: •  PMDI / PUR

A 5.6

A 5.7

Wood-based material

Bonding agent

Particle board

urea-formaldehyde resin (UF) modified melamine formaldehyde resin (MUF + MUPF) phenol formaldehyde resin (PF) polymeric diphenylmethane diisocyanate (PMDI)

Resin percentage 5 – 20 %

MDF (medium density fibreboard)

urea-formaldehyde (UF) modified melamine formaldehyde resin (MUF) phenol-formaldehyde resin (PF) polymeric diphenylmethane diisocyanate (PMDI)

8 –13 %

Fibreboard (soft board)

polyurethane (PUR)

0.5 – 3 %

OSB (oriented strand board)

phenol formaldehyde resin (PF) modified melamine formaldehyde resin (MUF) polymeric diphenylmethane diisocyanate (PMDI)

5 –10 %

Veneer plywood

phenol formaldehyde resin (PF) modified melamine formaldehyde resin (MUF)

10 – 20 % A 5.8

The following classification is applied to woodbased materials according to the amount of ­formaldehyde released: Emissions class E 1 Emissions class E 0

[μg/m3]

[ppm]

= 124

= 0.1 1)

no formaldehyde emission, but often PU adhesive with isocyanates

RAL UZ 76 / RAL UZ 38

= 60

= 0.05

natureplus

= 36

= 0.029

1) 

test chamber measurement as per DIN EN 16 516 A 5.9

A 5.5  Example indoor air guide values for substances with possible relevance for wood and woodbased products A 5.6  Formaldehyde emissions of untreated wood A 5.7  Formaldehyde within adhesives A 5.8  Wood composite materials and share of bonding agents containing formaldehyde A 5.9  Classification according to emissions class A 5.10 Guide values for indoor air formaldehyde (as of January 2021) A 5.11 TVOCs of different types of wood

tion and integration of building products, the interdependencies with other ­materials / products, indoor humidity (Marckowicz und Larsson, Lund University 2015), air exchange rate (Projekt Wood-2New, Fürhapper 2017) and in particular, user activity (Höllbacher, TU Wien 2014) [7]. VOC emissions in indoor air The TVOC (total volatile organic compound) indicator is used when evaluating the results from measurements taken of the concen­ tration of indoor air emissions. It indicates a sum total of all VOCs measured in the indoor air. The resulting value does not ­distinguish between substances that are hazardous to health, allergenic, malodorous or those that are harmless to health, which makes it difficult to conduct a related toxicological evaluation. According to the guideline of the German Environment Agency (Umweltbundesamt) the TOC value measured in the indoor air is categorised according to five levels, each of which includes an hygienic assessment and recommendations for action. The compliance with VOC values for indoor air varies according to different certification guidelines (BNB, DGNB, LEED, HQE, NaWoh etc.). Quality levels for indoor air hygiene should be defined according to certification systems and/or contractual terms prior to planning. Specific VOC reference values in indoor air In order to evaluate the indoor air concentration of individual VOCs, the guide value recommendation (Fig. A 5.5) of the German Committee on Indoor Air Guide Values (Ausschuss für Innenraumrichtwerte, AIR – previously, Ad-Hoc Working Group) of the German Environment Agency, still valid in its current form, can be referenced [8]. The nVOCs that originate in natural wood, such as terpenes, aldehyde or acids should be measured and assessed separately. They

35

I N D O O R A I R Q U A L I T Y – T H E I N F L U E N C E O F T I M B E R CONSTR UCTION

The following reference values for formaldehyde in indoor air are valid (as of January 2021) WHO

100 μg/m3 (30 min.)

= 0.08 ppm

Austria

100 μg/m3 short term (30 min.) 60 μg/m3 long term (24 hrs)

= 0.08 ppm = 0.05 ppm

Switzerland

125 μg/m3

= 0.1 ppm

France

50 μg/m3 short term (2 hrs) 10 μg/m3 long term

= 0.04 ppm = 0.008 ppm

Germany

100 μg/m3

= 0.08 ppm

Certification as per BNB, DGNB, NaWoh

< 30 μg/m3 = full score (target value) > 120 μg/m3 = non-certifiable (limit value) A 5.10

Formaldehyde Due to its low boiling point, the frequently mentioned formaldehyde is not classified as a VOC, but as a VVOC (very volatile organic compound). In the EU in early 2016 formaldehyde was classified as a category 1B carcinogen, verified by animal testing. Small amounts of formaldehyde are present in natural wood, which may emit it, although related minor amounts are not considered harmful to health (Fig. A 5.6). Formaldehyde serves as a component for bonding agents such as adhesives or glues (Figs. A 5.7 and A 5.8) used in the production of wood-based materials, insulation materials, paints and varnishes, cleaning agents, etc. Building product formaldehyde ­emissions Formaldehyde emissions from building products have been subject to regulation in Germany since the 1980s. The Chem­ icals Prohibition Order (Chemikalien-­ Verbotsverordnung) in effect at the time determined that emissions from building products that come into contact with indoor air may not exceed an equilibrium concentration of 0.1 ppm (= 0.124 mg/m3 = 124 μg/m3) under defined testing conditions. A product that meets this requirement is labelled according to the emissions class E 1 (Fig. A 5.9) and is categorised as a low formaldehyde product. The order was replaced by the DiBt guideline 100 (guideline on the classification and monitoring of formaldehyde release

from wood-based panels) in 1994. The EU subsequently adopted the requirements specified in the guideline. Additionally, based on the AgBB scheme introduced in Germany in 2015 for the evalu­ ation of specific VOC levels, the value of 0.08 ppm (= 0.1 mg/m3 = 100 μg/m3) for ­formaldehyde concentrations in building materials is included in evaluations. Since 1 January 2020 stricter boundary values have been in place in Germany for formaldehyde emissions from composite wood. The boundary value for the emissions class E 1 remained unchanged at 0.1 ppm. ­However, compared to the reference stan­ dard DIN EN 717-1, previously in effect, the requirements for composite wood issued in the new DIN EN 16 516 are significantly higher – in fact, nearly twice as high. One reason for this, among others, is that the test chamber received a greater load, humidity was increased and air exchange was reduced by half. The test parameters for the test chamber, thus, have become stricter. According to DIN EN 717-1 (the previous reference standard) only 0.05 ppm are now permissible in order to comply with the boundary value of 0.1 ppm following DIN EN 16 516, which is why this value is communicated as E 05 according to DIN EN 717-1. As a result, the important goal of reducing formaldehyde emissions caused by building products has been achieved. For the majority of cases, indoor air mea­ SER [μg m-2h-1]

pose no health risks, yet when exceeding target values specified by the German Envir­ onment Agency, legal disputes may result. Even though the target values for nVOCs are considered hygiene-related target values and not based on toxicological material evaluations, discussions on deficiencies in the context of wood buildings are becoming more frequent [9].

surements according to DIN ISO 16 000 based on proper test room preparation have demonstrated that formaldehyde ­values were clearly lower than the boundary ­values. Formaldehyde in interior air The use of low-formaldehyde building products (E 1 class) is a crucial prerequisite for ensuring that concentrations of pollutants in indoor air remain low. Nevertheless, the following influencing factors must also be considered during planning: • quantity of material and installation ­situation • volume of indoor air • air exchange rate • indoor air temperature (or ambient ­temperature, e.g. air temperature near heating system or due to sunlight, etc.) • humidity • surface treatment • cleaning agents used Different EU Member States define different guide values for indoor formaldehyde concentrations (Fig. A 5.10). The WHO recommends a level of 0.08 ppm (= 0.1 mg/m3 = 100 μg/m3). The German Committee on Indoor Air Guide Values (Ausschuss für Innenraumrichtwerte, AIR), adopted this guide value in 2016. In addition – similar to the various indoor air VOC guide values – there are different certification systems that

4,000

3,700

3,500 3,000 2,500 2,000 1,400

1,500 1,000 500 0

30

30

20

110

210

Ash

Beech

Maple

Birch

Oak

60 Cherry

Pine

Spruce

(SER = specific emissions rate) A 5.11

36

Prevention values Target value TVOC for sensitive individuals DGNB / BNB Prevention values Target value TVOC 0 500 / BNB 1,000 for sensitive individuals DGNB Typical new construction 0 500 1,000 Typical newschool Secondary construction 116 – 447 μg/m3 Secondary school a

Limit value TVOC A 5.12 DGNB / BNB Limit value TVOC DGNB3,000 / BNB 3,000

116 – 447 μg/m3

0 Typical new construction 0 Typical newschool Secondary construction Secondary school b

Target value formaldehyde DGNB / BNB Target value formaldehyde 30 / BNB 40 60 DGNB

83

30

83

40

60

Limit value formaldehyde DGNB / BNB Limit value formaldehyde 100 DGNB / BNB 100

7.4 – 37 μg/m3

– 37secondary μg/m3 Four weeks after completion 7.4 of the school in Diedorf the air in select rooms was measured and formaldehyde and TVOC levels were determined. The following levels were identified and compared with recent recommended levels: • TVOCs in indoor air: levels measured were far below 3,000 μg/m3 for TVOCs. 500 μg/m3 was set as target level. Limit value formaldehyde 116 – 447 μg/m3 were actually measured. Target value formaldehyde DGNB / BNB levels of formaldehyde were far below recent target DGNBand / BNB 3 • Formaldehyde in interior air: at 7.4 – 37 μg/m measured Target value formaldehyde 3 Limit value formaldehyde limit values as well target value of 60 μg/m60 . 100 0 as the previously higher 30 40 83 DGNB / BNB DGNB /A BNB 5.13 Typical new construction 0 Typical new Secondary school Building material construction Naturally grown Secondary school softwood (fir, spruce)

Naturally grown hardwood (oak, beech, maple, ash, etc.)

30 Relevant emissions

40

60

terpenes (α-pinene), 7.4 – 37 μg/m3 higher aldehydes (hexanal), typical coniferous wood scent 3 7.4 – 37 μg/m species-typical wood scent

Glued laminated timber, plywood, solid wood panels, cross-laminated timber panels

Wood content: terpenes (α-pinene), higher aldehydes (hexanal), typical coniferous wood scent possible formaldehyde emissions from the adhesive system

OSB

Wood content (usually high proportion of pine): terpenes (α-pinene), higher aldehydes (hexanal), strong coniferous wood scent possible formaldehyde emissions from the adhesive system

Particle board

Wood content: terpenes (α-pinene), higher aldehydes (hexanal), typical smell of coniferous woods possible formaldehyde emissions from the adhesive system

Medium density fibreboard (MDF)

Wood content: terpenes (α-pinene) and higher aldehydes (hexanal), also furfural, weak coniferous wood scent possible formaldehyde emissions from the adhesive system

Plywood (birch)

Wood content (birch): acetic acid (acetate), acetaldehyde, acetic acid smell possible formaldehyde emissions from the adhesive system

100 83 Strategies for high-quality interior air

none required

Wood content: none required Adhesive system: • none required for formaldehyde-free glued products • obtain information from the manufacturer on adhesives containing formaldehyde

Wood content: none required; large-scale use may cause strong smells that are a nuisance to sensitive individuals. Adhesive system: • none required for formaldehyde-free glued products • obtain information from the manufacturer on adhesives containing formaldehyde

A 5.14

recommend different guide values for formaldehyde concentrations in indoor air that can serve as orientation. Certification under the BNB (Sustainable building evaluation system – “Bewertungssystem Nachhaltiges Bauen”) of the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety, for example, defines maximum indoor air formaldehyde levels of 100 μg/m3 [10]. In this certification system, complete compliance is achieved at a level of 30 μg/m3.

Impact of Untreated Wood Indoor air emissions from untreated timber components have yet to demonstrate concentrations that are hazardous to health. The metastudy HOMERA states that the use of wood in the test spaces of the researched studies was evaluated in a more positive manner than reference spaces comprised of other materials [11]. VOCs The typical scent of fresh coniferous wood (e.g. pine, spruce, larch and stone pine) is caused by terpenes, which are natural solvents. The scent of deciduous wood originates from aldehydes and carboxylic acids (e.g. acetic acid). Terpenes and aldehydes are both VOCs. TVOC levels

Classroom, secondary school, Diedorf (DE) 2015, Architekten Hermann Kaufmann / Florian Nagler Architekten A 5.13 Test measurements of indoor air emissions, Diedorf secondary school. a Comparison of TVOC levels measured in Diedorf secondary school with typical new buildings b Comparison of formaldehyde levels measured in Diedorf secondary school with typical new buildings A 5.14 Strategies for achieving good-quality indoor air A 5.12

I N D O O R A I R Q U A L I T Y – T H E I N F L U E N C E O F T I M B E R CONSTR UCTION

depend on the type of wood (Fig. A 5.11, p. 35) and circumstances of processing, such as the temperature applied for drying wood [12]. Untreated timber usually doesn't emit TVOCs in concentrations that are hazardous to health. The interactions of these nVOCs and their effects on health are the focus of ongoing research projects [13]. Formaldehyde Formaldehyde is present in untreated wood and can be perceived even at low concentrations, although the small amounts emitted by untreated wood are toxicologically harmless [14]. Certain production processes such as drying, hot pressing or heat treatment may, however, lead to the creation and emission of additional formaldehyde. Individuals with sensitivities People who are sensitive to chemicals or have allergies may experience reactions to natural emissions of VOCs and formaldehyde. Unfortunately, timber emissions can vary not only among types of wood, but within a single tree trunk, which makes it ­difficult to reliably categorise this natural product. If a building is under construction for individuals who are sensitive to emissions, precise target values and recommendations for action related to the production process must be determined during planning and for product selection.

Impact of Glued Structural Timber Products The invention of glued structural timber products resulted in the development of materials that have had a wide-ranging, major influence on building with wood. Products such as glued laminated timber, cross-laminated timber and stacked /dowel laminated timber elements have opened up new dimensions in timber construction.

VOC emissions Similar to untreated wood, structural timber products can emit wood-based natural ­solvents into indoor air. Formaldehyde emissions The glue used in glued structural timber products often contains formaldehyde. ­Formaldehyde-free adhesives such as PMDI and PUR are available. In general, the assumption is that the following glued structural timber products contain the following glues and shares of adhesives [15]: • glued laminated timber (glulam): adhesive share approx. 1– 2 % (MUF or PUR) • plywood (laminated solid wood): adhesive share approx. 0.5 – 2 % (MUF or PUR) • cross-laminated timber: adhesive share approx. 1 % (MUF or PUR) Detailed information should be obtained from the manufacturer.

Impact of Wood-based ­Materials The development of a range of different wood-based materials enables homogenising certain natural wood properties, such as anisotropy (directional dependency due to grain direction and fibre structure), thereby expanding the range of applications for wood-based materials. The type of wood that is used for the various wood-based materials is first reduced to small pieces through technical processes (sawing, bark stripping, machining or separation of wood fibres) before being bonded together by adding bonding agents (glues). The degree of wood in relation to the particular finishing process of composite wood panels makes it possible to estimate the amount of adhesives they contain. This can vary greatly depending on the product and its purpose (Fig. A 5.8, p. 34).

37

VOC emissions Reducing wood to small pieces increases its emitting surface, potentially enabling increased emission of natural wood VOCs (Fig. A 5.11, p. 35), depending on the type of wood. Specific production processes such as heating and pressing may further influence these emissions: • Terpene emissions decline with increasing temperatures and longer processing times because they evaporate during ­processing. • Aldehydes are subject to other effects, because they take longer to form. Aldehyde emissions increase when tem­ perature increases. More details on this effect should be obtained from the manufacturer. Formaldehyde emissions Formaldehyde emissions from wood-based materials may result from two factors: first, additives such as glues that contain formaldehyde (Fig. A 5.7, p. 34) and second, additional formaldehyde that may form and be released due to thermal, hydrolytic and / or oxidative processes. Many composite wood board manufacturers have switched to PUR-based glues since 2001. Nevertheless, related production processes still use glue containing ­formaldehyde e.g. for large-size glued ­laminated timber beams. Certificates for components and information on any expected emissions should be obtained from the manufacturer early on in order to assess whether the use of such building materials is non-hazardous. Installation situation and processing of composite wood boards Increased indoor air concentrations of formaldehyde and VOC can result from the type of construction or the composite wood used for building furniture. Selecting E 1-classified products (according to DIN EN 16 516) ensures that guide values

38

confirmed by AIR in Germany on indoor air formaldehyde concentrations are adhered to in every indoor space in the future. This is related to the room size, the quantity of inbuilt panel material, air exchange, installation situation, as well as indoor climate (moisture, temperature, etc.). Risks persist if coated panels exceed the E1 value prior to coating. Open drill holes such as those within acoustic panels as well as edges that remain without coating may increase emissions, because they increase the emitting surface. Further, the risk exists that interior glue layers containing formaldehyde are exposed when drilling through multilayer panels. Building materials with treated surfaces (coated, oiled, waxed and painted) may contain generally used solvent types (TVOCs) as well as non-volatile substances such as phthalates or fire retardants that can also negatively impact indoor climates and indoor air quality. Details on such additives should be obtained from the manufacturer in the form of an emissions certificate to ensure that the emissions expected in a particular installation situation and the processing of panels comply with indoor emission target values.

a

Strategies for Managing ­Emissions

b

Since no uniform emission standards exist, target levels for indoor air emission concentrations (e.g. UBA, DGNB, BNB, LEED etc.) and emission concentrations of building products (e.g. E 1 according to DIN EN 16 516, the AgBB scheme, Blauer Engel, natureplus, Ecolabel, Nordic Swan, the EU Ecolabel etc.) should be determined prior to planning. To ensure relatively low emission concen­ trations of VOCs and formaldehyde by selecting low-emission products, the following steps should be taken into account: c

A 5.15

• Information provided by building product manufacturers should be checked for hazardous substances and planning should be coordinated with regard to construction methods, layers that products are comprised of, etc. • Precise details on the desired quality ­levels should be defined in the tender documentation. • Before work begins, specific qualities of building products should be reviewed by the building contractors and presented within comprehensive documentation, including permits, conformity documents, test certificates, environmental product declarations, etc., pending approval by the planners. • Use of approved building products must be monitored on the construction site and use of unlisted building products should be prohibited by construction management. • Concluding measurements of ambient air (for TVOCs and formaldehyde) should confirm compliance with previously set target levels (Fig. A 5.13, p. 36; see project example p. 262ff.) • In order to receive certification according to DGNB/BNB, indoor air measurements need to take place within four weeks after completion of construction, without furnishing (exception: inbuilt ­furniture). A significant precondition for code-compliant indoor air measurement according to DIN EN ISO 16 000 is the careful preparation of the test room. This includes: HEPA filter-based purification, sufficient ventilation, operational and cleaned HVAC system, properly sealing off the room, suspending construction work in the vicinity of the monitoring room (also outdoors), proper shading of the monitoring room. • Compliance with quality targets set for indoor air can be ensured by a ventilation concept that is guaranteed to function during actual use.

I N D O O R A I R Q U A L I T Y – T H E I N F L U E N C E O F T I M B E R CONSTR UCTION

Conclusion It is impossible to precisely forecast which air pollutant concentrations to expect within a planned building, due to the previously mentioned complexity of the issues involved. For the new Schmuttertal secondary school building in Diedorf, the strat­ egies described above were applied during construction. The project demonstrates extremely low VOC and formaldehyde ­concentrations, even though the entire primary structure consists of exposed glued laminated timber elements, the inside of the building envelope is clad in OSB panels and the entire interior outfitting consists of exposed three-ply panels (Fig. A 5.12, p. 36). The meticulous selection of all components, all the way down to paints and adhesives, was decisive in achieving this result. Indoor air hygiene measurements conducted after the school was completed showed that emissions were lower than the BNB target figures and even the precautionary levels recommended for sensitive individuals (Fig. A 5.13, p. 36) [16]. To conclude, timber construction does not result in hazardous indoor air emission levels, as long as the construction work and the selection of components is carried out carefully. However, a distinction must be made between emissions from wood as a natural product and those from additives resulting from technical processes. Further scientific research on the positive effects of wood on indoor climate and occupants is ongoing.

Notes: [1] Teischinger, Alfred: Interaktion Mensch und Holz. ­Vienna 2012 Teischinger, Alfred: Mensch und Holz – Eine Wechselbeziehung an ausgewählten Beispielen. In: Holzbautage Innsbruck 2012. Conference proceedings. Innsbruck 2012 [2] Evaluation der Auswirkungen eines Zirbenholzumfeldes auf Kreislauf, Schlaf, Befinden und vegetative Regulation. Joanneum Research Forschungsgesell­ schaft, Institut für Nichtinvasive Diagnostik (ed.). Weiz 2003 [3] Schule ohne Stress. Studie. Joanneum Research Forschungsgesellschaft, Institut für Nichtinvasive ­Diagnostik (ed.). Weiz 2007 [4] HOMERA. Gesundheitliche Interaktion Holz – Mensch – Raum. TU Munich 2017. Final report. DBU file number 33277-25, www.dbu.de/OPAC/ab/DBUAbschlussbericht-AZ-33277-01.pdf (accessed 12.02.2021) [5] Ohlmeyer, Martin; Mennicke, Friederike; Poth, Saskia: Erarbeiten eines objektiven Verfahrens unter Berücksichtigung der Besonderheiten von Holz und Holz­ werkstoffen bei der Bewertung ihres Einflusses auf die Innenraumluftqualität (HolnRaLu), TV 1: Unter­ suchungen unter realen Raumluftbedingungen. Thünen Report 81. Johann Heinrich von Thünen-­ Institut Braunschweig 2020 [6] ibid. [7] cf. note 5 for a complete list of referenced study ­titles. [8] table, current individual guide values, RWI and RWII, UBA: www.umweltbundesamt.de/galerie/die-richtwerte-i-ii-fuer-stoffe-in-der (accessed 12.02.2021) [9] Informationsdienst Holz: http://www.holz-und-raumluft.de/rechtsfragen (accessed 12.02.2021)

39

 Weinisch, Karl-Heinz: Hygienische Bewertung von Baumaterialien – richtig Planen und konstruieren. 9th European Public Health Congress, 2016 [10] Bewertungssystem Nachhaltiges Bauen (BNB), ­Unterrichtsgebäude, BN_UN 3.1.3, “Federal ­Ministry of the Interior and Community”, www.bnbnachhaltigesbauen.de/bewertungssystem/­ unterrichtsgebaeude/steckbriefe-bnb-un-2017/ (accessed 20.06.2021) [11] cf. note 5 [12] Paulitsch, Michael; Barbu, Marius Catalin: Holz­ werkstoffe der Moderne. Leinfelden-Echterdingen 2015 [13] Projekte zu Holz und Gesundheit „Gesundholz“ und „HolnRaLu“, www.kiwuh.de/holz/holz-gesundheit/ projekte-zu-holz-und-gesundheit (accessed 12.02.2021) [14] Marutzky, Rainer: Aspekte der Wohngesundheit beim Bauen mit Holz- und Holzwerkstoffen. In: Bauen mit Holz, 07-08/2010, p. 38ff. Mersch-Sundermann, Volker: Gesundheitliche ­Bedeutung von VOC in Innenräumen. Forum Holz l Bau l Energie. Cologne 2008 Salthammer, Tunga; Marutzky, Rainer: Bauen und Leben mit Holz. Informationsdienst Holz. Berlin 2013 [15] Rüter, Sebastian; Diederichs, Stefan: Ökobilanz-­ Basisdaten für Bauprodukte aus Holz. Arbeits­ bericht aus dem Institut für Holztechnologie und Holzbiologe Nr. 2012/1, Thünen-Institut; WECOBIS – Ökologisches Baustoffinformationssystem; see also: www.lignatur.ch/fileadmin/ablage/downloads/ Oekologie/lignum_produktliste_holzwerkstoffe_­ innenraeume.pdf (accessed: 27.9.2021) [16] Prüfbericht Schmuttertalgymnasium Diedorf zu VOC und Formaldehydmessungen aus dem Jahr 2015

A 5.15 Exterior and interior walls consisting of crosslaminated timber, left: exposed on the interior, additional inbuilt elements comprised of threeply panels. Existing building expansion for a full daycare facility, Markt Indersdorf (DE) 2019, Allmann Sattler Wappner Architekten A 5.16 Kindergarten, Bludenz (AT) 2013, Bernardo Bader, Monika Heiss – Farbe & Design A 5.16

41

Part B  Structural Systems

Beech laminated veneer lumber load-bearing structure, office building, Augsburg (DE) 2015, lattkearchitekten

1 Structures and Structural Systems From Linear to Planar Member Combining Construction Elements Combining Materials Structural Engineering in Timber Construction Timber Construction in Comparison Conclusion

42 43 45 45 48 49 54

2 Construction Components and Elements Dowel Laminated Timber Walls Frame Wall Construction Cross-laminated Timber Walls Laminated Veneer Lumber Walls Beams Dowel Laminated Timber Ceilings Beam Ceilings Box Ceilings Cross-laminated Timber Ceilings Laminated Veneer Lumber Ceilings Timber-Concrete Composite Ceilings A Comparison of Timber Construction Elements

56 57 58 60 61 62 63 64 66 68 69 70 72

42

Structures and ­Structural Systems Hermann Kaufmann, Wolfgang Huß, Stefan Krötsch, Stefan Winter

B 1.1

B 1.1 Office building, Vandans (AT) 2013, Architekten Hermann Kaufmann B 1.2 From linear to planar member: vertical and ­horizontal construction elements B 1.3 From linear to planar member: solid timber and lightweight construction elements

“Thus, the basic element of contemporary timber construction is the plate and no longer the post or beam” [1], declared Swiss architect Andrea Deplazes in 2000, stating that timber construction was becom­ ing a system of “plate tectonics”. Technical and structural innovations emerging around the turn of the millennium have, in fact, fun­ damentally changed timber construction. Some groundbreaking developments in terms of materials have taken place during this time and the conditions were favour­ able for reviving familiar construction types and developing them further for new fields of applications. The most impressive representations of an epic change in timber construction are the invention and distribution of cross-laminated timber and laminated veneer lumber, which minimise the inhomogeneity and anisotropy (i.e. directional dependency) inherent in the fibre structure of wood. They further enable the creation of high-performance planar building materials that can be pre­ cisely c ­ alculated according to dimensions that are limited only by production technol­ ogy. The use of less homogenised woodbased materials can lead to similar results if individual parts are combined into con­ struction elements that utilise the required characteristics of wood to an optimal degree. Box elements, for example, comprise linear ribs and planar sheathing that produce a compound structural effect that reduces the height of components and the cross section of ribs, while improving point support and dimensional stability. The development of fibre-based materials such as OSB and other panel materials began in the USA in the 1950s (see “Solid Wood and Wood-based Products”, p. 18ff.). From the late 1980s onward they found increasing use in Europe and are now avail­ able as standardised products that made it possible to further develop frame construc­ tion as a predominantly prefabricated and technically reliable construction method.

Dowel laminated timber structures have been used since the 1930s. This construc­ tion method was decisively further devel­ oped when nails, used to connect individ­ ual laminations in the original approach, were replaced by hardwood dowels or alu­ minium nails. Processing of such dowel laminated timber elements is similar to solid timber and reduces equipment damages. In addition, glued dowel laminated timber elements made of industrially produced glued laminated timber currently find wide­ spread use. Timber-concrete composite construction has been rediscovered and finds new fields of application. It had been first pa­­ tented during the time of resource scarcity between the World Wars, with the aim of reducing to a minimum the use of thenexpensive construction materials such as steel and concrete within ceiling slabs. Coinciding with these technological achieve­ ments, the architectural appearance and tectonic image of timber construction have also changed. Geometrical and hierarchical structures such as mortise-tenon joints or stacked beams were replaced by planar construction components with linear elem­ ents arranged within the plane. This type of construction was compact in spatial terms, which led to simplified connections, an expanded range of applications, the ­promotion of energy-efficient building enve­ lopes, as well as increased economic com­ petitiveness. Both an impetus for and consequence of this epochal change in timber construction was the extensive prefabrication of largesize elements comprised of either linear or planar members. The ideal preconditions for this are the relatively low weight of timber and its workability. Its diversity of applica­ tion is a further advantage – it can be used for insulation or load-bearing purposes, as a spatial enclosure, for interiors and exte­ riors, in linear or planar formats. This opens up a wide range of options for industrial

S T R U C T U R E S A N D S T R U CTUR A L SYSTEM S

dowel laminated timber / log construction

frame construction

cross-laminated timber / laminated veneer lumber

Vertical construction element

column

43

dowel laminated timber / stacked boards

rib ceiling / box ceiling

cross-laminated timber / laminated veneer lumber

Horizontal construction element

beam / joist

B 1.2

It therefore makes sense to consider con­ struction elements that are prefabricated to different degrees, rather than individual wood-based materials, as the fundamental elements of timber construction, distin­ guished according to horizontal and verti­ cal elements in relation to their primary requirements.

From Linear to Planar Member

solid timber element

Contemporary timber construction draws from a wide range of different construction components and products. Figure B 1.2 shows a selection of common construction

elements. The elements consist of solid wood-based materials (cross-laminated ­timber, laminated veneer lumber). Further, they are comprised of linear (dowel lami­ nated timber, log construction) or linear and planar materials (frame construction, hollow core or box ceilings). The structural characteristics of the construction elements are related to the employed linear members and planar wood-based materials. The tran­ sition between them can be fluid and the distinction between linear or planar member can be a gradual one. While the composition of components is important, their compound effect is de­­ cisive. In structural terms, solid wood ele­

lightweight construction element

From linear to planar members

production (see “Timber Production”, p. 158ff. and “Prefabrication”, p. 162ff.) and digitalised process chains (see “Plan­ ning”, p. 146ff.), which comprise pioneer­ ing alternatives in terms of building quality and production processes. These new con­ struction processes might even become more formative for the advancement of ­timber construction than new materials. This is neither limited to specific construc­ tion methods, such as standardised timber frame construction or large-format solid wood components, nor to ecologically ­optimised, adhesive-free construction meth­ ods (see Community Centre in St. Gerold, p. 258ff.).

B 1.3

Vertical construction element

44

Horizontal construction element

frame construction

solid timber con­ struction (dowel laminated timber)

frame construction

solid timber con­ struction (crosslaminated timber) B 1.4

S T R U C T U R E S A N D S T R U CTUR A L SYSTEM S

45

B 1.5

ments such as dowel laminated timber or stacked log walls resemble a sequence of individual linear members and, thus, match the characteristics of their individual parts. The compound structure of linear and planar members, such as in the case of frame construction or box elements, ­produces ­planar construction components that can equally function as a ceiling slab or wall plate. According to construction type, solid wood construction and elements comprised of lin­ ear and planar members can be arranged in relation to specific configurations, ranging from linear to planar members (Fig. B 1.3, p. 43). Rather than the solidity or homo­ geneity of a wood-based material, the com­ pound effect of individual parts is decisive for their function as a planar construction component.

methods such as different types of frame construction or solid timber construction no longer seems sensible. The intelligent combination of different construction ele­ ments enables the creating of customised solutions for construction practice while maintaining maximum design freedom. One typical combination in timber residential construction features frame construction for exterior walls and ceilings and dowel lami­ nated timber or cross-laminated timber load-bearing interior walls, thus making optimum use of the individual construction types in terms of their thermal insulation, soundproofing and fire safety characteris­

tics (see “Protective Functions”, p. 78ff. and project examples, “Residential Complex in Ansbach”, p. 212ff., “Residential Complex in Munich”, p. 216ff., “Residential Complex in Munich”, p. 220ff., “Residential Buildings in Zurich”, p. 232ff.). Combining frame construction with planar construction elements is a long estab­ lished, common practice in order to stiffen a structure and create spatial partitions. The same is true for complementing a structure comprised of slabs and plates with beams, posts and columns in order to create openings and transitions between spaces (Fig. B 1.4).

Combining Construction ­Elements Combining different construction elements into hybrid constructions has almost become everyday practice. Different ele­ ments of an overall system are combined in a manner that allows their different char­ acteristics to correspond ideally to the respective requirements placed on the component (Fig. B 1.4). The more specific and the greater these requirements are, the more difficult and costly the use of a uniform construction type for an entire structural system will be. In this context, the systematic categorisation of timber ­construction into common construction B 1.4 Combinations of different timber construction ­elements B 1.5 Expanding possible combinations by including further materials – with a composite timber-­ concrete ceiling (dowel laminated timber with poured concrete top layer) as example B 1.6 Hybrid construction elements, hybrid construc­ tion types and hybrid structures B 1.6

46

a

b

Combining various materials within building components, structures or construction methods follows comparable strategic aims. By combining the different characteristics of different materials, an overall system can be optimised (Fig. B 1.5, p. 45). In timber construction, this allows compensating dis­ advantages inherent to the materials used, without fundamentally putting timber struc­ tures as such into question. Hybrid construc­ tion methods expand the range of applica­ tions of timber and will likely be significantly further developed in the future.

In the history of architecture, hybrid (from Latin hybrida: mixture, crossbreed) struc­ tures are the rule rather than the exception. Brick or stone plinths or ground floors are common to certain historic timber buildings. Before concrete slabs were widely distrib­ uted in the 1960s, combining timber beam ceilings and masonry walls was standard practice in European cities. In contempo­ rary multi-storey timber construction, access cores (as emergency exits and to stiffen buildings), firewalls or ground floors entirely comprised of reinforced concrete are com­ bined with timber structures (Fig. B 1.9). Currently, reinforced concrete frames and

Combining Materials

B 1.7

B 1.8

parallel shear wall construction combined with building envelopes comprising timber frame elements with thermal insulation are increasingly used. Materials can be combined at a structural, construction or construction component level (Fig. B 1.6, p. 45). Timber and concrete Concrete displays characteristics that com­ plement timber, such as comparatively large mass and incombustibility. Thus, combining the two materials in multi-storey buildings is sensible. In the case of a mixed-use resi­ dential and commercial building in Berlin

B 1.9

S T R U C T U R E S A N D S T R U CTUR A L SYSTEM S

(p. 194ff.), the staircases consist of in-situ concrete. The building further features solid timber ceilings and wall components that were combined with steel beams, timber posts and a reinforced top layer of concrete (Fig. B 1.10). Timber-concrete composite ceilings are, perhaps, the most well-known hybrid struc­ tural component. They consist of a top layer of concrete exposed to compressive forces and a bottom layer of timber or wood-based materials subject to tensile stress with shear-resistant bond, creating an overall cross section of high structural performance. Compared to structures only made of wood, this combination of materials offers the following advantages: •  enlarged spans • improved vibration and deflection be­ haviour due to the greater stiffness of ­construction components • creation of very stiff ceiling slabs • increased fire safety due to pouring in-situ concrete, which produces a continuous non-combustible and highly smokeproof layer • enhanced soundproofing due to the increased mass of construction compo­ nents • minimised vertical settlement due to mir­ rored vertical ties (vertical loads trans­ ferred through an intermediary concrete cover; Fig. B 1.7 a) • protective function of the in-situ concrete top layer for the timber construction below, either during construction (see “Office Building in Vandans”, p. 240ff.) or in the case of leaks

t­imber, unless the mass of construction components needs to be increased in order to meet soundproofing requirements (Fig. B 1.7 and B 1.10). Combining access cores and reinforced concrete ground floors with a timber struc­ ture featuring timber-concrete composite ceilings above it (Fig. B 1.8) offers various advantages. Complementary ground floor uses such as shops or offices often require different floor plans and spans. Further, such timber structures are raised above the range of splash water and soil mois­ ture. Thus, transitions between interiors and exteriors are possible, while taking into

47

B 1.7   Different means of transferring loads into ceiling supports without settlement: a Connecting a timber-concrete composite ­ceiling and a concrete edge beam to loadbearing columns. This prevents transverse compression in timber members caused by vertical load transfer in tall hybrid timber build­ ings. LifeCycle Tower (LCT ONE), Dornbirn (AT) 2012, Architekten Hermann Kaufmann b Primary beam connected to support via steel members, e 3 residential building, Berlin (DE) 2008, Kaden Klingbeil Architekten B 1.8  Hybrid timber building with timber-concrete composite ceiling B 1.9  Hybrid timber building with concrete ground floor and emergency staircase B 1.10 Combination of solid timber ceiling and wall ­elements with steel beams, timber columns and a poured concrete top layer (shown here prior to pouring), c 13 residential and office building, Berlin (DE) 2013, Kaden Klingbeil Architekten

For timber-concrete composite ceilings, the European Technical Specification TS 19 103 provides interim general design rules for practice to be integrated in the ­regular Euro­code for the Design of Timber Structures following trials [2]. Composite timber-concrete structures can be heavier than those made only of B 1.10

48

a

b

account construction-based wood protec­ tion, without need for elaborate detailing. Planning emergency exit routes from ­staircases to the exterior and fire vehicle access requires no heightened fire safety measures. Reinforced concrete staircases and lift shafts are advisable in timber buildings for reasons of stiffening and fire safety, yet not mandatory, as demonstrated by the administration building in Aalen (p. 237ff.). However, combining different materials within vertical construction components can also result in problems. Since the ­construction of concrete staircases, lift shafts or similar components usually needs to take place first, the time required for cur­ ing and related formwork processes can greatly prolong overall construction time. The dimensional accuracy and circum­ stances of settlement are different between concrete and timber buildings. When rein­ forced concrete shafts serve as ceiling sup­ port, add­itional expenditure is required. In comparison, building a solid ground floor, often in combination with an underground

out-of-plane loading Plattenwirkung Plattenwirkung

c

car park or basement level, is relatively less problematic. In this case, the timber structure is built from the ceiling above the ground floor upward, independently and largely without dimensional con­ straints. In the administration building in Aalen (p. 237ff.), for example, two crosslaminated timber cores house the stair­ cases, lift shaft and supply ducts. Only the flights of stairs consist of prefabricated ­concrete elements, installed on site by ­timber construction workers. This made it possible to install them floor by floor with timber construction precision and without additional expenditure. Timber and steel Timber and steel are often combined when the transfer of heavy point loads is required (Fig. B 1.7 b, p. 46). In such cases, steel parts can serve as connectors in frame construction, steel beams can be inte­ grated into box elements or other slab ele­ ments and steel cables can be used for ­prestressing beams or frame structures. In timber construction and engineering, hybrid building with timber and steel is a

in-plane loading Scheibenwirkung Scheibenwirkung

d

B 1.11

common practice when designing loadbearing structures with large spans. The top pin joints of three-hinged trusses are made of steel components just as the solid steel bearings of columns supporting heavy loads. Connections that require large cross sections and lengths from joint to beam edge in structures comprised only of timber can be minimised in size by using steel components. In many contemporary timber buildings, steel columns or beams are in part com­ bined with timber elements in order to increase spans, create flush downstand beams or minimise cross sections of ­columns (Fig. B 1.10, p. 47; see also ­project example p. 194ff.). Occasionally, steel frames are combined with timber ­secondary structures. Steel construction components are often used to transfer heavy loads in multi-storey timber build­ ings (Fig. B 1.11 h). When steel components are integrated into timber elements, the surrounding ­timber functions as fire protection and the enclosed steel components require no fire-retardant coating.

kombinierte combinedBeanspruchung loading als Platte und Scheibe kombinierte Beanspruchung als Platte und Scheibe

B 1.12

S T R U C T U R E S A N D S T R U CTUR A L SYSTEM S

e

f

Structural Engineering in ­Timber Construction The purpose of structural engineering is to enable the transfer of vertical loads into the subsoil in a manner as resource-efficient as possible. This includes dead, snow and live loads as well as horizontal loads due to wind, earthquakes or imperfections (inclin­ ation). The aim is to develop structural sys­ tems that transfer these loads as directly as possible through appropriate cross sections and materials. The more a design takes structural engineering requirements into account from the outset, e.g. the basic rules of stiffening [3], the more efficient and com­ petitive timber construction will prove to be, compared with other construction methods. Structural engineering of timber load-­ bearing structures is often considered highly complex in comparison to other building materials. At a closer look, however, this ­perception (or prejudice) is due to a lack of experience and routine in timber construc­ tion among planners. A more precise com­ parison of common building materials reveals many shared characteristics and a broad range of options for integrating differ­ ent systems within timber construction.

Timber Construction in ­Comparison Masonry and its presumably simple means of construction is considered especially easy to calculate. Actually, this is only true if sim­ plified rules are applied and shear walls pro­ vide adequate lateral stiffness, as is the case in single-family residential buildings. Masonry mostly absorbs in-plane stress. In contrast, slender masonry columns require in-depth calculation. Very delicate or slender masonry frame structures are only practicable in com­ bination with steel or reinforced concrete. Fire resistance ratings for masonry can be established quite easily by use of tables.

g

Due to its reliance on linear structural mem­ bers and related connection details (bolted, welded, glued), steel construction resem­ bles timber construction. For out-of-plane loads (ceilings), similar to masonry, mainly concrete or composite construction ele­ ments find use. Alternatives include corru­ gated sheet metal decking and, albeit sel­ dom, lattice grid structures. The individual components of structural elements are often very thin and, as a consequence, bending and buckling need to be considered, which requires considerable calculations. The same is true for fire resistance ratings when additional ratings for coatings or cladding are necessary, since steel loses its strength at temperatures above 400 °C. Similar to timber construction, reinforced con­ crete construction is very versatile and can be used to build linear and planar structural components such as slabs or plates (Fig. B 1.12) [4]. The notion of a system ranging from linear to planar members as described further above (Figs. B 1.2 and B 1.3, p. 43) can also be applied to reinforced concrete construction as well. Another shared char­ acteristic of reinforced concrete and timber are their anisotropic properties. They require consideration, for example, regarding the different load-bearing capacities in the case of tensile stress, related to the orientation of fibres within wood or the arrangement of reinforcement within concrete. This also applies to characteristics related to time or moisture content, such as creep and shrink­ age. With the exception of non-reinforced solid concrete or solid timber construction components, both materials typically find use as composite materials. In reinforced con­ crete construction and timber construction, as well as in masonry and steel construction, material characteristics can be adapted to particular requirements according to a broad range of applications (e.g. high density or lightweight concrete, combined glued lami­ nated timber). Connecting construction com­ ponents is the decisive issue: continuous

h

49

B 1.11

B 1.11 Support types for different wall and ceiling ­elements that prevent transverse compression and, thus, settlement: a Timber columns with steel pins support a box ceiling element, housing complex in Dornbirn (AT) 1997, Architekten Hermann Kaufmann and Christian Lenz b Frame wall construction with studs penetrat­ ing top plate and lateral slab connection c Frame wall construction with continuous studs and recessed notch as ceiling support, housing complex in Zurich (CH) 2016, Rolf Mühlethaler d Cross-laminated timber ceilings with drill holes infilled with mortar for settlement-free load transfer, H 8 residential and office build­ ing in Bad Aibling (DE) 2011, Schankula ­Architekten e Lateral ceiling connection, continuous wall construction f Indirect support, timber-concrete composite ceiling g Concrete edge beam, timber-concrete ­composite beam ceiling; LifeCycle Tower (LCT ONE), Dornbirn (AT) 2012, Architekten Hermann Kaufmann h Steel element as support and connector ­between columns and ceilings, student ­residence in Vancouver (CA) 2017, Acton Ostry Architects B 1.12 Loading of vertical and horizontal structural components: out-of-plane loading, in-plane loading, combined loading

50

wall framing

tension members

low

tension and compression member

cross-laminated timber

reinforced concrete very high

Stiffness

B 1.13

reinforcement and the option of subsequent­ ­ly pouring in-situ concrete often result in ­relatively simple, homogeneous connections, for instance, between walls and ceilings. By contrast, the separation of construction components requires a range of special solutions, such as impact soundproofing components for staircases or specialised built-in connectors for balcony slabs that minimise the occurrence of thermal bridges. The sheer volume of the related standards hints at the complexities of design. The standards related to calculations for normal temperatures in buildings and in the case of a fire (Parts 1-1 and 1-2 of the related Euro­

codes) occupy 347 pages for reinforced concrete, 195 pages for steel, 215 pages for timber and 201 pages for masonry, not counting national annexes. Summing up, to employ a material in a resource, energy and cost-efficient manner, it is necessary to deliberate on the material itself in a corresponding way. Unique features of timber structures – recommendations for construction Consideration of the following basic prin­ ciples of timber construction is advised: • The structural analysis of vibration and deflection is typically decisive for calculat­

Floor plan variant 1

Floor plan variant 2

Floor plan variant 3

Floor plan variant 4 B 1.14

ing ceilings. The first natural frequency of ceilings should be above 6 – 8 Hz to avoid inconvenient vibrations. To calculate the first natural frequency, the stiffness of a cross section is entered in the numerator, while the denominator contains the linear mass and the squared span. Mass with­ out bending stiffness (e.g. infill to improve soundproofing) reduces natural frequency. The chapter on “Construction components and elements” (p. 56ff.) illustrates and compares typical span ranges of various timber ceiling structures. • Wood is a highly anisotropic material. Compared to its weight, wood has high tensile strength, compressive strength and stiffness parallel to its fibre direction. Compressive strength and stiffness per­ pendicular to the fibre direction are, how­ ever, comparatively low and its transverse tensile strength is practically zero. • Particularly when erecting multi-storey buildings, the low compressive strength and stiffness perpendicular to the fibre direction result in the need to avoid ­transferring vertical loads across top or bottom plates subject to compressive stress, since this can lead to significant settlement. Timber elements subject to stress perpendicular to the fibre direction should be bypassed by steel compo­ nents or avoided completely by transfer­ ring loads directly through connectors attached to beam ends, parallel to the fibre direction. As a result, wood panel construction with vertical load-bearing wall elements is limited by nature: their application remains without problems for buildings with up to three storeys. For taller buildings, however, load transfer requires a specific composition of frame elements (Fig. B 1.11 b and c, p. 48, see project example p. 232ff.). Alternatively, combined structures featuring solid timber construction components (dowel lamin­ ated timber, cross-laminated timber) or frame structures are advised.

S T R U C T U R E S A N D S T R U CTUR A L SYSTEM S

• The low tensile strength of wood perpen­ dicular to the fibre has resulted in the con­ struction rule of avoiding the transfer of loads into wood components from the bot­ tom, but instead, introducing loads from the top, by using additional constructions or reinforcements as required. To prevent cracking, it is also necessary to avoid transverse stress resulting from shrinkage (e.g. by use of large steel components). Stiffening buildings Timber construction can draw from a range of elements for stiffening structures that vary in rigidity and require specific calculation. To transfer horizontal loads in timber con­ struction it is imperative to take the different degrees of rigidity into account. For build­ ings of limited height (according to build­ ing code, less than 7 m, which corresponds to a three-storey building, see Fig. C 1.2, p. 79), applying sheathing to timber frame construction is an effective stiffening mea­ sure. Mechanical connections between pan­ els comprised of wood or gypsum-based mater­ials and the wall frame provide the ­stiffening function. The connections (staples, nails, screws) offer only low shear resis­ tance. Their quantity determines transmissi­ ble force and stiffness. The distribution of forces depends on the length of walls sub­ ject to loading. In the case of frame structures, elements for stiffening such as steel tie rods or brac­ ing struts that concentrate forces locally find use (Fig. B 1.15 b). For taller buildings (topmost floor elevation above 7 m), predominantly cross-laminated timber or reinforced concrete walls serve for stiffening (Fig. B 1.15 a). Here, loads are distributed in relation to the in-plane bend­ ing stiffness of walls. As a result, stiffness is increased (Fig. B 1.13). Reinforced con­ crete construction components, typically access cores, can also be used to stiffen buildings (Fig. B 1.15 ). In such cases, and contrary to conventional wisdom, additional

stiffening elements may still be required in exterior walls or suitable interior walls in order to absorb horizontal forces. Not all wind and earthquake loads can be absorbed by cores, especially eccentric­ally positioned ones. Two cross-laminated timber cores, individual and laterally placed interior cross-laminated timber walls, as well as the gable end walls stiffen the seven-storey administration building in Aalen (p. 237ff.). Figure B 1.8 (p. 46) shows another sens­ ible arrangement of load-bearing elements and partitions. In addition to the planned reinforced concrete core, interior crosslaminated timber walls partly stiffen the structure. Towards the exterior, the loadbearing structure transforms into a frame structure, achieving an impression of light­ ness. Columns transfer vertical loads in ­conjunction with the cross-laminated timber walls. The non-load-bearing exterior wall elements only bear their own weight and wind loads per storey. This makes it easier to subsequently replace them, for instance due to energy conservation requirements or architectural redesign. Generally speaking, the closer horizontal stiffening elements are placed to the build­ ing perimeter, the lower the load transfer requirements are. If a building core and exterior wall plates serve combined stiffen­

51

a

b

B 1.13 Stiffness and horizontal load-bearing capacity of stiffening elements in hybrid timber construc­ tion. Note: horizontal loads always give rise to additional vertical loads. B 1.14 Floor plan variants with stiffening walls in dif­ ferent positions for a ten-storey building with ­exterior staircase; Kaden + Lager B 1.15 Different stiffening elements: a Cross-laminated timber wall panels achieve stiffening and load bearing, Via Cenni hous­ ing complex, Milan (IT) 2013, Rossiprodi ­Associati b Steel ties for stiffening a frame structure, e 3 residential and office building, Berlin (DE) 2008, Kaden Klingbeil Architekten c Reinforced concrete cores connected to a timber structure, student residence in ­Vancouver (CA) 2017, Acton Ostry Architects c

B 1.15

52

ing purposes, calculations are required to take the different degrees of stiffness into account by use of appropriate frame calcu­ lation or finite element programmes. In tim­ ber frame construction in particular, it can be helpful to simply position a tie or a brace to concentrate load-bearing at particular points. This can avoid the need for a large number of anchors and related complex load transfer. In principal, the following applies: in timber construction, more than in any other con­ struction method, the design must focus adamantly on the transmission of verti­ cal loads within construction components and, therefore, the arrangement of stiffen­ ing elements – particularly due to the lower bending stiffness of timber construction components in the case of lateral load transmission. In concrete construction, thick concrete slabs can conceal the ­necessary reinforcement or reinforcing

­ lements. Timber construction, on the other e hand, requires solid timber downstand beams or hybrid solutions to perform simi­ larly (Fig. B 1.10, p. 47). The direct transfer of vertical loads represents greater clarity in structural terms, while also being less expensive. However, this doesn’t have to constrain design freedom, as demonstrated by the floor plan variants for a ten-storey timber building, illustrated in Fig. B 1.14 (p. 50). The number of storeys in timber structures all over the world is increasing. As build­ ings become taller and climatic conditions change, wind loads are also increasing. Even in Central Europe, greater earthquake loads, as well as generally greater vertical loads and, at the same time, increased fire safety requirements demand in-depth structural engineering, ideally to be coord­ inated in the earliest design phases with all individuals involved in the planning. To

absorb the increasing horizontal loads resulting from the rising height of timber buildings, systems very similar to those used in reinforced concrete and steel ­construction can be used. This includes tube-in-tube systems (structures consist­ ing of two concentric layers of load-­ bearing or stiffening walls), trussed tubes or ­various hybrid systems. When comparing timber construction with reinforced con­ crete and steel construction, it is import­ ant to note that rigid timber frame corners are impossible or, at least, very difficult to build and demonstrate low degrees of stiffness. A completely unobstructed facade without any elements for stiffening is not ­feasible. Prestressed structures Timber construction components such as beams, columns, walls or ceilings can be combined with embedded steel cables to

B 1.16 Load-bearing lattice frame structure comprised of glued laminated timber beams with embed­ ded and glued steel cables to tension the entire structure into an overall system, House of Natu­ ral Resources, ETH Zurich (CH) 2015, Meyer. Moser.Lanz.Architekten B 1.17 Omnidirectionally cantilevered lattice frame structure with timber linear members, concrete joints and steel cable tensioning. Section, main beam, top view, lattice frame, design, education centre in Risch (CH), Peter Zumthor, Joseph Schwartz B 1.18 Prestressed beam, dining facility, Swiss Re Centre for Global Dialogue, Rüschlikon (CH) 2000, Meili Peter Architekten, Jürg Conzett (structural engineer) a visualised cantilevers b conceptual sketch by Jürg Conzett, pre­ stressing of cantilever beams, aimed at ­solving problems of deformation due to snow loads through load transmission into the column-free glass facade. B 1.16

S T R U C T U R E S A N D S T R U CTUR A L SYSTEM S

create prestressed structures. This allows, for instance, increasing spans and redu­ cing deflection in beams. At the scale of individual construction components, first examples were built in the 1990s, such as the prestressed primary beams of the Swiss Re Centre for Global Dialogue dining facility by Meili Peter Architekten and struc­ tural engineer Jürg Conzett (Fig. B 1.18). Pilot applications of prestressed compo­ nents at the building scale include pro­ jects by Andy Buchanan in New Zealand [5] and the ETH Zurich House of Natural Resources [6] (Fig. B 1.16). Since 2016 various research projects all over the world have aimed to further develop this technol­ ogy. Connecting individual timber beams or ­timber columns and beams through ten­ sioning makes timber construction types possible that were previously neither ­sensible nor feasible. This includes grid structures (Fig. B 1.17) or very slender

53

frame structures. Further, this allows con­ nections in these structures to be simplified, since related timber construction compo­ nents only need to transmit compressive stress, while tensile forces are transferred by tension cables without interruption. Load-bearing structures built according to the construction principles of historic East Asian timber structures and featuring geometrically complex, friction-based ­connections can provide new solutions for earthquake-resistant structures in com­ bination with pre-tensioning perpendicu­ lar to the grain. Cores comprised of solid timber panels can stiffen buildings much more effectively when built as prestressed structures. Hardwood Hardwood species such as beech, oak or ash display significantly greater strength than softwood. By using hardwood to trans­

B 1.17

Glued laminated timber beam with major deformation due to snow load.

Wood creep behaviour prevents use of a pre-formed beam with tensile connections in the facade plane.

Prestressing by use of embedded and glued steel ­cables enables dimensionally stable prestressing, ­allowing tensile beam connections in the facade plane without deformation due to snow load. a

b

B 1.18

54

IPE 270

Beech laminated ­veneer lumber

Beech glued laminated timber

Spruce laminated ­veneer lumber

Spruce glued laminated timber

h = 270 mm w = 135 mm m = 36.1 kg/m

h = 270 mm w = 160 mm m = 29.4 kg/m

h = 440 mm w = 160 mm m = 48.8 kg/m

h = 360 mm w = 160 mm m = 29.4 kg/m

h = 460 mm w = 160 mm m = 31.3 kg/m

Assumptions: Steel S 235: γm = 1.00 fy/x = 235 N/mm2 Beech and spruce laminated veneer lumber: use class 1 k mod = 0.9 γm = 1.20 (EN 1995-1-1) Beech and spruce glued laminated timber: use class 1 k mod = 0.9 γm = 1.25 (EN 1995-1-1)

B 1.19

fer vertical loads, new dimensions in timber construction become possible. Additional processing (hardwood-based glued lamin­ ated timber or laminated veneer lumber) can contribute to further advancements (Fig. B 1.19). For this purpose, it is also ­necessary to develop corresponding highperformance connections. The increas­ ing availability of hardwood leads to new opportunities in the production of beams predominantly subject to bending forces. The elasticity modulus of such flexural con­ struction components – and, as a result, their rigidity – does not increase to the same extent as their strength. Beech laminated veneer lumber has assumed an important role as an economi­ cally feas­ible construction material for trusses, which are predominantly subject to normal forces. The connection and fasten­ ing technology facility in Waldenburg is an impressive example, featuring trusses made of beech laminated veneer lumber as pri­ mary and secondary beams spanning 18.30 m to 42 m (Fig. B 1.21). Compared to steel or reinforced concrete, this permitted the ­creation of a structure of significantly lower weight and resulted in lower expendi­ ture for required foundation work and assembly of the large-size beams. Fire pro­ tection requirements were also realised at

substantially lower costs. The nodes between members comprise butt joints and carpentry-style woodworking joints that make use of the high lateral stress resist­ ance and shear strength of the material. Employed comprehensively for entire struc­ tures, beech laminated veneer lumber often also finds use when specific beams or ­columns of a load-bearing structure are supposed to bear stronger loads without having to deviate from the dimensions of the other members of the structure. Beech laminated veneer lumber is also an interesting option for multi-storey timber frame construction if columns and beams are required to bear heavy point loads (Fig. B 1.20). The expectancy is that further timber construction materials made of hardwood or hybrid construction materials comprising soft­ wood and hardwood will become marketable in the future. This includes, for instance, wood-reinforced timber consisting of soft­ wood and hardwood veneer [7], hardwood cross-laminated timber or hybrid hardwood and softwood cross-laminated timber [8].

Timber construction has undergone an astounding evolution in the last decades,

accessing more and more fields of appli­ cation. Building with wood has become a high-quality alternative to conventional construction methods. The combination of different timber construction types, yet also combinations of materials, by including other construction materials such as concrete or steel, allows for pre­ cise and custom solutions for very differ­ ent building-related tasks. Timber build­ ings are becoming increasingly competi­ tive in the context of everyday activities. Prefabrication as a specific construction process is also receiving increased appre­ ciation. It impacts topics relevant to the future of building, such as the improve­ ment of construction quality and speed or opportunities of digitalised and auto­ mated production processes. In addition, timber construction and its unique advan­ tages in ecological terms offers answers to urgent societal challenges, such as energy and resource efficiency, suitabil­ ity for purposes of a circular economy or ­climate neutrality. When architectural design and structural engineering take into account the specific characteristics of timber as a construction material while making use of hybrid construction types as required, there are hardly any limits to building with wood.

a

b

c

Conclusion

B 1.20

S T R U C T U R E S A N D S T R U CTUR A L SYSTEM S

Notes: [1] Deplazes, Andrea: Holz indifferent, synthetisch. In: DETAIL 1/2000, p. 23 [2] CEN / TS 19 103 Design of Timber Structures – Structural design of timber-concrete composite structures – Common rules and rules for buildings www.bgu.tum.de [3] Basic rules of stiffening: at least one ceiling plane is connected to three wall planes with their axes not intersecting in one point, or four wall planes with their axes intersecting in at least two points. [4] Horizontal slabs or horizontal or vertical plates are planar elements that can bear out-of-plane loads or in-plane loads; combined loading often occurs in wall, ceiling and roof elements [5] Newcombe, M.; Pampanin, S.; Buchanan, A. H.: Governing criteria for the lateral force design of posttensioned timber buildings. WCTE 2012 Proceed­ ings, Final Papers, Auckland 2012, p. 148ff. [6] Wanninger, Flavio; Franghi, Andrea: Experimental and analytical analysis of a post-tensioned timber frame under horizontal loads. Engineering Structures, Vol. 113, Kidlington 2016, p. 16 – 25 [7] Lechner, Markus; Winter, Stefan: Hybride Holz­ bauteile aus Laubholz-Furnieren und Brettschicht­ holz aus Nadelholz – Holzbewehrtes Holz. Research project Technical University of Munich. Bundesinsti­ tut für Bau-, Stadt- und Raumforschung (BBSR), Bonn, Research initiative “Zukunft Bau”; SWD10.08.18.7-18.21. Termin­ation date 06/2021 [8] Kaufmann, Hermann et al.: Research project. Devel­ opment of a material and energy-efficient timber con­ struction system with hard- and softwood (LaNaSYS). Fachagentur Nachwachsende Rohstoffe (FNR), ­Gülzow. Termination date 06/2023. www.ar.tum.de and www.bgu.tum.de

55

b

B 1.19 Comparison of different glued laminated timber and laminated veneer lumber (beech and spruce) column cross sections with a steel IPE 270 Å-beam B 1.20 Nine-storey administration building, Risch-­ Rotkreuz (CH) 2018, Burkard Meyer Architekten a, b  timber-concrete composite beam ceiling with beech laminated veneer lumber primary frame construction (columns /downstand beams) c The facade visually displays the frame con­ struction and the rhythm of structural members. B 1.21 Connection and fastening technology production hall, Waldenburg (DE) 2020, Hermann Kaufmann + Partner a primary truss girder, supported by column, high-performance beech laminated veneer lumber woodworking joint b secondary truss girder, supported by a pri­ mary beam, woodworking joint c production hall with a roof structure comprised of primary and secondary beech laminated ­veneer lumber truss girders c

B 1.21

56

Construction Components and Elements Stefan Krötsch, Wolfgang Huß

Contemporary timber construction is – beyond the confines of general construction methods – characterised by the free combi­ nation of prefabricated elements (see “From Linear to Planar Member” p. 43ff. and “Com­ bining Construction Elements” p. 45). Within the typical building processes in contem­ porary timber construction, prefabricated con­ struction elements that are assembled into components such as walls, ceilings and roofs are the basis for an understanding of cur­ rent timber structures. The following descrip­

tions of individual construction elements and components focus on those most commonly used in multi-storey timber construction. According to their principally different func­ tions within a load-bearing structure, they are discussed as vertical (walls) and hori­ zontal (ceilings and roofs) elements, and not according to material characteristics independent of the particular context. This supports a comparison of the different con­ struction components (see “A Comparison of Timber Construction Elements”, p. 72ff.).

B 2.1 Prefabrication of frame construction wall ele­ ments shortly before installing windows B 2.2 Prefabricated dowel laminated timber wall with OSB sheathing B 2.3 Dowel laminated timber wall element made of ­individual lamellae B 2.4 Various methods of joining lamellae: nailing, ­dowelling with wooden dowels, gluing B 2.5 Profiling of boards to interlock them and improve airtightness and soundproofing B 2.6 Improving low in-plane stiffness by adding ­stiffening sheathing B 2.7 Improving out-of-plane loading capacity by ­connecting lamellae to top and bottom plates B 2.1

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

57

Dowel Laminated Timber Walls

B 2.2

Dowel laminated timber structures were ­initially developed as ceiling elements. They consist of low-cost boards of low ­quality joined into high-quality, load-­ bearing solid wood construction compo­ nents. Continuous connections between mul­tiple boards compensate for their ­specific inhomogeneity. Dowel laminated timber walls mostly consist of 20 to 60-mm thick solid softwood boards that are aligned and joined together. Floorto-floor height wall elements are typically factory-produced in widths that permit easy handling and assembly on site. Boards can be either continuous within the con­ struction element or can feature finger joints or staggered butt joints. The thickness of the elements is limited only by the maximum board length of typically up to 240 mm, or less commonly up to 280 mm. Dowel laminated timber panels swell and shrink in relation to the fibre orientation of boards or lamellae, mostly parallel to walls. Panels display high dimensional stability from floor to ceiling. Originally, individual boards were nailed together, yet nails (usu­ ally steel) greatly disrupted subsequent work processes. By joining lamellae together with hardwood dowels (usually beech), the resulting elements can be processed and recycled similarly to solid wood. Extreme processes of drying and the resulting low wood moisture content of the hardwood dowels causes subsequent swelling when in contact with wood with a higher moisture content, resulting in stable, completely adhesive-free ­connections. Diagonal dow­ elling provides elements with increased dimensional stability. The adhesive bonding of boards into laminated panels – within a process matching the production of glued laminated timber – is currently increasing in practice. Laminated panels of this type fea­ ture a fundamentally different performance profile than dowel laminated panels: their inplane stiffness is significantly higher and, as a rule, only limited by the butt joints of the

r­ elatively slim boards. Swelling and shrink­ age take place across the entire panel width. When applying connectors to lami­ nated panels, the distance between indi­ vidual lamellae and the panel edge is ­irrelevant. Panels can be processed as an homogeneous type of wood, similar to glued laminated timber. Boards can be planed, rough-sawn, sharpedged or chamfered, depending on design requirements. They can feature different profiles, for instance to optimise characteris­ tics related to airtightness, soundproofing, acoustic properties and duct work (espe­ cially electrical wiring and computer cabling). Dowel laminated timber walls, even with slender cross sections, can bear very heavy vertical loads, because loading only takes place in the direction of the wood grain. Stacking boards prevents bending and buckling along their weak axis. Bond­ ing boards together ensures an homoge­ neous planar distribution of forces and min­ imises individual weak spots. Without any additional measures, nailed and dowelled laminated timber wall sections are relatively elastic when subject to horizontal lateral and transverse loads. Wall sections subject to lateral loads can be stiffened by apply­ ing wood composite boards (e.g. OSB or three-ply panels) to one side. Load-bearing connections between panel boards and a top plate can resist transverse loading of walls. Small openings (e.g. through walls for instal­ lations) can be created in dowel laminated timber walls without requiring headers. For larger openings, including windows or doors, it may be necessary to include hori­ zontal elements, such as headers or lintels.

B 2.3

nailing Vernagelung

dowelling with Verdübelung wooden dowels mit Holzdübeln

gluing Verleimung B 2.4

B 2.5

B 2.6

B 2.7

58

Frame Wall Construction

B 2.8

Frame wall construction or wall framing combined with sheathing is a further devel­ opment of frame construction that origi­ nates in half-timbered frame construction and finds widespread use in North Amer­ ica. Wall framing elements currently com­ prise mostly prefabricated, complex wall elements with various, case-specific build­ ing component layers, resulting in materialefficient construction types. Wall framing elements are also the most frequently used vertical building element in timber construc­ tion in Europe. When used to build exterior walls, their main advantage is that a single component layer can combine load-bearing structure and thermal insulation in a costefficient and space-saving manner. Floor-to-floor height prefabricated timber elements of this type usually consist of a load-bearing structure featuring linear ele­ ments, the actual stud frame, and sheathing on one or both sides for stiffness. Depend­ ing on requirements and the degree of ­prefabrication, further building component layers and infill materials can be included. A stud frame is usually made of solid con­ struction timber. Using glued laminated ­timber for this purpose enables bearing greater loads and creating wall sections of greater thickness (stud cross section > 240 mm). In contrast, Å-joists or open web timber joists permit reducing thermal transmittance. When choosing a sheathing material, the structural (stiffening) as well as the ­physical characteristics and the planned placement (interior or exterior) of sheath­ ing is decisive. Cost-efficient, airtight and diffusion-resistant oriented strand boards (OSB) are often used as stiffening interior sheathing. Laminated materials such as three-ply boards or laminated veneer lum­ ber are suitable for heavy-duty structural requirements. Wood board siding consti­ tutes a glue-free alternative and diagonally arranged boards can effectively stiffen structures.

The composite effect of a stud frame and sheathing reduces loads that joints are ­subject to. As a result, joints can remain ­simple, in many cases as butt joints with screw connections. Currently, woodwork­ ing joints such as dovetails often find use and can be created efficiently by CNC ­milling robots as joints consisting only of wood. Pneumatic power tools are used to drive nails or staples into sheathing and connect it to studs. Screw and glued-in screw connections are used for heavy duty applications. Vertical loads are distributed from top plates into studs, which transfer them to bottom plates. The horizontal members (top and bottom plates) are the weak spots of verti­ cal load bearing. This is also the reason why very few buildings consisting of con­ ventional load-bearing timber frame wall constructions exist that exceed five storeys in height. In such cases, specific measures are required, such as continuous studs or horizontal members consisting of hardwood. Sufficiently dimensioned studs resist buck­ ling transverse to walls, while the composite effect of studs and sheathing prevents inplane deformation and lateral buckling. In the case of high-load concentrations, studs of greater strength and, in individual cases,

a

steel members are integrated into frames. Sheathing occasionally serves to bear pla­ nar, vertical loads. Horizontal transverse forces result in bend­ ing that the sheathing is subject to and are transferred into correspondingly dimen­ sioned studs. Stud spacing and sheathing thickness are interrelated. Horizontal lateral forces are transferred by the sheathing into the wall supports, while the stud frame prevents the sheathing from buckling. Stud frames are typically based on a grid ori­ ented on the dimensions of commercially available panel materials (625 or 833 mm as factors of 2,500 mm). These sizes influ­ ence the dimensions of neither walls nor openings, since stud frames and sheathing can be easily adapted in proximity to panel edges or areas with large openings (with headers and parapets). Narrow openings are created by placing blocking or noggings into the stud frame. For large openings, the structural function of sheathing (one side or both sides) is ­sufficient in relation to the available height between lintels or headers and the top plate. Changes in sheathing material (e.g. LVL instead of OSB) can accommodate greater spans. If insufficient height is avail­ able between lintels or headers and the top

a

sheathing on both sides

reinforced stud

steel load-bearing sheathing b

B 2.9

b

B 2.10

59

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

top plate stud

sheathing

bottom plate horizontal in-plane load transmission

horizontal out-of-plane load transmission

vertical load transmission B 2.11

B 2.12

plate, reinforcement or alternate materials are advised (glued laminated timber or steel members).

B 2.8 Prefabrication of a frame construction wall B 2.9 Sheathing for special structural requirements a floor-to-floor height beam with sheathing made of suitable material on both sides and joined appropriately b load-bearing sheathing made of a suitable material with studs as stiffening against ­buckling B 2.10 Reinforcement of frame construction walls sub­ ject to heavy load concentrations by integrating glued laminated timber (a) or steel (b) studs to bear point loads or form a frame structure B 2.11 Diagram, frame construction wall B 2.12 Vertical and horizontal load transfer in a frame construction wall B 2.13 Linear structural elements B 2.14 Frame construction joints (between studs and top / bottom plate) B 2.15 Different means of creating openings in a frame construction wall a frame construction wall with no openings and undisrupted vertical load transfer in the stud frame b frame construction wall, small opening: gap in the stud frame to accommodate header, sill and additional studs c – f  frame construction wall, wide opening, different types of load-bearing headers /  lintels: reinforced header panelling (c), re­ inforced header (d), reinforcement with extra studs (made of steel, e), lintel beyond the ­element, e.g. in the parapet area of the ele­ ment above (f)

solid lumber VH

screw connection

cross-laminated timber BSH

CNC-milled tongue and groove joint

Å-joist Stegträger

open web Å-joist Leiterträger B 2.13

load-bearing connection of frame and sheathing B 2.14

wall framing, no openings a

solid construction timber KVH

c

reinforced ­sheathing reinforced stud

additional stud e

header reinforced header

sill

lintel beyond element

reinforced stud

b

d

f

B 2.15

60

Cross-laminated Timber Walls

B 2.16

B 2.17

B 2.18

B 2.19 saw cut opening opening created by insertion of header and sill

opening as gap between elements B 2.20

In 1998 the introduction of various crosslaminated timber products approved for use by building authorities in Germany and Austria marked a turning point in modern timber construction. Boards of various qual­ ities are adhesively bonded within planar, high-performance construction components for walls and ceilings. This minimises the anisotropic properties and inhomogeneities inherent in timber. This planar, solid material allows the creation of simple connections between building components, enabling contemporary demands to be met, even in regions with no tradition of or experience in building with wood. Cross-laminated timber elem­ents typically consist of layers of boards arranged crosswise and glued together to form a large panel. This config­ uration greatly reduces, even obstructs the swelling and shrinking of wood, which occurs mainly perpendicular to the wood grain. Resulting elements display very good dimensional stability. The number of board layers (mostly between three and eleven) and the thickness of individual boards determine the thickness of elements (mostly 60 – 400 mm). An odd number of boards is common in order to prevent ­material de­­formation due to asymmetrical stress. Cross-laminated timber usually con­ sists of spruce, pine or fir. Other wood ­species such as oak or birch (e.g. for hard or decorative surfaces) also find use. The outermost board layers can be glued together (through edge gluing) to create ­airtight, smokeproof elements, thereby increasing the fire resistance rating of con­ struction components. One specific type of cross-laminated timber features hardwood dowels that connect the boards, compris­ ing a glue-free, environmentally friendly alternative. Elaborate presses can serve to create corresponding cross-laminated tim­ ber elem­ents with curved surfaces. In theory, there is no limit to the dimensions of cross-laminated timber elements. In prac­ tice, dimensions are limited by manufactur­

ing processes and transport circumstances. Cross-laminated timber walls are delivered to building sites in functionally appropriate sizes, usually floor-to-floor height. Upon delivery they can be quickly assembled by use of simple connections (e.g. diagonal screw connections) into a shell structure. Based on their rigidity, surface quality and good workability, cross-laminated timber elements often find use in the prefabrication of complex construction components or entire room modules. Cutting elements to size and creating open­ ings typically takes place during prefabri­ cation. Window and door openings are cut into homogeneous panels without requiring additional measures such as trimmers or headers, as long as the opening is not too close to the panel edge. The amount of ­cutouts, shavings and chips (created by ­cutting windows or gable sections) can be considerable. Sensible element sizes and geometries can minimise unnecessary waste of high-quality material. In cross-laminated timber walls only vertical board layers can optimally bear vertical loads. Correspondingly, a wall compris­ ing vertical boards in its outermost layers performs better than a wall in which these boards are horizontal. Cross-laminated ­timber walls can absorb in-plane horizontal loads very well, due their planar, homoge­ neous cross section and strength. Therefore, they are suitable for stiffening multi-storey buildings. Cross-laminated timber walls can occasionally be installed as beams (e.g. parapet beams or floor-to-floor height beams) to accommodate long spans in the storey below.

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

61

Laminated Veneer Lumber Walls

B 2.21

Laminated veneer lumber (LVL) has long been in use in construction, for instance as sheathing for stud frame walls. Since the 1990s, laminated veneer lumber panels of greater thickness and consisting of soft­ wood veneer layers have been used as self-supporting construction components. Laminated veneer lumber consists of adhe­ sively bonded layers of rotary-cut veneer each roughly 3 mm thick. In contrast to veneer plywood, the fibre orientation is ­parallel throughout all layers. In certain cases individual layers are rotated by 90° in order to reduce the anisotropic charac­ teristics of wood (cross bonding). Unlike in panels, laminated veneer lumber used for beams typically lacks cross-bonded veneer layers. The combination of many thin layers neu­ tralises any wood-based inhomogeneities, creating a building material that permits ­reliable calculations. Generally, laminated veneer lumber is made of softwood. Since 2013, high-strength beech laminated veneer lumber has been approved for construc­ tion tasks by building authorities. Previ­ ously beech, which swells and shrinks ­significantly due to its growth behaviour, was hardly suitable for use in construction. Processed into homogeneous laminated veneer lumber, Europe’s most common deciduous wood species can serve as a cost-efficient load-bearing building mate­ rial. Beech can be used very efficiently in this manner: crooked and warped logs unsuitable for processing into planed square edge timber or boards are sawn into straight pieces roughly 2 m long, rotarycut and almost completely processed into veneer. Laminated veneer lumber can also be used to produce curved surfaces by use of an adjustable hydraulic press. Due to its high quantity of glued layers, lami­ nated veneer lumber contains a much higher share of adhesives than glued lami­ nated or cross-laminated timber. Similar to cross-laminated timber, laminated

veneer lumber panels are limited in their dimensions only by production processes and transport circumstances. Their manu­ facture is geared to typical panel widths of 2.50 m. Cutting, creating openings, assembly and connecting elements match the processing of cross-laminated timber (see opposite). Vertical loads are optimally transferred by laminated veneer lumber walls with a majority vertical fibre direction, which en­­ ables bearing very heavy loads. Laminated veneer lumber walls are also highly suit­ able for absorbing in-plane horizontal loads (in order to stiffen buildings), due to their planar, homogeneous structure. In add­ ition the material performs excellently when used for beams, especially if the veneer fibre direction is horizontal. Due to the very good structural characteristics of laminated veneer lumber, it is occasionally also used to reinforce supports, connections, etc. of other timber structures.

B 2.22

B 2.23

B 2.24 B 2.16 Cross-laminated timber wall installation on site B 2.17 Diagram, cross-laminated timber wall, crosswise board layers B 2.18 Vertical load bearing takes place predominantly in vertical layers (left). In the case of horizontal layers (right), when loads are identical, required wall cross sections are greater. B 2.19 Cross-laminated timber element as floor-to-floor height beam B 2.20 Different means of creating openings B 2.21 Laminated veneer lumber functions as a rigid plate and is highly suitable for stiffening build­ ings B 2.22 Laminated veneer lumber wall, Kronenraum­ forschungsturm (research tower at Kaisers­ lautern Technical University) near Trippstadt (DE) 2011, Kirchspitz Architekten B 2.23 Processing beech wood into laminated veneer lumber: beech logs are sawn into 2-m-long straight sections, milled into a cylindrical form and rotary-cut into veneer layers B 2.24 Composition, veneer layers with parallel fibres B 2.25 Laminated veneer lumber without crosswise ­layers (left): all fibres in the veneer layers are parallel. Laminated veneer lumber with cross­ wise layers (right): the fibres of some layers (e.g. every fifth) are rotated by 90°. B 2.26 Laminated veneer lumber beam with horizontal and vertical layers

B 2.25

B 2.26

62

Beams

a

b

c B 2.27

Beams serve as linear supports for slabs and roof elements and transfer loads into point supports. They are installed as individual elements or as part of a system, such as a hierarchically organised ceiling structure (frame construction). They can be used as downstand, flush or upstand beams or joists. Because they are subject to structural bend­ ing loads, beams are almost always installed with upright, sometimes very slender cross sections, in relation to construction type and size. Beams can also be integrated into other horizontal construction components, such as beam ceilings or hollow core or box ceilings. Solid beams consisting of solid lumber or solid construction-grade timber feature ­limited cross section dimensions. High-­ performance wood-based materials such as glued laminated timber or laminated veneer lumber can be used for greater loads, when larger cross sections are required, or where less structural height is available. High-­ performance materials such as multi-layer panels can be manufactured into hollow core or box beams or other beam geometries. Within a single span beam subject to bend­ ing stress, its upper part experiences com­ pressive forces while its lower part bears tensile forces, as long as the connection between the two parts is shear-resistant. The load-bearing capacity rises exponen­ tially when the distance between the upper

and lower parts of the structurally effective cross section is increased. Many different beam geometries utilise this: glued lamin­ ated timber beams use high-performance boards or hardwood as upper and lower layers, while lower-quality softwood is used for the layers in-between. Å-joists comprise thin panels made of woodbased products with solid-timber top and bottom chords that absorb tensile and com­ pressive forces and brace the thin webbing against buckling. Box beams follow the same principle, but their geometry provides better resistance against lateral buckling. The upper and lower layers function as top and bottom chords. Box beams and Å-joists feature adhesive bonding or adhesives and mechanical fasteners. In a trussed beam, web thickness is reduced to a minimum in order to form a shear-resistant connection between top and bottom chords. All mem­ bers are subject to normal forces. Only the top chord experiences bending loads. A trussed beam makes use of the fact that the bottom chord only bears tensile forces. A steel cable can serve as a bottom chord, with vertical compression members main­ taining the required distance to the top chord. Within beams of this type, comprised of individual linear members, mostly load transfer within connection points is decisive for dimensioning required members.

d

a

B 2.28 b

c

d

e

f

B 2.29

B 2.27 Installing a beam on site B 2.28 Different beam material types: Solid lumber (a), solid construction timber (b), glued laminated timber (c), laminated veneer lumber (d) B 2.29 Different beam geometries: Beam with a solid cross section (a), box girder (b), Å-joist (c), truss beam (d), beam with invert­ ed truss (e), prestressed beam (f) B 2.30 Different methods of connecting beams and ceiling elements to columns in multi-storey buildings: Heavy loads are transferred from upper to lower supports without transverse compression in ­timber members. B 2.30

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

63

Dowel Laminated Timber ­Ceilings

B 2.31

Dowel laminated timber ceilings are a con­ tinuation of historic structures with layers of boards placed next to each other con­ tinuously and featuring systematic and loadbearing connections. Research carried out by Julius Natterer in the 1970s promoted the distribution of dowel laminated timber ceilings with the aim of using low-cost and low-quality boards as lamellae for the pro­ duction of high-quality, load-bearing solid wood construction components. A dowel laminated timber ceiling is similar to a dowel laminated timber wall in terms of its material, production and assembly (see p. 57). Boards can be planed, rough-sawn, sharpedged or with chamfered edges in order to meet different design requirements. Various types of profiling can improve airtightness, soundproofing, acoustic properties, duct work (especially electrical wiring and com­ puter cabling) and shear-resistant connec­ tions in composite timber-concrete and similar elements. For optimal results, the fibre direction in dowel laminated timber ceilings should match the span direction. Boards are placed upright and, therefore, are efficient in struc­ tural terms. Such ceiling elements have the lowest structural height of all timber ceil­ ing structures, but always require a linear support. Ideally it should be assumed that every lamella is load-bearing, meaning that

it is continuous between supports. Continu­ ously connecting several lamellae ensures that adjacent lamellae become active when elements are subject to point loads, which equalises inhomogeneities or weak points in individual lamellae. With the exception of laminated elements, dowel laminated timber ceiling slabs are not sufficiently rigid to function as plates that stiffen buildings. Suitable wood-based material panels can be connected to them by use of mechanical fasteners such as nails or screws, which provides the neces­ sary rigidity and airtightness. Smaller openings can be created within ceiling slabs (e.g. for minor service lines) by mechanically connecting lamellae by use of screws. Larger openings require trimmers.

B 2.31 Prefabricated dowel laminated timber element B 2.32 Diagram, dowel laminated timber element made of individual lamellae B 2.33 Different connection types B 2.34 Various types of dowel laminated timber: made of boards (a), made of squared timber (b), made of offset boards, e.g. for timber-concrete slabs (c), profiling to interlock boards to improve airtightness and fire protection (d, e), profiling to form cavities (f), acoustic profiling (g), special form of dowel laminated timber slab consisting of box beams (h) B 2.35 Structural function, out-of-plane and in-plane loading

B 2.32

surface loads transferred to linear support

distributing point loads to multiple boards

low stiffness in the case of in-plane loads

nailed

glued

straight hardwood ­dowels

diagonal hardwood dowels B 2.33

a

b

c

d

e

f

g

h

sheathing with ­stiffening effect B 2.34

B 2.35

64

Beam Ceilings

Beam ceilings consist of beams covering the primary span and panels or boards extending from beam to beam to form a ceiling. This principle applies to ceiling structures with a wide range of beam spa­ cings: slim beams with minimum spacing (approx. 25 – 50 cm off-centre) create a structured underside with a flat appearance. Commonly used beam ceilings (spacing approx. 60 – 90 cm off-centre), a centuriesold and widespread construction type, con­ tinue to play an important role in construc­ tion, due to their versatility, simplicity and cost-effectiveness. Beam spacing results from the span of typical boards (e.g. wood boards, oriented strand board, three-ply panels) with thicknesses of 20 to 30 mm. Spacing can be expanded indefinitely if boards are comprised of a corresponding material capable of the related span (threeply panels, cross-laminated timber, lami­ nated veneer lumber) and layer thickness is increased. Common beam ceilings can be built without adhesives by using solid wood products. Beam ceilings with spans of 4 to 5 m are particularly cost-effective. Glued cross sec­ tions are required for ceiling beams with a longer span and tributary area or when dimensional stability requirements are high. If very heavy loads occur in specific areas due to trimmers or other special ­circumstances, beams comprised of lami­ nated veneer lumber or steel are suitable for related members. In order to create ­stiffened ceiling slabs, appropriate woodbased material panels can be mechanic­ ally fastened to ceiling beams. When floor­ boards are used, board thickness, span direction and type and spacing of fasteners require related adjustment. Similar to frame construction wall elements (see “Frame Wall Construction”, p. 58f.), boards can be arranged diagonally. Openings parallel to the direction of the span have little impact on the load-bearing structure of beam ceilings. Installing trim­ B 2.36

mers for openings perpendicular to the direction of the span changes the ceiling load distribution in a fundamental way: due to the interruption in the ceiling structure, point loads are transferred by lateral mem­ bers into the beams that border the open­ ing. In order to maintain the structural height of the ceiling, the following measures are recommended: • identical dimensioning of all ceiling beams: in the case of exposed ceiling constructions, this results in oversizing beams not subject to additional loads. • increasing widths of related ceiling beams: in the case of moderate load concentra­ tions, beams subject to particularly heavy loading can be reinforced by increasing their width. • changing materials: ceiling beams sub­ ject to greater loads are built of a stronger material, thereby maintaining structural height. Beam ceilings are either prefabricated as elements or assembled on site using individual linear members and boards or panels. On-site assembly can be a sens­ ible alternative in situations in which lifting large elements into place would be expen­ sive or impossible (e.g. rehabilitation or renovation).

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

65

B 2.37

a

b

c sheathing without stiffening effect

sheathing with stiffening effect B 2.38 d

e

f

good arrangement of openings

bad arrangement of openings

a Balken überoversized dimensioniert beams Balken überdimensioniert

b

Balken nach beams dimensioned auftretender Last according dimensioniert Balken nach to loads auftretender Last dimensioniert

breiter Balken zur wide structural Lastaufnahme beam zur breiter Balken Lastaufnahme

Balken nach auftretender beams dimensioned Last dimensioniert according loads Balken nach to auftretender Last dimensioniert

B 2.39

BSH glued laminated VH timber KVHBSH solid lumber VH solid construction timber KVH

Stahl steel Stahl

BSH glued laminated timber BSH

B 2.41

B 2.40

B 2.36 Different construction types according to ­spacing of primary beams B 2.37 Prefabricated beam ceiling prior to installation on site B 2.38 Deflection of a beam ceiling subject to in-plane stress with and without stiffening sheathing B 2.39 Openings in beam direction are typically pos­ sible without special measures (a). Openings across beams require trimmers and are typ­ ically complex (b). B 2.40 Different sheathing materials: a boards b diagonally arranged boards c tongue & groove boards d oriented strand board e three-ply panel f laminated veneer lumber panel B 2.41 Different types of trimmers for openings across beams

66

Box Ceilings

B 2.42

sheathing (top)

ribs edge beam sheathing (bottom)

B 2.43

three-ply panel

laminated veneer lumber oriented strand board

Box ceilings, sometimes also called hollow core ceilings, are a further development of beam ceilings. They comprise prefabri­ cated, lightweight ceiling elements, in which the compound effect of ribs and panelling produces a high-performance planar loadbearing structure that enables the structural ceiling height to be minimised. The anisotropic and inhomogeneous prop­ erties of wood are counteracted not by ­producing an homogeneous material, but instead, by creating a composite element that utilises the advantageous characteris­ tics of its constituent parts. Box ceilings are complex and costly to manufacture and are mainly installed in order to cover medium and long spans. Box ceiling elements consist of slim ribs ­oriented in the direction of the ceiling span. Together with the edge beams, they con­ stitute a frame that acts as a structural ­system in combination with panels con­ nected on top or on the underside. From a construction point of view, the result is a composite element comprised of individ­ ual parts – a box. Ribs and edge beams are usually made of solid construction tim­ ber or glued laminated timber. Laminated veneer lumber also finds use, yet seldom. Depending on the type of support, add­ itional cross beams can be built into a box

element. Steel beams are commonly used in box ceilings to partially increase loadbearing capacity or to connect ceiling elem­ ents to supports. Panelling, planking or sheathing of a box element is an essential part of load trans­ mission and consists of material with loadbearing capacity, such as three-ply panels, laminated veneer lumber or oriented strand boards. The panelling material needs to demonstrate the highest possible dimen­ sional stability. Cavities between ribs can be filled with insulation or other infill material as required. Elements 2 to 3.50 m wide and 5 to 20 m long are typical, due to transport limitations. In theory, there are no limits to ­element length and, thus, span. In box ceilings, the compound effect of ­linear elements and sheathing is decisive for load transmission. The connections between frame members play a minor role and can be created with screws or woodworking joints. Sheathing is typically connected to the frame based on con­ trolled measures subject to authorisation, such as glued or pressure-glued screw connections. The compound effect of ribs and sheathing creates an H-shaped load-bearing cross section (grey area in Fig. B 2.47). The effec­

B 2.44

Verschraubung Verschraubung screw connection

CNC-gefräste zimmermannsmäßige CNC-gefräste zimVerbindung mermannsmäßige Verbindung tongue CNC-milled and groove joint

combined- Verleimung screw and pressure glued Schraub-Press Schraub-Press - Verleimung

B 2.45

glued Verleimung Verleimung B 2.46

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

B 2.42 Attaching the top layer during production of a box ceiling element B 2.43 Diagram, box ceiling B 2.44 Sheathing materials for box ceilings B 2.45 Frame construction joinery B 2.46 Frame and sheathing connections, glued or combined screw and pressure glued B 2.47 The compound effect of ribs and sheathing ­creates an H-shaped beam cross section. B 2.48 Different support types of box slab elements and related configuration of ribs, edge beams and trimmers, forming a compound element ­together with the sheathing a linear support: ribs lie squarely on supports.

tive structural height h is increased by the thickness of both layers of sheathing. The sheathing makes ribs resistant against buckling and tilting, which allows for narrow beam widths (b/h < 1/4). The off-centre spacing of ribs is typically relatively narrow as well (40 –70 cm). Box ceilings can transfer loads as planar construction components into linear or point supports. The main load-bearing direction follows the ribs. The compound effect of frame and sheathing allows ­transmission of bending moments through interruptions between ribs (e.g. cross beams) by leading force components into the sheathing as tension and compression forces. This enables the creation of a frame structure in the same plane with point ­supports and cantilevers that acts as a ­continuous beam in primary and secondary load-bearing directions. Openings within box ceilings are created by use of trimmers, similar to beam ceil­ ings (see “Beam Ceilings”, p. 64f.). The compound effect of frame and sheathing reduces point loads in individual ribs.





a

point support b

linear support, cantilever

d

point support, cantilever

e

point support, double cantilever

‡ H-shaped cross section h   structurally effective cross section

B 2.47



b point support: an edge beam transfers loads from the ribs into the supports. c linear support, cantilever: ribs lie squarely on supports and, together with the sheathing, secure the cantilever. d point support, cantilever: ribs are connected to a trimmer, the cantilever utilises tension and compression forces in the top and bot­ tom sheathing. e point support, double cantilever: the canti­ lever is supported in the primary span direc­ tion similar to a single cantilever and is sup­ ported by the trimmers in the secondary span direction.

linear support

c

h



67

B 2.48

68

Cross-laminated Timber ­Ceilings

B 2.49

Cross-laminated timber (CLT) ceilings and walls typically consist of an odd number of layers that are adhesively bonded and stacked crosswise. In order to adapt them to specific requirements, ceilings can be ­custom-made: featuring two layers oriented in the primary load-bearing direction, with reinforced bottom layer lamellae in order to improve the fire resistance rating and burnout time, or with even numbers of layers for square, two-way ceiling slabs. Theoretically unlimited dimensions are, however, limited by production processes and transport circum­ stances. Cross-laminated timber ceiling slabs up to 4 m wide and 22 m long can be assem­ bled on site relatively quickly and with simple fasteners (e.g. diagonal screw connections). Depending on required stiffness, airtightness or fire protection, cross-lamin­ated timber ­elements can be connected with butt joints, lap joints, surface spline joints or tongue and groove joints. Cutting of elem­ents and cre­ ation of openings often takes place during ­prefabrication. In structural terms, cross-­ laminated timber elements function as rela­ tively homogeneous plates. Their span depends on slab thickness and type of sup­ port. Cross-laminated timber elements have a primary and secondary load-bearing direc­ tion, depending on the arrangement and quantity of board layers. The primary or main load-bearing direction is parallel to the outer­ most layers. The board layers following the span direction determine structural perfor­ mance. A linear support that evenly transfers loads is optimal for cross-laminated timber elements, yet point supports are also pos­ sible. In proportion to their load-bearing ca­­ pacity elements can cantilever in both primary and secondary load-bearing directions and can be used similarly to continuous beams. Rearranging point supports from the corners towards the panel centre alleviates load dis­ tribution within the element. Cross-laminated timber elements comprise rigid plates and can effectively stiffen buildings if ceiling ­elements are connected appropriately.

linear support in ­primary load-­ bearing direction h

h

H: element ­thickness h:  structurally ­effective cross section h

h

H

linear support in ­secondary load-­ bearing direction non-load-bearing top layers

B 2.50

butt joints between ­elements

linear support, cantilever

splice joint between elements

point supports

lap joint between elements with wood-based ­material board

point supports, double cantilever

B 2.51

B 2.52

standard 3-ply hardwood bottom layer

standard 5-ply standard 7-ply

H

outermost layers 3-ply panel

outermost double layers

special cross sections, boards laminated crosswise B 2.53

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

69

Laminated Veneer Lumber ­Ceilings

B 2.54

Laminated veneer lumber (LVL) has been in use since the 1990s for ceiling and wall elements, without material-specific ­differentiation. Initially made only of soft­ wood veneer, in 2014 building authorities approved the use of beech laminated veneer lumber (LVL). In terms of material characteristics, pro­ duction and assembly, LVL ceilings are no different from LVL walls (see p. 61). Laminated veneer lumber ceilings func­ tion as homogeneous structural plates with a clear primary span direction match­ ing the direction of veneer layer fibres. As a result, linear supports are required. A secondary load-bearing direction and point supports are possible with laminated veneer lumber panels featuring layers that are arranged crosswise. Spans depend on the panel thickness and type of support. Laminated veneer lumber elements consti­ tute rigid plates that can effectively stiffen buildings if ceiling elements are connected appropriately.

span follows primary load-bearing direction linear support

span follows secondary load-bearing direction only possible with crosswise layers

hh h

hh h

linear support, cantilever B 2.55

B 2.49 Installation of a cross-laminated timber ceiling element B 2.50 Diagram, cross-laminated timber ceiling: odd number of crosswise boards B 2.51 Means of joining elements in cross-laminated timber slabs: The two lower joints create rigid plates B 2.52 Structural function, depending on the direction of top layers and support type B 2.53 Cross sections, cross-laminated timber B 2.54 Laminated veneer lumber ceiling, Grüne ­Universität pavilion, Stuttgart (DE) 1993, Peter Cheret B 2.55 Diagram, laminated veneer lumber ceiling ­element with parallel fibre veneer layers in span direction B 2.56 Laminated veneer lumber – no crosswise layers (above): All fibres are parallel in all veneer layers Laminated veneer lumber with crosswise layers (below): Some board layers (e.g. every fifth) are rotated by 90° B 2.57 Span direction and support type

point supports

point supports, double cantilever

high degree of ­in-plane stiffness B 2.56

B 2.57

70

Timber-Concrete Composite Ceilings

concrete Aufbeton top layer

Holzdecke timber ceiling

B 2.58

beam ceiling with ­concrete top layer

dowel laminated timber ceiling with ­concrete top layer

staggered stacked beams with concrete top layer

Timber-concrete composite ceilings were developed in the 1920s in order to reduce the amount of concrete and steel used in ceiling slabs. Following World War II, this construction type mainly served to reinforce and repair old timber beam ceilings. Since the 1990s, timber-concrete composite ceil­ ings have been increasingly installed in new buildings and currently constitute the most frequently used hybrid component in timber construction. Compared with a structure only comprised of timber, they improve structural performance, soundproofing and fire protection characteristics, while their extra mass reduces unwelcome vibrations. Compared to reinforced concrete struc­ tures, they allow CO2 emissions to be reduced significantly and they can be recy­ cled, yet only according to their constituent elements. They are especially suitable for creating medium to long spans. The concrete compression zone and the timber tension zone require a rigid, shearresistant connection in order to achieve their compound load-bearing effect. Com­ posite timber-concrete ceiling slabs can be optimally used as single-span beams or girders, yet are only partly effective as continuous beams. They are not suitable for deep cantilevers, because the bending moment reverses within column supports.

The homogeneity and rigidity of the con­ crete layer facilitate transmission of horizon­ tal forces in the ceiling plate. Typically, the tension zone is a beam ceil­ ing or a ceiling comprised of dowel lamin­ ated timber, cross-laminated timber or ­laminated veneer lumber. A 6 to 12-cm ­thick layer of in-situ concrete is usually poured onto the timber construction, with reinforce­ ment added to prevent cracking. Also used are prefabricated concrete ­elements or composite timber-concrete ceiling ele­ ments, which only require filling or grouting of gaps between elements. This allows for a largely prefabricated and dry construction process. Openings in timber-concrete composite slabs depend mainly on the properties of the timber structure of the tension zone. Within the concrete layer, trimmers and bracing can be created by use of additional reinforcement. The following connection types are common for timber-concrete composite ceilings: • Notching (by cutting into the timber ceil­ ing element, transverse to the direction of shear forces) enables effectively con­ necting concrete and timber (Fig. B 2.61). Screws are additionally required to absorb uplift forces resulting from eccentric con­ nections.

cross-laminated timber ceiling with ­concrete top layer

laminated veneer ­lumber ceiling with concrete top layer

1  compression zone 2  tension zone 3 shear-resistant connection

11

33

22 B 2.59

B 2.60

C O N S T R U C T I O N C O M P O N E N T S A ND ELEM ENTS

71

B 2.61

• Glued-in flat steel connectors reduce the load-bearing capacity of the timber layer only insignificantly. Creating continuous beams is subject to building authority approval. • Flat steel lock connectors are common in dowel laminated timber construction types. Flat steel elements are inserted at a 5-degree vertical angle into saw-cut grooves of 4 % less width. This system is permitted for flexural members with a single span of no more than 10 m. • Building authorities can issue permits for different systems of connectors, such as bars and bolts. The top section of ­specially developed fully threaded bolts are profiled to optimise their compound connection with concrete. • Screw connectors between prefabricated concrete elements and timber load-­ bearing structures enable extensive pre­ fabrication and dry construction. This also enables construction materials to be separated during disassembly and demolition. • Load-bearing adhesive bonding of timber and concrete components is currently still at the research stage.

B 2.58 Diagram, timber-concrete composite ceiling B 2.59 Types of timber-concrete composite con­ struction B 2.60 Structural function of a timber-concrete ­composite ceiling B 2.61 Assembly of prefabricated timber-concrete composite elements with cross-laminated ­timber tension zones B 2.62 Common types of shear-resistant joints in ­timber-concrete composite ceilings

notches and screws

flat steel lock connectors in saw-cut groove

vertical specialised screws

glued-in expanded metal elements

screw pairs arranged crosswise

prefabricated concrete element with inlaid pipe connectors for on-site screw connections with beams B 2.62

72

A Comparison of Timber ­Construction Elements

The figures B 2.63– B.2.66 compare the structural components described above (p. 51–71) based on the following parameters. Load-bearing capacity As a rule, common frame construction walls are not suitable for buildings taller than three storeys, unless built according to a specific construction type (Figs. B 1.11 b and c, p. 48). Cross-laminated timber, laminated veneer lumber and, most of all, dowel lamin­ ated timber walls can bear very heavy ­vertical loads and are, therefore, suitable for erecting tall buildings. In-plane stiffness The in-plane stiffness of frame construction and dowel laminated timber walls is minor compared to that of relatively homogeneous cross-laminated timber and laminated veneer lumber walls, the performance of which is sufficient to stiffen taller buildings. Additives Adhesives comprise the majority of addi-

tives for wood-based materials, construction components and elements. Using ­hardwood dowels as connectors enables the creation of adhesive-free dowel laminated ­timber and cross-laminated timber walls, as well as dowel laminated timber ceilings. The same applies to frame construction walls and beam ceilings, where the stiffening function is achieved by diag­ onally arranged boards, instead of woodbased material panels (three-ply panels, OSB, etc.). Spans Beam ceilings are seldom used for multistorey timber buildings and only for relatively short spans. In most applications, vibration and flexural behaviour are de­­ cisive for dimensioning construction components, rather than load-bearing capacity. Therefore, cross-laminated timber and dowel laminated timber ceilings are suitable for average spans, while timber-concrete composite ceilings and box ceilings are appropriate for long spans.

Wall elements

crosslaminated timber

frame construction with con­ tinuous studs

frame construction

glued laminated stacked boards

frame construction

low

dowelled crosslaminated timber dowel laminated timber frame construction with diagonal sheathing

0 %

high

load-bearing capacity

low

dowel laminated timber

laminated ­veneer stacked lumber boards

In-plane stiffness

glued laminated cross-­ laminated stacked timber boards

frame construction with OSB sheathing

Additives (glue percentage)

cross-­ laminated timber

laminated veneer lumber

high

laminated veneer lumber

3 % B 2.63

73

A C O M P A R I S O N O F T I M B E R C O N S T R U C TION ELEM ENTS

Ceiling elements unidirectional cross-laminated timber

beam ceiling

Span

5m

box ceiling

beam ceiling

0 %

laminated ­ veneer ­ softwood

Required material

stacked boards

beam ceiling

laminated veneer softwood

crosslaminated timber

0.22 m3/m2

crosslaminated timber

laminated veneer beech

CO2 storage capacity

low

dowel laminated ­timber, beam ceiling with board sheathing

10 m

laminated ­veneer beech, stacked boards

0.08 m3/m2

box ceiling

box ceiling, ­timber-concrete composite ceiling

bidirectional cross-­ laminated timber, stacked boards

timber-concrete composite ceiling, bidirectional crosslaminated timber, timberconcrete composite ceilingdowel laminated timber

beam ceiling with OSB sheathing, glued stacked boards, cross-­ laminated timber

high

laminated veneer ­lumber

box ceiling with laminated veneer lumber sheathing

Additives (percentage of glue)

3 % B 2.64

74

Support

a

a timber-concrete composite ­ceiling with laminated veneer lumber (LVL) b timber-concrete composite ­ceiling with cross-laminated ­timber c timber-concrete composite ­ceiling with beam ceiling d timber-concrete composite and dowel laminated timber ceiling

e laminated veneer lumber ceiling with crosswise layers f cross-laminated timber ceiling g box ceiling h dowel laminated timber ceiling i beam ceiling j timber-concrete composite ­ceiling with LVL and crosswise layers k LVL with crosswise layers

b

CO2 storage Solid timber ceilings comprise greater CO2 storage capacity than lightweight ceiling structures, due to the greater amount of material used for their construction. Using hardwood increases this effect, as demonstrated by beech laminated veneer lumber.

c

d e

e

f

f

g

g

e

h

h

f

i

i

g

Linear supports Linear supports are an ideal solution for all ceiling elements. Timber-concrete composite slabs are mostly used as single-span beams, because the bending moments reverse near the supports of cantilevers and con­ tinuous beams. As a result, concrete layers in these areas are subject to tension and timber structures to compression. In contrast, a cantilever or continuous beam effect transverse to a linear support can be easily achieved with all timber ceiling elements. However, this is occasionally avoided in multi-storey timber buildings, in order to create acoustic separations or enable uninterrupted load transfer from the storeys above. Cantilevers in two directions (primary and secondary load-bearing directions) are only possible with cross-laminated timber or laminated veneer lumber plates or box ceilings that feature corresponding cross beams.

linear support cantilever in two directions

linear support cantilever in span direction

linear support single span

Point supports Only elements that span in two directions, such as those made of cross-laminated timber, laminated veneer lumber with crosswise layers, box ceiling elements and timberconcrete composite slabs combined with cross-laminated timber or laminated veneer lumber are suitable for point supports. Similar to a linear support, cantilevers and continuous beam effects in the primary and secondary load-bearing directions can be achieved with cross-laminated timber, laminated veneer lumber and box ceilings of corres­ ponding design, yet only to a very limited extent with timber-concrete composite slabs.

j b

k

k

k

f

f

f

g

g

g

point support single span

Required material In terms of required material, lightweight structures such as box and beam ceilings are far more efficient than solid timber ­ceilings of the same span made of dowel laminated timber elements, cross-laminated timber or laminated veneer lumber. Therefore, lightweight structures offer a greater substitution potential.

point support cantilever in span direction

point support cantilever in two directions

B 2.65

A comparison of various slab structures Figure B 2.66 compares the structural height of different ceiling elements for a ­residential building with spans of 4.50 and 6 m. The ceiling types are comparable in terms of their fire protection and soundproofing characteristics.

Balkendecke

A C O M P A R I S O N O F T I M B E R C O N S T R U C TION ELEM ENTS

75

Balkendecke Balkendecke Ceiling construction

Span [m]

Structural thickness [mm] (beam cross sections)

Overall ceiling thickness [mm]

20 mm flooring Balkendecke 80 mm cement or anhydrite screed, separation layer 30 mm mineral fibre impact soundproofing Balkendecke 25 mm wood-based material sheathing 120 /240 – 320 mm timber beams, solid construction timber or glued laminated timber GL24 h/c (spacing 625 mm off centre) Kastendecke 100 mm inlaid mineral wool insulation 20 mm rubber mount suspension 30 mm battens Kastendecke 2≈ 18 mmKastendecke fire-retardant gypsum board /gypsum fibreboard

4

240 (120/240)

481

5

280 (140/280)

521

6

320 (120/320)

561

20 mm flooring Kastendecke 50 mm cement or anhydrite screed, separation layer 30 mm mineral fibre impact soundproofing Kastendecke 27 mm three-ply panel 80/140 – 220 mm glued laminated timber ribs, GL 28 h/cKastendecke (spacing 625 mm off-centre) 140 –160 mm inlaid mineral wool insulation 27 mmBrettstapeldecke three-ply panel 20 mm elastomeric bearing for fire-resistant cladding 2≈ 18 mm fire-retardant gypsum board /gypsum fibreboard Brettstapeldecke Brettstapeldecke

4

194 (80/140, 27, 27)

350

5

234 (80/180, 27, 27)

390

6

274 (80/220, 27, 27)

430

20 mm flooring 50 mm cement or anhydrite screed, separation layer 30 mmBrettstapeldecke mineral fibre impact soundproofing 80 mm crushed stone infill 120 – 200 mm dowel laminated timber, C 24 Brettstapeldecke

4

120

300

5

160

340

6

180

380

4

140

320

5

180

360

6

220

400

4

220

360

5

240

380

6

260

400

4

200

340

5

200

340

6

260

400

Composition Balkendecke

Beam ceiling

Box ceiling

Dowel laminated timber ceiling

Brettstapeldecke

Brettsperrholzdecke Cross-laminated timber ceiling

20 mm flooring 50 mm cement or anhydrite screed, separation layer Brettsperrholzdecke 30 mm mineral fibre impact soundproofing Brettsperrholzdecke 80 mm crushed stone infill 140 – 220 mm cross-laminated timber, C 24 Brettsperrholzdecke Brettsperrholzdecke

Composite timber-concrete ceiling

Brettsperrholzdecke 20 mm flooring Holz-Beton-Verbund 50 mm cement or anhydrite screed, separation layer 30 mm mineral fibre impact soundproofing 40 mm additional mineral fibre insulation Holz-Beton-Verbund 100 mm concrete top layer Holz-Beton-Verbund 120 –160 mm dowel laminated timber, C 24 Holz-Beton-Verbund Holz-Beton-Verbund

Reinforced concrete ceiling

20 mm flooring Holz-Beton-Verbund 50 mm cement or anhydrite screed, separation layer Stahlbeton 30 mm mineral fibre impact soundproofing 40 mm additional mineral fibre insulation 200 – 260Stahlbeton mm reinforced concrete Stahlbeton

Stahlbeton B 2.66

Stahlbeton Stahlbeton Function: ceiling slabs in residential construction 2 qk = 1.5 kN/m with lateral distribution or qk = 2.0 without lateral distribution Soundproofing: as per DIN 4109-1 and -2: R'w ≥ 54 dB, L'n, w ≤ 50 dB To take flanking transmission into account Rw ∫ R'w and Ln, w ∫ L'n, w are subject to a correction value of -3 dB or +5 dB Fire safety class: F 60, F 60 – K260 for beam and box ceilings

B 2.63  Comparison, wall elements B 2.64  Comparison, ceiling elements B 2.65  Comparison, support types B 2.66 Comparison, ceiling composition structural height

77

Part C  Construction

1

Protective Functions Fire Protection Moisture Protection Soundproofing and Acoustic Requirements Timber Preservation Thermal Insulation in Winter and Summer

78 78 85 88 89 92

2

Thermal Insulation in Summer – A Question of Planning Physics of Summertime Insulation Effective Thermal Mass Solar Gains and Shading Heat Discharge – Natural Cooling Conclusion 

94 94 95 96 97 97

3 The Layer Structure of Building Envelopes Building Envelope Requirements Functions of Construction Component Layers Technical Soundproofing Aspects Technical Fire Safety Aspects  Further Criteria for Choosing Exterior Wall Structures Further Criteria for Layer Composition of Horizontal and Sloped Construction Components Polyfunctional Layers Principles of Joinery Building Simpler 

110 113 113 118

4

126 127 133 133

The Layer Structure of Interior Construction Components The Layer Structure of Timber Ceilings The Layer Structure of Interior Walls Principles of Joining Interior Construction Components

5 Building Services Technology – Particularities of Timber Construction Planning Prospects of Prefabrication The Influence of Penetrations and Cavities General Principles for the Integration of Building Services Technology Measures for Wet and Humid Rooms Outlook: Thermal Activation of Solid Timber Construction Components 

Residential building, Bergen (NO) 2015, ARTEC

98 98 98 106 107 108

136 136 136 136 137 141 143

78

Protective Functions Stefan Winter

C 1.1

Similar to other building types, the structure of a timber building must provide load-­ bearing functions while also performing other functions, including fire, moisture and noise protection, wood preservation and ensuring thermal insulation in winter and summer without undermining specified performance levels. The relevant protection goals and their implementation in timber construction are described below.

Fire Protection Preventive fire safety plays an essential role in the design, planning, detailing, ­construction, quality assurance and oper­ ation of multi-storey buildings of all kinds. This is valid all over the world, whatever the predominant construction material may be. Unlike reinforced concrete, masonry or steel, wood is a combustible construction material. Thus, it can add to a building fire load in the case of a fire. The com­ bustibility of the material and the awareness of past devastating fires in medieval cities and during the major wars have given rise to continuing mistrust of the fire safety of modern timber buildings. This mistrust is not based in fact, as the following investigation of various typical issues shows.

C 1.1  C 1.2  C 1.3  C 1.4 

Aged shingle facade Building classes as defined in the MBO (2019) Building material classes Fire resistance classes

Fire risk in timber buildings The risk of a fire developing in a building is not inherently linked to its construction material. Studies carried out in the 1990s showed a direct correlation between the risk of a fire developing in residential buildings and their inhabitants, yet not due to specific construction methods [1]. The same is likely true of office buildings. The risk of a fire starting in a building results not from the construction material of a building, but from technical installations and, more significantly, from human behaviour and error. A saucepan of milk forgotten on a stove or faulty electrical installation, as

well as forgotten Christmas tree candles and people falling asleep while smoking are typically the main causes of fire risk. A timber structure as such does not pose an inherent fire risk. Fire safety performance requirements Fire safety performance requirements are the same the world over in terms of: • preventing fire from developing and fire and smoke from spreading, • enabling the rescue of people and animals, and • facilitating effective rescue and fire extinguishing measures. These performance requirements must be met by all buildings equally. By doing so, a range of parameters must be considered, such as: • the size of functional units that are compartmentalised for fire safety purposes • existing fire load(s) • escape routes and emergency exits, depending on function • the building context, including accessibility, setbacks, distance to neighbouring buildings etc. • facade design • equipment designed to prevent fire, such as alarm or sprinkler systems These performance requirements can be specified further for certain areas. Facades, for example, are supposed to prevent fire and smoke from spreading within them. Large burning facade elements must not drop during a fire. Based on the requirements outlined above, most countries continuously update prescriptive (i.e. detailed and mandatory) fire prevention rules for buildings and technical equipment standards and describe them in related building regulations. Examples include the fire resistance requirements imposed on load-bearing and stiffening structural components, depending on

79

P R O T E C TIVE FUNCTIONS

Building class

Number of storeys, approx.

Topmost floor elevation above specific average ground level

>8

> 22 m

High-rise

Description

High-rise building

8 5

7

≤ 22 m

6 5

4

Medium-height building

≤ 13 m

4 3

1 to 3

2

≤7m

Low-rise building

1 C 1.2

Building authority designation

the height and dimensions of a building, because these greatly influence the ability of firefighters to extinguish a fire and ­rescue people. Their stipulations form the basis for the fire resistance requirements imposed on buildings in specific building classes, which in Germany are stipulated in the current valid German Model Building Code (Musterbauordnung – MBO) [2] (Fig. C 1.2). The MBO permits detached houses (class 1 buildings) to be built without a specific fire resistance duration, because all building materials, as a minimum requirement, must be of “normal combustibility”. Class 2 buildings (semi-detached houses and duplexes) must fulfil a fire resistance requirement of 30 minutes. A fire resistance of 30 minutes is sufficient for class 3 buildings (low multi-storey buildings regardless of use), because it is assumed that a limited building height also means that users can be rescued promptly. Limiting the top floor elevation to 7 metres above the average ground level is based on the ladders available to firefighters, which can be easily used for buildings up to a parapet height of around 8 metres. For taller buildings, such ladders are no longer an adequate second emergency escape route. Here, firefighters must resort to turntable ladders or elevating rescue platforms if there is no fixed second emergency escape route, e.g. an access balcony with two staircases. Without alternative built emergency escape routes, only a small number of people will be able to be rescued in an appropriate amount of time and it will take firefighters much longer to rescue them. Thus, class 4 (topmost floor elevation ≤ 13 metres) and class 5 (topmost floor elevation ≤ 22 metres) buildings require longer fire resistance durations of 60 and 90 minutes. A further reason is that fires are principally harder to extinguish the taller a building is. Additional performance requirements are imposed on even taller

Additional requirements No smoke

No burning droplets

European class as per EN 13 501 Construction products except pipe thermal insulation and flooring

Linear pipe thermal insulation

Flooring

‡

‡

A 1

A 1L

A 1fl

‡

‡

A 2-s1,d0

A 2L-s1,d0

A 2fl-s1,d0

‡

‡

B-s1,d0 C-s1,d0

BL-s1,d0 CL-s1,d0

A 2-s2,d0 A 2-s3,d0 B-s2,d0 B-s3,d0 C-s2,d0 C-s3,d0

A 2L-s2,d0 A 2L-s3,d0 BL-s2,d0 BL-s3,d0 CL-s2,d0 CL-s3,d0

A 2-s1,d1 A 2-s1,d2 B-s1,d1 B-s1,d2 C-s1,d1 C-s1,d2

A 2L-s1,d1 A 2L-s1,d2 BL-s1,d1 BL-s1,d2 CL-s1,d1 CL-s1,d2

A 2-s3,d2 B-s3,d2 C-s3,d2

A 2L-s3,d2 BL-s3,d2 CL-s3,d2

D-s1,d0 D-s2,d0 D-s3,d0 E

DL-s1,d0 DL-s2,d0 DL-s3,d0 EL

normally combustible building materials

D-s1,d1 D-s2,d1 D-s3,d1 D-s1,d2 D-s2,d2 D-s3,d2 E

DL-s1,d1 DL-s2,d1 DL-s3,d1 DL-s1,d2 DL-s2,d2 DL-s3,d2 EL

A 2fl-s2 Bfl-s2 Cfl-s2 Dfl-s1 Dfl-s2 Efl

easily combustible building materials

F

FL

Ffl

non-combustible building materials

‡

low combustibility building materials ‡

‡

Bfl-s1 Cfl-s1

‡ = applicable

s (smoke); = smoke development; d (droplets) = burning droplets / falling; fl (flooring) = flooring materials L (linear pipe thermal insulation products) Building authority designation

Load-bearing structural elements

C 1.3

Non-loadbearing interior walls

Non-loadbearing exterior walls

Raised floors

Separate hung ceilings

REI 30

EI 30 (a ↔ b)

Non-partition wall 1)

Partition wall 1)

fire-retardant

R 30

REI 30

EI 30

E 30 (i → o) and E 30-ef (i → o)

highly fire-retardant

R 60

REI 60

EI 60

E 60 (i → o) and E 60-ef (i → o)

EI 60 (a ↔ b)

fire-resistant

R 90

REI 90

EI 90

E 90 (i → o) and E 90-ef (i → o)

EI 90 (a ↔ b)

fire resistance period of 120 min.

R 120

REI 120

–

–

_

firewall

–

REI 90-M

EI 90-M

–

–

 For steel construction components coated with reactive fire protection systems, the specification “IncSlow” as per DIN EN 13 501-2 is additionally required. i → o (in → out) = from interior to exterior; a ↔ b (above ↔ below) = top ↔ down C 1.4

1)

80

Fire behaviour of combustible construction components or structures

Fire behaviour of non-combustible construction components or structures

Building authority designation adjoining building materials taken into account

fire-retardant

DIN EN 13 501-1  fire behaviour classification of construction products and types – fire behaviour of construction products

REI 30

fire outbreak

fire-resistant

DIN EN 13 501-2  fire behaviour classification of construction ­products and types – fire resistance tests

temperature

Test standard

      

fire growth

REI 90

full-scale fire

cooling

Diagram, fire development flashover

ignition

30 min

90 min time

Risks

combustibility

spread of flames on surfaces

building materials: heat build-up, smoke and toxicity construction components: load-bearing capacity (R), partition (E; flame passage, residual strength) and heat transition (I) C 1.5

buildings (high-rise buildings with a topmost floor elevation of more than 22 metres above ground): firefighters may be unable to effectively extinguish fires above these heights. Such buildings should be able to withstand a complete burnout without their load-bearing structure collapsing. The related special building regulation prescribes a fire resistance of at least 90 minutes and the use of non-combustible construction materials for high-rise buildings. Their structural components are required to maintain their long-term load-bearing functions, even in the post-fire cooling phase [3]. The 90-minute period is calculated based on an average fire load in ­residential and office buildings of 600 to 750 MJ/m2, which a fully ventilated fire has typically consumed in 90 minutes, i.e. the temperature in the impacted space falls relatively quickly to below 200 °C in the cooling phase (Fig. C 1.5). Combustibility and fire resistance It is imperative to clearly distinguish between the combustibility of building materials (defined in building material classes) and the fire resistance of construction components (defined by the fire resistance classes of construction components). The combustibility of building materials essentially influences the spread of fire

immediately after ignition and as it develops. DIN 4102 divides building materials into non-combustible (A1 and A 2) and combustible materials classes (B 1 to B 3). DIN EN 13 501 specifies seven “Euroclasses” (A1, A 2, B, C, D, E, F) and classes s1, s2 and s3 for smoke emission (s = smoke), for burning droplets (d = droplets) classes d 0, d1 and d 2 and special classes for floorings (fl = floorings) (Fig. C 1.3, p. 79). The fire resistance of a construction component describes its capacity to remain stable (criterion R) and the cap­ acity of a construction component that encloses spaces to prevent the transmission of smoke and fumes (criterion E), as well as heat (criterion I) for the required fire-resistance duration. Construction ­components are classified in fire resis­ tance classes, which use the building authority terms “fire-retardant”, “highly ­fire-retardant” and “fire-resistant”, according to duration of fire resistance (specified in 30-minute intervals) (Fig. C 1.4, p. 79). ­Load-bearing structural elements may also enclose spaces, e.g. party walls between ­residential units (REI), while individual ­columns only need to be designed to retain their structural integrity (R). Figure C 1.5 shows the principles of fire development and allocation of the requirements outlined above.

The combustibility of a building material and the fire resistance of a construction component are not directly related. Some examples that illustrate this fact include: • A steel column (class A building material – non-combustible) that is neither protected by fire protection cladding nor fire protection coating typically loses its load-bearing capacity after 30 minutes. In contrast, a glued laminated timber ­column will burn on its exterior, but can retain its structural integrity for more than 90 minutes in a fire, without any additional protective cladding or coating. • A pane of glass is not combustible, but heat passes through it almost immediately. While a 30-mm thick softwood fibre panel can burn, it can significantly obstruct heat transmission, preventing an increase in temperature on the side not exposed to the fire for up to 15 minutes. Combustibility plays a major role in the ­ignition and growth phases of a fire. Thus, prescriptive building regulations feature requirements for non-combustibility of surfaces in emergency escape routes (e.g. in staircases and corridors) or the provision to use low-combustibility building ­materials as facade cladding, in order to meet the general performance requirements described above. New research [4]

81

P R O T E C TIVE FUNCTIONS

C 1.6

confirms the influence of exposed timber construction components on fire development. In particular in the case of multi-­ storey residential buildings, restrictions are necessary and are formulated within policy, for instance the new model timber construction directive (Muster-Holzbaurichtlinie, MHolzBauRL) [5]. Timber construction performance ­characteristics A timber building must ensure the same ­levels of safety as other construction types. The fire behaviour of timber and timber structures must be realistically assessed, regardless of combustibility, to utilise the positive properties of the material in the event of fire. The basic fire safety perform­ ance requirements (see p. 78f.) for all structures must be equally met by timber structures. Planners, clients and others involved in the construction of timber buildings often want to create exposed wood surfaces (at least in some areas). Thus, the combustibility of the material in particular must be taken into account. The behaviour of timber construction elements in a fire is greatly influenced by the interrelation between surface to cross section and the densities of various species of wood. The greater the density of wood, the lower its burnout rate, i.e. the burnout in mm/min when impacted by fire (Fig. C 1.7). Burning timber contributes to the indoor fire load. On the side exposed to the fire, a charred layer forms that also protects the interior area it borders. The nominal char rate ßn takes increased charring of corners into account (Fig. C 1.6). Also, the thermal conductivity coefficient of wood is relatively low (≤ 0.13 – 0.17 W/mK). Thus, the inner, unburnt area remains cool and maintains load-bearing functions. Increasing the thickness of components beyond the structurally required dimensions can provide effective timber fire protection cladding. Another advantage of solid timber elements is that

Nominal One-dimensional burn rate ßn burn rate ß0 [mm/min] [mm/min]

Material

Softwood and beech glued laminated timber with a characteristic bulk density of ≥ 290 kg/m3 solid timber with a characteristic bulk density of ≥ 290 kg/m3

0.65 0.65

0.7 0.8

Hardwood solid wood or glued laminated timber with a characteristic bulk density of ≥ 290 kg/m3 solid wood or glued laminated timber with a characteristic bulk density of ≥ 450 kg/m3

0.65 0.50

0.7 0.55

Laminated veneer lumber with a characteristic bulk density of ≥ 480 kg/m3

0.65

0.7

Panels wood panelling plywood wood-based panels, except plywood

0.9 1) 1.0 1) 0.9 1)

1) 

Figures apply to characteristic bulk density of 450 kg/m3 and material thickness of 20 mm. C 1.7

fire can’t penetrate into cavities where it could spread unchecked and become almost inaccessible to firefighters. Burning solid timber elements are easy to extinguish, no subsequent ignition occurs. This makes it possible, and in many cases has been achieved, to install solid and visible timber construction elements with a fire resistance duration of 90 minutes (REI 90) in buildings below high-rise height and use them as an alternative to firewalls in staircases (REI 90-M; see “Administration Building in Aalen”, p. 237ff.). Planning for fire protection in the case of timber construction requires particular ­consideration of the following criteria: • The necessary corridors and staircases must be kept free of fire loads by means of non-combustible cladding or panelling. • Fire protection cladding for a defined protection period (encapsulation criterion, e.g. K 230 or K 260) limits the temperature on the side not exposed to fire within the period specified to T ≤ 300 °C and, thus, prevents the timber from burning and increasing the fire load. Encapsulation cladding in the case of frame construction with insulated or insulation-free cavities must also prevent fire from penetrating into a structure.

• The share of exposed timber surfaces in individual rooms should be limited to min­ imise the increase of the fire load through timber construction elements. The rule of thumb to limit non-mobile fire loads is: in the case of a ceiling comprised of visibly exposed solid timber construction components, walls must not be clad in combust­ ible materials. Alternatively, up to 25 % of wall surfaces can consist of exposed solid timber, as long as the ceiling underside is not clad in combustible materials. Add­i­tional and individual non-clad columns or downstand beams are permissible. ­The surface exposed to fire must not comprise more than 40 % of the overall wall surface, or in the case of an exposed timber ceiling, the flammable surface must not be increased by more than an equiv­ alent of 25 % of the ceiling surface. For ­typical screed construction using nonC 1.5 Diagram of fire development showing the influence of building materials and construction ­components C 1.6 Cross section of a solid timber beam exposed to fire. In contrast to the one-dimensional burn rate ß0, which measures the burn-off depth in the centre of a timber cross section, the nominal burn rate ßn takes the rounding of corners in the burning of cross sections and timber cracks into account. C 1.7 Combustion behaviour of various timber building materials as per DIN EN 1995-1-2

82

combustible screed comprised of cement or gypsum, flooring is not included in related calculations, since it is part of mobile fire loads. • Individual exposed and solid timber construction components (e.g. a freestanding glued laminated timber column) contribute to the development of a fire only to a very limited degree, as long as other surfaces are non-combustible. • Shafts, ducts and fire shutters for building services penetrations should be comprehensively planned. In timber construction, it has proven effective to position fire shutters within ducts in each ceiling and to provide separate shafts for each fire compartment (see “Shaft type B”, p. 140f.). This allows for free installation of building services on each floor. The ceiling areas penetrated by shafts can also be concreted and fire shutter systems typically approved for building services can be used. Special fire shutter solutions for timber structures are becoming increas-

ingly available. When applying them, the related building code certifications of usability, general building code test certificates (allgemeines bauaufsichtliches Prüfzeugnis, abP) or general design certifications (allgemeine Bauartgenehmigung aBG) need to be considered. Further, transfer rules for fire shutters for solid construction components have recently been published and have been acknowledged as equivalent solutions by building authorities [6]. • In the case of a normally combustible timber facade, facades of class 4 buildings and taller must be especially carefully planned and constructed. Related rules are included, for instance, in the new model timber construction directive (MHolzBauRL) [7] and other sources [8]. • For structures with heights between lowrise (topmost floor elevation ≤ 7 m above the average ground elevation) and building class 4 it is worth verifying in-depth whether low-rise building height regula-

tions can be complied with. In this case, all load-bearing and space-enclosing standard building components can be built to be fire-retardant, i.e. fire resistance class REI 30. Visible surfaces and timber facades are permitted by building regulations. As with restrictions on the size of functional units, the 7-m limit must be adhered to. Even slightly exceeding this height will result in classification according to the next highest building class. • Visibly exposed box structures and other elements containing cavities should only be installed in low-rise buildings, because there is a risk that fire will spread around them uncontrollably. Fire-resistant cladding must be installed in taller buildings. • If planar exposed timber construction components (ceilings, walls) are installed in buildings of medium height (topmost floor elevation > 7 m), using composite timber concrete floor slabs should be considered. It allows creating a “continuous non-combustible layer” on these firewall F 90-A+M fire-resistant F 90-A F 90-B+K260 F 90-B+K260 (from above) with exposed timber ceiling fire-retardant F 30-B; for non-load-bearing exterior walls W 30-B fire-retardant F 30-A composite thermal insulation system (building material class A) composite thermal insulation system (building material class B 1) back ventilated timber exterior wall cladding (building material class B 2) door dT

lift shaft access primary emergency escape route secondary emergency escape route provided by turntable ladder access position

necessary staircase

secondary emergency escape route provided by portable ladder access position

necessary corridor

smoke alarm

door RS door T30

C 1.8

P R O T E C TIVE FUNCTIONS

83

C 1.9

floors that will limit the spread of fire and smoke as required by certain building regulations. • Particularly interesting questions arise when, as part of urban consolidation, one or two-storey rooftop additions are built in timber, resulting in a change in building class. This is the case when, for instance, a structure in building class 4 is categorised as building class 5 due to such measures. According to the current consensus, the new structure must be classified according to current building codes. The existing structure can generally be classified as an existing ­variance. As a result, the fire resistance of related construction components does not have to be increased. However, the rules for interior finishes of staircases (e.g. apartment doors with gaskets and automatic closers) need to be observed by retrofitting. In exchange, easements for the construction of exterior staircase walls are possible, in order to enable building them in timber as well. For this purpose, the building authority of the City of Frankfurt has provided a productive manual [9].

walls must be built. Making smoke compartments as small as possible, e.g. by partitioning corridors with smoke control doors, is even more important. The smoke caused by fire poses a much greater risk than the direct exposure to fire. In office and school buildings, for example, two separate smoke protection compartments should ideally be permanently accessible as emergency exit routes. In most cases, the provision of related exit routes allows for a limitation of the required smoke protection period to 30 minutes. • Stairways must be kept free of fire loads. They serve not only as emergency exit routes for residents, but also as a basis for attack and retreat for firefighters. They must be built to ensure reliable fire protection. This is non-negotiable. • Sufficient provision of fire alarms (which have also become mandatory in residential units) and readily accessible fireextinguishing equipment. • Intensive inspections /quality assurance of all fire safety measures, especially proper

integration of shutters and other technical fire safety equipment. These should be installed as far as possible during early production phases of construction components, because industrial production processes guarantee fewer flaws and easier monitoring. All of these points are to be consolidated within fire safety concepts that contain an overall description of the technical fire safety concept and – if necessary – justify building regulation variances. Such variances are typically necessary in timber structures that qualify as high-rise buildings. C 1.8  Example of fire protection planning, staircase access via access balcony, eight-storey timber building H 8, Bad Aibling (DE) 2011, Schankula Architekten C 1.9  Advantage of a sprinkler system, exposed ­staircase construction, cross-laminated timber, Library at the Dock, Melbourne (AUS) 2014, Clare Design and Hayball C 1.10 Open timber construction and open floor plans with high fire loads due to sprinkler system, ­Library at the Dock, Melbourne

The following fire protection aspects apply to timber, as well as to all other types of construction: • Clear and unambiguous emergency exit routes. • A second fixed emergency exit route if possible, especially for spaces that may contain a large number of people (e.g. large conference rooms). For each inaccessible primary emergency exit route, only around twelve people can be rescued by firefighters using turntable ladders. • Clear configuration of fire and smoke compartments: this is unambiguously ­prescribed in building regulations, but usually costly to achieve, because firewalls, firewall-equivalent walls or partition C 1.10

84

C

B

A 1

2

3

4

5

C 1.11

Above this height, they must comply with the fire resistance class “fire-retardant” and comprise non-combustible building materials. Changes to many state building regulations and the model directive have made it possible, mostly under monitored circumstances, to build timber structures below the high-rise limit under consideration of the model timber construction directive (MHolzBauRL) [10]. Timber construction components must meet the requirement of “highly fire-retardant in place of installation” or “fireresistant in place of installation”. Deviations are only permitted for exceptional cases. Taking the points mentioned above into account, appropriate solutions can, however, usually be found, also in such cases. Compensation such as add­itional fire alarm equipment, stairways built as emergency exit stairs (with outdoor path of egress or as detached staircases; see fig. C 1.8, p. 82 and “Residential and Office Building in ­Berlin”, p. 194ff.), second fixed emergency exit routes, smaller smoke compartments and similar measures are usually sufficient in order to justify possibly required deviations. In the case of high-rise buildings, an additional sprinkler system is typ­ically required. Sprinkler systems Sprinkler systems in residential and office buildings are uncommon in Germanic countries, but very common in North America, Australia and the Nordic countries – in residential and office buildings below the highrise level. This is because, to date, there are no sprinkler systems adapted to these uses at lower expenditure (e.g. with water supplied from the drinking water network) than compared to a comprehensive sprinkler system (separate system with its own water reservoir), as is the case with “home fire sprinklers” in residential buildings in the USA and Canada. In Central Europe, unlike in North America and the Nordic countries, a sprinkler system is not perceived as a positive feature that increases safety, but

rather as an expensive investment. The risk of inadvertent activation is another issue. However, many years of experience in Scandinavia and other European countries have shown that this is not a problem at all. Nevertheless, sprinkler systems have not become established as technical equipment in Central Europe. As a result, their use does not automatically lead to a reduction of required fire resistance or fire protection cladding (and, thus, to lower investment costs for fire-resistant cladding). Housing developers and companies try to avoid maintenance costs for such systems, which – again – are not considered a problem in other countries. Fire protection coatings It is advisable to avoid fire protection coatings or impregnating timber with these kinds of substances. Their use on exteriors is questionable because no durable weatherproof products exist that result in a change of a building material class (from fire-retardant to highly fire-retardant). ­Coatings for ­timber in interiors aimed at changing the fire safety properties of wood are typically unnecessary – it is better to use solid, robust structures instead. The other disadvantage is that coatings impact subsequent recyc­ling. Their impact on indoor air must also be carefully tested. The same applies here as for structural timber protection (p. 89ff.): “structural measures are better than chem­ical measures”. Structural measures Structural fire protection measures include non-combustible layers built into solid timber construction components, such as those made of cross-laminated timber, which ­prevent the layers beneath them from combustion. Early solutions have already been tested and used in specific cases. The selfextinguishing behaviour of solid timber structures in particular requires further research [11].

1 optional existing structure 2 timber beam, e.g. Å-beam 3 composite wood or gypsum board 4 weather protection: cladding with ­ventilation, back ventilation or composite thermal insulation system 5 insulating material A facade: building material class as ­defined in LBO (B 1 or B 2) B facade element: EI matching non-loadbearing exterior wall (EI 30 / W 30) C load-bearing structure in new or existing building: REI compliant with building class (REI 30 – 90)

C 1.12

Structural measures for facades A non-combustible facade is unproblematic for a timber building, as long as a continuous, non-combustible layer is added to the structure behind it, e.g. 15-mm thick gypsum board. Figure C 1.11 shows the example of a ten-storey timber building in Melbourne with a sheet aluminium facade. Clients are often interested in visibly ex­­ posed timber facades for timber buildings below the high-rise limit. In such cases it must be ensured that a fire can’t spread autonomously beyond the primary ignition area and that no more than two storeys above the fire source are affected by a growing fire before firefighters arrive. This should be ensured prescriptively by using building materials of low combustibility as facade cladding. These requirements can also be met with normally combustible timber cladding by use of approved construction types (see “Administration Building in Aalen”, p. 237ff.). The essential structural fire prevention measure for facades is to interrupt facade ventilation or back ventilation between floors to prevent the chimney effect. This is reliable in terms of building physics, as a series of research projects has demonstrated, the results of which have been incorporated into the DIN 68 800 standards series. They indicate that ventilation (only one opening at the bottom, closed at the top) can adequately balance the moisture levels of a building (see “Moisture Pro­ tection”, p. 85ff. and DIN 68 800-2, para. 5.2.1.2). The fire protection behaviour of various facade cladding systems has been ­intensively researched in Germanic countries in the past ten years and a summary of the standards was published in 2014 [12]. The results verified an equivalent ­solution in terms of the “low combustibility” requirement. For facade elements, i.e. nonload-bearing exterior walls, particular ­attention must be paid to differences in fire

P R O T E C TIVE FUNCTIONS

prevention requirements (Fig. C 1.12). The element itself must be fire-retardant up to the high-rise level. Achieving this requirement is almost inherent to the system. Exterior wall cladding for low-rise buildings must be normally combustible. Any kind of timber cladding can be used here. For buildings of medium height and taller, exterior wall cladding must be of low combustibility. As previously described, timber cladding can be used only with a verification of equivalence to facade cladding of low combustibility. Exterior sheathing of the timber structure must then be built in a non-combustible manner, for example by use of 15-mm thick gypsum board. The requirements for facade elements used in renovations of existing buildings (see “Renovation of a Residential Building in Augsburg”, p. 228ff.), correspond to the requirements for non-load-bearing exterior walls, as long as the walls do not transfer roof loads. Verification of building code-compliant use of construction products and types In the context of fire protection, close attention must be paid to the verification of the building code-compliant use of construction products and types. The combustibility of construction products can be verified based on building product standards. For instance, construction grade timber is ­classified as normally combustible at a thickness of 22 mm or more and with a bulk ­density of 350 kg/m3 (DIN EN 14 081-1, para. 5.3). Building products not covered by standards are classified after testing according to DIN EN 13 501-1 and are issued a building authority verification of usability (in Germany, with a national technical approval or a national test certificate – abP). The fire resistance of load-bearing structural components and construction types can be verified either by calculations ­specified in DIN EN 1995-1-2 or by classi­

fications based on tests prescribed in DIN EN 13 501-1. In these cases as well, building authorities issue a verification of usability. Unfortunately, verification processes are not consistent in Europe and particular national rules must often be observed. To make these rules easier to deal with in practice, Holzforschung Austria has developed an online database system – dataholz.com, which has recently been expanded in scope by including further national partners within dataholz.eu [13]. By selecting a region (e.g. Germany, Austria, etc.) building coderelated usability certificates are stored for all construction types on file. Planners and builders can use related construction types without further verification, making planning and construction much easier. Conclusion As long as certain principal fire protection requirements are met, building with timber up to high-rise height is unproblematic in Europe. The relevant building code requirements are subject to continuous adaptation in many European countries. However, significant differences exist. In Switzerland and recently in many federal states in Austria and Germany, at least partial use of visibly exposed timber construction has become possible. In other countries it is permitted in buildings of medium height only with effective fire ­prevention cladding (Scandinavia and the United Kingdom) or with sprinkler systems (e.g. Finland). In order to create timber buildings with structures that are exposed to a major degree, or in the case of special building purposes (e.g. hospitals), permits are often required for deviations from valid fire protection regulations and demand justi­fication within a fire protection concept including compensations. Whether timber buildings will break through the highrise barrier in greater numbers will depend on the acceptance and improvement of sprink­ler systems, the further development

85

of cost-effective fire protection cladding and verification that timber load-bearing structures can withstand complete burnout ­without the intervention of firefighters. Individual pilot projects across the world have shown that this is generally possible (e.g. Mjøstårnet in Brumunddal in Norway by Voll Arkitekter).

Moisture Protection Wood is a natural material. Under related circumstances, it decomposes naturally. This forms the basis of the biological cycle in our forests. To initiate natural decompos­ ition processes, a higher moisture content than typical to timber in buildings is necessary (see “Timber Preservation”, p. 89ff.). As long as timber stays dry – according to DIN 68 800 with a moisture content um constantly at ≤ 20 % – no biological deg­ radation due to destructive fungi will occur. Dry timber used as a construction material can last for hundreds of years, as many ­historic buildings impressively demonstrate. The main task in building with timber is to protect the timber from persistent increases in moisture by means of appropriate moisture protection measures and to keep it dry in the long term. Brief increases in moisture levels, e.g. on timber surfaces in bathrooms, are not critical, as long as the surfaces can become dry again quickly. Potential moisture sources Sources of moisture in buildings and pos­ sible protective measures are described below. C 1.11 Cross-laminated timber building with an alu­ minium sheet facade, high-rise residential ­building Forté, Melbourne (AU) 2012, Andrew Nieland and Lend Lease Australia C 1.12 Technical fire prevention requirements and separation of non-load-bearing exterior walls from facade cladding, also for renovations of existing buildings

86

C 1.13

Material

Indoor climate

Outdoor climate

air temperature

20 °C

0 °C

relative humidity

50 %

80 %

saturated water ­vapour pressure

2,337 Pa

611 Pa

partial water vapour pressure

1,168 Pa

488 Pa

Diffusion exterior wall area 15 m2

M = 6.6 g/d

Convection groove: 3-mm wide, 1-m long pressure differential

M = 484 g/d convection

diffusion C 1.14

heat leak Wärmeleckage

outside

outside

inside

inside moisture leak Fechteleckage

C 1.15

differential pressure measurement door

Δp = 50 Pa ( 0.5 mbar )

. V = m3/h volume flow measurement

ventilator

.

n50 =

a

b

volume flow rate V building volume V

[1 /h ]

C 1.16

Condensation from diffusion Condensation can be caused by diffusion due to differences in partial water vapour pressure, typically in exterior construction components, although related amounts of moisture will be small. Moisture intrusion due to diffusion is usually unproblematic in standard timber buildings with interior vapour-retardant layers and exterior vapourpermeable layers, because it causes no or only very small amounts of condensate. The compliance of built structures with ­regulations is verified by means of the ­Glaser method prescribed in DIN 4108-3 or through numerical simulation processes specified in DIN EN 15 026. DIN 68 800-2, para. 5.2.4 must also be applied to verify condensation prevention. Condensation from convection Similar to diffusion, condensation can also be caused by convection, i.e. warm air flowing through exterior construction components from the inside outwards. If air has sufficient time to cool off, large quantities of condensate can form, more than a hundred times the amount of condensate caused by diffusion (Fig. C 1.14). Convection can be prevented by making structures sufficiently airtight, which also limits unwanted heat losses from leaks. A distinction is made here between pure “heat leaks” and “moisture leaks” (Fig. C 1.15). One example of a typical pure ­heat leak is a leaky joint between a window frame and the surrounding jambs and ­soffits. Quick airflow across short distances cools air below the dew point only outside of the structure. Thus, heat is lost, but the structure is not impacted by moisture. In the case of a moisture leak, the flow path through the structure is longer. Airflows cool off below the dew point while still inside the structure, resulting in large quantities of condensate. Airtightness is also an essential precondition for effectively operating ventilation systems with

87

P R O T E C TIVE FUNCTIONS

C 1.17

heat recovery. The airtightness of a building envelope is verified by means of a blower door test, i.e. a test of low and high pressure at a given pressure differential of 50 Pa (Fig. C 1.16). Properly constructed timber buildings can easily achieve air exchange rates of 0.2 ≤ n50 ≤ 0.6 and, thus, they usually comply with passive house standards without requiring further measures. Airflow only occurs between two openings with low flow resistance. Thus, structures should always have at least two flow-proof layers – a possibly undamaged airtight layer inside and a windproof layer outside (Fig. C 3.3, p. 99). The robustness of structures can be further improved beyond two layers of airflow security by installing blown-in insulation, because it completely fills the spaces to be insulated, making them highly flow-resistant. Cellulose blownin insulation in particular has proven effect­ ive, because it is highly flow-resistant (installation density approx. 55 kg/m3) and, if required, can provide buffering against any short-term moisture resulting from diffusion condensation. Moisture leaks Leaks in water supply and drain pipes, taps and valves, in leaky washing machines or dishwashers, in bathroom splash water areas and, in rare cases, malfunctioning sprinkler systems can introduce so much water into buildings that drops form and run or drip down surfaces. Timber buildings are more vulnerable to this kind of moisture than structures made entirely of concrete, for example, so they should always be doubly protected by at least two independent sealing layers. Various publications contain advice on constructing bathrooms in timber buildings [14]. Solutions for protecting structures from leaks are the topic of the section on “Measures for wet and humid rooms” (p. 141f.).

Moisture from driving rain The amount of moisture intrusion in a building due to driving rain grows with increasingly taller buildings and related wind loads (see “Particularities of Timber Construction”, p. 136f.). In tall buildings, rain can enter either horizontally or from below, due to turbulences. Thus, all joints and connections between construction components in the facade require a dedicated protection concept against driving rain. Again, at least two independent protective water-bearing layers must be installed. Particular attention should be given to the fact that – unlike ­render or rough timber surfaces – large quantities of water drops can form immediately on glass surfaces. The principle of providing two layers of ­protection from driving rain must be comprehensively applied to building facades. Facade systems of all kinds should also have at least two independent means of preventing moisture from permeating them. A distinction is made between backventilated curtain wall facade systems with upper and lower ventilation openings and ventilated systems only with one lower ­ventilation opening (Fig. C 1.13). From a building physics perspective, ventilation is sufficient to discharge small amounts of moisture resulting from diffusion. Research shows that in typical back-ventilated systems, no actually measurable volume flow occurs, while ventilated systems demonstrate adequate air exchange rates, due to wind-induced pressure fluctuations. No measurable differences in humidity behind the facades of both types of structures were observed. Ventilated facades are usually easier to build and perform much better in terms of fire safety, because they prevent the chimney stack effect. Building a second protective water-bearing layer behind the facade cladding is de­­ cisive and, thus, providing a vertical drainage layer to reliably discharge any water

C 1.18

that intrudes behind the facade through small leaks (see “Timber Preservation”, p. 89ff.). Moisture intrusion during construction High moisture increases and wetting in ­timber structures during construction must be adamantly avoided, for several ­reasons. Increased moisture levels followed by rapid drying will cause timber construction components to crack. Surface moisture can cause mould and result in unwelcome water stains that will remain visible. Timber structural components that swell up with moisture can also produce significant ­nternal stress. In the case of kiln-dried spruce, for instance, brief moistening such as due to a rain shower during installation is unproblematic because the moisture will not penetrate deeply. However, longerterm moisture intrusion due to leakage during construction can, in the case of crosslaminated timber, for example, lead to an overall increase of moisture content through existing gaps. Some hardwood species (e.g. beech) and wood-based materials (e.g. particle board) are even more sensitive to temporary moistening from water drops. When solid timber construction components such as glued laminated timber or crosslaminated timber ceilings dry out during building use, this can lead to the settlement of ceilings, which can become visible particularly along baseboards or transitions to

C 1.13 Ventilated (left) and back-ventilated (right) ­facade /exterior wall cladding C 1.14 Water vapour transport due to diffusion and convection (amount of water released in a ­24-hour period) C 1.15 Heat and moisture leaks C 1 16 Blower door test a  Structure in practice b Principle C 1.17 Waterproof roof level in the construction of a four-storey building, H 4, Bad Aibling (DE) 2010, Schankula Architekten C 1.18 Enclosing the construction site of a seven-storey building, Växjö (SE) 2009, Arkitektbolaget

88

a

b

reinforced concrete staircases. Thus, continuous measures to protect such mater­ ials from moisture during timber construction must be planned and implemented. In Sweden, entire building sites are often completely enclosed for this reason, even including gantry cranes beneath the cover (Fig. C 1.18, p. 87). In Germany, for reasons of limited space among others, moisture protection is usually integrated into ­ceiling elements (Fig. C 1.17, p. 87), which protects the components installed up to that point once an installation unit is completed (typically daily). If this protective layer remains in the finished structure, it can then protect the completed building from leaks, water from a sprinkler system or fire-extinguishing measures, as long as there are appropriate means for water drainage. Self-adhesive diffusion-perme­ able building layers have proven particularly effective and are either installed in the workshop or directly prior to assembly on site. Laminating the entire surface prevents small defects from compromising the layers – in particular for multi-storey buildings, this method is urgently advised. The film ­layers can remain within the building and, when joints and transitions are adhesively sealed, provide durable leak protection. In addition, these layers comprise airtight levels between functional units that simul­ taneously contribute to soundproofing and protection against smoke and odours. Together with largely prefabricated facade construction components that are watertight from the outset, this leads to a building envelope that is watertight from top to bottom already during construction and ensures dry construction conditions (see “Prefabrication”, p. 162ff.). For kiln-dried timber building products, if structures get wet briefly, e.g. due to sudden weather changes, the very low level of moisture absorbed during brief wetting and the ­possibility of quick drying are considered unproblematic.

Even if timber structures are protected from direct wetting during construction, the moisture content of timber construction components can still increase in this phase. Wood is a hygroscopic material and its moisture content can change, depending on the prevailing temperature and relative humidity. The pouring and setting of screeds or other intrusions of water in a building can cause the timber moisture content to increase to 18 % and more. Timber can be prevented from absorbing moisture during construction by applying diffusionresistant coatings. Especially large-format glued laminated timber components such as downstand beams with long spans or solid columns should not be allowed to dry too quickly during the transition from construction to building operation (e.g. at the beginning of the heating period, during the heat-drying of screeds etc.). Otherwise cracks will form due to the strong difference between initial and equilibrium moisture contents in cross sections. Before the drying period begins, it is advisable to measure the moisture content of timber in solid cross sections and slow down drying by humidifying interior air if necessary. If planners are in doubt, they should obtain appropriate expertise.

C 1.19

Soundproofing and Acoustic Requirements Soundproofing and acoustic requirements involve both protection from noise and control of spatial acoustics. The EU Construction Products Regulation (Bauprodukten­ verordnung, BauPVO) states that the general goal of soundproofing is to keep noise to a level that will “not threaten (people’s) health and will allow them to sleep, rest and work in satisfactory conditions” [15]. These requirements, with which timber structures must also comply, are oriented on a basic noise level of 25 dB(A). This serves to

ensure discretion for normal speech and protection from unacceptable nuisances. What is regarded as “satisfactory” is defined by the regulations of individual EU Member States as a minimum requirement and depends on various cultural and economic considerations. In Germany, DIN 4109 prescribes a weighted airborne sound reduction index of R'w ≥ 54 dB and a weighted impact sound level of L'n, w ≤ 50 dB for normal soundproofing between functional units. Stricter limit values for increased soundproofing can be agreed on in the private realm. The airborne sound reduction index for exterior construction components is set at R'w = 30 – 50 dB and is based on expected relevant outdoor noise levels. The prime symbol in the formula indicates that so-called “byways” are taken into account, distinguished from laboratory values. They are common in typical structures, because sound is transmitted not only by construction components, but also the connections between them. The weighted airborne sound reduction index means that calculations of these f­igures are based on people’s frequency-dependent hearing ability. In Europe and certain Member States, the weighting of impact sound insulation is expanded to include deep frequencies (droning). This refers to the 50 – 80 Hz frequency range (so-called Ctr value – an adapted range value). In Germany, this is not a requirement and has not yet been included in standards. Four different areas are crucial to any examination of soundproofing characteristics: ­airborne sound insulation, structure-borne sound insulation, impact sound insulation and spatial acoustics: • Airborne sound insulation is specified by the airborne sound reduction index R'w. Because this is a so-called insulation measurement, the greater the numerical value, the better the soundproofing characteristics are.

P R O T E C TIVE FUNCTIONS

89

C 1.20

• Structure-borne sound insulation is only taken into account for impact sound insulation. Knocking on a wall or drilling a hole are not regarded as constant use typical to a building. Soundproofing requirements basically assume that there is no absolute soundproofing and that a certain level of civility guides everyday life. • Impact sound insulation requirements are defined by the weighted standard impact sound level. This is a level measurement, so the lower the figure, the better the sound insulating properties of a ceiling. In a laboratory or during a building test, ceilings are struck with a standard hammer mill and the noise level in the space below is measured accordingly. The lower the noise level in the space below the active hammer mill (impact sound stimulation), the quieter it is – i.e. the better the soundproofing. • Spatial acoustics refers to the acoustic characteristics of specific spaces. This is a comfort parameter that building regulations do not require, but it is very significant to users, e.g. in concert halls (Fig. C 1.20). Hard or concave surfaces of a space can cause inconvenient reverberation that can give users an impression of interrupting themselves while they speak. Special features of soundproofing in ­timber structures Various research projects have made major progress in soundproofing in timber structures in recent decades. As a result, a broad range of construction types for walls and, most of all, ceilings are available that have been tested in laboratories and in practice. Compared to masonry and steelreinforced concrete, they display equivalent soundproofing characteristics. A timber structure does not have the heavy dead weight in particular of a reinforced concrete building. Heavy mass is much harder to stimulate by sound waves (airborne sound) or impact stress (impact sound) due to its

inertia and, thus, poses advantages in terms of soundproofing. However, it usually has a much weaker damping effect. Once a heavy mass is stimulated, it transfers sound very well. An example of the effect of structureborne sound transfer: you can wake up everyone in an apartment building by drilling into a reinforced concrete wall, while drilling into a cross-laminated timber wall may not even be audible in the next room (Fig. C 1.19). To achieve the required soundproofing and desired acoustic properties in timber buildings, two main strategies should be pursued: • For airborne sound insulation, acoustic decoupling by means of separate or ­elastically mounted facing shells or wall cladding. • For impact sound insulation, the introduction of additional mass by use of solid screed or heavy fill. The latter is especially effective because it does not possess inherent rigidity that can have a negative impact in certain frequency ranges. That is also the reason why solid timber ceilings, despite their greater mass, are considered similar to beam ceilings in soundproofing terms. In choosing and planning ceilings in timber structures, particular consideration must be given to two boundary conditions: • An impact sound reduction level, ΔLn, w is specified for flooring, screed and hung ceilings. In the case of manufacturer specifications not particularly issued for timber buildings, it should be acknow­ ledged that improvements are normally measured by testing concrete slabs. The different frequency responses of timber and concrete slabs mean that improvement measurements undertaken for timber slabs will usually be much lower than those specified by the manufacturer. • To reliably achieve planned soundproofing values in construction, soundproofing structures must be airtight.

Construction components weighted to accommodate specific acoustic properties can be found at www.dataholz.eu [16]. Examples of construction component joinery and composition are featured in figures C 3.16 and C 3.17 (p. 108f.) and the chapter on “The layer structure of interior construction components” (p. 126ff.).

Timber Preservation Timber preservation almost thwarted timber construction entirely in the 1970s and 1980s, because timber preservation had become associated with chemical agents and the prevailing opinion was that the only way to make timber durable was by using toxins. In the past 25 years, however, a paradigm shift has occurred. With the return to historic timber construction traditions and successful strategies, structural timber preservation has now again claimed clear priority against all other measures. The main task of structural timber preservation is to keep a timber structure dry in the long term. If the moisture content of timber is below the fibre saturation point, which for construction timber is between 28 and 35 % of the average moisture content, biologic­ ­al decay due to destructive fungi cannot occur. Only when the moisture content of wood is above these levels in the long term, will cells comprising water become available to wood-destroying fungi to facilitate their growth.

C 1.19 Creating connections in timber buildings is ­easier and produces less noise than in other construction methods a Power-driving a wood screw into a timber frame wall construction with a battery-­ powered cordless screwdriver b Inserting dowels into a reinforced concrete wall with a hammer drill C 1.20 Timber construction elements provide good ­interior acoustics, concert hall, Lahti (FI) 2000, Hannu Tikka and Kimmo Lintula

90

C 1.21

Timber is defined as dry in this context when it has an average moisture content of ≤ 20 % (DIN 68 800-1, tab. 1). The gap between this figure and the fibre satur­ ation point can be interpreted as a safety margin. If it is not complied with, neither will preventive chemical timber preser­ vation help in the long term. If timber is ­constantly exposed to moisture, chem­ ical timber preservation will at best delay infestation by destructive fungi but not ­prevent it – nor is chemical timber preser­ vation required to repel wood-destroying insects. Structural measures can effec­ tively prevent such infestation. Most insects need flight paths without obstructions in order to lay eggs. This is not given in fully insulated structures that are covered on all sides. It has also been shown that kilndrying timber achieves two things: it kills any insect larvae in green wood and the changes to its constituents makes timber unattractive to the insects that can infest dried timber. DIN 68 800-1 defines kilndried wood as follows: “Wood that has been dried in an appropriate technical plant within a controlled process at a temperature of T ≥ 55 °C for at least 48 hours to a moisture content below u ≤ 20 %” [17]. In the past ten years comprehensive research on load-bearing structures for hall buildings has also shown that, despite timber being freely accessible along the edges of roof structures, kiln-dried wood indicated no signs of insect damage. The comprehensive omission of chemical timber protection is justified by keeping hazardous substances out of workplaces and housing units and by providing better recycling options for untreated wood. If, however, individual construction situ­ ations occur in which increased hazards from moisture or insects can be expected (e.g. thresholds too close to soil, terrace floors or garden and landscaping construction elements that are exposed to weathering or bordering soil), resistant wood species

such as larch or Douglas fir heartwood and even more resistant types of wood such as oak or European chestnut can be used as an alternative to chemical timber preservation agents. Thermally or chem­ ically modified timber can also be used in special cases. So-called “thermo wood” or thermally modified wood is treated under pressure and at specific temperatures to transform its constituents so that it no longer provides nutrients for wood-destroying fungi or insects (Fig. C 1.25 d). The treatment, however, causes wood to change colour (from dark brown to black) and reduces its strength and stiffness. A colour change of timber can also occur in the case of chemically altering wood through acetyl­ ation (Fig. C 1.25 b). For multi-storey timber buildings, the following timber preservation rules can be summarised: • Exclusive use of kiln-dried timber: if woodbased materials such as glued laminated or cross-laminated timber or others are used, the basic materials (lamellae, woodchips etc.) should be already kiln-dried and do not have to be specified separately. • Consistent application of structural timber preservation, e.g. with cladding on all sides, complete insulation of structural elements, proper distance from soil etc. – no possible formation of water deposits and no open hollow areas or joints etc. [18] • Avoiding the use of exterior construction components exposed to the weather: exceptions may be applicable for columns made of resistant wood species or so-called sacrificial boards that have been historically used and permit simple replacement (e.g. end grain roof beam covers) [19]. • Consistent application of all necessary measures to protect structures from ­moisture (see “Moisture Protection”, p. 85ff. and “Facades”, p. 90ff.) • Use of resistant species of wood or chem-

ically modified timber if required • Avoiding preventive chemical timber preservation measures Relevant standards / regulations The DIN 68 800 series of standards contains the current rules on preventive structural and chemical timber preservation in Germany. The relevant parts regarding the principles and methods of preventive structural timber preservation were newly published in 2012, 2019 and 2020. The related practice commentary on timber ­protection offers further valuable information [20]. This series of standards classifies timber construction components according to use classes GK 0 to 5. GK 0 comprises use conditions in which the application of timber preservation agents is not necessary. Part 2 of the standard essentially defines structural measures that permit the specific classification. The wall, roof and ceiling construction types presented in this book meet requirements related to durability and can be employed without preventive chemical ­timber preservation. The installation of ­kiln-dried spruce or pine wood will usually suffice. Facades The construction of facades plays a special role in protecting timber – and directly connected to it, the protection of structures from moisture. In principle, adhering to structural timber preservation methods supports the architectural design of facades. Sufficient moisture protection of facades and of the timber construction it conceals is achieved according to the following construction types: • Ventilated or back-ventilated curtain wall facades (with vertical battens) with dur­ able effective weather protection, e.g. closed board siding, fibre cement boards, suitable wood-based material boards or sheet metal.

P R O T E C TIVE FUNCTIONS

C 1.22

C 1.23

• Air cavity without ventilation (horizontal battens) with small-format cladding, e.g. slate, shingles, boards. In these two cases, battens will not require prevent­ ive chemical timber preservation, but should be kiln-dried. Construction of a second water-bearing layer with diffusionpermeable film layers or suitable sheathing behind battens is recommended. • Composite thermal insulation system with rigid foam, mineral fibre or softwood fibre panels and render. In Germany, building authority proof of usability (allgemeine bauaufsichtliche Zulassung, abZ) is required. • Masonry facing shell with an air cavity (d ≥ 40 mm) and additional insulation and water-bearing layers added to the wall.

If structural boundary conditions are complied with (drip edges, no accumulation of water etc.), completely untreated timber can be used (Fig. C 1.21). The vertical arrangement of siding boards has proven favourable, because water drainage parallel to timber fibres is an advantage. Horizontal configurations of siding boards have also proven effective, as long as they are appropriately constructed. The top layers of panel materials such as solid timber panels must always be installed vertically, otherwise inevitable cracks in the top layer in parallel with the timber fibres will contain drained water, which may result in the top layer being damaged or peeling off. Facade appearance and colour treatment Untreated timber board or panel facades are usually made of especially robust wood species such as larch or Douglas fir. Facades made of untreated timber, yet also thermo wood, will inevitably change colour over time. The lignin in timber photooxidises. It will look almost black and its chemical bond with the bordering timber structure breaks apart. This darkens the

Timber facades A client request for a timber facade, especially in multi-storey building construction, raises the issue of maintenance and any necessary or desired coloured paint or coating. Timber facades don’t require preventive chemical measures to protect them.

91

C 1.24

timber in areas where it is shielded from driving rain. In areas exposed to weathering, the lignin washes out, leaving only the grey to silvery shiny cellulose (Fig. C 1.22). Different areas of a facade are exposed to water to varying degrees, such as areas beneath windowsills. Thus, facades do not become grey evenly. To achieve an homogeneous appearance, the facade can be colour-treated in advance with a grey or grey-silver varnish. In areas exposed to weathering, it will be “used up” and replaced by natural greying. In areas not exposed to weathering, it will be retained, giving the facade a more even appearance. Colour treatment should be applied to fine sawn surfaces, never to planed surfaces (Figs. C 1.23 and C 1.24). Fine sawn surfaces with an industrial colour treatment and diffusion-permeable, ideally not film-forming coating that allows the small amounts of water that permeate due to inevitable defects to dry out again can maintain colouration for more than 20 years. Colour coating should, if possible, only be applied after facade elem­ents are cut to size, otherwise great care must be taken in treating ele-

a C 1.21 Ideal connection between windowsill and ­reveal. NINA-huset, Trondheim (NO) 2013, Pir II C 1.22 Influence of slight variations in exposure to water on the colour of timber C 1.23 Dark glazed timber slats, carpenter’s workshop near Freising (DE) 2010, Deppisch Architekten C 1.24 Timber board siding, coloured finish, Södra ­tennis centre, Växjö (SE) 2012, Kent Pedersen C 1.25 Modified pine wood without coating, from left to right: beginning of observation, after 3, 6, 9, 12 and 18 months of exposure to weather, facing south at 45°, Vienna (AT) a untreated reference timber surface b acetylated timber c chromium-free salt impregnated timber d thermo wood e furfurylated timber

b

c

d

e C 1.25

92

Low-energy house (EnEV)

wall, 239 mm thick U = 0.2 W/m2K

3-litre house

wall, 270 mm thick U = 0.2 W/m2K

wall, 234 mm thick U = 0.15 W/m2K

Passive house / plus-energy house

wall, 305 mm thick U = 0.15 W/m2K

wall, 434 mm thick U = 0.1 W/m2K

wall, 300 mm thick U � 0.15 – 0.18 W/m2K

wall, 200 mm thick U � 0.25 W/m2K

wall, 485 mm thick U = 0.1 W/m2K wall, 500 mm thick U ≤ 0.1 W/m2K C 1.26

ments after they have been cut. A primer and at least one subsequent layer of coating must be applied on all sides to prevent surfaces from absorbing moisture to varying degrees. Back-­ventilated or ventilated areas of exterior wall construction components are often also subject to very high levels of relative humidity. In recent years coloured mineral-based paint now offered by some manufacturers has proven effective.

Thermal Insulation in Winter and Summer In most European countries, the level of requirements for the annual energy consumption of buildings is defined by legal ordinance. The shared goal of EU Member States is to minimise the energy consumption related to building operation, with the long-term goal of creating a climate-neutral building stock by 2050. Boundary values are typically set for annual primary energy consumption for heating, hot water, ventilation and cooling. In relation to particular climate conditions, different requirements are placed on the performance of building envelopes, since their insulation and airtightness significantly influence the amount of energy consumed

C 1.27

for heating, ventilation and cooling. The other major factor in this context is user behaviour, which is purely individual and determined by the overall residential indoor climate. Since November 2020, the new ­German Buildings Energy Act (Gebäude­ EnergieGesetz, GEG 2020) [21] has defined thermal insulation requirements. Thermal insulation in winter The main protective goal of thermal insulation in winter is to reduce transmission heat loss through the building envelope as far as possible. From a physical science perspective, in the heating period, due to the difference between indoor (interior heated to 20 °C) and outdoor temperatures (exterior climate resulting from geographic conditions), a transient heat flow develops that must be minimised by a building envelope with the highest possible thermal resistance. The heat transfer coefficient or U-­­ value [W/m2K] describes the related per­ formance of the exterior construction components of a building. Differences between e.g. masonry, prefabricated concrete or ­timber structures lie mainly in their opaque construction components, because windows, doors and ventilation flaps etc. are the same in all these construction types, depending on requirements levels. To minimise heat losses through a building envelope, structural elements must be ­insulated as strongly as possible and, thus, keep the U-value of construction components as low as possible. The challenge is to cover a building and relevant areas in an insulating envelope in a near-seamless manner. It should be noted that along every corner and in parts of a structure with low insulation performance, geometric and structural thermal bridges can occur that can lead to significant heat losses (Fig. C 1.28). Creating building envelopes that are as compact as possible and the use of construction materials with good insulating properties are advised.

Figure C 1.26 provides an initial overview of the required thicknesses of insulation for exterior timber walls. With exterior timber construction components, if the structure is moderately over-insulated, with insulated installation levels and external layers of insulation for components < 500 mm thick, U values of U < 0.1 W/m2K can be achieved, which is the level of insulation required for passive or plus-energy houses. The current consensus is that this level of insulation constitutes a reasonable limit. Further halving U-values would result in doubling the thickness of insulation or in the use of ultra high-performance insulation, e.g. comprehensively employed vacuum insulation – neither of which would be structurally or economically sensible. A significant reduction in thermal insulation to U-values of U ≥ 0.2 W/m2K also would not yield desired results, even if using renewable energy sources could reduce the primary energy consumption figures of a building, at least in terms of calculations. The main goal should be to prevent heat loss and min­ imise the energy consumption of a building, regardless of the energy source. U-values of U ≤ 0.2 W/m2K result in surface tempera­ tures on the insides of exterior construction components that are in the room temperature range, which ensures a pleasantly warm indoor climate because related heat losses that can affect users are reduced. This, in return, enables a building to be operated with significantly lower indoor temperatures while maintaining indoor comfort levels. Based on the low thermal conductivity of wood as building material, this also contributes to avoiding thermal bridges in planar structures and in corners very well, or at least minimising them. The consistently well-insulated building envelopes of timber construction elements and high temperatures along all interior ­surfaces of exterior construction components help avoid problems due to mould growth along these surfaces. A typical

P R O T E C TIVE FUNCTIONS

a

b

indoor climate does not lead to increased near-surface relative humidity levels above 80% or even condensation and, as a result, it does not create advantageous conditions for mould growth. In addition to good thermal insulation, a building envelope must be airtight to prevent heat losses from unintended venti­ lation. Such losses are caused by wind pressure and wind suction, as well as by indoor thermal lift conditions and the resulting differences in air pressure. In very leaky buildings this can lead to elec­ trical outlets notoriously venting cold air. ­Airtightness is also necessary to ensure the good soundproofing of exterior construction components, the effectiveness of ventilation systems and the prevention of moisture intrusion resulting from con­ vection in structures (see “Moisture Pro­ tection”, p. 85ff.). Common use of air con­ ditioning systems requires maintaining a limit value of n50 ≤ 1.5/h according to DIN 4108-7 [22].

ered when calculating insulation requirements to protect structures against heat in summer. Sunlight intake parameters or daytime hours with excessive temperatures are the basis for calculation, depending on the verification process. The former is a simplified process, while the latter involves dynamic simulation. In their calculations, both methods take effective storage mass, shading, type of glazing and nighttime ventilation into account. If planners are in doubt, more precise methods become appropriate. Simplified methods must always guarantee security, while advances in planning can be more precisely derived from more exact calculations. In Germany, summer insulation requirements are defined in the Buildings Energy Act [23], while calculation methods are included in DIN 4108-2. This is based on the fact that cooling often consumes more primary energy than heating.

Thermal insulation in summer Popular lore states that thermal insulation requirements in summer are hard to comply with in timber structures. This myth was born in the barracks built in the years following World War II and persists to this day. In fact, modern timber structures contain a range of storage mass types, from solid timber components comprised of cross-­ laminated or glued laminated timber to ­mineral screed systems. Thus, they are no longer purely lightweight structures. A strongly insulated exterior timber construction component deflects heat just as well as it insulates against cold. Thus, in timber structures, as in all other structures, much depends on the effective shading of non-opaque construction components (Fig. C 1.27). Simplified verification processes limit window areas or take shading factors into account. Local climatic boundary conditions of each site must be consid-

93

C 1.28

Notes: [1] Ondrus, Julia: Fire in low-rise residential buildings. In: Building Research & Information, 22, 1994 (No. 1) p. 43ff. [2] Musterbauordnung – MBO of November 2002, last amended by resolution of the conference of ­construction ministers (Bauministerkonferenz) on 21.09.2012, Arbeitsgemeinschaft Bau der Länder (ARGEBAU) [3] Muster-Richtlinie über den Bau und Betrieb von Hochhäusern (MHHR). www.is-argebau.de [4] TIMpuls – Brandschutztechnische Grundlagen­ untersuchung zur Fortschreibung bauaufsichtlicher Regelungen im Hinblick auf eine erweiterte Anwen­ dung des Holzbaus. Research Project TU Munich (project management) et al., terminated 03/2021, www.bgu.tum.de [5] Muster-Richtlinie über brandschutztechnische ­Anforderungen an Bauteile und Außenwandbekleidungen in Holzbauweise (MHolzBauRL). Fach­ kommission Bauaufsicht Bauministerkonferenz (ed.), 10.2020 [6] Lippe, Manfred et al.: Commentary and Application Advisory (Kommentar mit Anwendungsempfehlungen und Praxisbeispielen zu der Muster-Leitungs­ anlagen-Richtlinie MLAR, Muster-SystembödenRichtlinie MSysBöR, Muster einer Verordnung über den Bau von Betriebsräumen für elektrische Anlagen MEltBauVO, Teil J. Winnenden) 2011, p. 223ff. [7] see note 5 [8] Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln /-details für mehrgeschossige

 Gebäude in Holzbauweise der Gebäudeklasse 4. Forschungsinitiative Zukunft Bau, F2923. Stuttgart 2014   [9] Bauaufsicht Frankfurt am Main „Holzbau AG“. ­Entwurf: Hinweise zur Behandlung von Aufstockungen in Holzbauweise. 2020 (unpublished) [10] see note 5 [11] Entwicklung eines material- und energieeffizien­ ten Holzbausystems aus Laub- und Nadelholz ­(LaNaSYS). Research project. TU Munich. ­terminates 03/2024. www.ar.tum.de [12] see note 8 [13] Holzforschung Austria, www.dataholz.eu [14] Bäder und Feuchträume in Holz- und Trockenbau. Bundesverband der Gipsindustrie e.V., Industriegruppe Gipsplatten (ed.). Merkblatt 02/2014 www.gips.de/fileadmin/user_upload/download/ merkblaetter/gipsplatten_und_gipsfaserplatten/ 2014-01-20_MB5_Online_kor-2016_AU.pdf ­(accessed 20.09.2021) Informationsdienst Holz (ed.): Bäder und Feucht­ räume im Holzbau und Trockenbau. Merkblatt ­series 2, part 2, chapter 5, 06/2007 Informationsdienst Holz: Holzrahmenbau. holzbau handbuch, series 1, part 1, chapter 7. 06/2009 http://informationsdienst-holz.de/publikationen/ (accessed 20.09.2021) [15] Regulation No. 305/2011 (Construction Products Regulation, CPR), European Parliament and Council of the European Union 09.03.2011 [16] see note 13 [17] DIN 68 800: 2019-06 Holzschutz – part 1: Allgemeines [18] see e.g. Informationsdienst Holz (ed.): Holz im Außenbereich. holzbau handbuch, series 1, part 18, chapter 2, 12/2000, www.holzfragen.de/ bilder2/info_holz_aussenbereich.pdf (accessed 20.09.2021) [19] ibid. [20] Grosser, Dietger; Willeitner, Hubert; Radovic, ­Borimir et al.: Holzschutz – Praxiskommentar zu DIN 68 800 Teile 1– 4, 2. completely revised ­edition. Berlin 2013 [21] GebäudeEnergieGesetz (GEG). Federal Law ­Gazette Volume 2020. Part I no. 37. Bonn, 13.08.2020 [22] DIN 4108-7:2011-01 Wärmeschutz und EnergieEinsparung in Gebäuden, part 7: Luftdichtheit von Gebäuden – Anforderungen, Planungs- und Ausführungsempfehlungen sowie -beispiele [23] see note 21 C 1.26 Required insulation thickness, exterior timber walls, different requirement levels C 1.27 Effective shading for summertime heat protection, bathhouse, Lochau (AT) 2010, Lang + Schwärzler C 1.28 Thermal bridges a  geometric (regardless of construction type) b structural (overlapping geometric and mater­ ial-based thermal bridge-related i­nfluences)

Thermal Insulation in Summer – A Question of Planning Daniel Rüdisser

Probability

94

current climate

cold weather

extremely cold weather

future climate

hot weather

extremely hot weather

Temperature

indoor temperature indoor temperature indoor temperature

indoor temperature

C 2.1

day 1

day 2

day 3

day 1

day 2

day 3

day 1

day 2

day 3

Efficient cooling through natural ventilation Daytime heat gains can be appropriately discharged at night at cooler temperatures.

indoor temperature indoor temperature indoor temperature

day 1

day 1

day 2

day 2

day 3

day 3

Transitional area Daytime heat gains can be barely, yet sufficiently ­discharged at night (or nights to follow).

day 1

day 1

day 2

day 2

day 3

day 3

ature indoor temperature

Overheating Daytime heat gains can no longer be discharged at night. Heat accumulates in the building, temperatures rise continuously. C 2.2 day 1

day 2

day 3

Overheating in buildings is increasingly becoming a problem. It both impacts the well-being and health of users as well as their productivity. Overheating scenarios are also related to climate change: not only does it lead to an increase of average temperatures, but also to an increased occurrence of prolonged hot periods (and cold periods), particularly in ­moderate ­climate zones (Fig. C 2.1). The reason for this is increasing polar temperatures resulting in a weakening of the jet stream, which, in turn, determines mid-latitude weather patterns. Aside from climate change, reasons for overheating in buildings also include construction types with generously glazed surfaces in combination with airtight and highly insulated building envelopes. One result of overheating in buildings is the significant increase in energy required for cooling that, in return, further contributes to climate change. Thus, it becomes necessary to avoid overheating by intelligently planning buildings.

Physics of Summertime ­Insulation The key to optimal building planning is comprehending the related fundamental physical processes. In detail, these complex and multifaceted processes can only be modelled and predicted using – more or less accurate – dynamic building simulation tools. However, as is mostly the case in physics, a significantly simpler and more insightful approach to the topic is offered by viewing things from the superordinate level of energy conservation. Building heat balance on a summer day Analysing energy flows (i.e. heat flows) that determine the indoor temperature of a building without active cooling on a summer day shows that, during daytime hours, only heat gains occur. In the case of most

modern buildings and within typical usage, the direct and indirect heat flows caused by solar irradiation through glazed surfaces, referred to as solar gains, represent the predominant component. In the case of nonresidential use, high occupation rates and additional interior loads can play a role. Heating effects by venti­lation are only relevant if outdoor air tem­peratures are considerably higher and air exchange rates are significant, e.g. due to open windows, doors or ventilation systems without heat recovery. Transmission, i.e. the direct transfer of heat through the building envelope by thermal conduction, no longer constitutes a significant factor. This is due to current high insulation standards and the limited average indoor-outdoor temperature difference, compared to winter. Heat flows occurring during the daytime lead to an indoor temperature increase. This increase depends on the sum of all heat gains as well as on the so-called effective thermal mass, i.e. the capacity of the interior of a building for short-term heat storage. After sunset, the outdoor air temperature typically declines below the temperature of indoor air. Hence, heat flows through the building envelope are reversed. Transmission, again, plays a minor role. Hence, the predominant share of heat accumulated during daytime needs to be removed from the building through nighttime ventilation. The precondition for this, on the one hand, is a significant air exchange, e.g. through open windows. On the other hand, the air entering the building needs to have a significantly lower temperature than the interior of the building. Night-time ventilation The aim of nighttime ventilation is to release the heat that has been accumulated during daytime. This heat is stored in the thermal mass of the building and has to be discharged to the exterior. If this succeeds, the storage is “emptied” and once more regains the capacity to work as buffer

T H E R M A L I N S U L A T I O N I N S U M M E R – A Q U E S T I O N OF PLA NNING

95

heat gains day ¬ = 28.8 kJ/(m2K)

2 K) ¬ = 28.8 kJ/(m effective thermal mass

temperature increase night 25 mm gypsum board 2 K) 2K) ¬ = 28.8 ¬ = 28.8 kJ/(m kJ/(m 100 mm wood/mineral wool 25 mm gypsum board 20 mm mineral wool 25it again mm gypsum board when temperatures have on the ­following day. If the cooling is not at night 100 mm wood/mineral wool entirely successful, heat accumulates in the 25declined (Fig. C 2.3). This enables buffermm gypsum board

25 mm gypsum board 2 K) 2K) ¬ = 28.8 kJ/(m ¬ = 28.8 kJ/(m 100 mm wool heatwood/mineral discharge mass 25 mm gypsum board 20 mm mineral wool 25 mm gypsum board 2 [W/m ] north south east wool west 100 mm wood/mineral 2 2 ¬ 1000 =¬ 28.8 kJ/(m K) K)25 mm gypsum board = 28.8 kJ/(m

C 2.3 roof

building and average temperatures begin to ing temperature variations in the interior. A rise (Fig. C 2.2). The temperature increase systematic and cyclical cooling effect can 800 during the day, as well as the long-term rise only be expected within a 24-hour period. 25 mm gypsum board 25 mm 25 mm gypsum gypsum board board 25 mm gypsum board 100 100 mm mm wood/mineral woolwool 100depen­ 100 mm mm wood/mineral wood/mineral woolwool wood/mineral of average temperatures are both This is why the quantification of thermal 25 mm gypsum board 25 mm 25 mm gypsum gypsum board board 25 mm gypsum board 600 dent on the available thermal mass. However, mass or, more precisely, the “internal areal 20 mm mineral woolwool 20 mm 20 mm mineral mineral woolwool 20 mm mineral in the case of persistent overheating, even heat capacity” according to EN ISO 13 786, 25 mm gypsum board 25 mm 25 mm gypsum gypsum board board 25 mm gypsum board 100 mm wood/mineral woolwool 100 100 mm wood/mineral wool on cyclical temperature varia100 mm wood/mineral high thermal mass is only effective tomm a wood/mineral iswool based 2525 mm gypsum board mm gypsum board 400 25 mm gypsum board 25 mm mm gypsum gypsum board board 25 mm gypsum board 100 mm wood/mineral wool 100 mm wood/mineral wool ­limited degree. The reason is that it25not only tions within a periodic 24-hour cycle. The 2525 mm gypsum board mm gypsum board mitigates the long-term temperature rise, decisive aspect is that, according to these 2020 mm mineral wool mm mineral wool 200 ¬ = 13.3 kJ/(m2K) but also delays cooling in a corresponding boundary conditions (12 hours of temper­ 2525 mm gypsum board mm gypsum board 100 mm wood/mineral wool 100 mm wood/mineral wool manner [1]. Cyclical cooling effects can ature increase, 12 hours of temperature 2525 mm gypsum board mm gypsum board 0 only be assumed within the diurnal variation decrease), only the topmost, few centime3 6 9 12 15 18 21 24 of temperatures. Hence, the available effectres thick layers of surface material effectime [h] a tive thermal mass needs to be optimised for tively contribute to heat storage. All analythis 24-hour cycle. The heat storage capacses and efforts for optimising effective solarer Eintrag ity of the interior should be large enough ­thermal mass must focus on these layers Belegung Transmission 12.5 mm gypsum board 2 to effectively absorb daytime heat loads – close to the surface. Deeper layers typically ¬ = 13.3 kJ/(m K) 2K) ¬ = 13.3 kJ/(m 50 mm mineral wool sonstige Luftwechsel predominantly solar gains – and discharge do not contribute to cyclical heat storage. 30 mm air cavity innere Lasten 200 mm reinforced concrete them at night, when exterior temperatures Fig. C 2.4 shows two partition wall construc15 mm renderspeicherwirksame Masse are cooler. The required amount of thermal tions. As a result of the heavy panelling Tag mass is, thus, defined by the amount of of the timber construction wall, it offers a daytime heat loads and the capacity for more than twofold internal heat capacity Belegung nighttime heat discharge. This system concompared to the significantly heavier reinsonstige tains a bottleneck: the cooling capacity forced concrete wall construction. The 12.512.5 mminnere gypsum board mm gypsum board Lasten 50 mm mineral woolwool 50 mm mineral of nighttime ventilation. It is decisive with RIOPT study undertaken at TU Graz comspeicherwirksame Masse 30 mm air cavity 30 mm air cavity regards to the requirements for daytime pared overheating for buildings of solid 200 200 mm mm reinforced concrete reinforced concrete heat gain limitation and maximum feasible and timber construction types [2]. The 15 mm render 15 mm render Transmission thermal mass (see “Heat Discharge – Natustudy concluded that ventilation and shadLuftwechsel ral Cooling”, p. 97), since cooling potential ing were identified as decisive influencing Nacht b is limited, due to a number of reasons. The factors, whereas the influence of the conComparison of areal heat capacity interrelation between the three components struction type was less relevant. – heat gains, thermal mass, heat discharge – For the heat capacity of a surface, the prodtimber frame construction 28.8 is therefore decisive for the performance of uct of bulk density and thermal conductivity a building in relation to summertime thermal of layers close to the surface are decisive reinforced 13.2 concrete insulation. This explains the following focus (since mass related heat capacity is generon these three components. ally relatively constant). High values can, c C 2.4 thus, be achieved for tiles and concrete or stone surfaces, while carpet flooring or C 2.1  Climate development prognosis C 2.2 Effectiveness of cooling through natural venti­ lightweight panelling or cladding result in Effective Thermal Mass lation low values (Fig. C 2.8, p. 96). The precise timber timber frame frame construction construction 28.828.8 C 2.3  Functional principle of effective thermal mass values of a specific construction type can The primary function of effective thermal C 2.4 Comparison of thermal mass for a partition wall reinforced reinforced according to different construction types be calculated, e.g. with a freely available mass is to prevent an excessive temper­ 13.213.2 concrete concrete a timber frame construction tool [3]. The decisive aspect for the effecature increase by buffering daytime heat b reinforced concrete construction tiveness of the available thermal mass gains. When indoor temperatures increase, c comparison of both types with regards to is, however, the fact that sufficiently large interior surfaces absorb heat to discharge ­areal heat capacity

roof

250

south

east/west

north N

200 184

200

168

150

152

W

E

136

100 120 104

50

88

0

J

F

M

A

M

J

J

A

S O

N

D

S

Wall reinforced concrete, spackled

84

reinforced concrete, 15 mm render

77

tile on interior brick wall

51

interior brick wall, 15 mm render

47

cross-laminated timber, 18 mm ­gypsum fibreboard

43

cross-laminated timber, tile on facing shell

35

exterior brick wall, 15 mm render

34

timber frame, facing shell, 2≈ 12.5 mm gypsum fibreboard

30

lightweight construction, 2≈ 12.5 mm gypsum board

20

cross-laminated timber, facing shell, 2≈ 12.5 mm gypsum board

18

timber frame, facing shell, 2≈ 12.5 mm gypsum board

18

interior brick wall, facing shell, 12.5 mm gypsum board

18

reinforced concrete, facing shell, 2≈ 12.5 mm gypsum board

17

cross-laminated timber, facing shell, 12.5 mm gypsum board

12

reinforced concrete, facing shell, 12.5 mm gypsum board

12

interior brick wall facing shell, 12.5 mm gypsum board

12

timber frame, facing shell, 12.5 mm gypsum board

11

Floor 1) 20 mm natural stone

84

10 mm floor tile

79

5 mm vinyl flooring

67

12 mm oak parquet

63

7 mm laminate

62

20 mm oak parquet

56

5 mm carpet flooring

55

12 mm spruce parquet

55

20 mm spruce parquet

46

30 mm wool carpet on 12 mm oak ­parquet

18

1) 

floor construction: flooring on 7 cm floating screed, 3 cm impact soundproofing panels, fill C 2.8

h

h

h

h

h

h

h

h

h

h

h = effective height h h

C 2.6

C 2.7

surface area needs to be accessible. If the ventilation of surfaces is limited, e.g. through curtains or furniture, the effectively achieved heat buffering will be significantly lower – or will be determined by the surfaces of the covering furniture. Considering the exposure to air flows, flooring and, in particular, ceiling surfaces play an essential role. For all these reasons stated above, the construction-type related differences of the effective heat capacity of buildings are lower than one might think. Contrary to common perception, they are not related – to the total mass of building components. By considering the principles these processes are based on, sufficiently high values can be achieved both in solid as well as in timber construction. However, disregarding these principles can lead to disadvantageous conditions for all construction types.

south facade in summer are significantly lower than for surfaces facing east or west. It is also remarkable that north-facing ­surfaces, due to diffuse solar irradiation, achieve high values in summer. In fact, they range significantly above the solar gains of south-facing surfaces in winter. The highest values in summer are obviously reached by horizontal, i.e. roof surfaces. Based on these observations, the following recommendations can be made: first, all north-facing transparent surfaces should also be equipped with appropriate external shading devices. Second, the ­proportions and types of glazed surfaces should be sensibly selected in relation to requirements. For instance, south-facing glazing can significantly reduce heating energy consumption in winter. In summer, it poses no higher risk for overheating than east or west-facing glazing. Third, it is imperative to cautiously employ domes or skylights in roof areas, as they pose significant overheating risks and are usually difficult to shade. Shading devices are an often neglected, yet extremely important component of ­modern buildings. The high annual variation of midlatitude solar irradiation can only be sensibly counteracted through transparent surfaces with adaptive shading capabilities. While external shading ­systems still comprise the most effective measure, in recent years, switchable glazing has become available. In the case of multi-layer glazing or double-skin fa­­ cades, shading systems can be integrated in-between glazing layers, provided that the system is able to withstand the usually high temperatures there. Interior solar shading – while still in widespread use – does not constitute an appropriate solution since solar irradiation, once it has entered the room, can only be insufficiently reflected to the exterior again. In order to ensure effective use of shading devices, it is essential to consider the

C 2.5 Areal heat ­capacity [kJ/m2K]

72

average radiation intake May – September [W/m2]

average radiation intake 24 h [W/m2]

96

Solar Gains and Shading In particular, for residential and comparable building use, solar gains through transparent surfaces constitute the decisive heat source, regardless of construction type. Optimising summertime thermal insulation must, therefore, focus on this source above all others. If the reduction of heat gains is successful, the requirements for heat buffering (thermal mass) and heat discharge (effective cooling ventilation) decline proportionally. Figs. C 2.5 and C 2.6 show the annual distribution of irradiation gains for building surfaces with different orientation for the city of Munich. They are similarly valid for other mid-latitude locations. It can be seen that solar gains of surfaces oriented towards the east and the west can reach the value of south-oriented surfaces, due to the different incidence angles of the solar irradiation. If we additionally consider the angular characteristics of glazed surfaces and shading effects of the reveal or facade elements, the effective solar gains of the

h

h

h

h

h

h

h

h

97

T H E R M A L I N S U L A T I O N I N S U M M E R – A Q U E S T I O N OF PLA NNING

Munich city hot day > 25° Munich airport hot day > 25°

32 28

north irradiation [W/m2]

temperature [C°]

Munich city hot day > 30° Munich airport hot day > 30°

south

east

west

roof

18

21 24 time [h] C 2.10

1,000 800

600

24 400

20 200

16

0

12 0

demands of users, e.g. daylight needs, ­visual connections to the exterior or glare protection. Automated systems are recommended in all cases. However, they need to be capable of meeting user demands in a targeted way.

Heat Discharge – Natural ­Cooling The principle of natural cooling is based on the fact that daytime heat accumulated within a building can be discharged at night through cooler exterior air. The complex interplay of the relevant physical processes for natural cooling can only be insufficiently displayed by current dynamic building simulation capabilities. From the viewpoint of energy conservation, efficient nighttime cooling is possible if sufficiently large airflow can reach as many surfaces of a building as possible and if a sufficient amount of cool air is available. With regards to nighttime cooling, an additional consid­ eration is that the climate in mid-latitude regions is still conducive to natural cooling, despite the apparent effects of climate change. This means that nighttime outdoor temperatures are still significantly lower than indoor temperatures. However, the urban heat island effect is detrimental and leads to a significant increase of air temperatures in dense urban areas, especially at night (Fig. C 2.9). Aside from this meso-­ climatic effect and its importance for urban planning, micro-climatic effects, on the level of individual buildings, also require consideration. They can be influenced by the appropriate design of the surrounding building environment. Based on greening, reducing sealed surfaces, a corresponding material and colour selection, as well as consider­ation of wind flows, the surrounding of a building can be designed to optimise natural cooling. For cool air surrounding a building to become effective on its inside,

4

8

12

16

24 20 time [h] C 2.9

it is crucial to enable airflow through the building. Micro-climatic effects are predom­ inantly defined by pressure differences, openable surfaces and flow resistance. The necessary difference in air pressure can be created - or reinforced - by mechanical systems. In the case of passive cooling, however, it results from wind pressures or thermal buoyancy (Fig. C 2.7). In urban areas, wind effects only play a marginal role. On the one hand, wind shielding obstructs it. On the other hand, nighttime inversion, frequent in high-pressure hot weather periods, prohibits ­vertical wind motion close to the surface. However, thermally induced buoyancy is always a significant and reliable driver of natural cooling. It depends on the temperature differences between interior and exterior air and, thus, increases proportionally to the cooling demand or cooling potential. In addition, buoyancy is related to the height difference between inlet and exhaust, which has to be considered during planning. The effective height should be as large as possible, ideally from one floor to the next, or beyond. Tilted windows, for instance, can only be effective if an additional opening is available at another elevation, ideally on another floor.

Conclusion Problems related to overheating are increasing in both frequency and intensity. The reasons for this are based on con­ struction types with large degrees of glazed surfaces, changing usage habits and comfort requirements, as well as the impact of climate change in the form of rising average temperatures and prolonged high-temperature periods. Summertime thermal insulation without energy-intensive cooling is possible if the relevant aspects have been factored in already during planning stages. This is indispensable, since the increasing use of energy-intensive cooling devices causes

0

3

6

9

12

15

summertime thermal insulation itself to become part of the problem. The key to ­climate-neutral heat protection can be found in the optimisation of the summertime thermal balance of a building. The effective thermal mass plays an important, yet not a predominant role. The best possible reduction of heat gains and the optimi­ sation of heat discharge potentials are decisive. Significant influencing factors are ventilation and shading. The influence of a particular construction type is often not as significant and requires differentiated consideration. Translation into English: Daniel Rüdisser

C 2.5 Seasonal progression of solar irradiation by ­orientation in Munich (IWEC r­ eference year) C 2.6 Average directional irradiation exposure, ­May – September, Munich (IWEC ­reference year) C 2.7 Air exchange through thermal buoyancy and ­effective height (tilted window, chimney effect, separate rooms) C 2.8 Exemplary, area-related effective heat ­capacity (thermal mass) [in kJ/m2K] C 2.9 Average diurnal temperature cycles for summer days (> 25 deg.) and “hot days” (> 30 deg.), comparison between Munich city and vicinity (data source: DWD 2004-2020) C 2.10 Diurnal irradiation for Munich, 15 July, clear sky

Notes: [1] e.g. Ferk, Heinz; Rüdisser, Daniel et al.: Sommer­ licher Wärmeschutz im Klimawandel. Einfluss der Bauweise und weitere Faktoren. In: att.zuschnitt 01/2016 [2] RIOPT – Risiko-optimierte Gebäudeentwicklung ­aufgrund des Klimawandels, final report, TU Graz, AEA – Österreichische Energieagentur. Vienna 2015 [3] free calculation tool for effective storage mass: www.htflux.com/tool-iso13786

98

The Layer Structure of Building Envelopes Maren Kohaus, Hermann Kaufmann

C 3.1

Modern timber construction, given the ­special opportunities offered by wood as a natural, renewable building material, plays a pioneering role in environmentallyfriendly construction. Many passive energy and plus-energy buildings feature highly insulated building envelopes based on a timber construction type. Concerns related to past experiences with draughty interiors quickly overheating in summer are now unfounded. In fact, the opposite is the case. Timber construction offers a very effective means of achieving a low heat transmission coefficient with thin walls (Fig. C 3.2), as the many timber buildings that meet modern comfort standards prove. These advantages are being acknowledged not only in new buildings, but in renovated buildings as well. With the opportunities offered by prefabrication, building envelope systems based on timber structures increasingly find acceptance. The complex layer composition of timber structures, however, places high demands on planners and the professional execution of construction elements. As the number of layers of construction elements increases, the complexity of joints between elements in prefabricated structures in particular does so as well. Therefore, reducing the number of layers is considered a sensible aim (see “Building Simpler”, p. 118). Efforts are on­­going to control the variety of possible solutions through standardisation in order to achieve a better overview and greater planning reliability [1].

Building Envelope ­Requirements C 3.1 Low-energy timber houses, Mühlweg residential development, Vienna (AT) 2006, Architekten ­Hermann Kaufmann C 3.2 Building envelope construction layer development in timber construction (horizontal section) with focus on thermal insulation C 3.3 Polyfunctionality of construction component ­layers

Building envelopes must perform the ­following protective functions (see also ­“Protective Functions”, p. 78ff.): • weather protection (wind, rain, snow, sun / UV radiation) •  thermal insulation in winter / summer • airtightness

• condensation protection (due to convection or diffusion) •  fire safety •  soundproofing (incl. acoustic measures) Facades and roofs are subject to basically identical building physics requirements, although different functional requirements will call for different sequences of layers and materials in related construction ­components. To effectively manage the complexity of the functional allocation of individual layers of components, it is ­advisable to identify their functions in the early planning stages and specify them in detail plans and workshop drawings (Figs. C 3.4 and C 3.5, p. 100).

Functions of Construction Component Layers Individual layers are described in accordance with their functions as follows: •  exterior cladding • windproof layer / second water-bearing layer •  load-bearing / structural layer •  insulation layer •  airtight layer •  vapour barrier layer •  installation layer (with / without insulation) •  interior cladding or panelling Each function within a construction component can be assigned to a specific layer, but some materials are polyfunctional and can perform several functions at the same time (Fig. C 3.3). A vapour barrier layer and airtight layer are typically incorp­ orated into the same layer of a component, e.g. a wood-based material panel or film layer. Allocating functional requirements to component layers requires their con­ tinuity, which must be considered when ­creating joints and connections between components. An exposed cross-laminated

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

1982

U = 0.58 W/m K

Example exterior wall structures

U = 0.28 W/m K 2

22.45 cm

17.85 cm

2

2002

U = 0.25 W/m K

U = 0.18 W/m2K

28.75 cm

26.15 cm

2

solid timber structure (here: cross-laminated timber) U = 0.16 W/m2K

42.25 cm

1992

timber frame structure U = 0.16 W/m2K

38.40 cm

1972

99

C 3.2

timber panel of an exterior wall that has a load-bearing function can also serve as a vapour barrier and airtight layer. In this case, joints between elements must be tightly sealed. This can be achieved by ­covering joints with sealing tape or placing sealing strips between joints or into gaps (Fig. C 3.12, p. 103). Polyfunctional layers of construction components generally make it possible to reduce the number of layers and result in a reduced workflow in executing components. This reduction, however, usually also requires special connection details between components (e.g. by integrating interior compo-

nents or service lines into the building ­envelope). Careful planning and monitoring in the construction phase are therefore important.

Quelle: Informationsdienst Holz, sowie www.dataholz.com

Insulating layer and construction A principal distinction is made between two different types of primary insulation levels, in terms of construction and depending on their position in relation to the structure. Insulation can be placed either on the outside of the load-bearing structure, which is usually the case with solid timber structures comprised of cross-laminated, dowel lamin­ ated or glued laminated timber elements

(Fig. C 3.13, p. 104), or it can be infilled between linear structural members (Fig. C 3.14, p. 105). Structures with exterior insulation Rigid insulating materials that do not require a dedicated substructure are typically used for structures insulated on the outside. Soft insulating materials, in contrast, are infilled between a single, double or even three-layer substructure (Fig. C 3.9, p. 102) with members arranged crosswise, or between special members optimised for minimal thermal bridges (e.g. Å-joists) (Fig. C 3.13 a, E, p. 104).

Exterior wall protective functions weather protection

airtight- thermal condensation fire soundness insulation protection protection proofing

acoustics

°C Exterior wall functional layers

exterior

interior

polyfunctionality: 4 functions correspond to 1 construction component layer

exterior cladding

sarking layer (windproofing, second water-bearing layer)

thermal insulation (rigid/soft)

structural load airtight bearing layer layer

vapour barrier

2 mm sanded stainless sheet steel substructure back ventilation vapour-permeable facade membrane 380 mm three-ply mineral wool e.g. 72 mm cross-laminated timber element, ­adhesively sealed edges, airtight joints, interior exposed timber quality

interior cladding (with/without installation layer)

Exterior wall construction component layers C 3.3

100

Construction component layers solid timber wall, exterior insulation e.g. 95 mm cross-laminated timber diffusion-retardant adhesively sealed narrow edges, airtight interior exposed timber quality 160 mm insulation layer diffusion-permeable sarking layer 30/50 vertical / horizontal battens back ventilation

Functional layers

e.g. vertical siding

interior cladding (surface quality) substructure / installation layer vapour barrier

design-related effective surface finishing (e.g. glazing, painted finish, etc.)

airtight layer structural load bearing layer thermal insulation insulation protection exterior cladding substructure exterior cladding surface finishing

C 3.4

Construction component layers exterior wall, infill insulation e.g. 1≈ 12.5 mm gypsum board sheathing, OSB airtight and vapourretardant layer 80/160 mm studs 160 mm insulation layer 40 mm wood fibre panel as second water-bearing layer additional insulation 30/50 vertical / horizontal battens back ventilation

Functional layers

e.g. vertical siding

substructure / installation layer vapour barrier airtight layer

design-related effective surface finishing (e.g. glazing, painted finish, etc.)

interior cladding (surface quality)

structural load-bearing layer thermal insulation insulation protection exterior cladding substructure exterior cladding surface finishing

C 3.5

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

101

non-combustible termination of exterior wall cladding C 3.4 Axonometric illustration, interrelation between construction layers / functional layers, solid ­timber wall with exterior insulation C 3.5 Axonometric illustration, interrelation between construction layers / functional layers, exterior wall with infill insulation C 3.6 Schematic illustration, sheet metal fire safety ­separator between floors (free cantilever x) C 3.7 Facade firestop, sheet steel angle, circumferential, floor by floor, eight-storey apartment and ­office building, Bad Aibling (DE) 2012, Schankula Architekten C 3.8 Execution variants, fire stops for timber facades including resulting minimum cantilever (according to MHolzBauRL)

construction component

x C 3.6

Structures with infill insulation safety perspective – to protect construction Due to the low thermal conductivity of components from weather impacts and wood (λ-value approx. 0.13 W/mK), it is mechanical damage during installation and unproblematic in terms of building physics Schematische construction (Figs. C 3.14 a, D – F, p. 105, Darstellung einer brandschutztechnischen to omit covering timber components with Geschosstrennung; C 3.26, p.Ausführung 112). mit Stahlblech: z= Gesamttiefe insulation, such as studs in an exterior This type of extra layer can be advisable t= Blechdicke wall or rafters, because no condensation x= freiefor structures insulated on the outside (Figs. Auskragung forms there. T ­ hermal bridges can be C 3.13 a, D – F, p. 104 and 3.28, p. 113), in ­minimised by reinforcing insulation or by order to eliminate any thermal bridges in use of a specific geometry of load-bearing the substructure and protect components members (e.g. Å-joists) (Fig. C 3.14 a, E, during the construction phase. p. 105). In the case of composite thermal insulation systems, soft and inexpensive insulation Additional exterior insulation materials can be infilled between battens Where additional insulation is attached to and covered with a suitable, rigid load-­ a structure with infill insulation, rigid and bearing insulation layer that can also serve vapour-permeable insulation such as wood as a substrate for exterior render (Fig. fibreboard with a water-resistant surface C 3.13 b D – F, p. 104). This also requires often finds use – if applicable from a fire ­taking the related specifications of the

Cladding type

Construction material/ component

planar woodbased material

Examples

Alignment

bulk density ≥ 350 kg/m3 closed surface panel thickness ≥ 22 mm length ≥ 625 mm area ≥ 1.0 m2

solid timber panels veneer plywood laminated veneer ­lumber

horizon- ≥ 50 mm tal / vertical

interlocked siding

bulk density ≥ 350 kg/m3 board thickness ≥ 22 mm board width, pith free ≤ 160 mm relief grooves: •  remaining thickness ≥ 10 mm •  width ≤ 5 mm •  spacing ≥ 30 mm

board-and-batten siding tongue and groove

horizontal ≥ 50mm

frictionlocked

bulk density ≥ 350 kg/m3 board thickness ≥ 22 mm board width as required relief grooves: •  remaining thickness ≥ 14 mm •  width ≤ 5 mm •  spacing ≥ 30 mm

board-and-batten ­siding shiplap siding

horizontal ≥ 100 mm

bulk density ≥ 350 kg/m3 board thickness ≥ 22 mm board width as required board cross section ≥ 1000 mm2 relief grooves: •  remaining thickness ≥ 14 mm batten thickness ≥ 14 mm

open joint siding clapboard siding shingles

open joint ­siding

Schematic diagram

vertical

vertical

Firestop minimum projection

≥ 100 mm

≥ 150 mm

horizontal ≥ 200 mm

vertical

≥ 250 mm

C 3.8

C 3.7

­ omposite ­thermal insulation system proc vided by the manufacturer into account. Additional interior insulation The interior of a building envelope can be used to create an additional installation layer dedicated to service lines in order to avoid penetrations of the airtight layer or the vapour barrier. In this case, infill insulation improves the insulating properties of the construction component (Fig. C 3.13 C, F, p. 104 and C 3.14 C, F, p. 105). The rule of thumb is that the share of insulation on the inside of a vapour barrier layer should not exceed an equivalent thickness of approx. 20 % of the total insulation thickness. If the inner insulation is thicker, a calculation of building physics characteristics is advised (Glaser method or hygrothermal calculation). Exterior cladding layer / weather ­protection Exterior cladding material for a timber ­building is chosen based on the same ­principles as those applied to conventional construction with mineral-based building materials. In general, almost all cladding materials can be used for an exterior wall or roof. However, in the case of prefabricated exterior wall elements, particular products do not permit assembly in the workshop. This is due to the fact that ­transport requires a certain degree of robustness and elements need to allow for repairs should they be damaged in transit. The necessity of providing an airspace, ­cavity or gap behind a cladding layer is dependent on the diffusion behaviour of the cladding material in relation to the other construction component layers. A ­distinction is made between, on the one hand, ventilated and back-ventilated ­exterior wall cladding (Fig. C 1.13, p. 86) and, on the other, cladding with a non-­ ventilated, enclosed layer of air. The ­latter, lacking a water-bearing drainage level,

C3.9

102

has significantly lower potential for discharging condensation or surface water penetrating a building due to driving rain. Thus, it should be avoided (see “Moisture Protection”, p. 85ff.).

C3.8

C3.9

C3.7

C3.8

C3.9

C 3.9

C 3.10

C 3.11

Fire safety for facade cladding The fire safety requirements an exterior wall component needs to meet will vary depending on building class and height (see “Fire safety performance requirements”, p. 78ff.). For this purpose, exterior facade cladding only needs to limit the spread of a fire beyond the primary point of ignition. Facade cladding of buildings up to three storeys high (building class 1– 3) is not ­subject to any special requirements, with the exception of special-purpose buildings where project-specific standards may exist. Therefore, building materials of normal flammability (B 2 as defined in DIN 4102-1) such as timber cladding and biogenic ­insulating materials (made of renewable raw materials) can be used as exterior insulation and for composite thermal insulation systems. According to MHolzBauRL [2] for taller buildings with four to seven storeys (building class 4 and 5) timber cladding materials are permitted for ventilated or back-­ ventilated facades (see “Combustibility and fire resistance”, p. 80f.). The precondiC3.7 tion is that particular measures to prevent fire spread are in place, such as non-­ combustible borders of exterior wall components (Fig. C 3.6, p. 101) that can be created by use of e.g. non-flammable, mineralbased, 15-cm thick substrate panels, by limiting the width of ventilation gaps to a maximum of 30 to 50 mm, or by horizontal fire stops between floors [3]. Such fire stops prevent fire from spreading through a facade air layer from one floor to the next by use of a sheet steel element or a mineral-based panel (Fig. C 3.6 and C 3.7, p. 101). Depending on the composition of the facade and the percentage of joints

C3.8

C3.7

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

A

B

C

additional film on sheathing interior or exterior as airtight layer

interior sheathing as airtight layer

solid construction components as airtight layer

single-sided adhesive tape

double-sided adhesive tape

single/double-sided adhesive tape

exterior exterior a

in the facade surface, a fire barrier can extend beyond the surface cladding by 50 to 250 mm while being connected to the non-flammable substrate panel of the actual exterior wall component. The applied connectors need to penetrate into the loadbearing structure of the underlying wall ­construction. This will prevent fire from spreading through the air layer or within ­layers of the substructure. In the composite thermal insulation systems of taller buildings (building classes 4 and 5) only insulating materials of low flammability (B 1 as defined in DIN 4102-1) can be used. It should be noted that only approved composite thermal insulation systems are permitted. The suitability of a system based on renewable insulation materials requires case by case approval. Only non-flammable materials in building material class A1 may be used as facade cladding for high-rise and very tall buildings. Windproof layer / second water-bearing layer A second water-bearing layer serves as additional security for ventilated or backventilated facades and sloped roof structures. It also constitutes a windproof layer and prevents outside air from passing through the insulation or joints between insulation panels, which would otherwise greatly impair their insulating function. A windproof layer also supports the airtightness of the entire construction component. This greatly reduces the amount of warm, moist air that can permeate a structure through leaks in the airtight layer and, thus, considerably minimises condensation (see “Condensation from diffusion”, ­“Condensation from convection”, p. 86f.). Windproof layers in facades Materials used for windproof layers need to be as vapour-permeable as possible, with an sd value of < 0.3 m (DIN 68 800) (see “Correlation with other construction

single-sided adhesive tape

exterior exterior b

component layers”, p. 106), possess waterbearing surfaces and permit creating airtight joints (e.g. tongue and groove joints or lamination). Vapour-permeable films, wood-based materials (e.g. constructiongrade MDF boards) or wood fibre insulation boards are all suitable. If fire safety requirements are more stringent, mineral-bonded wood-based materials (e.g. cement-bonded particle board) can be used, which requires a related degree of vapour diffusion resistance on the interior of the construction ­component. Alternatively, gypsum-bonded panelling (fire-resistant gypsum boards, gypsum fibreboard) can protect the construction component exterior, based on fire safety requirements (Figs. C 3.16, p. 108 and C 3.17, p. 109). The latter can serve as a windproof layer, but must also be ­protected from moisture by a vapourperme­able film. If facade cladding features open joints or perforations, the windproof layer will be the only water-bearing layer. Absolutely airtight sealing and unobstructed water dissipation is indispensable. Depending on construction type, cladding can only minimise the impact of precipitation. In facade types without an air layer, e.g. standard certified composite thermal insulation systems, the exterior render layer must fully adopt the functions of the windproofing and water-bearing layer, because there is no second water-bearing layer. Windproof layers in back-ventilated roof structures A second water-bearing layer in the form of a sarking board or layer is built into backventilated sloped roofs to allow any moisture forming due to condensation or leaks in the roof membrane to dissipate (Fig. C 3.25 – C 3.29, p. 112). Flat roofs can also be backventilated (Fig. C 3.24, p. 111), but such roof types are rarely built in practice, for reasons of cost and because such structures need to be sufficiently thick to facilitate a functioning flow of air.

single-sided adhesive tape

exterior exterior c

103

pre-compressed sealing tape

C 3.12

Polyfunctional windproof layers Creating the windproof layer of a facade or sloped roof by use of panel materials, e.g. suitable wood fibreboard, can help to protect a prefabricated construction ­component from moisture and mechanical damage during transport and installation. During the construction phase, it can also be used to seal the building or serve as temporary roofing and, at the same time, as a second water-bearing layer. Wood fibreboard with a thermal conductivity between 0.09 and 0.045 W/mK and appropriate thickness can function as additional insulation and can also minimise any thermal bridges surrounding studs or rafters (Figs. C 3.13, p. 104 and C 3.14, p. 105). Airtight layers Airtight layers are highly important, because leaks can impair and even completely destroy the protection that other layers offer – from heat, noise, fire and condensation. This can result in energy loss, noise transfer, condensation from convection and may allow smoke and fire to spread in the event of a fire.

C 3.9   Back-ventilated facade structure for a solid ­timber building with sanded sheet steel exterior cladding. Prefabricated room modules received exterior cladding on site. Hotel Ammerwald near Reutte, Tyrol (AT) 2009, Oskar Leo Kaufmann, ­Albert Rüf C 3.10   Back-ventilated facade structure for a solid ­timber building with fibre glass-reinforced ­concrete exterior cladding. The stiffness of these elements allows for greater spacing of ­aluminium substructure members. Residential and office building, Zurich (CH) 2010, pool ­Architekten C 3.11   Facade structure with a composite thermal ­insulation system for a timber frame building. Residential and office building, Berlin (DE) 2014, Kaden Klingbeil Architekten C 3.12   Possible execution of airtightness level, ­horizontal sections a  with additional film layers b  lamination of wood-based material panels c solid timber element with corresponding ­element gaps

Significance of the airtight layer The significance of the airtightness of ­building envelopes was underestimated for a long time. Leaks lead to the intrusion of humid, warm air into structures and result in strong condensation formation that is more harmful than anything vapour diffusion could cause (Fig. C 1.14, p. 86). Air leaks are mostly due to faulty work­ manship along seals at penetration points, along transitions between construction components, along window and door joints, and in ceiling, floor and roof connections or due to incorrect construction or damage to the airtight layer itself. To avoid the most

frequent source of flaws, service lines should always run along the interior side of an airtight layer, in order to avoid penetrations. Exposed solid timber elements that also serve as airtight layer require specific detail solutions. Within these elements, service lines can only be embedded in construction components up to a certain depth. This allows the remaining layers of timber to be sufficiently airtight and vapour-proof. Otherwise additional sealing measures will be required (see “Protective Functions”, p. 78ff. and “Building Services Technology – Particularities of Timber Construction”, p. 136ff.).

Airtight layer construction Airtight layers are typically made of plastic foil materials, specially coated paper, wood-based materials, gypsum fibreboard or gypsum boards. In timber frame elem­ ents, this layer also typically has a stiffening function and can even possess loadbearing functions. In this case, sheathing must demonstrate adequate flow resistance and joints between elements must be sealed airtight. Cross-laminated timber ­elements can also form an airtight layer if the timber laminate layers are adhesively sealed along their edges and joints between elements are airtight, e.g. by use of joint

Structure with exterior insulation

Additional panel material / additional insulation a

windproofing film

C installation layer with infill insulation, ­improves U-values additional airtight film /  optional vapour barrier

E

F

vapour-permeable sheathing as wind­ proofing, second water-bearing layer and for ­mechanical protection during transport additional exterior insulation, e.g. paraffin wax-coated softwood fibre panels, improves U-values and offers mechanical protection during transport Å-beams reduce thermal bridges

installation layer with infill insulation, ­improves U-values additional airtight film / vapour barrier if cross-laminated timber edges are without adhesive seal

b

B

cladding

installation layer

solid timber structure

composite thermal insulation system

cladding

installation layer

solid timber structure

composite thermal insulation system

installation layer

solid timber structure

exterior insulation

cladding

additional airtight film / vapour barrier if board edges are without adhesive seal for installations within the cross-laminated timber layer

additional non-flammable sheathing ­possibly required for fire safety reasons; in such cases: airtight layer / vapour barrier, can be installed on the interior

D

A

cross-laminated timber, exposed, as vapour barrier and airtight layer, edges with adhesive seal Single layer composite thermal insulation system

Single second water-bearing layer

B

Composite thermal insulation system without air layer

Composite thermal insulation system on an additional insulating layer

A

air layer

cladding cladding

installation layer

Back-ventilated / ventilated

solid timber structure

exterior insulation

104

cross-laminated timber, exposed, as ­vapour barrier and airtight layer, edges without adhesive seal with additional airtight film / vapour barrier (if board edges are without adhesive seal or installations within the cross-laminated timber layer) an additional substrate panel for com­posite thermal insulation system possibly required (see manufacturer spec­ ifications) additional non-flammable sheathing ­possibly required for fire safety reasons; ­in such cases: airtight film / vapour barrier, can be installed on the interior

C installation layer with infill insulation, ­improves U-values additional airtight film / optional vapour ­barrier D

composite thermal insulation system as ­additional exterior insulation on exterior ­insulation infilled between battens /  counterbattens

E

additional non-flammable sheathing ­possibly required for fire safety reasons

additional airtight film / vapour barrier, can also be installed on the interior F

installation layer with infill insulation, ­improves U-values additional airtight film / vapour barrier if cross-laminated timber edges are without adhesive seal C 3.13

sealing material (EPDM tube seal, pre-­ compressed sealing tape) placed into joints or by adhesively connecting joints with adhesive tape. Film used in an airtight layer must be laminated along joints (Figs. C 3.12 a, p. 103), because overlapping is insufficient. It is strongly recommended to test airtightness within a blower door test (see “Condensation from convection”, p. 86f.). This should be carried out before interior sheathing is installed. Element joints and component connections in prefabricated elements must remain accessible so that possible leaks can be located and repaired.

Vapour barrier layer A vapour barrier is installed on the inside of an insulating layer to stop condensation from forming within a structure. Construction components in building envelopes must generally be as vapour-permeable as ­possible and as vapour-resistant as necessary. Construction layers should always become more vapour-permeable from the interior to the exterior, in order to prevent more water vapour from intruding into the structure than water vapour diffusing outward. Vapour-permeable structures have proven effective, based on their ability to dry out, and are regarded as very robust.

C 3.13   Schematic diagram, layer composition, ­structure with exterior insulation, cross-­ laminated timber element a  back-ventilated / ventilated b composite thermal insulation system without air layer C 3.14   Schematic diagram, layer composition, ­structure with infill insulation, timber frame ­construction a  back-ventilated / ventilated b composite thermal insulation system without air layer

Structure with infill insulation

C

oil windproofing

installation layer with infill insulation, improves U-values

E

additional exterior insulation (moisture-proof) as windproofing / second water-bearing layer, for ­mechanical protection, improves U-values Å-beams reduce thermal bridges

F

additional airtight film / vapour barrier if interior sheathing lacks airtight adhesive seal

B

b

cladding

installation layer

structure with infill insulation

cladding

installation layer

composite thermal insulation system

exposed stiffening sheathing as vapour ­barrier and airtight layer, airtight joints ­required, e.g. adhesive seal additional airtight film / vapour barrier if ­interior sheathing lacks airtight adhesive seal additional non-flammable sheathing, ­possibly required for fire safety reasons additional airtight film / vapour barrier, can also be installed on the inside

C self-supporting insulation panels, e.g. soft wood fibre panels installation layer with infill insulation ­improves U-values D

additional vapour-permeable sheathing as ­windproofing / second water-bearing layer for ­mechanical protection during construction, can also be installed due to production technology (level of prefabrication, non-self-supporting ­insulating material such as cellulose wadding, etc.) Composite thermal insulation system on an additional insulating layer

Single second water-bearing layer

additional airtight film / vapour barrier, can also be installed on the inside

D

a

additional non-flammable sheathing, possibly ­required for fire safety reasons

Single layer composite thermal insulation system

additional airtight film / vapour barrier if interior sheathing lacks airtight adhesive seal B

A

exposed stiffening sheathing as vapour barrier and airtight layer, airtight joints required, e.g. adhesive seal

structure with infill insulation

composite thermal insulation system

Without air layer, as composite thermal insulation system

cladding

installation layer

structure with infill insulation

air layer

cladding cladding

installation layer

A

Additional panel material / extra insulation

structure with infill insulation

Back-ventilated / ventilated

air layer

cladding

105

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

additional airtight film / vapour barrier if ­interior sheathing lacks airtight adhesive seal additional exterior sheathing due to production technology (level of prefabrication, ­non-self-supporting insulating material such as cellulose wadding, etc.)

E

additional non-flammable sheathing, ­possibly required for safety reasons additional airtight film / vapour barrier, can also be installed on the inside

F

additional airtight film / vapour barrier if ­interior sheathing lacks airtight adhesive seal C 3.14

construction component

106

construction component

vapour barrier airtight layer

C 3.15   Vapour barrier continuity, integration into a ­ceiling slab, residential complex, Jenbach (AT) 2010, Architekten Hermann Kaufmann a  vertical section, scale 1:20 b  construction site photo

a

b

Correlation with other construction component layers The rule of thumb is that the thickness of the water vapour-equivalent layer of air of the vapour diffusion-regulating layer, as represented by the sd value, must be at least five to six times as high as the sd value of the exterior layer(s) [4]. Previously, for ­ventilated or back-ventilated exterior wall components, film with sd values of 500 to 1,000 m found use, while sd values currently range from 5 – 20 m. Alternatively, moisture-adaptive vapour barriers can be employed [5]. If the aim is to build an exterior wall structure free of film materials, with infill insulation, ventilated or back-ventilated exterior cladding and a vapour-permeable windproof layer of sd < 0.3 m, an interior layer of OSB with an sd value of 2 m, for example, can provide both airtightness and vapour barrier functions. Butt joints between elements and connections to other construction components must be built to be accordingly airtight. The rule of thumb is: sd interior = 5 - 6 ≈ sd exterior target value inside: sd interior = 6 ≈ 0.3 m = 1.8 m; actual value inside: sd OSB = 2.0 m; comparison: 2.0 m > 1.8 m

Moisture-adaptive vapour barriers Moisture-adaptive vapour barriers can change their sd value. If relative humidity is low, they strongly resist diffusion. Where relative humidity is high, they are very diffusion-­permeable. Any moisture accumulating in the structure from condensation or leaks can dry out, which is essential in flat roofs with infill insulation, yet without back ventilation (see “Flat roof structures”, p. 110f.).

Sealing layers with sd values of sd ≥ 100 m are now used for flat roofs insulated on the outside without an air layer. The resulting sd value of the vapour barrier on the inside should be sd ≥ 500 m. This can only be achieved with film materials or related ­bituminous layers, which can also serve as temporary roofing during construction. DIN standards (DIN 68 800) and databases such as www.dataholz.eu contain construction and composition types from ­different manufacturers that have already been ­certified. If in doubt, calculation ­methods prescribed by building authorities should be used to verify the construction of exterior wall and roof components.

C 3.15

Interior cladding The interior cladding of a building envelope involves design aspects and must also meet functional requirements, such as fire prevention, acoustic qualities, soundproofing and moisture protection. Effective storage mass can be increased if the appropriate materials are used. The following types of cladding are commonly applied: • Sheathing directly placed on the loadbearing layer: direct sheathing is ­sometimes used for economic reasons. If its construction is carefully monitored, it can also function as airtight layer and vapour barrier. Perforations in this layer due to service lines should be avoided. • Sheathing and load-bearing layer sep­ arated by a cavity (installation layer): an extra facing shell can be built as an installation layer on the interior side of a construction component. Service lines can be advantageously installed on the inside of the airtight layer without penetrating it. The additional space required for this construction type is ­usually balanced against the benefits of simpler installation and safer execution. Adding extra insulation to this ­installation layer can further improve U-values, reduce any thermal bridges, and have a positive effect on the sound reduction index of the entire construction component.

Technical Soundproofing ­Aspects Despite their lack of mass, timber structures with appropriate layer structures can provide good soundproofing and guarantee compliance with current standards (see “Soundproofing and Acoustic Requirements”, p. 88f. and “The Layer Structure of Interior Construction Components”, p. 126ff.). Various exterior wall composition types have been approved by building authorities and can be found in construction component catalogues. The fundamental prerequisite for good ­airborne sound insulation and impact sound insulation is the airtight construction of construction components. Specific layer compositions can be supported by calculations. Attention should always be paid to estimates on secondary noise transfer paths. For solid timber construction components, the airborne sound insulation index is also dependent on the execution of joints. Assembly of exterior and interior cladding and infill insulation reduces its impact [6]. Improving soundproofing in exterior walls The sound reduction index of the inwardfacing side of exterior walls can be improved by taking the following measures. The featured guide values refer to an exterior wall exposed on the interior and consisting of cross-laminated timber with a composite thermal insulation system [7]: • direct 12.5 mm gypsum board cladding on cross-laminated timber wall with ­composite thermal insulation system: ∫ improvement of approx. 0 –1 dB • direct 2≈ 12.5 mm gypsum board cladding on cross-laminated timber wall: ∫ improvement of approx. 1– 2 dB • facing shell with mineral wool insulation on cross-laminated timber wall: ∫ improvement of up to approx. 6 dB

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

• facing shell with 2≈ 12.5-mm gypsum board cladding and mineral wool insulation, attached with sound insulation clips to cross-laminated timber wall: ∫ improvement of up to approx. 15 dB • facing shell on cross-laminated timber wall, completely acoustically separated, cavity (85 mm) insulated with mineral fibre cavity insulation (50 mm), metal stud frame with 12.5-mm gypsum board: ∫ improvement of up to approx. 22 dB • facing shell on cross-laminated timber wall, completely acoustically separated, cavity (85 mm) insulated with mineral fibre cavity insulation (50 mm), metal stud frame with 2≈ 12.5-mm gypsum board: ∫ improvement of up to approx. 23 dB Construction components with infill insulation generally have good soundproofing characteristics in the high frequency range, with an increase of 12 dB per octave compared to only 6 dB per octave for solid ­timber construction components [8]. As a result, the soundproofing effect of facing shells in connection with timber frame wall construction is lower than in the case of solid timber walls. The reason is that construction components with infill insulation already possess higher soundproofing ­characteristics. The construction type of exterior cladding also influences the sound reduction index of a construction component. In composite thermal insulation systems, for example, the dynamic rigidity and bulk density of insulation panels and bulk density and thickness of render layers are relevant to soundproofing characteristics. The linear flow resistance r of insulating materials is an important aspect of insulation placed on the exterior of a back-ventilated facade [9]. Information on specific structures and installation situations should be requested from insulation mater­ ial manufacturers. The sound reduction index of back-ventilated facades can be improved by diligent plan-

ning of the points at which the substructure is attached to the studs of the cavity insulation. This is relevant if the facade substructure and battens of an interior installation layer are not in the same plane with the studs of a timber frame structure or the battens of exterior infill insulation of a solid timber structure insulated on the outside. This can improve the sound reduction index in timber panel structures by up to 7 dB [10]. Sound insulation for adjoining functional units Where construction components of the building envelope or slabs extend across several functional units, the transmission of airborne and structure-borne sound must be prevented. Measures frequently used to achieve this include integrating slabs into the facade structure [11] or decoupling structural components by installing elastomeric bearings at structural support points (see “Decoupling layers within construction components”, p. 134f.). Additional flexible layers such as facing shells for walls and ceilings (see “Cladding”, p. 131) are also sometimes used. All construction components must be sealed airtight.

Technical Fire Safety Aspects For tall timber buildings (more than four ­storeys) the increased requirements placed on fire protection are generally met by use of corresponding cladding (see “Timber construction performance characteristics”, p. 81ff.). Typically gypsum fibreboard or fire-­resistant gypsum board find use as fire protection cladding. A composite thermal insulation system with mineral wool insu­ lation and silicate render applied to gypsum fibreboard or fire-resistant gypsum board can also be used as fire protection cladding on the exterior of a wall (Fig. C 3.17 a, p. 109). Effective fire-rated cladding must be ­executed according to technical build-

107

ing regulations or feature building code approved proof of usability (abP, abZ, ETA). Gypsum fibreboard or fire-resistant gypsum board cladding can perform further functions and, thus, reduce the amount of layers within a construction component: they can, for example, serve as design-oriented inter­ ior cladding and as an airtight layer in the form of direct sheathing / cladding without an installation layer (Figs. C 3.16, p. 108 and C 3.17, p. 109). Such boards and their relatively low sd values (μ value of approx. 13 : 13 ≈ 0.018 m = 0.23 m = sd) can, however, only be used with an additional vapour barrier film with an sd value of ≥ 2 m, given that no other construction component layer, such as e.g. interior OSB sheathing assumes this function (Fig. C 3.17 c, p. 109). However, wall framing construction types clad in gypsum fibreboard or fire-resistant gypsum board have comparatively low ­horizontal load-bearing capacity, so supplementary wood-based material boards are used as a substrate, particularly in multi-­ storey buildings. Their advantage is that they make it possible to safely attach picture frames, cabinetry etc. to walls. If an interior installation layer is provided, the interior sheathing should not be built as an airtight layer or necessary fire protection layer. The airtight and fire protection-related sealing of penetrations for service lines is feasible, yet requires precise planning. It should, if possible, occur in the workshop in the case of prefabricated elements or under strictly controlled conditions.

108

Solid timber structure with composite thermal insulation system

Solid timber structure, back-ventilated

Solid timber structure (interior exposed), back-ventilated, minimal use of film

Construction component layer Construction component layer

Construction component layer

10 mm exterior render 180 mm mineral wool 12.5 mm fire-resistant gypsum board (additional airtight layer, optional) 140 mm cross-laminated timber (with μ = 50; sd = approx. 7 m) 2≈ 18 mm fire-resistant gypsum board installation layer, optional

back-ventilated facade sheathing layer (sd ≤ 0.3 m) 180 mm mineral wool 18 mm fire-resistant gypsum board 140 mm cross-laminated timber (with μ = 50; sd = approx. 7 m) 2≈ 18 mm fire-resistant gypsum board installation layer, optional

possible values without installation layer: REI 90 (+ effective fire protection cladding) U = 0.152 W/m2K R w, R = 39 dB

back-ventilated facade windproofing, optional wood-based material board (e.g. cement-bonded particle board) 180 mm mineral wool lamella insulation T ≥ 1,000 °C; t ≥ 40 mm 15 mm gypsum fibreboard 140 mm exposed cross-laminated timber (with μ = 50; sd = approx. 7 m)

possible values: REI 60 U=a  pprox. 0.15 W/m2K R w, R = n.s.

possible values ­without installation layer: REI 90 (+ effective fire protection ­cladding) U = 0.15 W/m2K R w, R = 40 dB

Function

Function

Function

render system: weather protection, windproof layer, exterior fire fire safety cladding

weather protection

weather protection

windproofing, second water-bearing layer

load-bearing layer, vapour barrier

exterior fire safety cladding

windproofing, second water-bearing layer, additional insulation

airtightness, interior fire-resistant cladding

load-bearing layer, vapour barrier airtightness, interior fire-resistant cladding

exterior fire safety cladding load-bearing layer, vapour barrier, airtight layer, dimensioned to withstand complete burnout (building related fire safety certificate required)

a

b

c

Further Criteria for Choosing Exterior Wall Structures

loading of top and bottom plates becomes too great (Figs. B 1.11 b and c, p. 48). Even taller buildings can be created with timber wall framing by using hardwood ­bottom plates or supplementary structural measures. In solid timber walls, loads should be ­transferred directly through the end grain. Slabs should only be partly placed on top of walls or should be connected to walls with consoles or brackets. Vertical loads can be transferred through steel structures integrated into ceilings or cut-outs filled with grout (Fig. B 1.11 d, p. 48). A frame structure with appropriately dimensioned columns that transfer loads directly into the columns below them represents the most suitable construction method for tall buildings, including those above the high-rise threshold (see “Student Residence in Vancouver”, p. 190ff.). In such cases, facade elements that enclose interior spaces no longer constitute load-bearing parts of the building envelope, leading to a related reduction of fire safety requirements (see

“Fire Protection”, p. 78ff.). Non-load-bearing walls in non-high-rise buildings only need to be fire-retardant (REI 30). Above the highrise threshold, the fire resistance requirements depend on the specific fire safety concept.

Aside from the building envelope requirements described above, the following factors should be considered when choosing an exterior wall construction type. Structural factors If the building envelope is part of the ­relevant primary load-bearing structure, ­timber wall framing or solid timber walls consisting of cross-laminated timber ­elements (see “Residential and Office Building in Berlin”: rear building timber frame construction, front building solid timber ­construction, p. 194ff.) or dowel laminated panel elements (see “Residential and ­Commercial Building in Zurich”, p. 204ff.) are applicable. Load-bearing timber wall framing with ­continuous top and bottom plates can be installed in a standard structure up to a maximum height of three to four storeys, otherwise the settlement due to the lateral

C 3.16

Indoor climate factors Exposed solid timber structures influence the indoor climate of a building. The low thermal conductivity of wood, its relatively high bulk density and high specific thermal capacity (c = 2,100 J/kgK) increase thermal inertia, making timber buildings very ­comfortable to live in during summer (see “Thermal insulation in summer”, p. 93 and p. 94ff.). Cross-laminated timber can provide almost three times the storage capacity of timber frame walls at compar­ able U-values [12]. The ability of wood to absorb moisture from indoor air and release it again after a certain amount of time ­balances the humidity of indoor air and improves the comfort of rooms enclosed by exposed construction components.

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

Wall framing with composite thermal insulation ­system

109

Wall framing, back-ventilated

Wall framing, back-ventilated, minimal use of film

Construction component layer

Construction component layer

back-ventilated facade vapour-permeable sheathing sd ≤ 0.3 m 2≈ 18 mm fire-resistant gypsum board 240 mm mineral wool vapour barrier (sd ≥ 2 m) 2≈ 18 mm fire-resistant gypsum board installation layer, optional

back-ventilated facade windproofing, optional laminated insulation, wood-based material board (e.g. cement-bonded particle board) 2≈ 18 mm fire-resistant gypsum board 240 mm mineral-based thermal insulation 24 mm OSB (sd = approx. 4 m), airtight 2≈ 18 mm fire-resistant gypsum board installation layer, optional

Construction component layer 10 mm exterior render 40 mm mineral wool lamella insulation T ≥ 1,000 °C; t > = 40 mm 12.5 mm fire-resistant gypsum board 240 mm mineral wool vapour barrier (sd ≥ 2 m) 2≈ 18 mm fire-resistant gypsum board installation layer, optional

possible values without installation layer: REI 60 (+ effective fire protection cladding) U = 0.14 W/m2K R w, R = 47 dB

possible values without installation layer: REI 60 (+ effective fire protection cladding)

possible values without installation layer: REI 60 (+ effective fire protection cladding) U=0 ­ .165 W/m2K R w, R = 49 dB

U=a  pprox. 0.16 W/m2K R w, R = n.s.

Function

Function

Function

render system: weather protection, windproofing, exterior fire safety cladding

weather protection

weather protection

windproofing, second water-bearing layer

vapour barrier

exterior fire-resistant cladding

windproofing, second water-bearing layer, additional insulation

stiffening, airtightness, interior fire-resistant cladding

vapour barrier stiffening, airtightness, interior fire protection cladding

exterior fire safety cladding stiffening, airtight and vapour-resistant layer interior fire-resistant cladding

a

b

Economic factors The cost of a building envelope depends not only on the material costs of its individual layers, but also on the efficiency of ­production and assembly processes related to prefabrication. Thus, very careful and timely planning is essential. There is considerable potential for rationalisation, for example, in the detailing of element joints and connections to other construction components. A rational construction and assembly process, the degree of prefabrication of elements and transport options must be coordinated with construction ­companies early on. This is usually difficult in the case of publicly commissioned ­buildings, because contractors have often not yet been commissioned when detail planning is already underway. Alternative contracting processes should be developed here to accommodate prefabrication (see “The Planning Process”, p. 146ff.). The ways in which individual t­imber ­construction companies work can make it necessary to adapt plans, which can

be complex and expensive when it occurs ­during advanced planning stages (see “Characteristics of Timber Construction Planning”, p. 146). Environmental factors The more timber is used in a building, the more carbon it binds in the long term The resulting CO2 sink has a positive effect on the ecological assessment, that increases with the amount of timber used for construction. From a sustainability perspective, planners and designers need to balance the efficient use of energy and material with carbon storage capacity. Using resources carefully and sparingly is also necessary in the case of renewable resources. Choosing a particular insulation material based on ecological considerations is becoming increasingly important and can affect the construction type and layer structure. Preparing accompanying ecological assessments at an early stage can help planners make the right choices.

c

C 3.17

C 3.16   Typical facade structure with exterior insulation, multi-storey timber buildings, including fire ­prevention cladding (structure of a and b as per Merk, Michael et al.: Erarbeitung weiter­ führender Konstruktionsregeln /-details für ­mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014) a solid timber structure with composite thermal insulation system b solid timber structure, back-ventilated c solid timber structure (exposed interior) back-ventilated, low degree of film use C 3.17   Typical facade structure with infill insulation, ­multi-storey timber buildings, including fire ­prevention cladding (structure of a and b as per Merk, cited in Fig. C 3.16) a timber panel structure with composite ­thermal insulation system b timber panel structure, back-ventilated c timber panel structure, back-ventilated, low degree of film use

110

insideinside inside inside inside inside inside

ceiling: ceiling: ceiling: ceiling: ceiling: ceiling: ceiling: as in as as asin as as in inas in in in exterior exterior exterior exterior exterior exterior exterior wall structure wall wall wall wall wall structure structure wall structure structure structure structure floor:floor: floor: floor: floor: floor: floor: as in as as asin as as in inas in in in flat roof flat flat flat flat flat roof roof roof flat roof roof roof structure structure structure structure structure structure structure with air with with with layer with with air with air airlayer air air layer layer air layer layer layer

outside outside outside outside outside outside outside

Further Criteria for Layer ­Composition of Horizontal and Sloped Construction Components

C 3.18

When the functional layers described above are incorporated into vertical, horizontal and sloped construction components of building envelopes, there are further aspects of the layer composition that must be taken into account, depending on their position. Slabs bordering the exterior The underside of a projecting volume or the edge of a loggia are subject to the same

composite composite composite composite composite composite composite with air with with with layer with with air with air airlayer air air layer layer air layer layer layercomposite composite composite composite composite composite composite exposed exposed exposed exposed exposed exposed crossexposed crosscrosscrosscrosscrosscrossthermal thermal thermal thermal thermal thermal thermal thermal thermal thermal thermal thermal thermal thermal laminated laminated laminated laminated laminated laminated timber laminated timber timber timber timber timber timber insulation insulation insulation insulation insulation insulation insulation insulation insulation insulation insulation insulation insulation insulation system system system system system system system system system system system system system system

a

b

building physics rules as an exterior wall component in terms of the composition of their construction component layers (Figs. C 3.18 – C 3.19). They can be built with infill insulation or exterior insulation (or, in rare cases, with insulation on the interior), as ventilated or back-ventilated structures or without air layers. The structural inter­ dependencies of construction component ­layers in terms of moisture protection follow the principles described previously. To ensure a continuously airtight building ­envelope, the airtight layers of an exterior wall component and floor element must be adhesively connected at transitions

between components. This is often complex and must be precisely considered in planning, especially for prefabricated elements. If the top of a floor slab borders the exterior, as is the case with a recessed top floor or loggia, the construction component must be built like a walkable flat roof (Fig. C 3.21).

c

C 3.19

Flat roof structures Flat roof structures are usually built without a back ventilation layer, because such simple construction types are both functional and cost-effective (Figs. C 3.21 and C 3.24). Back-ventilated flat roofs are rare, although a sarking layer offers the additional security

C 3.18  Schematic layer diagram, loggia C 3.19 Example illustration, layer composition of ceiling components, cantilever / loggia, vertical sections a  structure with infill insulation b structure with exterior insulation (cross-laminated timber) c structure with interior insulation (cross-laminated timber) C 3.20 Loggia, residential and office building, Berlin (DE) 2013, Kaden Klingbeil Architekten C 3.21 Flat roof with exterior insulation, without back ­ventilation: protective layer sealing layer rigid thermal insulation to falls vapour barrier / airtight layer (temporary seal during construction) load-bearing structure (shown in red) C 3.22 Flat roof with infill insulation, without back ­ventilation: sealing layer (with additional exterior insulation and additional sealing layer as temporary ­weather protection as required) exterior sheathing thermal insulation in the construction layer moisture-variable vapour barrier / airtight layer interior cladding (sheathing as required), with / without installation layer C 3.23 Seven golden rules for a flat roof with infill ­insulation, additional certification not required C 3.24  Overview of various flat roof construction types C 3.20

111

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

sealant sealant

beam beamceiling ceiling

gravel gravel

dowel dowellaminated laminated timber timberceiling ceiling

extensive extensivegreening greening

hollow hollowbox boxceiling ceiling

terrace terracepaving paving

hollow hollowbox boxceiling, ceiling, limited limitedinfill infillinsulation insulation

cross-laminated cross-laminated timber timberceiling ceiling

without withoutadditional additionalexterior exterior insulation insulation(structural (structuralphysics physics certification certificationrequired requiredfor for green greenroofs, roofs,gravel gravellayers layers etc., etc.,see seealso alsoCC3.23) 3.23)

with withadditional additional exterior exteriorinsulation, insulation, optional optionalsealing sealing layer layeras astemporary temporary seal seal

beam beamceiling ceiling

C 3.21

Flat roof with infill insulation, without back ventilation It is possible to build flat roofs without back ventilation and with insulation infilled between roof beams. However, they are prone to deficiencies and are considered special construction types that are not ­generally recommended [13]. Difficulties arise in practice because moisture can enter even through minor construction flaws or due to damage in the airtight layer or vapour barrier layer. Creating an opportunity for drying out towards the ­interior is indispensable, otherwise structures can rot or fail entirely. Using a moisture-adaptive vapour barrier is one solution. However, its effectiveness depends not only on the sd values of other construction component layers, but on external factors, such as: • type of roof structure: green, not green, gravel-covered, bare • solar absorption of exterior surface layer or sealing layer: light, dark

1.  Slope ≥ 3 % before or ≥ 2 % after deformation 2.  Dark roof surface (solar radiation absorption a ≥ 80 %), unshaded 3.  No cover layer (gravel, green roof, terrace paving) 4.  Moisture-adaptive vapour barrier 5.  No cavities that prevent inspection on the cold side of the insulation layer 6.  Proven airtightness 7. Documentation of the moisture content of timber in the load-bearing structure and cladding (should be u ≤ 15 ± 3 %) and wood-based material sheathing (should be u ≥ 12 ± 3 %) before the structure is sealed Consensus of speakers at the 2nd International Holz[Bau]Physik Congress on “Timber Protection and Building ­Physics” in Leipzig, 10/11 February 2011, on the rules that must be observed in planning a flat roof with infill ­insulation. Valid for buildings with normal residential indoor climate as per DIN EN 15 026 or WTA notice 6-2.

C 3.23 Flat roof without back ventilation

Flat roof with back ventilation

exterior protective layer sealing layer thermal insulation layer, to falls vapour barrier / airtight layer

exterior protective layer / sealing layer back ventilation layer vapour-permeable sarking layer thermal insulation vapour barrier / airtight layer

exterior protective layer sealing layer (possibly additional insulation) thermal insulation in the structural layer moisture-variable vapour barrier / airtight layer interior cladding (possibly sheathing) no additional insulation: see Fig. C 3.23

exterior protective layer / sealing layer rear ventilation layer vapour-permeable sarking layer thermal insulation in the structural layer vapour barrier / airtight layer interior cladding (possibly sheathing)

Structure with exterior insulation

Flat roof with exterior insulation The structure of a flat roof with exterior insulation is the same as for an ordinary warm roof. In the case of a flat roof, the vapour barrier serving as exterior sealing layer ­features a five to six times higher sd value and also functions as an airtight layer and ­temporary roof during construction. In ­timber construction, this is indispensable in preventing the structure from wetting ­during assembly. In this type of structure, the construction components are in the vapour diffusion-regulating, airtight layer and in the warm indoor climate, so no ­condensation can accumulate within it.

C 3.22

7 golden rules for a flat roof with infill insulation without requiring additional certification

Structure with infill insulation

of a second water-bearing layer. Similar to exterior walls, a distinguishing characteristic is whether the thermal insulation layer is placed on the exterior of the load-bearing structure (Fig. C 3.21) or is infilled between structural members (Fig. C 3.22).

possibly additional sealing layer

C 3.24

112

•  outdoor and indoor climate • periods during which the roof surface is shaded, etc.

•  back ventilation layer •  insulation infilled between rafters roofing (schematic diagram, sheet metal roofing) with roof sheathing back ventilation layer exterior sheathing / sarking layer vapour-permeable rafters / thermal insulation interior sheathing as vapour barrier / OSB, airtight

C 3.25

•  back ventilation layer •  insulation infilled between rafters roofing (schematic diagram, sheet metal roofing) with roof sheathing back ventilation layer diffusion-permeable sarking layer additional rigid insulation, vapour-permeable rafters with thermal infill insulation vapour barrier / airtight layer interior sheathing gypsum board

C 3.26

•  back ventilation layer •  insulation on top of structure (exposed rafters) roofing (schematic diagram, sheet metal roofing) with roof sheathing back ventilation layer diffusion-permeable sarking layer rigid thermal insulation vapour barrier / airtight level / temporary seal interior sheathing / cladding exposed rafters

C 3.27

These dynamic interdependencies mean that flat roofs with infill insulation must be calculated by means of hygrothermal simulation if they do not comprise a standard structure as defined by DIN 68 800. This construction type is not reliably leak-proof and must be built very meticulously. This is why prefabrication in the workshop and verification of functionality through moisture monitoring are recommended (Fig. C 3.23, p. 111) [14]. Only economic reasons in ­specific cases can justify this type of solution. To prevent increased condensation in and around the load-bearing structure, additional insulation is often laid on top of a flat roof construction with infill insulation (Fig. C 3.22, p. 111). Related to the assembly process, an additional sealing layer on top of a prefabricated construction component with infill insulation can be appropriate. This can prevent moisture intrusion within the structure during construction. For multistorey timber construction, roof layer compositions that feature a top layer of insulation are recommended. Sloped roof types Sloped roof types typically comprise a ven­ tilated roof with a sarking panel or layer (Fig. C 3.25 to C 3.28). The structure can be built with insulation infilled between structural members or placed on top of them. If the sd value of a sarking panel or layer is low, back ventilation of the roof membrane allows the entire structure to remain vapour-permeable. Compared to roof structures without back ventilation, they are considered very robust and secure structures. A sloped roof without back ­ventilation is possible and can be built like a flat roof (Fig. C 3.29). However, there is no second layer of security, such as offered by a sarking membrane or panel

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

113

C 3.25 Infill insulation between rafters, back-ventilated, low degree of film use C 3.26 Infill insulation between rafters, back-ventilated, additional insulation C 3.27 Infill insulation on top of rafters, back-ventilated C 3.28 Insulation on top of solid timber element, backventilated C 3.29 Insulation on top of solid timber element, ­unvented (warm roof principle)

of a back-ventilated structure. Thus, the water-bearing layer must be very carefully planned and built, especially concerning the detail points along the eaves, roof ridge and gable rake.

Polyfunctional Layers The number of layers in a building envelope can vary greatly, depending on the construction type or component layers. A cor­ respondingly dimensioned solid timber wall can, in principle, perform all functions in one layer: load-bearing capacity, insulation, protection from wind and weather and robustness in terms of building physics. Each functional requirement placed on an entire construction component can also be met by a separate component layer. It is advisable to build with as few layers as possible and as many layers as necessary, using polyfunctional materials to meet several requirements at the same time. It is also advisable to select construction types that demand only a minimum of film materials, because they are more robust and reduce the variety of required materials.

dimensional thinking and construction skills are decisive. Joints between exterior wall and floor slab The example of integrating a floor slab into an exterior wall displays how the ­fundamental requirement of layer continuity in combination with variations in support geometry results in different details. Setting a slab on the entire thickness of an exterior wall in a timber frame structure weakens the continuity of the insulating layer, and additional insulation will be needed on the exterior to reduce thermal

•  back ventilation layer •  insulation on top of structure (cross-laminated timber) roofing (schematic diagram, sheet metal roofing) with roof sheathing back ventilation layer vapour-resistant sarking layer additional vapour-resistant rigid insulation insulation vapour barrier / airtight layer cross-laminated timber element, exposed

Principles of Joinery In joining construction components, it must be ensured that individual functional layers are applied continuously throughout the building envelope, across joints between construction components. The ­allocation of particular functions to certain construction component layers in the ­building envelope is more distinct in multilayered structures than in structures with few layers. Joints between construction components should, thus, be very carefully planned. Joints between layers within the same level or plane are relatively easy to control, compared to joints between layers on different levels or offset layers. Three-

C 3.28

•  without back ventilation •  insulation on top of structure (cross-laminated timber) roofing (schematic diagram, sheet metal roofing) with roof sheathing thermal insulation vapour barrier / airtight layer cross-laminated timber element, exposed

C 3.29

114

C 3.30 Integration of floor slabs into exterior walls in structures with infill insulation or with exterior ­insulation, according to different support ­geometries C 3.31 Exemplary joinery for integrating floor slabs into exterior walls (as per www.dataholz.eu)

Frame wall structure

Ceiling component

Solid timber structure

ceiling set on entire thickness of exterior wall

ceiling set partially on exterior wall

ceiling suspended from exterior wall

Frame wall structure

Wall component

ceiling

Solid timber structure

a

ceiling

b

ceiling

d

ceiling

c

ceiling

e

ceiling

f

C 3.30

115

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

3

2 1 5

4

6

3

bridges (Fig. C 3.30 a). The airtight layer must pass around the slab edge and be adhesively connected to the airtight construction component layer above. Vapour barriers in the area of the slab edge must also be continued, while taking the changed layer composition into account. For a solid timber wall insulated on the exterior, the insulating layer in the area of the slab edge is not weakened, while element joints must feature airtight adhesive connections (Fig. C 3.30 d). If the floor slab is not set on the entire thickness of an exterior wall, filling the resulting recess in front of the slab edge with insulation will compensate for the weakening of the insulating layer (Fig. C 3.30 b). Thus, for wall construction types insulated on the exterior, compression forces impacting support points in and around the floor slab can be avoided (Fig. C 3.30 e, see also project example, axonometric illustration, p. 235). Adhesive seals along joints between exterior wall elements achieve airtightness. To meet soundproofing and fire safety requirements, airtightness between separate floors must be ensured. In the case of facade elements with infill insulation or insulation on the exterior, if a slab is not integrated into an exterior wall, e.g. because the slab span direction requires no support, the airtight layer con­ tinuity only needs to be ensured along joints between airtight elements (Figs. C 3.30 c and f). Fig. C 3.31 shows example joint solutions for integrating floor slabs into ­exterior walls. Prefabrication and assembly The building envelope is often prefabricated in order to keep assembly time on site short and ensure that the building envelope is quickly sealed off. Due to economic reasons and under consideration of maximum transport dimensions, elements are built to be as large as possible. This limits the quantity of joints between elements to a necessary minimum and, as a result, reduces possible

Integrating a ceiling slab into an exterior wall with solid timber construction components two functional units, 60 min. fire resistance exterior wall, directly applied sheathing, optional ­installation layer for service lines ceiling slab: solid timber, exposed underside, ­soundproofing through increased fill

2 3 1 5

4

6

1 film for airtight joints between construction components 2  element butt joint 3 airtight connection between exterior wall and ceiling slab 4 solid timber, e.g. cross-laminated timber, as airtight layer, airtightness must be provided along surface and joints 5  joint execution as per producer assembly guidelines 6 elastic bearing for acoustical decoupling as per soundproofing requirements

2 6 1

53

4

6 2

1 a

5

Integrating a ceiling slab into an exterior wall with a solid timber ceiling two functional units, 60 min. fire resistance exterior wall: wall framing, directly applied sheathing (2≈ 18 mm gypsum board) with optional installation layer ceiling slab: solid timber, hung ceiling (2≈ 18 mm ­gypsum board)

4

6

6 3

1 diffusion-permeable film for airtight joints between ­construction components 2  element butt joint 3 airtight connection between exterior wall and ceiling slab 4 solid timber, e.g. cross-laminated timber, as airtight layer, airtightness must be provided along surface and joints 5  joint execution as per assembly guidelines 6 elastic bearing for acoustical decoupling as per soundproofing requirements

2

1

6 3 5

2

4

6

1 b

Integrating a ceiling slab into an exterior wall with a beam ceiling two functional units, 60 min. fire resistance exterior wall: wall framing, directly applied sheathing (2≈ 18 mm gypsum board) with optional installation layer ceiling slab: beam ceiling, partial insulation, hung ceiling (2≈ 18 mm gypsum board)

5

4

6 5 3

2

1 diffusion-permeable film for airtight joints between ­construction components 2  element butt joint 3 airtight connection between exterior wall and ceiling slab 4  joint execution as per assembly guidelines 5 elastic bearing for acoustical decoupling as per soundproofing requirements

1

4 5 5 c

3

2

C 3.31

116

Prefabricated load-bearing layer

Prefabricated load-bearing and insulating layers

When assembling the load-bearing layer on site, all work on joints and connections between ­components also takes place on site. The advantages of completely prefabricated elements and producing all individual ­construction layers under controlled climate conditions and constant temperatures in the workshop, as well as shorter assembly time, are not applicable in this ­construction type.

When prefabricating the load-bearing and insulating ­layers and delivering them to the site, the joints between ­elements and connections to other construction components require diligent planning. In order to protect the construction component and, in particular, the insulation from moisture or mechanical damage, an exterior ­weather protection layer is added to the component.

Joint complexity

When prefabricating the exterior wall component and ­including the cladding layer, planning is required to ­consider how components are assembled and connected on site. The exterior cladding and the support frame it is mounted on are often prefabricated as successive elements and delivered separately to the construction site (Fig. C 3.34, p. 118). high

Vertical structural component joint

Horizontal element joint

Structure with infill insulation

Structure with exterior insulation

low

Prefabricated load-bearing, insulating and cladding layers

low

Degree of prefabrication

high C 3.32

8.

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T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

7. 3.

6. 5. 4. 2. 1. 10.

9. C 3.32 joint types in relation to degree of prefabrication of elements C 3.33 prefabrication and assembly process, three ­decisive building envelope details: parapet, ­integration of floor slab, pedestal, housing, Hummelkaserne, Graz (AT) 2016 sps architekten (as per www.dataholz.eu)

8.

7. 3.

6. 5.

a

errors during assembly. A high degree of prefabrication generally and decisively increases the quality or workmanship compared to ­on-site construction (Fig. C 3.33). The degree of prefabrication of exterior walls is also dependent on design requirements. Due to the high transport-related risk of damages, it is impossible to assemble every exterior or interior cladding layer in the workshop. For soundproofing and fire safety reasons and taking into account the completion of installations, it can be sensible to prefabricate ­interior cladding only partially and complete interiors on site. In many cases, ­successive handling and packaging of ­separate components is advantageous. It is self-evident that a high degree of prefabrication requires comprehensive prior planning, including building services. It is sensible to assemble window elements including sun protection in the workshop. Airtight connections to wall components can be executed precisely, under supervision and under controlled climate conditions and constant temperatures (Fig. C 3.34 b and c, p. 118). Typically, manufacturers develop the type of joint between elements. Thus, architects should anticipate the possible sequence of assembly steps already during detail planning – in ideal cases, with the support of the manufacturers – and consider the results within planning. In order to avoid ­far-reaching changes in advanced planning stages, different planning, tendering and bidding scenarios exist (see “The Planning ­Process”, p. 146ff.). It is principally possible to build prefabricated elements in a manner that prevents the need for reworking joints and connections after assembly. Otherwise adequate space should be reserved in the area of joints and connections in order to allow ­professional workmanship on construction layers after moving elements in place (Fig. C 3.32).

8.

4.

3.

2. 5. Assembly process:   1. assembly of a prefabricated exterior wall ­element incl. facade cladding on ­elastomeric bearing   2. placement of cross-laminated timber ­elements with temporary seal   3.  erecting the parapet element   4. joints between wall and ceiling and sealing layer adhesively sealed   5. integration of roof construction   6. UV-resistant sealant and parapet adhesively connected   7. extensive green roof  8. parapet coping   9. assembly of interior gypsum board cladding 10. assembly of hung ceiling

7.

3.

6.

1. 10.

5. 4.

6.

2.

9. 1.

2.

4.

10. 7. 1. 9. 5.

b 3. 5. Assembly process:   1. assembly of a prefabricated exterior wall element incl. facade cladding on ­elastomeric bearing   2. placement of cross-laminated timber ­elements with airtight adhesive edge seal   3. erecting the top prefabricated exterior wall elements on elastomeric bearing   4. completion of facade along slab edge with sheet metal coping   5. assembly of interior gypsum board ­cladding   6. integration of floor construction   7. assembly of hung ceiling

3.

6. 5. 2.

4. 7. 1. 6. 5. c

Assembly process:   1. creation of a reinforced concrete floor slab and pedestal including thermal insulation   2.  mortar levelling layer  3. moisture barrier   4. erecting the prefabricated exterior wall ­element including facade cladding and self-adhesive sealant placed into joints as airtight adhesive seal and pedestal sealant   5. connection between floor and wall, airtight adhesive seal   6. assembly of interior gypsum board ­cladding   7.  XPS pedestal insulation   8. fibre cement panel as exterior pedestal cladding   9. thermal insulation fill and EPS thermal ­insulation 10.  floor construction

2. 4. 4.

6. 7. 1.

10.

5.

9.

5. 3. 2.

1.

8.

d 4.

3. 7.

6.

C 3.33 10.

118

C 3.34 Prefabrication of exterior wall elements, secondary school, Diedorf (DE) 2015, Architekten ­Hermann Kaufmann, Florian Nagler Architekten a exterior wall element load-bearing structure with insulation b  installation of window elements c  adhesively sealing of joints d  transport of exterior wall elements a

Occasionally, in the case of energy-efficient refurbishment or retrofitting, prefabricated large-format exterior wall components pose advantages due to rapid assembly and resulting short construction time. As a result, residents don’t have to temporarily leave their homes (see “Solutions for Modernising and Expanding of Existing Buildings”, p. 172ff.). Solid timber elements are occasionally handled, packaged and delivered on site by cross-laminated timber manufacturers, for immediate assembly. Assembling further components can take place on site or by use of related prefabricated partial elements. b

Exposed construction types In the case of exposed construction types, particularly diligent planning is required for joints and connections between construction components. Adhesive sealing of airtight layers and fire safety-related grouting and jointing are supposed to remain concealed. Connecting airtight layers to floor elements can, thus, be realised simply. The floor construction is typically installed later on, which allows concealing joints and connections. Exposed ceilings and exterior walls, on the other hand, may require the creation of airtight adhesive connections on the exterior of elements or from the storey above, prior to placement of successive wall elements.

c

Building Simpler Contemporary comfort, security and energy efficiency requirements coincide with a strong increase in the degree of technical equipment and complexity of construction methods of modern buildings. This is accompanied by rising costs for construction and maintenance, growing resource consumption and a greater variety of avail­ able materials. This variety calls for critical examination against the background of d

C 3.34

existing capacities for demolition and re­­ cycling. Certain developments aim towards less complex, more robust and more dur­ able structures. From an historical perspective, these aren’t new developments. Many traditional timber buildings are, in fact, very simple in terms of their construction. The walls of historical log cabins are monolithic, comprising only one layer. In the late 19th century, in some regions they were even­ tually covered with additional layers comprising shingles, siding or cladding. This construction type led to an increased consumption of high-quality timber. As a result, construction types were developed in ­parallel that attempted to conserve material resources, such as half-timbered construction. Here as well, the building envelope was kept simple, the structure remained ­visible, the infill comprised a single layer of loam or brick. In the early 20th century, while timber construction faced increasing industrialisation tendencies, timber frame construction found widespread use, supported by the development of wood-based panel materials, such as plywood and later, particle board and gypsum fibreboard. This development led to the emergence of many types of construction layers based on functional differentiation (Fig. C 3.5, p. 100). Timber building envelopes today are highperformance construction components that can achieve good building physics characteristics with low degrees of material consumption (Fig. C 1.26, p. 92). At the same time, they permit economically efficient prefabrication. Reduction of complexity Since it has become difficult to keep track of the variety of possible construction layer combinations and the resulting different construction components, standardisation is needed. For this purpose, construction component data banks such as dataholz.eu have been created. Beyond this development, there are efforts to return to construc-

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

tion types with a more limited quantity of layers. This aims at either simplifying the details of joints and connections, the successive demolition at the end of a building life cycle, or the replacement of construction components and individual construction ­layers during maintenance. Considerations on how to recycle valuable resources play a role, leading to a renewed interest in ­monolithic construction types. The current availability of suitable wood-based materials such as cross-laminated timber and dowel laminated timber is conducive to such developments. The low thermal conductivity rate of timber (λ-value = 0.13 W/mK) allows achieving ­satisfactory U-values by use of sufficiently thick solid timber walls. Studies show that the actual performance characteristics of solid timber construction components is better than calculations indicate in terms of thermal insulation [15]. In the case of test buildings comprising log structures with 20-cm thick solid timber walls, the mea­ sured ­heating energy consumption was 35 – 40 % lower than calculated. A closer look at the thermal insulation characteristics of related timber construction components has revealed values significantly lower than the normative values for thermal conduc­ tivity for solid ­timber according to DIN EN 12 524 with a λ-value of 0.13 W/mk. This observation is based on the actually mea­ sured thermal conductivity of λ = 0.0856 to 0.0979 under consideration of the average wood moisture content (u = 7.6 %). If the solid timber structure features additional air cavities, for instance in the case of longitudinal milled grooves, even lower thermal conductivity rates of λ = 0.07 to 0.08 W/mK can be achieved [16]. Interrelation of building physics requirements Aside from thermal insulation characteristics, further building physics requirements for exterior walls demand consideration: a

solid timber wall needs to be sufficiently ­airtight across its surface and along joints between elements in order to minimise transmission heat losses and to prevent excessive condensation within the component. The airtightness leads to interdependencies of soundproofing and fire safety qualities of a particular construction component. Thanks to the fact that wood is diffusionpermeable, moisture that develops within a construction component due to diffusionrelated processes can be discharged to the exterior layer and, in the case of a ventilated or back-ventilated facade, dry out sufficiently. Typically, these outward-directed diffusion processes occur in winter. In summer the diffusion direction reverses, leading to potential increased moisture entering interiors. Experience shows that this is unproblematic in the case of monolithic exterior walls. Nevertheless, it is recommended to closely observe diffusion processes within an entire construction component. An holistic look at construction types Only a precise simulation of complex ­interrelations allows coordinating all components in a manner that leads to a robust, organic system. By using timber, the careful coordination of all building physics characteristics of construction components based on specific functional requirements and in combination with appropriate building ­services allows the creation of simplified construction types comprising a limited quantity of layers, even monolithic ones. the following example demonstrates this fact: the exterior wall of a five-storey residential and commercial building features a 30-cm thick dowelled solid timber wall with exposed interior surface, additional thermal grooves and a resulting thermal conductivity of λ = 0.079 W/mK (Fig. C 3.35, p. 120). A 22-mm thick softwood fibre panel serves to cover the timber element joints in a ­sufficiently ­airtight manner. Successively applied 6-cm thick flax fibre insulation is covered by verti-

119

cal siding without an additional air layer in order to protect the structure from weather effects. These prefabricated cladding ­elements are designed to allow easy replacement of individual parts in the case of damages related to moisture intrusion. The orientation of the building and the degree of fenestration are precisely coor­ dinated with the possible storage capacity of the solid timber walls and the timber­ concrete composite ceiling with a rammedearth top layer. Indoor temperatures neither drop below 18 °C in winter nor rise above 25 °C in summer. This makes mechanical ventilation or heating unnecessary [17]. From 2016 to 2020, the “Building Simply” research project looked at how to create monolithic construction components with simple details using three building ­materials – lightweight concrete, solid ­timber and highly thermally insulated masonry brick [18]. For this purpose, three residential building prototypes were erected in Bad Aibling. The walls of the timber ­building consist of solid timber with re­­ inforced concrete ceiling slabs. The solid ­timber walls are 30-cm thick and feature three layers (Fig. C 3.38, p. 121). The two exterior layers comprise 40-mm thick horizontal spruce ­layers laminated to a middle layer made of vertical spruce lamellae with milled ventilation slots, similar to vertically perforated brick. As a result, an U-value of 0.224 W/m2K is achieved for the exterior wall. The solid timber wall is polyfunctional, i.e. it is load bearing, sufficiently airtight and adequately thermally insulated (Fig. C 3.3, p. 99). On the exterior, back-ventilated ­vertical siding offers weather protection for the solid timber wall. Due to the diffusionpermeable wall composition, the drying potential of the structure is sufficient to respond to possible moisture intrusion [19]. For this project, an additional thermal insulation layer and a separate airtight layer were intentionally omitted. The exterior wall composition building physics requirements were

120

C 3.35 Residential and office building, Zweisimmen (CH) 2014, N11 Architekten a elevation b  axonometric illustration, exterior wall C 3.36 Woodcube, Hamburg (DE) 2013, Architektur­ agentur Stuttgart a elevation b  axonometric illustration, exterior wall C 3.37 House MaxAcht, Stuttgart (DE) 2019, ­Architekturagentur Stuttgart a elevation b  axonometric illustration, exterior wall

C 3.38 Research project “Building Simply”, Bad Aibling (DE) 2020, Florian Nagler Architekten  a axonometric illustration, exterior wall, timber building b  elevation (centre: timber building)  c, d  adhesive seal, floor slab area, timber ­building  e adhesive seal, solid timber wall, area of ­windowsill / jambs / soffits C 3.39 Comparative illustration, individual construction components (roof / exterior wall / floor slab), taken from Part E – project examples, scale 1:20 (Fig. p. 122 –125)

identified by use of simulation calculations that took a prognosis on user behaviour and air exchange through a mechanical ventilation system into account [20]. In the case of monolithic structures, guaranteeing the ne­cessary airtightness and, as a result, preventing condensate is a particular challenge in the area of construction component joints and connections. For this example, the ­element joints of the exterior wall feature

a layer of sealing tape placed into the joints, covered by an airtight exterior adhesive strip seal. The gaps between window elements and solid timber walls are sealed along all sides with joint sealing tape. The ventilation slots of the timber wall received airtight adhesive seals in the areas of door and window soffits and sills and along the ceiling support (Fig. C 3.38 c – e). This reduced degree of airtightness becomes

312 mm 180 mm

306 mm

300 mm

possible thanks to the ventilation concept for the apartments. Ventilation to prevent moisture intrusion leads to an air exchange rate of 0.2 in order to balance higher userspecific indoor air moisture intrusion. In the coming years, the three buildings of the research project – the lightweight concrete building, the solid timber building and the highly thermally insulated masonry brick building – will be subject to monitoring [21].

312 mm

306 mm

180 mm

b

b

b

306 mm solid timber wall (cross-laminated timber, dowelled, with thermal grooves) 22 mm softwood fibre panel 60/60 mm substructure 6 mm flat insulation 60 mm vertical wood siding (fat logs) 30 – 80 mm U-value: 0.153 W/m2K

312 mm solid timber wall (cross-laminated timber, ­dowelled, with thermal grooves) 35 mm softwood fibre panel; horizontal battens 40 mm softwood fibre panel; diffusion-permeable ­sarking layer; substructure; unvented air layer (firestop) horizontal siding U-value: 0.19 W/m2K

180 mm solid timber wall (stacked boards, cross lap joints); 140 mm mineral insulation (battens / counterbattens); diffusion-permeable sarking layer 30 mm vertical battens with horizontal c­ounterbattens horizontal siding U-value: 0.166 W/m2K

a

C 3.35

a

C 3.36

a

C 3.37

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

312 mm

306 mm

121

300 mm

300 mm solid timber wall (cross-laminated timber with air cavities, laminated); back ventilation 30 mm vertical battens; 30 mm horizontal counterbattens; 30 mm vertical wood siding U-value: 0.224 W/m2K

This will include observations of user behaviour, energy consumption of technical systems and their operating condition, as well as indoor climate in relation to temperature, humidity and noise. Moisture monitoring of construction components will serve to test assumptions on building physics values of the related simplified monolithic construction types. Demolition / recycling Currently about 80 % of annual reclaimed timber stock in Germany is used as fuel and only 20 % is employed for the production of particle board [22]. The use of simple construction components featuring a limited quantity of layers can facilitate the recycling and reuse of individual components within their respective material cycles. It therefore becomes necessary to consider demolition at the end of a building life cycle already during the planning of construction component and element joints and connections. It is therefore also necessary to develop joints and connections that enable clean separation and sorting. Ongoing research projects deal with the related and different fields of enquiry within circular construction. New developments in this future-oriented realm are to be expected soon [23].

a Notes:   [1] internet-based construction component catalogue of Holzforschung Austria: www.dataholz.eu ­(accessed 19.09.2021)  [2] MHolzBauRL, www.dibt.de/fileadmin/dibt-website/ Dokumente/Amtliche_Mitteilungen/2021_04_MHolzBauRL.pdf (accessed 19.09.2021)   [3] Winter, Stefan; Merk, Michael: Partial project TP 02 Brandsicherheit im mehrgeschossigen Holzbau. High Initiative Bayern – Holzbau der Zukunft. ­Bayerisches Staatsministerium für Wissenschaft, Forschung und Kunst (ed.). 15.07.2008; http://hdz.devweb.mwn.de/HDZ/forschungs­ berichte/teilprojekt-2.pdf (accessed 26.09.2021)   [4] Marutzky, Rainer et al.: Timber protection practice commentary, DIN 68 800 parts 1 to 4. Berlin 2013   [5]  see note 1   [6] Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz: Bauen mit Brettsperrholz im Geschossbau. Holzforschung Austria (ed.). Vienna 2014  [7] ibid.   [8] Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz: Holzrahmenbauweise im Geschossbau – Fokus Bauphysik. Holzforschung Austria (ed.). ­Vienna 2014   [9]  see note 4 [10]  see note 6 [11] Stein, René et al.: Konstruktionskatalog Fassaden­ elemente für Hybridbauweisen. TU Munich 2016 [12] Informationsdienst Holz (ed.): Bauen mit Brett­ sperrholz. Tragende Massivholzelemente für Wand, Decke und Dach. Timber construction handboook series 4, part 6, chapter 1, 04/2010 [13] Flachdächer in Holzbauweise. Informationsdienst Holz, series 3, part 2, chapter 1, Holzbau Deutschland-Institut e. V. (ed.), Berlin 2019 [14] ibid. [15] Nagler, Florian et al.: Einfach Bauen. Ganzheitliche Strategien für energieeffizientes, einfaches Bauen – Untersuchung der Wechselwirkung von Raum, Technik, Material und Konstruktion. Research ­report, TU Munich. Stuttgart 2019 [16] corresponding to the information provided by the following manufacturers of solid timber construction components: Holz 100 by Thoma Holz; H. R. W. Vollholz Wandsystem; Holzius [17]  db deutsche bauzeitung 03.2016, p. 42ff. [18]  see note 15 [19]  see note 15 [20] Research project Einfach Bauen 2, Jarmer, Tilmann et al.: Einfach Bauen 2 – Planen, Bauen, Messen. Munich 2021 www.einfach-bauen.net; www.bbsr. bund.de/BBSR/DE/veroeffentlichungen/bbsr-­ online/2021/bbsronline-11-2021.html (accessed 29.09.2021) [21] Research project Einfach Bauen 3, www.einfachbauen.net [22] https://altholzverband.de/2018/05/31/altholzver­ wertung-in-deutschland/ (accessed 24.3.2021) [23] Klinge, Andrea; Roswag-Klinge, Eike: Holz – ein zirkulärer Stoff. Holzbauforum Innsbruck 2019

b

c

d

e

C 3.38

122

01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 01 Student Residence in Vancouver, 02 Residential and Office Building see p. 190ff. in Berlin, see p. 194ff. 01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS 02-WOHN/GESCHÄFTSHAUS

Roof complete structure U-value

01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM 01-STUDENTENWOHNHEIM

04-WOHNANLAGE 04-WOHNANLAGE 04-WOHNANLAGE 04-WOHNANLAGE

round gravel 80 mm filter layer 50 mm 2-ply sealant insulation to falls 200 mm vapour barrier OSB 15 mm dowel laminated timber ceiling 160 mm

sealant insulation to falls 210 – 390 mm vapour barrier cross-laminated timber 160 mm

0.15 W/m2K

0.14 W/m2K

0.12 W/m2K

high-pressure laminate panel 8 mm substructure 25 mm thermal insulation 50 mm sarking layer 2 mm exterior sheathing 13 mm metal studs, thermal insulation 152 mm vapour barrier 2 mm gypsum board 16 mm

render thermal insulation gypsum fibreboard vapour barrier cross-laminated timber 2-ply gypsum fibreboard

fibre glass-reinforced concrete elements 70 mm substructure, back ventilation 30 mm sarking layer thermal insulation 160 mm dowel laminated timber wall 100 mm thermal insulation 80 mm substructure 30 mm sheet felt gypsum fibreboard 2≈ 12.5 mm

silver fir cladding 20 mm battens 40 mm sarking layer OSB 15 mm wood studs, mineral wool 280 mm OSB, joints adhesively sealed 15 mm gypsum board 12.5 mm

0.35 W/m2K

0.22 W/m2K

0.13 W/m2K

0.15 W/m2K

flooring screed cross-laminated timber gypsum board drywall profile spring clamps gypsum board

flooring 16 mm screed 74 mm separating layer impact soundproofing 30 mm temporary seal bonded concrete top layer 120 mm cross-laminated timber ceiling 140 mm

flooring screed separating layer impact soundproofing hollow box element with 50 mm crushed stone fill spring clamps gypsum fibreboard

REI 90; L’n, w ≤ 46 dB; R’w ≥ 54 dB

REI 60; L’n, w = 50 dB; R’w = 62 dB

6 mm 12 mm 114 mm 2 mm 12 mm

0.23 W/m2K

Exterior wall complete structure U-value

03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS

04-WOHNANLAGE 04-WOHNANLAGE 04-WOHNANLAGE 04-WOHNANLAGE 06 Residential Complex in Ansbach, see p. 212ff. 04-WOHNANLAGE 04-WOHNANLAGE 04-WOHNANLAGE 04-WOHNANLAGE

round gravel 80 mm protective layer 10 mm sealant 7 mm insulation to falls 150 – 250 mm vapour barrier 3.5 mm OSB 10 mm dowel laminated timber ceiling 200 mm airtight foil spring clamps 27 mm gypsum fibreboard 18 mm

sealant bituminous panel insulation to falls variable vapour barrier gypsum fibreboard corrugated sheet metal steel beams to falls hung ceiling

Ceiling slab complete structure REI; impact sound insulation; airborne sound insulation

03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS 04 Residential and Commercial ­Building in Zurich, see p. 204ff. 03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS 03-WOHN/GESCHÄFTSHAUS

40 mm 169 mm 16 mm 38 mm 19 mm 2≈ 16 mm

120 min.; L’n, w = 55 – 60 dB (estimate); R’w = 58 dB (estimate)

15 mm 140 mm 18 mm 85 mm 36 mm

10 mm 70 mm 30 mm 240 mm 27 mm 18 mm

flooring screed separating layer impact soundproofing bonded crushed stone fill temporary seal cross-laminated timber

10 mm 65 mm 40 mm 80 mm 180 mm

F60-B / fire-retardant; L’n, w = 50 dB; R’w = 65 dB

123

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

NHÄUSER

05-REIHENHÄUSER 06-WOHNHAUS/PARKEN

07 Residential Complex in Munich, see p. 216ff.

05-REIHENHÄUSER 06-WOHNHAUS/PARKEN 05-REIHENHÄUSER 06-WOHNHAUS/PARKEN

06-WOHNHAUS/PARKEN 07-AUFSTOCKUNG 06-WOHNHAUS/PARKEN 07-AUFSTOCKUNG

Ceiling slab complete structure REI; impact sound insulation; airborne sound insulation

Exterior wall complete structure U-value

Roof complete structure U-value

HÄUSER HÄUSER

06-WOHNHAUS/PARKEN 07-AUFSTOCKUNG

08 Residential Development in ­Munich, see p. 220ff.

08-WOHNHÄUSER 07-AUFSTOCKUNG

09 Residential Buildings in Zurich, see p. 232ff.

08-WOHNHÄUSER 07-AUFSTOCKUNG 08-WOHNHÄUSER 07-AUFSTOCKUNG

09-ILLWERKE 08-WOHNHÄUSER

13 Office Building in Vandans, 09-ILLWERKE see p. 240ff.

08-WOHNHÄUSER 09-ILLWERKE 08-WOHNHÄUSER

green roof 80 mm drainage panel 20 mm sealant thermal insulation 2 % to falls 275 mm thermal insulation 240 mm vapour barrier cross-laminated timber 160 mm

round gravel drainage 40 mm building protection mat 6 mm sealant insulation to falls 20 – 200 mm thermal insulation 60 mm latex-bonded crushed stone fill 60 mm vapour barrier, temporary seal cross-laminated timber 140 mm

extensive green roof 128–328 mm sealant insulation to falls 10 –190 mm thermal insulation 140 mm vapour barrier ribbed ceiling with laminated 22 mm OSB panel 242 mm cavity, installation, ventilation 68 mm cavity insulation 50 mm gypsum board 15 mm

extensive green roof 100 mm sealant thermal insulation 300 mm insulation to falls 140 mm vapour barrier composite timber-concrete ribbed ­ceiling: reinforced concrete 80 mm glued laminated timber ribs 240/280 mm acoustic panel

0.05 W/m2K

0.13 W/m2K

0.08 W/m2K

0.10 W/m2K

silver fir cladding with silicate coating 24 mm battens 24 mm back ventilation 40 mm prefabricated timber frame element: windproofing gypsum fibreboard 2≈ 18 mm wood studs, thermal insulation 240 mm gypsum fibreboard 2≈ 18 mm installation level 75 mm

larch facade cladding 19 mm horizontal battens 35 mm vertical battens 15 mm sarking layer gypsum fibreboard 2≈ 12.5 mm wood studs, thermal insulation 200 mm gypsum fibreboard 12.5 mm PE film vapour barrier gypsum fibreboard 12.5 mm

silver fir cassette facade 22 mm back ventilation 33 mm sarking layer gypsum fibreboard 15 mm wood studs, thermal insulation 360 mm OSB, joints adhesively sealed 15 mm gypsum fibreboard 18 mm

shiplap siding 27 mm counterbattens 40 mm back-ventilation battens 40 mm cement-bonded particle board 16 mm structure, thermal insulation 340 mm vapour barrier 18 mm OSB 18 mm thermal insulation /  installation layer 110 mm oak panelling 20 mm

0.13 W/m2K

0.24 W/m2K

0.12 W/m2K

0.12 W/m2K

flooring 5 mm screed 55 mm separating layer impact soundproofing 40 mm latex-bonded crushed stone fill 100 mm trickle protection cross-laminated timber 140 mm

flooring 15 mm screed, separating layer 53 mm impact soundproofing 27 mm bonded fill installation layer 30 mm OSB 15 mm dowel laminated timber ceiling 180 mm gypsum fibreboard 18 mm cavity, installation, ventilation 50 mm cavity insulation 50 mm gypsum fibreboard 15 mm

flooring 10 mm mineral-based material panel 38 mm insulated installation level 122 mm cavity insulation 30 mm composite timber-concrete ribbed ceiling: reinforced concrete 80 mm glued laminated timber ribs 240/280 mm hung ceiling

REI 60; L’n, w = 50 dB; R’w = 55 dB

REI 90; L’n, w = 30 dB; R’w = 60 dB

parquet 15 mm heating screed 65 mm PE film, impact soundproofing 30 mm perlite fill 90 mm trickle protection cross-laminated timber, exposed surface 220 mm

F60-B below; REI 60 K260 above; REI 60; L’n, w = 53 dB; R’w = 54 dB L’n, w = 53 dB (Ln, w = 41 dB); R’w = 57.9 dB

C 3.39

124

RKE E

11-VERWALTUNGSBAU 11-VERWALTUNGSBAU 11-VERWALTUNGSBAU

10-BÜROGEBÄUDE 10-BÜROGEBÄUDE 10-BÜROGEBÄUDE 14  Office Building in St. Johann in 10-BÜROGEBÄUDE 10-BÜROGEBÄUDE 10-BÜROGEBÄUDE Tyrol, see p. 246ff.

RKE E

KE EERKE

11-VERWALTUNGSBAU 11-VERWALTUNGSBAU 11-VERWALTUNGSBAU

Exterior wall complete structure U-value

Roof complete structure U-value

10-BÜROGEBÄUDE 10-BÜROGEBÄUDE 10-BÜROGEBÄUDE

16 11-VERWALTUNGSBAU Administrative Building in 11-VERWALTUNGSBAU 11-VERWALTUNGSBAU Clermont-­Ferrand, see p. 254ff.

17 Community Centre in St. Gerold, 12-GEMEINDEZENTRUM 12-GEMEINDEZENTRUM 12-GEMEINDEZENTRUM see p. 258ff.

12-GEMEINDEZENTRUM 12-GEMEINDEZENTRUM 12-GEMEINDEZENTRUM

13-GYMNASIUM

14-EU

18 Secondary School in Diedorf, see p. 13-GYMNASIUM 262ff.

13-GYMNASIUM

sealant 10 mm thermal insulation 280 mm vapour barrier 4 mm OSB on wedge-shaped battens cavity 22 mm hollow box: OSB on glued laminated timber ribs 740 mm

extensive green roof 70 mm sealant thermal insulation 210 mm vapour barrier laminated veneer lumber with gypsum board 40 mm glued laminated timber beam 250 mm

0.16 W/m2K

0.20 W/m2K

0.10 W/m2K

0.10 W/m2K

corrugated sheet metal battens, sarking layer OSB timber structure, thermal insulation vapour barrier thermal insulation gypsum board

rough-sawn silver fir battens 30 mm battens 30 mm counterbattens / back ventilation 30 mm sarking layer diagonal sheathing 25 mm studs, wood fibre insulation 125 mm diagonal cladding 25 mm studs, wood fibre insulation 200 mm sheathing, vapour barrier 25 mm battens, installation layer acoustic insulation 40 mm silver fir cladding 20 mm

vertical battens horizontal battens vertical battens wood fibre panel structure, thermal insulation structure, thermal insulation OSB (= vapour barrier)

0.40 W/m2K

0.12 W/m2K

0.13 W/m2K

flooring dry screed impact soundproofing honeycomb fill cross-laminated timber hung cooling ceiling installation layer

flooring 27 mm floor sleepers with loam panels 62 mm wood fibre impact soundproofing panel 30 mm dowelled stacked timber 220 mm installation layer cavity insulation 40 mm gypsum fibreboard 15 mm installation layer acoustic insulation 30 mm trickle protection fleece silver fir battens 40 mm

flooring 5 mm screed 85 mm impact soundproofing 30 mm levelling insulation 50 mm separation layer bonded reinforced concrete 98–120 mm OSB 22 mm beam level 320 mm soundproofing 40 mm acoustic panel 35 mm

REI 30; L’n, w = 48 dB; R’ = 65 dB

n.s.; L’n, w = 53 dB; R’w = 55 dB

vertical larch battens battens sarking layer wood fibre insulation board timber structure, thermal insulation OSB

85 mm 85 mm 32 mm 280 mm 22 mm

flooring with impact soundproofing 10 mm OSB 18 mm impact soundproofing 32 mm hollow box element 520 mm with crushed stone fill 60 mm gypsum board 2≈ 20 mm suspension, cable routing 500 mm OSB 18 mm REI 90; L’n, w = n.s.; R’w = n.s.

30 mm 30 mm 10 mm 145 mm 60 mm 2≈ 10 mm

10 mm 25 mm 15 mm 30 mm 147 mm 495 mm

REI 60; L’n, w = 82 dB; R’w = 38 dB

14-EU

14-EU

2-ply sealant 5 mm timber cladding 27 mm substructure, ventilation 500 mm PE film 2 mm timber sheathing 27 mm floor sleepers to falls, wood fibre insulation 40 – 230 mm wood blocking, wood fibre insul. 180 mm wood beam, wood fibre insul. 110 mm timber sheathing, vapour barrier 27 mm installation layer 110 mm soundproofing 30 mm trickle protection fleece silver fir battens 40 mm

0.12 W/m2K

Ceiling slab complete structure REI; impact sound insulation; airborne sound insulation

12-GEMEINDEZENTRUM 12-GEMEINDEZENTRUM 12-GEMEINDEZENTRUM

extensive green roof 150 mm sealant thermal insulation 20 mm wood battens, thermal insulation 60 mm thermal insulation 160 mm wood battens, thermal insulation 160 mm vapour barrier separating layer laminated veneer lumber panel / mineral bonded wood wool board 51 mm glued laminated timber rafters 100/360 mm

30 mm 40 mm 50 mm 16 mm 140 mm 220 mm 18 mm

T H E L A Y E R S T R U C T U R E O F B U I L D ING ENVELOPES

MNASIUM GYMNASIUM

14-EUROP.SCHULE 14-EUROP.SCHULE

14-EUROP.SCHULE 14-EUROP.SCHULE

21 Agricultural Training Centre in 15-SANIERUNG 15-SANIERUNG ­Altmünster, see p. 276ff.

22 Student Housing in Hamburg, 16-HOTEL see p. 280ff. 16-HOTEL

23 Office Building in Alpnach, see p. 284ff.

16-HOTEL 16-HOTEL

15-SANIERUNG 15-SANIERUNG

Exterior wall complete structure U-value

Roof complete structure U-value

GYMNASIUM MNASIUM

16-HOTEL 16-HOTEL

15-SANIERUNG 15-SANIERUNG

19 European School in Frankfurt am 14-EUROP.SCHULE 14-EUROP.SCHULE Main, see p. 268ff.

GYMNASIUM MNASIUM

125

sealant insulation to falls min. 120 mm vapour barrier cross-laminated timber 80 mm thermal insulation 50 mm wood wool acoustic panel 25 mm beech laminated veneer lumber beam 360 mm

extensive green roof 110 mm sealant 13 mm insulation to falls 300 – 500 mm vapour barrier 4 mm 3-ply sheeting 40 mm joists, air layer 360 mm installation layer 290 mm sheep wool 30 mm acoustic fleece 1 mm silver fir wood slat ceiling 30 mm

extensive green roof 80 mm sealant insulation to falls 40 – 200 mm thermal insulation 200 mm bituminous temporary seal cross-laminated timber 160 mm

canted sheet aluminium timber sheathing counterbattens sealant thermal insulation thermal insulation 5-ply solid timber element

0.18 W/m2K

0.11 W/m2K

0.13 W/m2K

0.136 W/m2K

0.25 W/m K

fir cladding 30 mm battens / counterbattens 60 mm sarking layer cladding 20 mm timber structure / thermal insul. 370 mm sheathing, vapour barrier 20 mm gypsum board 12.5 mm installation layer / thermal insul. 40 mm silver fir cladding 20 mm 0.09 W/m2K

flooring 2,5 mm dry screed 38 mm impact soundproofing 25 mm cross-laminated timber 80 mm levelling insulation (module joint) 60 mm cross-laminated timber 60 mm soundproofing 60 mm acoustic panel 25 mm beech laminated veneer lumber beam 560 mm

flooring 27 mm floor sleepers, infill insulation 30 mm impact soundproofing 40 mm expanded clay fill 53 mm bonded reinforced concrete 120 mm dowel laminated timber element 200 mm installation layer 290 mm soundproofing 30 mm acoustic fleece 1 mm silver fir wood slat ceiling 30 mm

natural rubber particle board impact soundproofing PE film crushed stone fill cross-laminated timber thermal insulation cross-laminated timber

n.s.; L’n, w = n.s.; R’w = n.s.

n.s.; L’n, w = 48 dB; R’w = 57 dB

REI 90; L’n, w = 41 dB; R’w = 61 dB

sheet aluminium wind paper thermal insulation beech laminated veneer lumber column

1 mm 120 mm 120 mm

Ceiling slab complete structure REI; impact sound insulation; airborne sound insulation

2

3 mm 27 mm 60 mm 5 mm 60 mm 120 mm 260 mm

larch facade panel 26 mm substructure / thermal insulation 2 00 mm sarking layer rough sawn spruce cladding 30 mm substructure / thermal insulation 2 00 mm 6-ply solid timber element 180 mm cross-laminated timber 125 mm 7-ply solid timber element 206 mm 0.17 W/m2K

0.193 W/m2K

0.4 mm 2≈ 19 mm 30 mm 60 mm 80 mm 70 mm 60 mm

beech parquet 20 mm solid beech, milled grooves for underfloor heating 44 mm impact soundproofing 60 mm 3-ply spruce lattice grid 150/36 mm infilled crushed limestone solid beech, milled grooves 60 mm 2-ply beech lattice grid 150/36 mm REI 60; L’n, w = n.s.; R’w = n.s. C 3.39

126

The Layer Structure of Interior Construction Components Christian Schühle

C 4.1

Interior construction components of multistorey timber buildings, such as ceilings and partition walls, are highly important in subdividing buildings into functional units and fire compartments. Planners must take the related soundproofing and fire safety requirements into account. In contrast, the necessary thermal insulation installed ­between functional units results from the construction type and does not call for any further measures. Moisture protection is only necessary in wet and humid rooms. The airtightness of structures is an important criterion in ensuring fire safety and soundproofing. Air, smoke or fumes flowing through leaks within construction components or leaky joints between components can facilitate the growth of a fire. Such leaks will also significantly impair the sound reduction index of construction components. The layer structure of ceilings and walls is influenced by more than building physics requirements. Service line layout and design aspects are also crucial in the planning and construction of functional layers (Fig. C 4.2). The chapter on “Protective Functions” features a detailed description of the various related requirements (p. 78ff.).

C 4.1 Research and office building, Prince George (CA) 2014, Michael Green Architecture C 4.2 Functional layers and construction component layers of ceilings, example: residential buildings in Zurich (CH) 2016, Rolf Mühletaler (areas / aspects in grey are not or not necessarily relevant to interior construction components)

Soundproofing Due to their low mass, timber structures are typically built with multiple ­layers in order to meet the required soundproofing requirements. The sound reduction level that can be achieved in such structures depends on the properties of individual layers, their connections between each other and insulation material filled into cavities. Flexible shells with large surface mass can be used as cladding in order to achieve good soundproofing values. Decoupled connections can further improve soundproofing characteristics. During construction it must be ensured that layer element joints are sealed. Ceiling structures provide

the required impact soundproofing mostly by adding mass, either in the form of heavy fill, a layer of concrete block, a load-bearing layer of concrete – in the case of composite timber concrete structures, or by decoup­ ling the floor construction. In general, ­ceilings that meet impact soundproofing requirements also meet airborne soundproofing requirements. Precisely determining soundproofing target values is recommended and, in parallel, planning of soundproofing measures under consideration of byways. Fire protection The political will to promote timber construction as an important contribution to climatefriendly construction is reflected in the amendment to the Model Construction Directive (MBO) in the most recently enacted September 2019 version. Under particular circumstances, it permits the use of combustible construction materials for loadbearing and stiffening construction components serving as partitions that meet the “highly fire-resistant” requirement (R 60 / REI 60). Non-load-bearing construction components that serve as partitions with the required fire resistance class “fire-resistant” (EI 90) as per MBO can be built as combust­ ible construction types if fire safety cladding consists of non-combustible building materials and non-combustible insulation materials find use. Under consideration of technical construction regulations, it is possible – with very few exceptions – to produce fire-resistant construction components from combustible building materials without needing to apply for an exemption. The new Model Timber Construction Directive (Musterholzbaurichtlinie, M-HFHHolzR) offers concrete information on component construction types. Construction components for timber frame and wall framing construction types are permissible up to building class 4, i.e. a building height of five full storeys without setbacks. The precondition

T H E L A Y E R S T R U C T U R E O F I N T E R I O R C O N S T R U C T I O N COM PONENTS

faces can remain exposed. Expert groups view the new MHolzBauRL, despite the included easements, in part critically and as not sufficiently extensive. For instance, the encapsulation criteria of the previous 2004 directive were adopted while ignoring more recent advances in research from Germany, Austria and Switzerland. The introduction of MHolzBauRL in all federal German states endangers the progress made in timber construction as initiated by specific approaches of particular federal states. In return, this would lead to significant setbacks for timber construction. Aside from the legal provisions described above, a variety of different manufacturer-specific fire protection tests and licences exist for relevant construction materials in timber construction. Planners and contractors can easily be overwhelmed by this variety, which

Construction component layers of ceiling slabs 15 mm upright lamella parquet flooring, adhesive bond 53 mm anhydrite heating screed PE film separation layer 2≈ 20 mm mineral wool impact soundproofing 15 mm OSB 180 mm dowel laminated timber ceiling 18 mm gypsum fibreboard 30 mm installation clearance 25 mm hung ceiling slats connected to spring clips 50 mm cavity insulation between battens 15 mm gypsum board

Protective functions of ceiling slabs

weather protection

airtight layer thermal insulation condensation protection

°C

REI 60 Ln, w' < 53 dB R'w > 52 dB

likely constitutes a decisive obstacle to the broad application of multi-storey timber construction in Germany and Austria. The standardisation of construction components and details that serve as a basis for verification have been implemented in the inter­ active construction component ­catalogue dataholz.eu.

The Layer Structure of Timber Ceilings The layer structure of timber ceilings differs greatly in its complexity from that of timber partition walls, due to impact soundproofing requirements (Fig. C 4.2). Typical ceilings can comprise the following layers: flooring screed/ substructure separation layer acoustic decoupling

(additional mass)

(trickle protection)

airtight layer

load-bearing structure

Functional layers of ceiling slabs

in such cases is that timber construction components are continuously clad in two layers of non-flammable panel materials, termed as K 260 encapsulation. Certified fire safety cladding typically consists of gypsum board of 36-mm total thickness. Nonflammable insulation materials with a melting point above 1,000 °C must be installed in cavities. Building services installations can only be routed to a very limited extent through load-bearing and stiffening construction components. Standard buildings based on solid timber construction types are permissible up to building class 5, i.e. below the high-rise threshold, while the area of functional units must not exceed 200 m2. In such cases, solid timber construction components must feature 18-mm gypsum board cladding. Ceilings or alternatively 25 % of wall sur-

127

fire protection installation layer soundproofing cavity insulation acoustics ceiling cladding/panelling C 4.2

128

Floor construction: • flooring • substructure: wet or dry screed, sleepers, raised floor construction •  impact soundproofing •  additional mass / levelling fill •  trickle protection as required Load-bearing layer: •  beam ceiling •  box ceiling element •  dowel laminated timber ceiling •  timber concrete composite ceiling •  specific applications Ceiling underside:

• direct cladding or hung ceiling, acoustic applications as required •  infill insulation •  trickle protection as required The soundproofing and fire safety strategies for ceiling structures will vary, depending on whether an unfinished ceiling is supposed to remain exposed or become concealed. The fire resistance of an unfinished ceiling must be designed for burnout in the case of fire loads from below. For soundproofing tasks, this means that it is essential to add mass on top of a ceiling structure, since only few layers are available for the reduction of sound transmission.

Floor construction Although the choice of floor covering mate­ rials can positively affect the soundproofing properties of a floor construction, floor covering is not included within soundproofing verification, because it is often replaced during building operation. The selection of floor covering materials is not a criterion specific to timber construction and will, thus, not be explicated here. Screed systems In timber buildings, typical wet and dry screed systems find use. Wet screeds possess soundproofing advantages, due to their greater mass. Cement screed is prefer-

Box ceiling 50 mm cement screed 40 mm impact soundproofing 200 mm box ceiling element L n, w = 62 dB R w = 60 dB

50 mm cement screed 40 mm impact soundproofing 60 mm crushed stone fill 200 mm box ceiling element L n, w = 46 dB R w = 71 dB

50 mm cement screed 40 mm impact soundproofing 30 mm crushed stone fill 200 mm box ceiling element with fill 50 kg/m2 L n, w = 42 dB R w = 76 dB

Cross-laminated timber ceiling 60 mm cement screed 30 mm impact soundproofing 60 mm fill, elastic bond 140 mm cross-laminated timber 70 mm direct hanger 60 mm mineral wool insulation 12.5 mm gypsum fibreboard L n, w = 46 dB R w = 62 dB REI 60

60 mm cement screed 30 mm impact soundproofing 60 mm fill, elastic bond 140 mm cross-laminated timber L n, w = 46 dB R w = 73 dB REI 60

Beam ceiling 50 mm cement screed 30 mm impact soundproofing 40 mm loose fill 18 mm OSB 220 mm construction grade timber 100 mm mineral wool 24 mm spruce formwork boards 27 mm spring rail 2≈ 12.5 mm gypsum board L n, w = 41 dB R w = 70 dB REI 60

25 mm creed element 30 mm impact soundproofing 60 mm fill, elastic bond trickle protection 140 mm cross-laminated timber L n, w ≤ 50 dB R w ≥ 62 dB REI 60

Timber concrete composite ceiling 65 mm dry screed element with impact soundproofing 18 mm OSB 200 mm construction grade timber 200 mm infilled mineral wool 24 mm spruce formwork boards 60 mm direct hanger, acoustically detached 2≈ 12.5 mm gypsum board L n, w = max. 43 dB R w min. = 76 dB REI 90

74 mm heating screed PE film separation layer 30 mm mineral wool insulation 120 mm concrete 140 mm glued laminated timber Ln, w = max. 46 dB R w min. = 54 dB REI 90

C 4.3

T H E L A Y E R S T R U C T U R E O F I N T E R I O R C O N S T R U C T I O N COM PONENTS

129

C 4.3 Common ceiling structures with various loadbearing layers

able to anhydride screed, because of its lower water content. Impact soundproofing must demonstrate the lowest possible dynamic rigidity of s' ≤ 10 MN/m3 to min­ imise the resonant frequency of a floor construction, a critical aspect of timber structures. The rigidity of an insulation material must always be coordinated with the overall screed system. Values for improving the soundproofing characteristics of screeds in combination with unfinished timber ceilings, infills and hung ceilings are included in manufacturer information or certifications for complete structures. Figure C 4.3 shows common examples. Screed usually forms the relevant fire protection top layer of a floor construction. Wet screed layers of more than 50-mm thickness and with corresponding mineral wool edge insulation strips meet the precondition “highly fire-resistant”. Most dry screed gypsum panel elements feature factoryassembled laminated impact soundproofing layers. Their advantages include dry installation and reduced thickness. The required classification “highly fire-retardant from above” can be achieved by installing 18-mm thick dry screed gypsum fibre panels [1]. They feature much lower mass than wet screeds and, as a result, require add­ itional soundproofing measures, which can negatively impact their reduced thickness. Cavity or double floors Raised floor systems often find use in office buildings in order to enable flexible routing of service lines. In such cases, fire safety in timber buildings can be achieved by including cladding on top of the unfinished structure. Otherwise, installing service lines in floor cavities and every vertical penetration would cause problems. Floorboards on sleepers One specific construction type is the com­ bination of floating floor systems on top of

flooring sleepers. In such cases, battens are mounted on top of impact soundproofing, while cavities are fully infilled with rigid insulation panels or additional mass. Timber floorboards are mechanically fastened to battens with screws or nails and placed on top of the underlying construction. This is a particularly environmentally friendly and adhesive-free construction type. It found use in the community centre in St. Gerold (Fig. C 4.4, p. 130; see also p. 258ff.) and the renovation and new construction of a boarding school (see p. 276ff.). Additional mass / levelling infill In most cases, a heavy layer must be installed beneath the impact soundproofing in order to achieve necessary soundproofing values. Dry crushed stone fill (if required, in honeycomb cardboard) typically used for this purpose is flexible and, thus, dampens resonance effects. Rubber latex can be used for bonding fill to keep it sufficiently flexible. Bonding with cement must be avoided under all circumstances, because this increases the fill rigidity in a disadvantageous way. Small-format concrete or loam panels can also be used for adding weight. However, they are not as effective as fill with the same mass, due to greater rigidity. Fill within a floor structure also permits laying out service lines. Related installations must be completely covered with fill materials to prevent them from transmitting sound pressure. Penetrating the impact soundproofing layer must be completely avoided. In exposed ceilings between functional units, services lines for ceiling lights etc. should not be routed within the floor ­construction of the functional unit above, because penetrating the airtight layer makes it impossible to meet the necessary soundproofing and fire safety requirements. In addition, organisational problems arise when electrical lines cross units operated by different parties or owners (see “Building

Services – Particularities of Timber Construction”, p. 136ff.). Exposed beam ceilings or those comprised of dowel laminated timber or crosslaminated timber can only achieve the required level of soundproofing for ceilings that separate functional units by introducing additional mass (see “Protective Functions”, p. 78ff.). Trickle protection Film layers, building wrap, cladding and panelling with adhesively sealed joints mounted to an unfinished ceiling prevent both fill from trickling through and, thus, its uncontrolled settling. They also provide the airtightness necessary for soundproofing and fire safety purposes. Crosslaminated timber ceilings with adhesively sealed edges and glued joints do not require trickle protection and are also ­airtight. Dowel laminated timber ceilings without adhesive connections are typically covered by panel materials with a stiffening function that also offer adequate trickle ­protection. If joints are adhesively sealed, necessary airtightness is achieved. Trickle protection in the form of a fleece layer is necessary for perforated acoustic ceilings to prevent fibres from insulation installed to dampen noise in cavities or to enhance the room acoustics from trickling through. The load-bearing layer The construction of the load-bearing layer has a major influence on the layer structure of a ceiling component. Clad timber beam ceilings or box ceiling elements, with their inherently multilayered structures, display advantages for soundproofing due to the considerable distance between upper and lower layers of sheathing or cladding. In combination with appropriate cavity soundproofing, this results in soundproofing values that are better than those achieved by ­monolithic solid timber ceilings. Connecting a hung ceiling or ceiling cladding to battens

130

Function Construction component layer flooring 27 mm rough-sawn silver fir ­floorboards, nailed to substructure 62 mm sleepers with inlaid loam panels impact soundproofing 30 mm wood fibreboard load-bearing layer dowel laminated timber ceiling 220 mm 110 mm hung ceiling clearance cavity insulation 40 mm sheep wool felt insulation fire protection/ 15 mm grouted gypsum fibresoundproofing board 36 mm installation level acoustic insulation 30 mm sheep wool felt insulation black trickle protection fleece sound permeable 40/35 mm silver fir battens cladding / panelling L'n, w = 48 dB R'w = 65 dB REI 30 C 4.4

Function Construction component layer flooring 10 mm oak mosaic parquet, oiled finish screed 65 mm heating screed separation layer PE film separation layer impact soundproofing 40 mm mineral wool additional mass 80 mm bonded crushed stone fill elastomeric bitumen temporary sealant load-bearing layer 180 mm cross-laminated timber L'n, w = 49 dB R'w = 65 dB REI 60 C 4.5

Function Construction component layer flooring 16 mm parquet 74 mm screed separation layer PE film separation layer impact soundproofing 30 mm mineral wool load-bearing layer /  120 mm concrete mass load-bearing layer 140 mm glued laminated timber L'n, w = max. 46 dB R'w = min. 54 dB REI 90

C 4.6

Function Construction component layer floor covering 10 mm carpet flooring substructure 38 mm raised floor clearance impact soundproofing 122 mm installation layer cavity insulation 30 mm mineral wool load-bearing layer / 80 mm concrete mass load-bearing layer 240/280 mm glued laminated ­timber beam L'n, w = max. 30 dB R'w = min. 60 dB REI 90

C 4.7

combined with spring clamps or spring bars, which allows decoupling for sound transmission purposes, can improve soundproofing by 10 –12 dB compared to rigid connections [2]. Some box ceiling elements are already equipped with infill or cavity insulation during manufacture (Fig. C 4.7). When combined with an appropriate floor construction, additional soundproofing measures can become unnecessary. In contrast, solid timber ceilings, despite their greater weight and due to their rigidity – even if mitigated by a hung ceiling or ceiling cladding that is decoupled for sound transmission purposes – still require additional mass to ensure a minimum impact soundproofing level of L'n, w ≤ 53 dB. They can be a suitable choice for exposed timber structures because they comprise no cav­ ities. In relation to the specific fire safety concept, timber cladding or panelling can be attached to the underside of a solid timber ceiling (stacked timber consisting of glued laminated or cross-laminated timber) for spatial acoustics and fire protection ­purposes. Such cladding or panelling can serve as a sacrificial fire protection layer and can be easily replaced after a fire of limited extent. Timber-concrete composite ceiling construction types benefit from the load-­

C 4.4 Ceiling structure: functions and construction component layers, community centre, St. Gerold (AT) 2010, Cukrowicz Nachbaur Architekten C 4.5 Ceiling structure: functions and construction component layers, residential complex, Ansbach (DE) 2013, Deppisch Architekten C 4.6 Ceiling structure: functions and construction component layers, residential and office building, Berlin (DE) 2014, Kaden Klingbeil Architekten C 4.7 Ceiling structure: functions and construction component layers, office building, Vandans (AT) 2013, Architekten Hermann Kaufmann C 4.8 Approximate values for impact soundproofing and levels of improved impact soundproofing for various layer combinations

131

T H E L A Y E R S T R U C T U R E O F I N T E R I O R C O N S T R U C T I O N COM PONENTS

Unfinished ceiling type

Ln, w [dB]

exposed timber ceiling

85 – 87

concealed timber beam ceiling

74 –75

  with flexibly hung ceiling

64 – 65

solid timber ceiling

76 – 80

Improvement values, substructure types

DLn, w, H [dB]

cement screed on polystyrene / soft wood fibreboard

14 –16

cement screed on mineral fibre impact soundproofing mat

19 –20

dry screed Improvement values, mass types

6 –10 DLn, w, H [dB]

concrete panels /stone pavers 80 kg/m2

ca. 10

fill, elastic bond 80 kg/m2

ca. 16 C 4.8

bearing, fire safety and soundproofing ­characteristics of concrete. In such cases, a conventional decoupled floor construction is sufficient to meet soundproofing requirements for ceilings between separate functional units. By way of example, the ­residential and office building in Berlin (Fig. C 4.6; see also p. 194ff.) and the office building in Vandans (Fig. C 4.7; see also p. 240ff.) demonstrate the related simplification of ceiling construction types according to layer composition. Hung ceilings, cladding and panelling To conceal the load-bearing layer or underside of a ceiling construction and the service lines routed along it, or if specific room acoustics requirements need to be met, hung ceilings or cladding along the ceiling underside comprise typical solutions. Cavity insulation Insulation materials in construction com­ ponent cavities absorb noise within the component and prevent cavity resonance. Highly porous building materials with a ­linear flow resistance of r ≥ 5 kPa s/m2 are suitable for this purpose. Mineral wool is mostly used as cavity insulation. Cellulose, sheep wool, flax, cotton and open-cell insulation foam can also be used as insulation material, provided that their use complies with fire safety requirements. The latter is often used as acoustic insulation in order to avoid problems caused by loose fibres that are not sealed off from indoor air. Since the effect of complete ­insulation infill is not significantly better than that of partial infill, typically only one third or half of a cavity is insulated. Along ceiling edges and for fire safety reasons, complete insulation infill may be required in order to enable cavity-free connections to vertical construction components. Beam ceilings in combination with hung ceiling systems that dampen vibrations comprise an exception. In such cases, greater thickness of cavity

insulation yields particularly positive results – doubling the insulation thickness leads to an improvement of 1– 3 dB. Compared to cavities without infill, a typical beam depth of 20 cm combined with complete infill yields a weighted impact sound level improvement L'n, w of 7 dB [3]. Cladding Aside from design aspects, building ­physics issues such as fire protection, soundproofing and room acoustics must be considered when selecting a type of cladding. If non-flammable surfaces are required for fire safety reasons, mineralbased cladding materials such as gypsum board, calcium silicate or loam panels ­typically find use. Due to different national requirements and depending on fire-­ resistance periods and corresponding ­ceiling structures, cladding may range in thickness from 12.5 mm for REI 30 structures to up to 36 mm for encapsulated REI 90 structures. Cladding can be single-­ layered or multi­layered and applied as direct cladding, as facing shell or as a hung ceiling. Joint grouting results in airtight ­planar cladding layers. Edges can become airtight by adhesive sealing, filling combined with sealing or appropriate joint tape. An effectively flexible shell tightly mounted to the ceiling underside, if decoupled, can improve soundproofing by up to 12 dB. ­Multilayered cladding consisting of thin boards provides better results, due to lower bending stiffness, compared to singlelayered cladding of the same total thickness. Thus, cladding with two 12.5-mm thick gypsum board panels is preferable to a single 25-mm thick layer. A flexibly hung ceiling must provide at least 50 mm of clearance underneath the unfinished ceiling in the case of solid timber construction components, in order to prevent resonance. Building physics necessities can appear contradictory in terms of the requirements

placed on cladding. Room acoustics mea­ sures usually demand sound-absorbing ­surfaces, while fire prevention and soundproofing call for the exact opposite: airtightness. As a result, a design-oriented interest in exposed timber surfaces can, under certain circumstances, be incompatible with fire safety requirements, or it may not be possible to route service lines through a fire prevention layer. In such situations, the requirements are often assigned to several, separate construction component layers, e.g. direct cladding of the underside of a timber structure with gypsum board, or a decoupled hung ceiling structure comprised of fire-resistant panels (Fig. C 4.4). The clearance above an acoustic hung ceiling and the effective soundproofing and fire safety layers may be used for technical installations and to integrate ceiling lights. For a precise prognosis on soundproofing values, the broad range of exposed ceiling structures in timber construction, as well as the combinations of layers for floor and ­ceiling structures, exact verification based on existing certificates, standards specifications or the use of calculations is necessary. Figure C 4.8. provides reference points.

132

Single-layer solid timber walls 100 mm crosslaminated timber REI 60 Rw = 33 dB

25 mm gypsum fibreboard 78 mm cross-laminated timber 25 mm gypsum fibreboard REI 90 Rw = 38 dB

1≈ 12.5 mm gypsum fibreboard 70 mm battens, acoustical mounting 50 mm mineral wool 100 mm cross-laminated timber

2≈ 12.5 mm gypsum fibreboard 85 mm facing shell, freestanding 50 mm mineral wool 100 mm cross-laminated timber

REI 60/60 Rw = 51 dB

REI 60/90 Rw = dB 62

2≈ 12.5 mm gypsum fibreboard 70 mm battens, acoustical mounting 50 mm mineral wool 100 mm cross-laminated timber battens on 70 mm 2≈ 12.5 mm gypsum fibreboard REI 90 Rw 53 dB

2≈ 12.5 mm gypsum fibreboard 85 mm facing shell, freestanding 50 mm mineral wool 100 mm cross-laminated ­timber 85 mm facing shell, freestanding 2≈ 12.5 mm gypsum fibreboard REI 90 Rw = 68 dB

Single-layer wall framing elements 15 mm gypsum fibreboard 60/80 mm wood studs 60 mm mineral wool 15 mm gypsum fibreboard EI 30 Rw = 38 dB

2≈ 12.5 mm gypsum ­fibreboard 60/80 mm wood studs 60 mm mineral wool 2≈ 12.5 mm gypsum ­fibreboard EI 60 Rw = 43 dB

2≈ 12.5 mm gypsum ­fibreboard 15 mm OSB 60/100 mm wood studs 100 mm mineral wool 15 mm OSB 2≈ 12.5 mm gypsum ­fibreboard

2≈ 18 mm gypsum ­fibreboard OSB 22 mm 60/120 mm wood studs 120 mm mineral wool 22 mm OSB 2≈ 18 mm gypsum ­fibreboard

REI 60 Rw = 50 dB

REI 90 Rw = 56 dB

2≈ 12.5 mm gypsum fibreboard battens, acoustical ­mounting 50 mm mineral wool 95 mm cross-laminated timber 50 mm mineral wool 95 mm cross-laminated timber 12.5 mm gypsum fibreboard

2≈ 15 mm gypsum fibreboard 85 mm facing shell, ­freestanding 60 mm mineral wool 90 mm cross-laminated timber 50 mm mineral wool 10 mm cavity 100 mm cross-laminated timber 12.5 mm gypsum fibreboard

Double-layer solid timber elements 94 mm cross-laminated ­timber 30 mm mineral wool 94 mm cross-laminated ­timber REI 60 Rw = 48 dB

2≈ 12.5 mm gypsum ­fibreboard 90 mm cross-laminated timber 30 mm mineral wool 90 mm cross-laminated timber 2≈ 12.5 mm gypsum ­fibreboard REI 60 Rw = 56 dB

REI 90 Rw = 62 dB

REI 90/90 Rw = 65 dB

12.5 mm gypsum fibreboard 90 mm cross-laminated timber 2≈ 15 mm gypsum fibreboard 60 mm mineral wool 50 mm cavity 2≈ 15 mm gypsum fibreboard 100 mm crosslaminated timber 12.5 mm gypsum fibreboard

2≈ 12.5 mm gypsum fibreboard 90 mm cross-laminated ­timber 2≈ 15 mm gypsum fibreboard 50 mm mineral wool 50 mm cavity 2≈ 15 mm gypsum fibreboard 100 mm crosslaminated timber 2≈ 12.5 mm gypsum fibreboard

REI 60 Rw = 70 dB

REI 90 Rw = 75 dB

Double-layer wall framing elements 2≈ 12.5 mm gypsum fibreboard 60/100 mm wood studs 100 mm mineral wool 2≈ 12.5 mm gypsum fibreboard 20 mm mineral wool REI 60 Rw = 58 dB

2≈ 12.5 mm gypsum ­fibreboard 15 mm OSB 60/100 mm wood studs 100 mm mineral wool 15 mm OSB 2≈ 12.5 mm gypsum ­fibreboard 20 mm mineral wool REI 90 Rw = 60 dB

C 4.9

T H E L A Y E R S T R U C T U R E O F I N T E R I O R C O N S T R U C T I O N COM PONENTS

133

C 4.9  Common single-layer and cavity wall structures

The Layer Structure of Interior Walls Interior walls can be built as solid timber walls or as more or less prefabricated timber wall framing elements. For both construction types, solutions are available that meet all soundproofing and fire safety requirements. Their layer structure consists of a load-bearing layer and either direct cladding, flexibly mounted cladding, or freestanding facing shells. Cavity wall ­construction types are required for solid exposed timber partition walls, in order to meet soundproofing requirements. Wall framing elements that serve as nonload-bearing interior walls without fire safety requirements have the advantage that building services installations can be routed inside wall cavities almost without any restriction (Fig. C 4.11, p. 134). They also offer greater flexibility, due to the fact that they are easy to remove and generally ­display a better airborne sound reduction index compared to single-layer exposed solid timber wall structures. The advantage of routing service lines through the cavities of a wall framing element is lost in the case of a load-bearing wall in a multi-storey building, due to limitations resulting from fire safety requirements. Similar to solid ­timber walls, an additional installation layer is required. As a result of load concentrations, the need for highly rigid construction components and the problematic settlement behaviour of wall framing elements in buildings taller than three to four storeys, solid timber walls become preferable as load-bearing construction components. Due to their greater surface mass, they offer soundproofing advantages in deeper frequency ranges, although these are not in the range relevant to standards and, therefore, only partially impact required calculations. Solid timber walls without additional cladding are only suitable for areas with low-level sound and

acoustics requirements, e.g. within residential units. In combination with facing shells, freestanding components or cladding mounted on soundproofing clips, such walls can become effective construction components in terms of soundproofing. Installing facing shells with offset joints and appropriate joint grouting makes them sufficiently airtight. Thus, additional airtight planar film layers are not required. As mentioned above, connections to other construction components must display airtightness by use of adhesive joints and permanent sealing. The Model Timber Construction Direct­ ive (MHolzBauRL) stipulates that areas through which more than three electrical lines are routed to supply an adjoining room require the separation of fire prevention and building services functions. In detail, this means that the timber structure must first be clad to comply with fire safety requirements before the installation layer is added in front of it. Facing shell cladding can comprise either typical gypsum board, exposed woodbased material panels, exposed cladding with sealed joints or acoustic cladding. To achieve the required soundproofing ­values, e.g. for partition walls between ­functional units or walls bordering common circulation spaces and lifts, it is advisable to create cavity walls consisting of two completely decoupled load-bearing layers. Depending on the building physics requirements, such walls can also feature either decoupled or directly mounted additional layers of cladding. Partition walls in buildings are generally executed as cavity walls, due to building codes and reasons of structural engineering, soundproofing and fire safety. In terms of fire safety requirements, they are regarded as equivalent to a fire safety wall. Their fire resistance from the inside outward, i.e. from the interior towards the exterior surface of a building, matches the fire resistance of the respective building class. From the outside, i.e. from the exterior building surface towards the interior, they

require a fire resistance of 90 minutes, provided by use of corresponding cladding. Advantages in terms of sound and acoustics most of all related to soundproofing of frequencies lower than 100 Hz can be achieved by increasing the width of cavities between the individual wall layers. Figure C 4.9 shows an overview of common singlelayer and cavity wall structures.

Principles of Joining Interior Construction Components In order to meet soundproofing and fire ­protection requirements, the execution of joints between construction components is crucial. Whether requirements for creating partitions can be met or whether noise byways decrease the soundproofing levels of construction components according to ­laboratory measurements depends on the careful planning of joints and their precise construction on site. Airtightness between functional units is indispensable as a soundproofing and fire protection flanking measure. Within functional units, only airtight connections on at least one interior side ensure effective insulation from noise and odour. Continuity of functional layers A fundamental prerequisite for meeting building physics requirements is the con­ tinuity of individual functional layers. Layers with fire protection relevance must be continuously joined to prevent fire and hot gases from impacting flammable construction elements or entering cavities within ­construction components. To ensure sufficient airtightness and, thus, to prevent the transmission of smoke, gas, noise and odour between spaces or functional units, planar airtight construction components must also feature airtight connections between components. This may sound trivial, but often emerges as a complex

134

C 4.10 Connections, exterior wall / ceiling and partition wall / ceiling a proper type of structure for flanking transmission prevention b type not permissible in terms of soundproofing, exposed ceiling without joints C 4.11 Installation wall, shell construction, residential and commercial building in Zurich (CH) 2010, pool Architekten C 4.12 Types of joints a  rigid connection, flanks decoupled b  rigid connection, flanks not decoupled c decoupled connection to improve soundproofing

fully clad clad construction fully fully clad construction construction fully clad construction

exposed wall wall and ceiling ceiling exposed exposed wall and and ceiling exposed wall and ceiling

issue in practice. Exposed structures or ­airtight connections between individual intersecting construction components, such as beams or columns, can make execution difficult. In order to maximise the quality of workmanship and optimise required construction time, the prefabrication of interior construction components offers distinct advantages. In practice, to a major degree, only partially prefabricated construction components find use, since building services and finishes are usually installed after the building envelope is completed. Modular structures consisting of stacks of room cells that are delivered on site with finishes are an exception.

clad wall, wall, exposed ceiling ceiling clad clad wall, exposed exposed ceiling clad wall, exposed ceiling

clad wall, wall, exposed ceiling ceiling clad clad wall, exposed exposed ceiling clad wall, exposed ceiling

Decoupling layers within construction components Due to low mass, soundproofing requirements in timber construction can, for the most part, only be met by decoupling multilayered structures. This applies to construction components as such, as well as their jointwork, which can enable sound transmission along individual construction component borders. In construction types that are fully decoupled for soundproofing purposes, cladding and panelling of ceilings and walls prevents the transmission of sound energy into the underlying structure and, thus, pre-

clad ceiling ceiling clad clad ceiling clad ceiling

clad ceiling ceiling clad clad ceiling clad ceiling

NE 1 1 NE 2 NE NE NE 1 NE 2 2 exposed wall, wall, ceiling ceiling exposed NE 1 NE 2 exposed wall, ceiling exposed wall, ceiling a

NE 1 1 NE 2 2 NE NE NE 1 NE 2 exposed wall, ceiling ceiling exposed wall, NE 1 NE 2 exposed wall, ceiling exposed wall, ceiling c

NE 1 1 NE 2 NE NE NE 1 NE 2 2 exposed wall, wall, ceiling ceiling exposed NE 1 NE 2 exposed wall, ceiling b exposed wall, ceiling

C 4.10

C 4.11

vents sound from being transmitted into adjoining spaces or functional units. Executing joints within the cladding of such structures is relatively unproblematic. What is much more difficult is when planners and clients desire a partly or completely exposed load-bearing structure. As a result, the related construction components are exposed to indoor sound energy and, without additional measures, they will transfer sound directly. To prevent this socalled “flanking transmission”, load-bearing elements must be decoupled by means of elastomeric bearings or joints. Figure C 4.10 shows possible assembly types, ranging from exposed components to completely decoupled facing shells with examples for connections between exterior wall / ceiling and partition wall / ceiling. In the case of visible load-bearing walls and ceilings, elastomeric bearings (shown in red) must be installed along the top and bottom of ceilings. A ceiling placed on top of a partition wall and the wall itself must be separated by a joint. In order to meet required soundproofing values, the related wall must comprise a cavity wall construction. If the walls on both floors feature decoupled facing shells, the transmission and radiation of sound energy through the walls is prevented. In such cases, elastomeric bearings are not required. However, a joint between the partition wall and the ceiling element is nevertheless required. In a structure consisting of an exposed wall and a hung ceiling construction, attaching an elastomeric bearing to the top or bottom of the ceiling will also prevent sound from being transmitted across the ceiling, from wall to wall. In this case, a joint is not required, because the hung ceiling reduces sound energy. To prevent longitudinal flanking sound transfer through partition walls between functional units, exposed ceiling structures require acoustic decoupling. The creation of exposed ceilings that func-

T H E L A Y E R S T R U C T U R E O F I N T E R I O R C O N S T R U C T I O N COM PONENTS

tion as a continuous beam extending across several functional units is not permissible in timber construction. Therefore, exposed structures require strict discipline when organising floor plans. Longitudinal flanking sound transfer in ceiling structures means that partition walls on successive floors must not be vertically offset. In such cases, it is not possible to decouple construction components (Fig. C 4.10 b). Creating joints At a first glance, the prerequisites of “con­ tinuity” and “decoupling” described above for achieving the building physics requirements placed on construction component joints seem to contradict each other. Joints often need to be airtight and fireproof, yet are also supposed to minimise flanking sound transmission. With the appropriate design, it is possible to meet both requirements (Fig. C 4.12 a, c). In the case of structures completely clad in gypsum board, corresponding execution variants with manufacturer recommendations exist. Rigid connections can be created by grouting joints with gypsum filler. To ensure airtightness, joints of the unfinished building structure must be adhesively connected. Joints with gypsum filler will not remain airtight permanently. A further option that serves to absorb any deformation due to shrinkage and offers a certain degree of decoupling for soundproofing purposes is the use of elastic ­sealing materials for joints. Principally, both types of joint formation can be used to ­connect timber construction components, although the problem of flanking sound transmission prohibits the creation of rigid connections between a gypsum board shell and a timber construction component (Fig. C 4.12 b). Such connections are not suitable for meeting soundproofing requirements. A research project at the Technical University of Munich tested the fire safety behav-

iour of joint variants optimised and decoup­ led for soundproofing purposes and verified them accordingly [4]. A gap of up to 10 mm was left between layers of cladding or cladding and an exposed timber surface and was infilled with mineral wool and sealed with acrylic fire protection sealing compound or foam. Alternatively, joint tape consisting of intumescent materials can be used to seal off spaces. Such joint tape expands when exposed to heat and forms an insulating layer with low thermal con­ ductivity (Fig. C 4.12). If an elastomeric bearing is installed in the joints of an exposed timber structure, in order to decouple construction components for soundproofing purposes, sealing off a space (E) is achieved by flexibly filling the gap between the timber construction elements with mineral wool. A joint tape made of intumescent material can be used to close joints along exposed interior surfaces.

135

floor construction

100 mm max. joint width, joint filled with non-flammable insulation ­material, melting point of > 1,000 °C or fire protection foam

a

floor construction

butt joint without grout, with grout

Notes: [1] Allgemeines Bauaufsichtliches Prüfzeugnis Knauf Brio Trockenestrich-Elemente [2] Köhnke, Ernst Ulrich: Schallschutztechnische Ausführungsfehler an Holzdecken. 4. HolzBauSpezial Akustik und Brandschutz. Bad Wörishofen 2013, p. 5f. www.forum-holzbau.com/pdf/HBS_bauphysik_13_ Koehnke.pdf (accessed 20.09.2021) [3] Holzbau Deutschland Institut (ed.): Schallschutz im Holzbau – Grundlagen und Vorbemessung. Informationsdienstholz. holzbauhandbuch, series 3, part 3, chapter 1. Berlin 2019, p. 39 [4] Gräfe, Martin et al.: Erarbeitung weiterführender Konstruktionsregeln/-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Forschungsinitiative ZukunftBAU, F 2923, TU München (project man­ agers Merk, Michael; Werther, Norman). Stuttgart 2014, p. 71, 119f. www.irbnet.de/daten/rswb/14109008377.pdf (accessed 20.09.2021)

b

floor construction

100 mm max. joint width, joint filled with non-flammable insulation ­material, melting point of > 1,000 °C or fire protection foam elastomeric bearing c

C 4.12

136

Building Services Tech­ nology – Particularities of Timber Construction Martin Teibinger, Klaus Mindrup

In recent years building technology and building services equipment have grown increasingly important due to rising demands placed on the energy efficiency and comfort of buildings. Ventilation ­systems in ultra-low energy and passive energy buildings now make an indispens­ able contribution to reducing heat losses from ventilation. Building services engineers have assumed a central position in the ranks of consulting engineers and ­planners. In prefabricated timber con­ struction, the requirements placed on the ­precise planning of details from the perspective of technical timber construction, building physics and manufacturing are ­particularly high [1].

Planning Building services pipes and cables and ­routing them within timber structures should receive consideration in the early ­planning stages, ideally during the design phase. To avoid obstacles to planning and construction, it is important to organise the position and size of any required vertical shafts that penetrate multiple ­storeys as well as the principal layout of ­service lines early on and in correspondence with the structural engineering ­concept. In all cases, subsequent planning changes increase planning and construction costs and usually impair the quality of construction workmanship. It is a decisive precondition to coordinate experts in the fields of timber construction, building ­physics and building services technology in order to ensure the creation of a highquality timber building. The higher the level of prefabrication, the earlier decisions on building services technology must be made, the more precisely detail planning must be organised, and the more detail planning must be coordinated among involved trades.

Prospects of Prefabrication

C 5.1

A decisive advantage of timber construction in terms of production technology and economic feasibility lies in the potential for a high degree of prefabrication, meaning the possibility for producing construction components or modules in the workshop or factory, under controlled circumstances. This ensures high-quality workmanship despite short assembly time on the building site. The use of prefabricated, pre-installed building services technology has become commonly applied practice in the prefabricated housing industry and in the field of room module construction (Fig. C 5.2) [2]. Element prefabrication involves assembling individual components in a factory, while a large part of installation work still occurs on the building site (Fig. C 5.3). This offers significant and extensive potential for progress. To further improve quality and shorten construction times, more prefabricated building services technology components should be made available. In rooms with a high degree of moisture (bathrooms), many ­different construction tasks require coordination and supervision. For sanitary rooms in modern multi-storey timber buildings, it is therefore advised to use prefabricated modules that are subject to quality control in the workshop (Fig. C 5.2).

The Influence of Penetrations and Cavities In the planning of penetrations and cavities for building services technology, the following cases can be distinguished in relation to the load-bearing structure of buildings. Openings in stiffening wall plates Wall plates must be designed to absorb vertical and horizontal loads. Eurocode 5 defines calculations for wall plates. DIN EN 1995-1-1 states that wall plates with open-

BU IL D IN G S E R V I C E S T E C H N O L O G Y – P A R T I C U L A R I T I E S O F T I M B E R CONSTR UCTION

137

C 5.1 Building services technology installation in timber construction C 5.2 Assembly of a comprehensively detailed prefabricated sanitary pod. This room module contains the complete building services installations and the actual wet room. C 5.3 Prefabricated building technology shaft with sheathing on one side in the “Kölner Holzhaus”, Architekturbüro Laur C 5.4 Overview of geometric requirements for non-­ reinforced slab penetrations (spacings also apply to beams of changing depth) C 5.5 Overview of geometric requirements for reinforced slab penetrations (spacings also apply to beams of changing depth. Here, h must be applied to the least opportune position at the edges of the penetrations) C 5.2

ings (door or window openings, also large installation openings) may only be used for load transmission in areas without openings. For a wall plate with openings, this means that the areas next to the ­openings must generally be treated as ­separate wall plates. When calculating loads, individual openings in sheathing smaller than 20 ≈ 20 cm can be ignored. If there are several openings, the sum of their length must be less than 10 % of the plate length and the sum of their height less than 10 % of the plate height. The impact of larger openings must be separ­ ately verified. Beam penetrations Beam penetrations are openings in solid web beams with a clear height of more than 80 mm or with a diameter greater than h/10 (h = beam depth). Smaller ­penetrations are not structurally relevant. Penetrations should be considered at an early ­planning stage in order to determine ­necessary beam dimensions. A distinction is made between reinforced and non-­ reinforced beam penetrations.

Non-reinforced beam penetrations are permissible when the following preconditions are met: •  no planned transverse tensile stress • no strong climate-related impact (e.g. inadequately insulated heating ducts or lines) • permissible only in use classes 1 and 2 as per DIN EN 1995-1-1 • in compliance with geometrical requirements as per Fig. C 5.4 Along the corners of non-reinforced beam penetrations, the stress components (transverse and shear stress) must be verified. Larger openings and penetrations for which the requirements of stress and tension analyses for non-reinforced beam penetrations cannot be met require reinforcement in order to absorb transverse loads along the penetration corners. Reinforcement can be provided in the form of wood-based material panels laminated to both sides, glued interior steel rods (threaded rods or reinforcing rebar) or screwed-in steel rods (fully threaded screws). Penetrations must meet the geometric requirements shown in Figure C 5.5.

C 5.3

General Principles for the ­Integration of Building Services Technology From the perspective of building physics, the integration situations of building services technology can be distinguished as ­follows. Installations in exterior walls In typical cases, installation layers (at least 40-mm thick) arranged on the interior side of exterior wall framing components enable the installation of electrical equipment ­without damaging the airtight layer. An installation layer is not required in walls that were industrially prefabricated according to specially monitored production conditions and service lines can be routed outside of the airtight layer in such cases. However, airtight cavity wall sockets must be installed (Fig. C 5.6, p. 138). Subsequent installations are only permissible when carried out by authorised contractors. In the case of cross-laminated timber walls, with the exception of fire compartment

a lV ≥ h h

permissible areas for penetrations

hro ≥ 0.35 · h

rounded corner r ≥ 15 mm

hd hd ≤ 0.15 · h

hd ≤ 0.15 · h

lA ≥ 0.5 · h hru ≥ 0.35 · h

h

permissible areas for penetrations

hro ≥ 0.25 · h

hd

hru ≥ 0.25 · h

hd = 0,7 · d

a

a ≤ 2.5 · hd

C 5.4

a

rounded corner r ≥ 15 mm

hd hd ≤ 0.30 · h lv ≥ h

hd ≤ 0.30 · h

lA ≥ 0.5 · h

d

lA ≥ 0.5 · h lA ≥ 0.5 · h

lz ≥ 1.5 · h ≥ 30 cm a ≤ 2.5 · hd

lV ≥ h

lV ≥ h

d hd hd = 0.7 · d

lA ≥ 0.5 · h lA ≥ 0.5 · h a

lz ≥ 1.0 · h ≥ 30 cm a ≤ h ≤ 2.5 · hd

a ≤ h ≤ 2.5 · hd

C 5.5

138

C 5.6

walls, electrical cables, switches and power sockets of typical size and quantity can be directly milled into walls. The remaining ­timber cross section must be evaluated in terms of fire safety requirements. Service lines may not be routed transversely to the cover layer without consultation with a structural engineer. Penetrations in exterior construction components must be airtight and windproof (Fig. C 5.7).

C 5.7

15 cm (Fig. C 5.8). Should this not be the case, power sockets installed in cavities must be enclosed with suitable nonflam­mable materials (Fig. C 5.9) or certified ­fire-resistant power sockets (Fig. C 5.10) must be used.

Installations in partition walls and fire compartment walls In the following, installation options for partition walls and fire compartment walls will be analysed for wall framing and solid timber construction types. Wall framing In timber wall framing structures, which are typically subject to fire safety requirements, it is principally advised to route ­electrical installations behind facing shells. Service lines can be routed through the load-bearing structure layer if mineral wool insulation with a melting point ≥ 1,000 °C, a minimum bulk density of 30 kg/m3 and a thickness of at least 5 cm is used. In such cases, the distance ­between installations and vertical load-­ bearing members should be more than

Solid timber construction In the case of solid timber partition cavity walls, electrical installations can be directly milled into wall components, similar to exter­ior walls. For fire compartment walls, it is recommended that installations are placed behind insulated facing shells, which also improves sound insulation. Installations in ceilings within resi­ dential units To minimise pipe and cable lengths in ­ceilings in one residential unit (e.g. a ­two-storey maisonette apartment), ­ventilation ducts can be laid out within the floor construction of the storey above (Fig. C 5.11). Outlets can then be arranged within the ceiling of the ­storey below or within the floor of the ­storey above. This optimised pipe and cable routing can only be integrated in ­ceiling elem­ents that are not subject to any building physics and fire safety requirements. This type of structure is

>>150 150mm mm

>>150 150mm mm

a

cavity cavityceiling ceilingsocket socket

cavity cavityceiling ceilingsocket socket

dd

>>150 150mm mm

dd

≥≥50 50mm mm b

Installations in ceiling slabs between ­different units For reasons of subsequent conversion or retrofitting, as well as fire safety and soundproofing purposes, installations should generally remain within functional units. Service lines should not be laid out within the construction layer (e.g. cavities between joists) of ceilings that separate ­different units, for fire safety and sound­proofing reasons. ­Electric cables, water lines and heating pipes should be laid out on top of the floor structure, usually within the fill material layer (Fig. C 5.12). A direct ­connection between the screed layer and the unfinished ceiling due to ­service lines penetrating or intersecting the ­construction will impair impact sound­ proofing by up to 4 dB, therefore, caution is advised [3]. Particularly when service lines intersect, the fill layer must display ­sufficient thickness. A hung ceiling installed beneath a ceiling slab can permit routing electrical cables and ventilation pipes in the clear space above it. The height required for cables, pipes and any necessary intersections

dd

dd cavity cavityceiling ceilingsocket socket

not advised for ­ceiling elements that separate different ­residential units.

≥≥50 50mm mm C 5.8

dd

dd C 5.9

C 5.10

BU IL D IN G S E R V I C E S T E C H N O L O G Y – P A R T I C U L A R I T I E S O F T I M B E R CONSTR UCTION

139

ventilation pipes adjacent space

C 5.11

must receive consideration in planning. Inadequately coordinated planning can lead to major difficulties in practice. When ­laying out electrical lines for ceiling lights etc. in exposed cross-laminated t­imber ­ceilings, it must be ensured that penetrations through walls, including those within residential units, are airtight, for soundproofing reasons. These service lines are usually routed along the underside of the unfinished ceiling. Any necessary milling for service lines must occur longitudinally to the timber cover layer. Lateral milling into the cover layer is only permissible after consultation by a structural engineer. Pipes and channels for cables must be installed in order to allow subsequently drawing individual cables through them as required. Ventilation pipes led horizontally through the construction layer of ceilings separating different units are neither permissible nor compatible with fire protection requirements. Ventilation pipes must be laid out within corresponding installation layers, such as above hung ceilings, behind ­facing wall structures or underneath floors (Fig. C 5.13). Penetrations within the ­construction components of fire safety ­compartments must be encapsulated (see also “Protective Functions”, p. 78ff.). C 5.6    Airtight cavity wall socket C 5.7  Airtight pipe penetration using a prefabricated collar C 5.8  Compensation by use of mineral wool (melting point ≥ 1,000 °C, bulk density ≥ 30 kg/m3, ­secured against shifting / falling) a  in load-bearing walls b  in non-load-bearing walls C 5.9  Compensating installation integration with a ­gypsum board enclosure C 5.10  Cavity wall power socket with a coating that forms an insulating layer C 5.11   Ventilation ducts laid out on top of a ceiling slab C 5.12 Electrical cables laid out on top of an exposed timber ceiling slab, solid timber construction C 5.13 Laying out of ventilation pipes in a hung ceiling C 5.14 Enclosed penetration, pipe penetration within a flat roof, vertical and horizontal sections C 5.15 Schematic diagram of shaft type A C 5.16  Schematic diagram of shaft type B

indoor residential space

C 5.12 screws 4 ≈ 40 mm

C 5.13

screws 4 ≈ 40 mm

particle board

drain pipe set into groove

particle board with milled groove drain pipe

a

a

round groove filled with insulation material

screws 4 ≈ 40 mm

aa

screws 4 ≈ 40 mm

pre-drilled holes C 5.14

1

1

EI tt (ve, i↔ o)

EI tt

2

2 3

EI tt (ho, i↔ o )

no requirement 3

EI tt (ve, i↔ o) EI tt

no requirement

EI tt (ho, i↔ o) 4

EI tt (ve, i ↔o)

EI tt (ve, i↔o) 1 Ceiling slab 2 Shaft wall with fire safety requirement 3 Installation lines 4 Shutter between basement and ground floor

1 Ceiling with horizontal shutter 2 Shaft wall without fire safety requirement 3 Installation lines C 5.15

C 5.16

mm board pe as per 83-1

cution as ufacturing s

ble firestop op

cution as ufacturing s

ant

140

metal pipe

plastic pipe

Type A

cables

metal pipe

20 ≈ 50 mm gypsum board GM-F type as per EN 15 283-1

gap execution as per manufacturing guidelines

classified shaft wall system 2≈ fire-resistant gypsum board

plastic pipe

cables

C 5.17 Example shaft construction, Type A, solid Type A ­timber ceiling 20 ≈ 50 mm gypsum board C 5.18 Example shaft construction, Type A, timber GM-F type as per frame ceiling ENType 15 283-1 C 5.19 Example shaft construction, B, solid ­timber ceiling C 5.20 Example shaft construction, Type B, timber frame ceiling C 5.21 Dry and prefabricated firestop for cables ­penetrating a cross-laminated timber element C 5.22 Plastic drainage pipe with fire protection collar, gapmineral execution as remaining gaps are filled with wool classified shaft manufacturing C 5.23  Leakage protection, facingper shell wall system C 5.24 Sealing an unfinished floorguidelines surface and curb 2≈ fire-resistant with bituminous natural rubber sealant and butyl gypsum board tape for render application (white), integration of a detection tube

C 5.17 metal pipe

plastic pipe

cables 20 ≈ 50 mm gypsum board GM-F type as per EN 15 283-1

Type A

gap execution as per manufacturing guidelines

classified shaft wall system 2≈ fire-resistant gypsum board

C 5.18 metal pipe

plastic pipe

cables

Type B mineral wool fire-resistant gap filler

multi-cable firestop soft firestop

20 ≈ 50 mm gypsum board GM-F type as per EN 15 283-1

gap execution as per manufacturing guidelines fire-resistant collar

1≈ fire-resistant gypsum board

C 5.19 metal pipe

plastic pipe

cables

Type B mineral wool

20 ≈ 50 mm gypsum board GM-F type as per EN 15 283-1 1≈ fire-resistant gypsum board

multi-cable firestop soft firestop

gap execution as per manufacturing guidelines fire-resistant collar C 5.20

Installations in roofs Pitched roofs are subject to the same general planning principles for the installation of building services technology as exterior walls. Generally, an installation layer on the interior side of the vapour barrier is recommended for laying out different service lines. In the case of flat roofs with exposed timber ceilings, service lines must be flow-proof and adapted to the related means of protecting the building site (e.g. against water impacting exposed surfaces). Penetrations must be flow-proof. Structures with infill insulation require penetrations that are sealed off from the infill, as shown in figure C 5.14 (p. 139). The cavity between the penetrating service lines and the encapsumetal pipe plastic pipe cables lation must be filled with insulation. The service lines must be joined to the interior side of B the airtight layer by an airtight joint. If Type encapsulation is not possible, pipe collars mineral wool can be used to create airtight joints around multi-cable firestop soft firestop penetrations. Vertical distribution in installation shafts The dimensions of an installation shaft of execution the building 20depend ≈ 50 mm on the configurationgap as gypsum boardtechnology concept. services particular, perIn manufacturing GM-F type as the installation of controlledguidelines residential per EN 15 283-1 ­ventilation systems requiresfire-resistant a large amount 1≈ fire-resistant collar gypsum board of space. The vertical distribution of installations extending beyond individual functional units or fire safety compartments typically takes place by use of installation shafts. Based on the position of dampers or shutters within penetrations, shaft types are ­distinguished according to shaft type A (Fig. C 5.15, p. 139) and shaft type B (Fig. C 5.16, p. 139). Shaft type A Type A shafts are subject to fire resistance requirements with regard to the shaft walls and their penetrations. These requirements apply from the outside inwards and from the inside outwards. Shafts must feature shutters between the first floor above ground

and the basement level, as well as between the top floor and an unfinished attic space. Shaft walls often comprise stud wall constructions clad in gypsum board. They must be classified and built to meet requirements. The same applies to shutter systems and inspection openings of shaft wall penetrations. Ceiling opening reveals must receive nonflammable lining, such as a minimum of 2≈ 12.5 mm fire-resistant gypsum board. It must be ensured that full surface bonding takes place between the gypsum board ­lining and the timber reveal surface. If this is not the case, the timber surface and the joint between the gypsum board and the timber component must be sealed using a product with verification of use or according to the current technological state of the art. If the corners of a ceiling opening are, due to manufacturing reasons, not sharpedged, or gypsum board lining is not properly applied, possible joints must also be coated with an intumescent product. Such products prevent the transmission of smoke and toxic gases by foaming up when they are exposed to heat, closing any remaining openings [4]. DIN EN 15 283-1 requires that at least one 20 ≈ 50 mm fire-resistant gypsum board (type GM-F) element must be attached to the inside of the shaft in the area connecting shaft wall and timber ceiling element (Figs. C 5.17 and C 5.18) [5]. Shaft type B Walls in type B shafts are not subject to any fire safety requirements. These shafts are shut off horizontally at each floor in accordance with the fire-resistance requirements of ceilings. Soft or hard firestop systems or intumescent products in combination with fire resistant pipe collars and multi-cable firestops and similar products are appli­ cable (Figs. C 5.19 and C 5.20). After solid timber penetration reveals have been lined with gypsum board, subsequent concrete

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141

C 5.21

pours can be applied in related ceiling areas. Fire protection shutters can then be installed according to the typical standards for reinforced concrete construction. In practice, the lining of reveals with gypsum board panels results in significant problems in the corners of penetrations with regards to execution and resulting smoke proofing. Penetrations milled in the workshop feature manufacturing-related curves in corners that impair the application of lining. The authors estimate that, at the time of publication, ­ventilation duct shutters for solid timber ­construction components with a permit that facilitate practical application do not exist on the German market. However, some manufacturers have indicated that improvements are under development. For instance, shutters for air vents as per DIN 18 017-3 will be approved for insulated shutters in solid timber ceilings. This allows a similarly efficient execution as in the case of noncombustible water pipe systems. The ­chapter on “The layer structure of interior construction components” displays different installation options (p. 126ff.). DIN EN 15 283-1 requires that at least one 20 ≈ 50 mm fire-resistant gypsum board element must be attached to the inside of a shaft in the area connecting the shaft wall and the timber ceiling element, similar to a type A shaft [6]. The reveal around the firestop does not have to be covered. Exposed ­timber ­surfaces in the shaft, however, must be ­covered in non-flammable cladding. Since no fire safety requirements have been ­formulated for the walls of type B shafts, they can also feature single-layer construction. However, to meet soundproofing requirements, shafts should comprise multilayered construction and insulation. The area of reveals surrounding penetrations requires full surface bonding. Where this is not the case, joints must be covered with an ­intumescent coating. If a soft firestop is installed, reveals do not require lining. This may even be counter-productive, if full sur-

face bonding is not applied. For soft firestops, coated mineral fibreboard with a ­minimum bulk density of 150 kg/m3 and melting point of ≥ 1,000 °C is applicable. A hard firestop is usually made of gypsum or cement mortar. To permanently connect a construction component and a hard firestop, reinforcing rods or threaded bolts are often used. Soft firestops can be installed with or without lining the reveals of timber elements. In creating gypsum reveals, full surface bonding with the timber surface must be ensured, otherwise timber surfaces and joints between gypsum and timber must be sealed. The reveal (gypsum or ­timber surface) and the edges of the mineral fibreboard must receive an intumescent or ablative coating [7]. The chapter on “The layer structure of building envelopes” provides installation details and construction recommendations (p. 98ff.). In the case of solid timber ceilings, it has been demonstrated in practice that rectangular openings often feature manufacturing-related circular edge cut-outs with a radius of approx. 10 cm. Since applying gypsum board lining or installing tested ­rectangular shutter systems have both been proven to be highly complex, circular openings are preferable for penetrations, since they permit installing shutters more easily (Fig. C 5.21 and C 5.22). Tested and certified systems for timber construction have recently become available.

C 5.22

C 5.23

Measures for Wet and Humid Rooms The following recommendations for the installation of building services technology also apply to bathrooms in apartments, hotels and other forms of accommodation, yet do not apply to wet rooms or public baths subject to stringent requirements. Long-term wetting of timber structures must be generally prevented due to the risk of damages related to rot. Water pipe ruptures C 5.24

142

temperature

relative humidity

C 5.25 Hygrothermal interaction between heating and cooling capacity and moisture balance of wood C 5.26 Thermally activated solid timber element with ­integrated airflow and connection points to the supply level of the floor construction C 5.25

in wet rooms are usually discovered quickly, due to the large amount of water leaking in a short period of time. Repairs and drying out can occur quickly. Diligent sealing measures are required in areas where small amounts of water can leak over a long period of time, such as bathroom fixture penetrations, tile grouting or shower tray joints. Elastic joints must be regularly ­maintained. For damp rooms in timber buildings, DIN 18 534 requires a sealant layer on top of an unfinished floor and extending it upward along walls. Installing a sealant layer on a sloped surface with a controlled floor drain,

as proposed by this standard, comprises a theoretical optimum of structural timber protection. However, for practical and ­building physics reasons (laying out of pipes, creating sloped surfaces) and by assessing risk in comparison with the potential water ­damage in other rooms, such as kitchens (drains, dishwashers), a sloped, curbed waterproof floor construction for a private bathroom is considered a disproportionate measure [8]. Far more important is the sealing of fixtures and sanitary hardware in showers and the careful execution of joints surrounding shower trays and baths to prevent water from seeping continuously

collector / distributor duct

activation duct

heat radiation into interior

crosslaminated timber

heat exchanger

insulation vent ventilator air inlet

water inflow

distribution channel

water outflow

floor slab C 5.26

into the structure. Compared to ­building with mineral-based materials, ­different approaches are necessary when installing building services technology in timber ­buildings. When laying out water-bearing pipes, their length should be reduced as far as possible. It is further recommended to lay out service lines behind facing shell ­constructions that allow simple maintenance and control. In addition, the advancement of prefabricated room modules should be promoted. For instance, ­sanitary cells that are prefabricated in the workshop can include all required building services technology lines, thus allowing their integration into the shell construction and their connection to other modules in a “plug & play” manner. In this field in ­particular, there is a need for advancement that can contribute to reducing costs for building services ­technology and increasing the quality of ­timber structures. The Nordic countries offer very ­interesting solutions for applied leakage protection: prior to installing service lines on top of a wall ­construction, additional sealant layers are applied to the first water-bearing layer. As a result, water leaks become instantly visible (Fig. C 5.23, p. 141). In addition, f­unnel-shaped connectors that surround heating pipes can direct water from pos­sible leaks through tubes into a floor drain within the shaft (Fig. C 5.24, p. 141). Pro­ponents of robust lowtech solutions have introduced a so-called inspection hatch into unfinished ceilings in the form of a built-in plastic tube with a sealed connection to the ceiling sealant layer. Water leaks can be detected very quickly along the underside of the ­ceiling. This measure is recommended in particular for solid timber ceilings. Manufacturers also offer sealable assembly boxes with transparent sealant layers as an alternative solution mostly for shower trays installed flush with floors. They allow detecting ­possible leaks early on in the apartment impacted.

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Notes: [1] Teibinger, Martin et al.: Haustechnik im mehrgeschossigen Holzbau. In: Zuschnitt Attachment – Sonderthemen im Bereich Holz, Holzwerkstoff und Holzbau. proHolz Austria. Vienna 2014 [2] Hausladen, Gerhard; Huber, Christian; Hilger, ­Michael: Holzbau der Zukunft. Partial project 12: Modulare, vorgefertigte Installationen in mehr­ geschossigen Holzbauwerken. Reihe Holzbauforschung, Vol. 7/12, Stuttgart 2009 [3] Köhnke, Ernst Ulrich: Fehler werden nicht verziehen. Typische Einbaufehler und deren Auswirkungen auf den Schallschutz. Conference proceedings, 3. Internationaler Holz[Bau] Physik-Kongress 2012. Leipzig 2012, p. 97–101 [4] Intumescent coating products foam up and close off residual openings when subject to thermal stress or

in the case of a fire. They, thus, prevent the distribution of smoke and toxic gases. The carbonised layer that forms after certain temperatures are exceeded also protects the underlying building materials or surfaces from heat impact. The related spatial expansion process requires consideration in planning. [5] Teibinger, Martin; Matzinger, Irmgard: Brandab­ schottung im Holzbau. Planungsbroschüre der ­Holzforschung Austria. Vienna 2012 [6] ibid. [7] So-called ablative coatings contain materials that ­undergo chemical reactions when impacted by heat. In such cases, they either vaporise, sublimate (i.e. directly change from a solid into a gaseous state) or melt. This allows cooling of the coated ­materials. [8] Köhnke, Ernst Ulrich: Schlagregen im Bad. Abdich-

tung von Bädern und Feuchträumen im Holzbau. In: Holzbau, die neue quadriga 04/2007, p. 22 – 27 [9] Wehsener, Jörg et al.: Untersuchungen zu mehrlagigen Massivholzplatten als Heiz- und Kühlelement. In: Bauphysik 38, 3, 2016, p. 129 –134. Kornadt, Oliver et al.: Dynamisch thermischhygrisches Verhalten von Massivbaukonstruktionen: Entwicklung eines Wärmespeicherfähigkeitsindex für Gebäude aus Mauerwerk und thermisch aktivierbare Massivholzelemente. Final report. Kaiserslautern 2018 Mindrup, Klaus: Raumklimatisierung durch thermisch aktivierte Massivholzelemente – Konzeptentwicklung, Leistungsbetrachtung und Ableitung von Ausle­ gungs­werkzeugen. Dissertation, TU Munich 2020; https://mediatum.ub.tum.de/doc/1482317/1482317. pdf (accessed 11.07.2020)

Outlook: Thermal Activation of Solid Timber Construction Components

thermally activated elem­ent and the supply infrastructure of the building. Due to crosswise lamination of lamellae, it can be assumed that indoor air and system air conveying heat are ­separated by an airtight layer. The thermal effectiveness of the system is defined by the thickness of the covering timber layer, meaning the thermal resistance between system air and the wall surface facing the indoor space. The greater the thickness of the timber layer bordering the thermally ­activated air duct, the greater the required temperature lift of system air in order to achieve the desired thermal effect. Thick covers also negatively impact the reaction time of the system.

pared with established surface heating and cooling systems widely available on the market and applied within mineral-based construction types [9]. This revealed the great potential offered by the technology for indoor climate conditioning by use of exposed timber surfaces. Within initial prototypes, the measured heating and cooling performance of the system indicated suit­ ability for year-long indoor climate conditioning of modern timber buildings.

No marketable solutions exist as yet for the thermal activation of solid timber elements. The technology described in the ­following can potentially support the reali­ sation of a surface-integrated heating and cooling system in spaces with surfaces ­consisting of visibly exposed solid timber construction components. This allows using walls, floors and ceilings to actively heat or cool the space they enclose – similar to a wall heater, yet by employing exposed cross-laminated timber elements. Compared to conventional heating and cooling convectors, thermal comfort is increased significantly by using surface-integrated heating and cooling systems. A further advantage of this new concept is related to production costs and expenditure. Based on a high degree of prefabrication in the workshop, production processes can be moved from the construction site into the workshop. This allows construction time to be reduced and increases the quality of workmanship. Application in construction practice Opportunities for integrating thermally activated solid timber elements include ceilings, floors or walls. Floors are excellently suited for heating, yet only to a limited degree for cooling. In the case of ceilings, this is reversed. Walls appear best-suited for year-long indoor climate conditioning, since they can be used for heating and cooling to equal degrees. Fig. C 5.26 shows the schematic diagram of a thermally activated solid timber construction component bordering the system air layer connected to the supply level of the floor construction. This is where the so-called air conditioning unit is installed. It adjusts the temperature of the system air that passes through the element. It serves as the interface between the

Limiting factors Similar to any other surface heating and cooling system, the thermally effective output is dependent on the difference between surface temperature and operative indoor temperature. The greater the surface temperature, the greater the heat output. Similarly, the cooling capacity increases when the surface temperature declines. The dew point temperature of indoor air constitutes a clear boundary. If temperatures fall below it, in order to increase cooling capacity, water vapour in indoor air can condensate along surfaces of cross-laminated timber elements and lead to collateral moisture related damages. For this purpose, as is typical for surface cooling systems, the cooling capacity is limited in the coldest part of the system, by use of a dew point sensor. Yet, even before reaching the dew point, the thermal structure of the system already influences the degree of moisture along timber surfaces. This is due to the hygroscopic characteristics of the material (Fig. C 5.25). Performance analysis In the course of multiple research projects, prototypes for thermally activated solid timber construction components were tested and, according to their performance, com-

145

Part D  Process

Assembly of a prefabricated facade element, student housing, Vancouver (CA) 2017, Acton Ostry Architects

1 Planning Characteristics of Timber Construction Planning The Planning Process Conclusion

146 146 146 152

2 Digitalisation in Timber Construction Digital Process Chains in Timber Construction BIM Added Value for Timber Construction Conclusion

154 154 155 156 157

3

Timber Production The Raw Materials Industry Industrial Panel Prefabrication Subtractive Timber Production Additive Timber Production Combination of Subtractive and Additive Timber Production Conclusion and Outlook

158 158 158 159 160 160 160

4 Prefabrication Prefabrication and Uniqueness From Linear Member to Room Module Prefabrication Methods The Influence of Prefabrication on Design and Construction Maximum Prefabrication: Room Module Construction Types

162 162 164 166 167 169

5 Solutions for Modernising and Expanding Existing Buildings Adding Storeys Facades

172 174 178

146

Planning Wolfgang Huß, Sonja Geier, Frank Lattke, Manfred Stieglmeier, Sandra Schuster

D 1.1

Planning a contemporary timber building is different from planning a conventional building, in particular due to prefabrication and the special characteristics of timber as a construction material.

Characteristics of Timber ­Construction Planning

D 1.1 Regular coordination meetings in the planning phase are indispensable for a successful planning process D 1.2 Planning phases, from the initial enquiry to ­element production with related central issues. Completion of preliminary phases constitutes the basis for subsequent phases.

Basic architectural questions, yet also very specific factors related to timber construction require consideration in early design phases and integration into planning. The linearity of timber as a material gives rise to interdependencies between the production of space and a load-bearing structure that is appropriate for a timber building (see “Structures and Structural Systems”, p. 42ff.). The framework conditions of fire safety, prefabrication, energy concepts and building physics will shape the structure and influence its design and planning. By including safe emergency exit route concepts in planning, timber can be employed in areas beyond those building regulations determined as safe for its use. An appropriate arrangement of spaces that emit sound and other areas where noise must be avoided can lead to lowering required soundproofing levels for construction components. Prefabrication is essential to contemporary timber construction processes. The sizes and assembly sequences of elements must be integrated into design considerations because transport and manufacturing options will influence the preliminary design. This is most evident in the planning of room modules, the prefabrication of which demands definite decisions at an early stage. It is ­almost impossible to make subsequent corrections on site because any changes made while the planning process is ongoing will have an increasing impact on deadlines, quality and costs (see “Prefabrication”, p. 162ff.). The main difference between timber construction and solid construction is that tim-

ber construction is literally multifaceted and, thus, more complex. An overwhelming variety of exceedingly differentiated mate­ rials offering a wide range of construction options are now available on the market. Building authority approvals are often issued only for specific products and are not valid for supposedly identical products by competitors. There is currently no overarching standardisation process for timber construction in place. Each timber construction ­company prefers its own structures and details – depending on production cap­ acities, supply network and experience, ­making it harder to plan independently of a specific firm. Fire safety and sound insulation in interior construction and thermal insulation and protection from moisture in the building envelope are functions assumed by the entire layer structure, i.e. the shell and finishes in sum. Planners must consider and coordinate all layers of a structure comprehensively. Planners must also design facades and interiors of exposed timber structures simultaneously and during the same design phase as the timber structure, which increases the complexity of planning (Fig. D 1.2).

The Planning Process Every construction project has its own specific features and dynamics. One frequent cause of problems in the planning process is a failure to comply with certain fundamental preconditions, an issue that not only affects timber construction. Planners are advised to define general requirements and aims during the project development phase, in cooperation with the client and as far as possible. The budget and schedule, the functional requirements and personal conceptualisation are important elements of planning. The project-specific need for expert planning, in the interests of an integrated planning approach, should be

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defined at a very early stage. The planning team should be assembled and its tasks assigned at an early stage as well. Only the involvement of the specialist knowledge of expert planners in initial design considerations will produce a coherent overall result. The leanWOOD research project displays related approaches to solutions and recommendations (Fig. D 1.5, p. 149) [1]. Scheduling and communication Resource planning among all participants should be based on a realistic and binding schedule. A good communication structure with regular coordination meetings is indispensable. Clear agreement among all parties involved should exist on planning progress and change management. A complete conclusion of individual service phases coordinated with all involved parties in planning can lead to a successful process. Results should be regularly monitored with clients. The aim should be to permit corrections only during individual service Basic assessment

phases and not across different phases. Defined planning tasks of all participants should be communicated in a coordinated manner. In particular, an understanding of the demands and perspectives of other disciplines supports effective cooperation. Planning period In timber construction in particular, it is important to specify a planning period that is adequate to the complexity of the task at hand. A longer planning process is usually offset by time savings in the construction phase. Expertise and experience in t­imber construction should ideally be pres­ent in the disciplines of architecture, structural engineering, fire safety and structural ­physics, as well as the planning of building services equipment. A clear definition of interfaces is very important in this regard. Critical points at interfaces between construction, fire safety und building services equipment must be identified at an early stage and the responsibilities related to

Preliminary planning supervision + revision: results – costs – deadlines

Design planning

planning services in each phase clearly defined and agreed upon. Defining system borders During planning, the load-bearing structure, the interior finishes and the building services equipment require coordination. ­Specifically the planning of building services equipment should be configured according to timber construction requirements. The location of shafts and ducts, intersections and penetrations must be dimensioned according to real situations. For this purpose, it is necessary to precisely determine dimensions and cross sections in early planning phases. This means that functions and occupation as well as building energy systems must be defined early on. Fire protection and soundproofing requirements must be defined by all parties involved in the planning. ­Determining the scope of services at the system border between building services (layout of service lines) and construction (architecture /structural engineering) is

Implementation planning

supervision + revision: results – costs – deadlines

147

Production planning

supervision + revision: results – costs – deadlines

Initial enquiry programme

Defined tasks Synthesis, preliminary design

site

spatial concept

requirements

structural engineering

budget / time frame

prefabrication

planning team

fire safety building physics energy / building services

spatial concept

Synthesis, design

structural engineering

structural engineering

prefabrication

prefabrication

fire safety

fire safety

building physics

building physics

preparation of CNC

energy / building services

energy / building services

capacities

Synthesis, implementation planning

Production

process material orders

Framework conditions

Concepts

Detailing

Organisation D 1.2

148

tendering + award of bids

other contractors

other expert planners

input coordination / synthesis building physics planning

timber construction company

fire consultant

architect

building services engineer

structural engineer

Status quo:

Planning

Implementation

a

Strategy 1:

tendering + award of bids

specific timber construction expertise

Planning

Implementation

implementable planning

b

c

overlap = cooperative planning

Planning

tendering + award of bids

Strategy 2:

Implementation

D 1.3

important, most of all due to conflicts that can arise in relation to unclear responsibility in the case of construction component penetrations (Fig. D 1.9, p. 153). Degree of detailing Within the planning process, the definition of the degree of required detailing in relation to the degree of project maturity supports the shared understanding of a project. Comprehensible information limited to the necessary minimum simplifies communication within the project process and related design, implementation and workshop planning. Not everything has to be illustrated in full detail from the very beginning. At an early design stage, for instance, it is sufficient to illustrate a multilayered wall by only indicating its borders. The wall thickness should, however, take the overall thickness of layers into consideration. In modern timber construction, prefabrication means that major decisions must be made earlier than in conventional construction. It is, therefore, advisable to assign essential project determinations to individual service phases (Fig. D 1.6, p. 150): • Preliminary design phase: definition of the main requirements for all disciplines (fire safety, soundproofing, energy, loadbearing structure, prefabrication) and integration within the development of the spatial concept. • Design phase: development and clarification of all fundamental concepts involving the load-bearing structure, timber construction system, layer structure, jointing, finishes, definition of interfaces, degree of prefabrication and element sizes. • Implementation planning by architects and expert planners: detailed development of concepts defined by the design; coordination of assembly sequences and connection methods (element joints and other types of connections). • Workshop and assembly planning of contractors: merging of the implementation

plans of the architect and structural engineer to establish a coherent plan status, implementation of planning specifications using specific construction products approved for use by building authorities. At the conclusion of this process, if the ­topical and technical issues have been resolved in the workshop and assembly planning, planners can concentrate on the organisational aspects of production and assembly (e.g. work preparation with capacity and operational planning, ordering materials). Integrative tendering and cooperation models suitable for timber construction The term “tendering and cooperation model” describes a type of awarding contracts and organisational structure for cooper­ ation in planning and execution. The model defines responsibilities, roles and information, as well as communication channels. The selected tendering and cooperation model will depend on the client profile, the specific construction task and its framework conditions. In German-speaking countries, the sepa­ ration between planning and execution has been established on the basis of procurement directives. From this perspective, procurement and tendering models guarantee independence from economic interests and are based on detailed descriptions of services with related specifications that determine the awarding of bids according to individual trades. Hierarchically organised structures separated according to profession in planning and execution constitute the basis for these models (Fig. D 1.3 a). In the context of conventional construction types, they have long proven their effectiveness. However, they meet their limits when expertise related to the specifics of timber construction is not represented within the planning team: without specialised knowledge on timber construction in early

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149

Service share of timber construction engineering office

Architecture D 1.3 Status quo and possible planning and implementation strategies a Status quo: the award can be an obstacle to communication, separation of planning and implementation b Strategy 1: integration of specific timber construction expertise into planning c Strategy 2: award at an earlier project phase D 1.4 Professional profile of timber construction engineering D 1.5 Comparison of a conventional planning process and planning with a cooperative planning team

Structural engineering

Timber construction engineering

Timber contractor D 1.4

planning phases, a redesign phase often becomes necessary after the awarding of contracts. This is exacerbated by the fact that timber contractors often have their own specifics related to the mode of production, expertise, planning expertise or supply network that can influence the ­construction. The awarding of contracts according to individual trades, however, contradicts the principles of prefabrication. In modern timber construction, it is advis­ able to merge the building envelope (facade, windows, temporary roof) and the timber structure in order to create sealed building envelopes already during manufacturing. For the integration of specific timber conConventional award of bids (in theory)

struction skills in early phases of the project, two main strategies are suggested: • Strategy 1: integration of specific timber construction expertise (Fig. D 1.3 b) • Strategy 2: awarding contracts at an early project phase (Fig. D 1.3 c) In the first case, the planning team introduces the necessary expertise into the planning process. This can include the consultation services of a timber contractor or an independent expert, such as a ­timber construction engineer, as is the case in Switzerland, where they have become an established presence in the field (Fig. D 1.4). The degree of services

planning architect + engineers

that a timber construction engineer con­ tributes differs according to the timber ­construction expertise of the other parties involved in the planning and will be more or less comprehensive in relation to the ­particular project. Timber construction ­engineers typically assume responsi­bility for structural engineering and tendering for the timber structure, contribute to detail planning and are often trained to c ­ reate workshop and assembly plans for related contractors. In part, they also offer planning services for fire protection and building physics. This allows closing the gap between planning and execution independently of contractors. The service fees for

contract timber construction company

completion and handover

workshop planning timber construction company prefabrication assembly

Conventional award of bids (in practice)

planning architect + engineers

Input

Redesign = delay due to delayed integration of timber construction competence workshop planning timber construction company

completion and handover

Delay prefabrication

assembly

contract timber construction company

Collaborative planning

planning architect + engineers timber construction expertise

contract timber construction company

Delay

completion and handover

workshop planning timber construction company prefabrication assembly

Time-saving D 1.5

150

D 1.6 Scope of services as defined by HOAI 2013 ­including input on “timber structure” D 1.7 Comparison of the advantages and disadvantages of conventional and collaborative planning models from the client point of view

timber construction engineers strongly depend on the actual services carried out in each individual case. If consulting services are conducted by timber construction engineers, they can be integrated into planning teams and paid accordingly, regardless of whether they might be tasked with execution services at a later date. In the second case, the timber construction expertise enters the planning process through tendering at an earlier date. Public clients are bound by procurement directives, while private clients can freely nego­

tiate the type of cooperation and contract. Generally, a contract is awarded according to the methods defined in the specifications. Aside from a general description of the construction task, a detailed description of partial services or specifications is included for a range of services. The latter is also described as functional tendering. The range of services of a functional tendering procedure includes a description of the required qualities in terms of design, function and construction while defining a scope of action for optimisation. It is important to

define the interfaces between trades and to publish the relevant eligibility and award criteria. The latter should, in any case, be included in the tendering documents. Both strategies are also represented in the full service general contractor model. The full service contractor model A full service contractor takes on both execution and planning tasks. In particular, large construction companies show an interest in this model. Increasingly, large timber construction companies with process-related

Basic assessment

Preliminary planning

Design planning

Permit planning

Implementation planning

Building services engineering

•  clarification of tasks •  planning framework • advice on services required

• basic analysis • development of planning concept with variants and preliminary dimensions • creation of functional ­schematics • clarification on processes, framework conditions, ­interfaces • preliminary negotiations with authorities • cost estimate

• planning concept • definition of systems and components • technical equipment ­dimensioning • handover of calculations • cost calculations • negotiation with authorities

• completion of construction documentation • completion of plans and calculations

• implementation planning • calculations update • planning of penetrations • schedule update • execution planning • review of contractor planning

Structural ­engineering

• clarification of tasks • summary of planning aims

• basic analysis • structural engineering ­advice • planning concept ­collaboration • collaboration on preliminary negotiations on permit ­approval status • cost estimate collaboration • scheduling collaboration

• structural engineering ­solution • estimate on dimensions • structural detail concept • estimate on quantity survey • collaboration on project ­description, negotiation with authorities, cost calculations

• auditable calculations • detailed structural design • coordination with plan ­review authorities • completion of plans and calculations

• in-depth planning •  formwork plans •  construction drawings • list of steel parts for ­connections • ongoing coordination with plan review authorities

Architecture

• clarification of tasks • site survey • clarification of services ­required • definition of required expert consultants

• basic analysis • coordination of aims • preliminary planning of ­variants • clarification of interrelations • coordination of expert ­consultants • preliminary clarification of permit approval status • cost estimate • preliminary schedule

• design • coordination of expert ­consultants • project description • handling of permit approval status • cost calculations • schedule update

• completion of construction documentation • submission for plan review

• implementation planning • coordination of expert ­consultants • execution planning • review of contractor planning • update schedule

Input timber construction

• client advisory

• cost advice • element concept

• master details • degree of prefabrication • element dimensions

•  construction component layers • connection and joint details • production coordination • element dimensions • assembly process D 1.6

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151

Conventional models of separating planning and execution

Collaborative models of integrating contractors ­responsible for execution in planning

+ submission of services and quality allows comparison, due to precise specifications of services as clear basis for decision-making

– comparison between different bids requires qualitative and differentiated evaluation

+  single solution approach

+ creative solutions possible

– costs and schedule compliance requires continuous ­supervision

+ cost and schedule compliance increased by integrative development

– client bears risk of unexpected events during construction phase

+ execution team bears risk of unexpected events D 1.7

in-house planning departments also offer comprehensive services mostly for private and commercial clients. For clients, a single contractor for planning and execution offers the advantage of one single point of contact, as well as budget and scheduling reliability, already at early stages. Disadvantages of the model include: • Cost and quality control is turned over to the full service contractor. This results in follow-up risks: the four-eyes prin­ ciple, meaning the mutual control exerted between those responsible for planning and execution, is omitted. In addition, it is possible that timber construction is impacted by cost pressures the full ­service contractor is subject to. User demands and aspects of building culture are no longer viewed according to economically independent, objective perspectives. • Clients can no longer benefit from the ­professional expertise and trusteeship of an architect. • Room for interpretation relating to speci­ fications can lead to loss of quality and follow-up costs. • Changes that occur after contracts have been signed are seldom without impact on costs.

Timber contractor criteria matrix An aspect often undervalued in the selection of a (timber construction) contractor is assessment and award. According to procurement regulations, the tender is not to be awarded to the cheapest bidder, but instead, to the most economical. In the case of pre­fabricated timber construction, qualitative assessment criteria of the contractor are of specific importance. Only the optimal execution of all processes from workshop planning to prefabrication and assembly enables efficient utilisation of the advantages of prefabrication. Criteria such as delivery of quality according to specifications and execution on schedule are commonly known. In addition, it is also important to integrate topics such as quality of workshop planning, experience of the technical consultants, concepts for element panelisation, logistics concepts, phasing of module delivery and an assembly concept into the assessment. The expertise and experience of the ­timber construction contractor in all of these aspects is decisive for a smooth process. In return, the following is also true: the least expensive price loses relevance significantly when the previously described necessary process chain is interrupted or is not under control.

Functional tendering Functional tendering enables contracts to be awarded based on early planning stages. A construction company obtains tenders based on plans approved by building authorities and architectural master details, leaving the company the flexibility to suggest suitable construction solutions. Detailed technical development is then ­carried out in a team including the architects. Particular attention must be paid to the definition of qualities and the scope of services, in order to avoid budget conflicts. The disadvantage of this model is that change orders cannot be carried out based on customary procedures.

“Bouwteam” models Integrative planning approaches that combine planning and construction expertise, ideally at early stages, are nothing new. In Germany, many government funded model projects have been implemented by adopting the Dutch “Bouwteam” model. The different approaches and project management types of the initial German Bouwteam project show that there was no consistent standard for handling processes in place, which is why these are referred to as “Bouw­ team” models. The only contractually binding relationship provided for in these early Bouwteam models was a contract between the building team and the client.

In the Netherlands, newer Bouwteam models feature improved aspects of legal liability and are now based on separate binding contracts between individual planning and execution participants and the client, to ­better manage liability issues. An additional Bouwteam framework agreement manages the performance criteria of collaborative development in the Bouwteam and defines “exit clauses” in the case of lacking success within the team. Tendering for services is carried out on a functional tendering basis. In another type of Bouwteam model, the construction contractor is included in technical planning and optimisation with a Bouwteam contract based on an architectural design. If the contractor can ensure completion of the project on schedule and within the defined budget after planning has concluded, they are awarded a construction contract. If no agreement is reached, the contractor is compensated and the client can obtain alternative bids based on the services rendered to date. These integrative planning approaches are based on the principle of involving all necessary technical and construction disciplines at an early stage and are still in an early phase of development. Within a Bouwteam, as opposed to a conventional architectural competition or tendering procedure, high-quality design and economic execution are considered part of a coherent whole. In the application of prefabricated timber construction, the model offers the opportunity for an early integration of timber contractors and all involved advantages this entails in terms of collaborative development. The model is applicable to private client projects without restriction. In the case of public clients, particular procedures require consideration due to legally binding framework conditions. The competitive dialogue Early cooperation on equal terms between all involved parties is basically also possible in the case of projects for public clients,

152

a

b

c

within the context of the so-called competitive dialogue procedure: “In the case of the competitive dialogue, the client, after publicly inviting an unlimited number of contractors to submit applications for participation in construction projects, can enter into dialogue with select applicants on all aspects of the contract. The aim of the ­dialogue is to identify a solution or multiple solutions related to the needs and requirements of the client, which serve as the basis to invite respective applicants to submit their tenders” [2].

design phase, the established planning ­status quo serves as the basis for successive and smooth project development and execution with a high degree of budget and scheduling reliability. This leads to a shift among services rendered within the typical scope of services determined by valid fee structures and recommendations. The related scope of services is based on the principles of conventional construction tasks, in which a comprehensive elabo­ ration on planning takes place no earlier than the execution planning and, in part, in parallel to ongoing construction tasks. The valid fee structure, however, offers the opportun­ity to respond to planning processes that are specific to timber construction. A shift in the related scope of services is, therefore, possible. The definition of the required services and the related scheduling is project-specific and requires contractual definition upon awarding contracts.

ent collaborative models and degrees of complexity of projects offer architectural offices the opportunity to enter the field of multi-storey timber construction or to educate themselves further in this field. For a successful planning process, it is important that expertise and experience in ­timber construction are either present in the planning team or their integration in the planning process is ensured by early integration of contractors responsible for execution. For private and public clients alike, processes exist that are suitable for both strategies. Interfaces and communi­cation within the planning team and with the parties involved in execution require definition and standardisation. Timber construction engineering is becoming an established profession that offers solutions for structural engineering, fire protection and building physics. In future it will likely be possible to close the expertise gap between planning and execution. These developments are further and significantly re­­inforced and simplified by the progressing standardisation of available timber construction solutions.

This scenario offers public clients the opportunity to award contracts for construction services early on. The advantage of the competitive dialogue procedure is the collaborative development of solutions that can be tailored to the specific and often complex needs of clients. However, the process of this procedure is highly complex and extensive as well and requires a significant amount of time for both clients and bidding contractors. The competitive dialogue is, therefore, predominantly applicable to complex construction tasks that are difficult to manage within standard procedures. Planning services fees In planning prefabricated timber structures, decisions related to the level of detailing need to be made at earlier stages than in the case of conventional and construction site-based building tasks. As a result, architectural offices and professional consul­ tants, as well as clients, are required to invest more time in early planning phases. The need for an early and binding definition of a construction type and system, joints between construction components and their layer structure demands early integration and coordination of all involved expert planners. An in-depth elaboration on planning must be undertaken prior to completing the design phase. Upon conclusion of the

Conclusion It is decisive for the success of a timber construction project to define a suitable award or cooperation model for both the project and the client. Different models are applicable in timber construction. The related decision-making is strongly dependent on how complex the building is and which demands regarding detailing are expressed by the client and the architect. Functional tendering procedures achieve convincing results for simple construction tasks based on appropriate master details. In the case of complex buildings, mature workshop planning is recommended as a basis for tendering procedures that require the early integration of timber construction competence, represented by those responsible for execution or, in particular, timber construction engineers (Fig. D 1.7, p. 151). Design work appropriate for timber construction requires planning expertise. Differ-

D 1.8

Notes: [1] Kaufmann, Hermann et al. (eds.): LeanWOOD. ­Innovative und optimierte Prozesse und Koopera­ tionsmodelle für die Planung, Produktion und den Unterhalt von Gebäuden in Holzbauweise. Research report. TU Munich 2018, http://go.tum.de/258299 [2] European public procurement law, Art. 30 Directive 2014/24/EU

D 1.8 Planning phases, e.g. secondary school in ­Diedorf (DE) 2015, Architekten Hermann ­Kaufmann, Florian Nagler Architekten a  structural engineering concept b  architectural working drawings, detail c  execution detail, timber construction company D 1.9 Decision-making in the planning process by way of example: the table is based on an example that shows the decisions made by planning participants in each planning phase. The example shows increasing focus from the building level to a particular detail point.

153

PLA NNING

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Structural engineering load transmission system grid

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Building services /energy duct layout location of building services rooms ventilation concept heating /cooling concept daylight /sun protection concept insulation standard building envelope

building physics

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fire safety

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energy

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building services engineering

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structural engineering

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timber construction

Room geometry building orientation spatial layers /plan floor-to-ceiling height access concept openings concept building volume

architecture

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standards and guidelines ­requirements technological state-of-the-art, rules requirements

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‡ product /construction type

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thickness of walls /ceilings location, size, swing direction of doors location, height of hung ceilings building services shaft ­perimeter

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‡ construction component and ‡ element dimensioning

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construction type, material preliminary dimensioning connections concept

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‡ certifications for all construc‡ tion components ‡ connection and joint details

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preliminary shaft dimensions preliminary ceiling duct ­dimensions orientation and intersection of cables outlets lighting concept coordination of penetrations firestop concept wiring revision concept

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‡ dimensioning of service lines ‡ insulation of service lines

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‡ connection of service lines

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‡ ­products ‡ underfloor heating system ‡ underfloor heating coils ‡ ‡

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building physics

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fire safety

building physics

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energy

fire safety

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building services engineering

energy

‡ ‡ ‡

structural engineering

building services engineering

‡ ‡ ‡

timber construction

structural engineering

Building code code requirements, statutes ‡ land use plan requirements ‡ building class ‡

Implementation planning

architecture

timber construction

Design planning

architecture

Preliminary planning

approvals

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‡ ‡

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‡ firewall to ceiling connections ‡ firewall products

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fire safety certification construction component composition

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‡

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Building physics soundproofing concept acoustics concept

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soundproofing certification acoustics measures

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‡ soundproofing detail review ‡ acoustics detail review

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Prefabrication 1D / 2D / 3D concept

‡

‡

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‡

element dimensions /transport ‡ approximate assembly ‡ ­sequence degree of prefabrication ‡

‡ ‡

‡ ‡

‡ ‡

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‡ ‡

‡ joint formation ‡ detail assembly

degree of prefabrication

‡ ‡ ‡

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‡ ‡ ‡

‡

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Fire safety concept (emergency ­egress, etc.) construction component ­requirements

Construction components construction component concept and requirements

‡  leading role ‡ collaboration ‡  no participation

‡

‡

‡

‡

‡

‡

spacing of service lines

switches, sockets, lighting

firewall spacing

Ceilings ‡ functional layer sequence floor thickness hung ceiling system floor construction element system

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flooring screed separation layer impact soundproofing fill hung ceiling system ceiling finishes

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Partition walls functional layer sequence wall thickness wall finishes element system

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facing shell system facing shell finishes insulation cross-laminated timber quality

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Glazed partition walls partitions wall thickness

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‡ thickness and quality of glazing ‡ joint formation

‡ ‡ frame geometry, material, finishes ‡

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Shaft wall construction principle

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wall thickness

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facing shell finishes ‡ insulation thickness and quality

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D 1.9

154

Digitalisation in Timber Construction Manfred Stieglmeier, Sandra Schuster

Digital Process Chains in ­Timber Construction

D 2.1 Three-dimensional CAM model as basis for CNC preparation and pre-fitting D 2.2 BIM model, office building in Stavanger (NO) 2019, Helen & Hard, SAAHA a  trade-specific model, ducts and ventilation b  trade-specific model, timber construction D 2.3 Preemptive and traditional planning process in timber construction – shift of expenditure and ­influence on cost development (cf. MacLeamy, Patrick: The Effort Curve, 2004).

The beginning of industrial prefabrication in timber construction coincides with related processes of digitalisation. For more than 30 years, timber construction contractors have been working with 3D models and enriching them with geometrical and alpha­ numeric information. The ideal digital process chain in timber construction is based on a coherent organisation of data, beginning with an adequate formulation of client plan­ ning needs that defines the rules of cooper­ ation and the requirements for the planned building as well as the long-term use of data. The data production during the entire planning process begins with the architec­ tural preliminary planning and becomes increasingly detailed within an iterative and collaborative process spanning con­ struction and calculations undertaken by expert planners. In an ideal case, all data sets are submitted in the form of a coordi­ nated data model to the timber contractor responsible for execution. At the end of the digital process chain, the model serves ­purposes of building operation and reuse of resources. Upon handing over CAD (computer aided design) data of workshop planning to CAM (computer aided manufacturing) planning of the timber contractor, consideration is given to optimisation processes in reducing waste wood as well as specificities of particular contractors related to possible manufactur­ ing processes (Fig. D 2.5, p. 157). Tradespecific CAD models of architects and expert planners do not include this infor­ mation. In order to use the geometrical and alphanumeric data mostly established by different software programs as a basis for CAM data, the IFC data interface format was developed. The CAM data sets created within a pre­ paratory phase form the basis for the machine control and tool selection of

D 2.1

CNC (computerised numerical control; see “Sub­tractive Timber Production”, p. 159) milling machines. Aspects of manufacturing such as waste wood, material consumption, structural dimensioning, element panelling etc. can be evaluated and optimised at this stage. At this point in the planning process, planning should be finalised and a “design freeze” should be agreed upon between all parties involved. Subsequent changes to planning will result in high financial expenditure and scheduling delays in exe­ cution (Fig. D 2.3). The need to shift planning decisions into the preliminary design and design phases is an aspect shared by modern timber con­ struction and the BIM (building information modelling) method, which describes an ­optimised process ranging from planning and execution to operation of buildings by use of 3D software. It serves to digitally capture all relevant building-related data and network the planning activity of all par­ ties involved within the digital data model. It also allows displaying buildings within a virtual 3D model in a geometrically descrip­ tive manner. This should be preceded by binding definitions regarding interfaces, ­degree of detailing and responsibilities at the beginning of the cooperation between the involved parties. Who delivers what, when and during which phase of the pro­ ject? The degree of collaboration between the parties involved in the project is de­ scribed by different maturity levels (BIM ­levels). Following BIM level 2, after data sets have been interlinked and those from other planning participants have been inte­ grated, it is appropriate to speak of BIM ­application. The model-oriented work pro­ cess, unlike conventional planning, requires more information in a specifically repre­ sented form at earlier points in time. This is why BIM, similar to planning prefabri­ cated modern timber construction projects, requires shifting planning processes into earlier planning phases (Fig. D 2.3) in order

D I G I T A L I S A T I O N I N T I M B E R CONSTR UCTION

BIM The term BIM is used rather excessively. What can be said with confidence is that BIM is neither a software product nor a tool. The term BIM encompasses a semantic data model that can consist of multiple models in practice that allow connections between them through a reference model. At the same time, BIM describes the man­ agement of the model or models with the purpose of planning and coordinating data and information flows. Beyond that, BIM also refers to the modelling process in which involved parties from a diverse set of disciplines participate. The principal aim of BIM is to facilitate a structured, seamless, data-driven cooperation between clients, contractors, experts and parties involved in a construction project and beyond. The client is integrated into the planning pro­ cess. In the course of requirement planning, the client can determine which requirements (client request for information) are included within the project. BIM management Aside from requirement planning, man­ aging the BIM process plays a central role in guaranteeing the effective integration of all services rendered by all project par­

D 2.2

a

b

ticipants. The precondition for this is an organised process of division of labour among participants and a project structure that manages the collaboration between participants. Within the planning process, new fields of expertise develop, such as BIM management. The role of the BIM ­management professional can – contin­ gent upon related education – be assumed by architects or timber construction engi­ neers, since they possess an overview of the entire process, ranging from planning to production. Architects are also the only planning participants who are aware of all service phases and all trades involved in execution.

technical, economic and legal, yet also related to planning cultures. The long-term expectation is that planners and contractors will view the potential offered by the BIM method for planning in the field of prefabri­ cated timber construction positively.

BIM in the timber construction trade Timber and BIM fit together well – the related processes are similarly structured. As a result, timber construction has the potential to play a pioneering role in digital­ isation in the field of construction. Timber construction offers excellent precondi­ tions for an integration in the BIM planning method. Many planners have acknowl­ edged this. Those who have been deliber­ ating on the topic for some time see the advantages it poses for quality improve­ ment and resource savings. Challenges are Effect

to create a timely basis for planning-related decision making. Potential collisions in plan­ ning among different planning experts can, thus, be promptly identified and avoided. Costly and time-consuming planning in par­ allel to execution, which is typical to con­ ventional construction, can be avoided with the BIM method. The precondition for a con­ tinuous planning and production process is the willingness of all professional partici­ pants to engage in interdisciplinary, trans­ parent and cooperative communication in combination with an open culture of identify­ ing errors.

155

Closed or lonely BIM models The most common form of BIM currently used in prefabricating components for tim­ ber construction is the so-called “closed” or “lonely” BIM model in use in the timber con­ struction company. Without the exchange of 3D data, this is defined as BIM level 1 (Fig. D 2.4, p. 156). Execution planning is transferred into workshop planning with software compatible with related systems and finds use as a CAM model in relation to in-house processes. The model is en­ riched with as much information as pos­ sible. Beyond creating plan illustrations, it can be used to calculate costs and quan­ tities, generate stock lists, quotes, tenders and invoices, and to organise building site logistics. In the case of repeated collabo­ rations, architects and professional consult­ ants can use an integrated closed BIM model with work planners and timber con­ struction planners by use of compatible software in order to reach BIM level 2.

Influence on function and cost Costs for design changes Preemptive planning process

Concept phase

Preliminary planning

Design planning

Traditional planning process

Implementation planning

Invitation to tender

Execution

Operation Time D 2.3

156

Level 0

Level 1

Level 2

BIM tools CAD Drawings, text paper exchange

2D 3D CAD

Models, objects, collaboration

Level 3

Integrated BIM ISO standards: IDM, IFC, IFD Life cycle management

Interoperable data Further development D 2.4

3D data models are mostly exchanged on the basis of matching software pro­ grams within related data models in order to directly generate workshop plans from the execution planning that contractors can use for their own p ­ urposes. Implementation planning is, therefore, shifted within the planning ­process, and predates specifica­ tion and tendering. Open BIM models In order to achieve a comprehensive, inte­ grated planning process, the data of all ­parties involved in planning and execution must be consolidated during early planning stages and adapted to the related produc­ tion processes. Architects, expert planners and involved companies process their data within dedicated trade-specific 3D models in accordance with a previous agreement on interfaces and the degree of detail work (also called an LOD – Level of Detail or Development). By use of a data exchange format (e.g. IFC) the dedicated models are merged into a shared 3D reference model on a data platform. Models are tested and coordinated before being introduced into the contractor workshop models. As a result, the advantages of prefabrication and BIM can efficiently complement each other. This object-related approach with a data platform that is jointly shared to a large extent corresponds to the open BIM model. However, no suitable software is currently available for integrating the timber construc­ tion company CAM files into a shared data model. Libraries of construction components with consistent standards are also not yet sufficiently developed and the exchange of data is still quite arduous, due to a lack of available interfaces. The information trans­ ported by use of the exchange format cur­ rently does not arrive at the recipient in the same manner as it was input by the sender. Much of the information attached to these files cannot be read by different kinds of software.

Intersections between timber construction planning – BIM Digitalisation in construction requires care­ ful planning that is appropriate for respect­ ive construction phases and coordinated among those involved. The 3D model of a timber contractor, with its fixed drawing standards and its own component library – coordinated to match in-house manufactur­ ing processes – largely corresponds to the structures of model-based planning. The high degree of prefabrication and automa­ tion in production requires building data modelling already in the practice of the tim­ ber contractor. The potential of digital timber planning can contribute to simplifying the related planning process. The 3D models of the conventional planning processes of the planners and of modern timber con­ struction can be harmonised by use of a shared cooperation and process model based on BIM.

major investment, additional costs and effort in managing projects, as well as acquisition of the necessary professional BIM manage­ ment expertise. The research project “Holz & BIM” conducted at TU Munich has con­ cluded that half of all surveyed planners decide against using BIM mostly for the above-mentioned reasons [2]. According to the survey, due to the problems in data exchange described above, 87 % of BIM users apply data only to their own, in-house BIM model. A continuous digital process chain from planning to prefabrication has not yet arrived in practice. Integrated collaboration based on a mutu­ ally agreed structure at the beginning of a project that leads to an integrated planning and production process under BIM man­ agement spanning design and machine control is the aim of a BIM-based planning process.

Standardisation of information models The further development of the Austrian construction component platform dataholz.eu contributes to the standardisation of con­ struction component libraries with tested construction component layer structures. However, the construction components are not available in a BIM-compatible form. Upon conclusion of the further development process, BIM-compatible construction com­ ponent libraries will likely become available, with tested proof of use as alphanumeric data annexes for construction components.

Added Value for Timber ­Construction

Distribution of BIM In German-speaking countries, in contrast to Anglo-American and Scandinavian coun­ tries, the use of BIM is not yet mandatory. Thus far, its distribution among architects here is limited to larger firms with a greater volume of projects. For small offices (of up to 9 staff members), which make up 90 % of architectural firms in Germany according to a 2021 survey [1], introducing BIM involves

In an ideal case and from the viewpoint of its comprehensive conceptualisation, the BIM-based planning process spans the phases of planning, manufacturing and assembly, as well as the entire life cycle of a building. This includes the definition of long-term planning goals, the design and planning phases, the permit and approval process, as well as manufacturing, logistics and the construction process. It further encompasses use, operation and mainte­ nance of an object, related conversion and alterations up to the point in time at which

D 2.4 BIM levels (cf. Bew-Richards BIM maturity model, 2008) D 2.5 Digital data model across the entire life cycle of a timber building RFI = client request for information BLP = BIM liquidation plan CDE = common data environment

Certification of sustainability criteria

D I G I T A L I S A T I O N I N T I M B E R CONSTR UCTION

location

technical quality ecological quality economic quality

project aims

site quality

cost targets

archi­tect  compe­ tence

sociocultural and func­ tional quality process quality

quality targets

schedule targets

build­ ing ser­ vices en­ gineer

157

formal designoriented targets

­structural engineer

­ xpert e consult­ ant 1

­expert consult­ ant 2

Design for Manufacturing

cloud CAM as built

digital twin

design

RFI

BLP

data

communication

CDE

facility management

remodelling, modernisation

maintenance

Demolition D 2.5

the object is demolished – preferably at the end of its technical life cycle (Fig. D 2.5). Comprehensive data sets that have been established and are used by different par­ ties involved in the different phases of the building life cycle can help to keep com­ plex structures up to date, and to alter, revise and manage them for many years. In the long term, this will result in added value for timber construction, since, for example, topics related to sustainability and certifi­ cation criteria can be introduced into the model early on. The added value of a care­ fully managed BIM model is the integration of data sets across disciplines that, in an ideal case, permit the seamless cooperation of numerous and different experts, contrac­ tors and collaborators spanning many dec­ ades. This is related to the basic intention of BIM to implement such long-term cooper­ ations at lower costs and with less room for error than would otherwise be the case. An aspect of BIM is the digital 3D model or a referenced set of models as source of all drawings, plans, sections and elevations. Beyond that, BIM – unlike other 3D model­ ling technologies – focuses on semantics, on important information that is attached to every planning project. BIM modelling is based on a catalogue of elements, such as walls, ceilings, roofs, windows or doors. It combines the geometrical information (3D illustration of the elements) with alpha­ numeric (descriptive) characteristics such as material, fire resistance, U-value, price or ecological assessment of a material, as well as possible interrelations with other elements of the project. Defined standards and standardised inter­ faces are indispensable to the success of a BIM project. This is particularly important for prefabricated timber construction. The previously described digitalisation of pro­ duction processes makes it sensible and necessary to allow all parties involved in the planning, as well as contractors, to store, access and edit data of a model or

models. BIM also implies coordinated action between segments of the timber con­ struction industry and timber construction contractors on the one hand and clients and authorities on the other, in order to find agreement on applicable and valid standards. The long-term goal is to follow a collabora­ tive approach that focuses on information and the related integrated and intelligent process: the early provision of a BIM model as the basis for timely validation and simula­ tion that allows testing a building in relation to its structural, functional, ecological and economic strengths, as well as exploring design options (e.g. life cycle assessment, energy simulations or collision detection) can simplify decision-making processes of all parties involved and support the ­long-term comprehension of decisions made. In this context, particularly timber as a renewable raw material can demonstrate its potential. At the same time, visualisations of the effects and impact of a building can help simplify the dialogue between involved stakeholders and support early decisionmaking relevant to timber construction. Qualitative modelling enables the verifi­ cation of factors of building optimisation already during the planning phase (e.g. through simulations of energy efficiency), much earlier than a subsequent evaluation of conditions. Precise and detailed quantitative and quali­ tative modelling that includes the rigorous integration of planning and execution up to the creation of a reliable and complete building documentation offers a solid basis for building operation. The so-called asbuilt model represents a building project across its entire life cycle in the form of a “digital twin” – exactly the way it was built. All changes that take place in the context of a remodelling or renovation project for a real building are based on the foundations laid by the existing data model. It is main­ tained, changed and amended in relation to

measures undertaken. This, however, also requires that data sets are updated continu­ ously without errors and managed accord­ ingly. This guarantees a basis for disruptionfree planning with a view to the eventual demolition of a building in the future.

Conclusion The use of BIM scenarios is currently sel­ dom requested by clients. A gapless digital value chain does not exist. Standards for a comprehensive display of sustainability aspects within digital building models are currently absent. Prefabrication in timber construction currently requires model-­ oriented workshop planning that serves as the basis for machine control. The goal is to directly enter production and assembly processes based on the digital data model established during planning and amended by production technology-related require­ ments of work planning. The high demands placed on prefabrication related to quality and precision in combination with the long years of experience in 3D modelling can render a timber construction “BIM-ready”. The observation and evaluation, for instance, of sustainability aspects within early planning phases results in long-term added value for timber as a renewable raw material.

Notes: [1] Federal Chamber of German Architects: Annual ­report 2019, special evaluation on office size devel­ opment [2] Holz & BIM – Building Information Modeling (BIM) als Planungsmethode im modernen Holzbau – eine Standortbestimmung zur Identifizierung von ­Anforderungen und Hemmnissen. Final report, TU Munich, 08/2019

158

Timber Production Wolfgang Huß

D 3.1

The timber production chain begins with timber harvesting. In Scandinavian countries, timber harvesting is largely industrialised, often involving the clearcutting even of large areas. In contrast, harvesting in Central Europe is rather small-scale in terms of the area harvested – with the exception of processing logs due to windthrow or forest calamities (bark beetle infestation etc.) – and, in ideal cases, by use of selection cutting, even of individual trees. The local context, aspects of light incidence and the resulting future growth of surrounding trees are evaluated and trees are still, in part, cut down by use of motor saws and delimbed by hand. If logs are removed within days or weeks, they are usually stacked in woodpiles on storage sites along logging roads. Still covered in bark, they retain the moisture content they had when they were felled. This is important for conserving the logs, because only wood cells filled with water resist air intrusion, which pests such as beetles need to survive. If logs need to be stored for longer periods of time, they can be stacked to dry after being debarked, which prevents fungal infestation. The precondition for the storage of debarked logs is that logs are healthy, i.e. not infested by pests or fungal rot. Following a forest calamity, the live ­conservation of a fallen tree that remains in place and is still connected to some of its roots is also common. Further, airtight film wrap is occasionally used. It may be necessary to store logs for several years in the case of an oversupply of fallen trees due to storm damage. In such cases, logs can be conserved by means of more complex and costly wet storage, which can involve sprink­ ling with or immersion in water (Fig. D 2.3). D 3.1 Workshop of a timber construction contractor with element production D 3.2 Circular saw unit on trimming machine D 3.3 Multiaxial arm of a CNC milling machine D 3.4 Overview of the automatic tools used for subtractive and additive production in timber ­construction

The Raw Materials Industry Wood as a raw material is increasingly processed by large-scale industrial companies with largely automated means. Smaller saw-

mills, in contrast, specialise in more select product ranges and qualities. The first step in the process is the delivery and sorting of logs. Then they are cut to length and debarked, inspected for any embedded metal and scanned with x-rays for defects, measured in three dimensions and sorted based on the criteria of wood type, quality, length, diameter and taper (decrease in log diameter from root to crown) and stacked for storage. Logs are then cut into core and side boards in a saw line. The side boards are processed further using combinations of various hardware, such as milling machines, chippers, gangsaws, bandsaws and circular saws. Processed wood is then sorted once more according to different wood types, dimensions and qualities. Sawn lumber is packaged. Wood is then dried in kilns to the desired degree of construction moisture within a few days. If wood with very precise dimensions or a smooth surface is required, or if rough-sawn wood is to be further processed into glued products, it will have to be planed. In glued laminated timber production, this usually takes place no more than 24 hours before the application of resin, when the dimensional stability of planks is highest. Resulting waste wood such as bark, chips and sawdust can be further processed to create bark mulch, wood-based material boards or pellets, or be used to supply energy for in-house production processes (drying etc.).

Industrial Panel Prefabrication Solid timber products and wood-based materials are manufactured by downstream processing industries. Wood-based materials consisting of fibres, chips or particles are exclusively produced as standard industrial items. In contrast, products such as glued laminated timber and cross-laminated timber are custom products created for

T I M BER PR ODUCTION

D 3.2

specific projects. Using the CAM files of the timber construction company, large-­ format glued laminated timber beams and columns containing drill holes, millings and built-in components can be precisely prefabricated for assembly (see “Digital Process Chains in Timber Construction”, p. 154f.). Cross-laminated timber panels are manufactured in a production facility according to customer specifications, ­prepared in a processing facility with all millings and cut-outs and often directly delivered to the construction site, if further prefabrication steps are not possible, for instance, in the case of ceiling slabs. If ­significant prefabrication steps take place in the workshop of the timber contractor, which is often the case for exterior wall ­construction components, longer transport routes can be acceptable.

Solid timber construction grade ­timber glued laminated timber

Panels: cut to size, openings cut, milled on five sides and drilled, marked and labelled

Timber workpieces max. 120 mm thickness

D 3.3 Additive production production of elements

Subtractive production preparation / pre-fitting / packaging

Linear members: cut to length and notched, milled and drilled on all sides, marked and labelled

159

Cross-laminated timber /glued laminated timber max. 480-mm thickness

Stud frame: joined and fixed (semi-automatic /  fully automatic)

Sheathing: placed, nailed and stapled, projections sawn off, openings and millings created

Wall framing elements ceiling elements roof elements

Wall framing elements ceiling elements roof elements

Subtractive Timber Production Subtractive production in timber construction refers to the preparation, pre-fitting and packaging of linear and planar members consisting of timber or wood-based materials. While small businesses prepare and pre-fit timber members manually or pass on processing of linear timber members to specialised facilities, medium-sized businesses generally possess machinery for preparing and pre-fitting of linear members by use of CNC. They are capable of translating the geometry of linear members defined by CAD drawings into an ­automated processing procedure that can autonomously select the appropriate processing method and tool head. The multiaxial capabilities of the machines and the possibility of moving both the workpiece and the tools during processing enable the creation of almost any conceivable ­geometrical form. Two different types of CNC milling machines find use in the processing of linear members:

CNC milling ­machine

Panel processing machine

Panel processing centre

Framing station

Multifunctional bridge

Combination wall system All above mentioned functions + additional functions: placement and alignment of parts, application of resin

Modular gantry system with robot arm and mobile assembly cell

Portal system with six-axis robot arm D 3.4

160

a

b

c

• Systems with arrays of individual modules that each employ one type of tool, such as multiaxial drills, end mills, side milling cutters, dovetail cutters, slot cutters, or marking and labelling machines, etc. (Fig. D 3.2, p. 159). These machines in particular permit optimisation for high volume companies, repetitive production steps and largely standardised structures. • Facilities with milling robots featuring ­multifunctional six-axis robot arms and alternating magazines containing a wide range of tool heads can perform various tasks and support highly flexible production, although processing times can be longer. These machines are ideal for complex, customised tasks (Fig. D 3.3, p. 159).

timber construction companies and pre­ fabricated housing makers, to a large degree, make use of the potential of automation: the production of a wall framing construction element usually begins with horizontal elements (Fig. D 3.6). Semi-­ automatic framing stations with automatic feed, positioning aids and automatic application of screws and nails allow assembly of stud frames by a single person working under ergonomic conditions. Then, ­multifunctional bridges largely automatically attach sheathing to wall framing elements. Vacuum lifters set panels in place and a robot stapler fixes them to the stud frame (Figs. D 3.5 b and c). Projecting parts of panels are cut off in a computer-controlled process and further cuts are created for window openings or installations. A butterfly table combined with a gantry system simplifies further processing of elements on both sides and, thus, creating closed elements (Fig. D 3.5 a). Cranes can also be used to rotate elements. This is often ­followed by the installation of pipes, elec­ trical cables and ventilation ducts and fire damper flaps in wall and ceiling elem­ ents – manually, due to the very specific requirements of individual projects. Attaching battens, siding and cladding is largely automated. Construction com­ ponents such as windows and sun pro­ tection blinds are then installed manually in a vertical assembly step. Elements are ­lowered into a narrow trench within the workshop floor to provide ergonomic working conditions.

custom construction components, while simplifying human-machine interaction: the length of a modular workbench is expand­ able as required and is limited only by the dimensions of the workshop itself. Tracks are aligned along the workbench for a mobile processing gantry that uses tool heads for all subtractive cutting work as well as applying nails and screws to sheathing and attaching battens. Reversible arms integrated into the workbench and conveyor systems enable processing on both sides and the flexible application of a diverse set of elements. Additional modules, such as for blowing in flock insu­ lation can be included. Manually operable gantry cranes simplify manual work steps. Modularity allows achieving a degree of automation that is optimised in relation to the requirements of a particular contractor. The entire assembly line is freely access­ ible to carpenters and woodworkers, with the exception of enclosed parts of the ­processing bridge. This allows the free combination of automated and manual worksteps, such as for the assembly of a wall framing element. In individual cases, timber contractors use gantry robots with six-axis robot arms that can perform all described subtractive and additive processing worksteps. Related facilities are capable of processing complex and large format construction components consisting of individual linear members and apply resin as well.

Combinations of Subtractive and Additive Timber Production

Based on the degree of digitalisation and automation, the large sawmills and the downstream wood-processing industry, including manufacturers of cross-laminated timber and wall framing elements, have achieved a status of industrial efficiency comparable to other industry sectors. In the production of construction elements,

Larger timber construction companies also use automated processing machines for cutting and milling wood-based material panels up to a thickness of 120 mm. Such machines use software that optimises the amount of wood waste, cuttings and shavings and integrates equipment with automatic feed systems. The fully automated process, the use of kiln-dried wood and the very small temperature-dependent changes in cross section and length enable the production of construction components with a maximum degree of dimensional precision in the millimetre range. Consideration is advised when combining construction types, in particular relating to connections and joinery.

Additive Timber Production The additive joining of processed linear and planar members to form wall, ceiling and roof elements is, in technical terms, now largely automated. However, a share of manual labour persists, especially in small and medium-sized companies. Large

Modular gantry systems with mobile assembly cells cross boundaries between additive and subtractive production. They permit both the processing of wall framing elements, cross-laminated timber elements and

D 3.5

Conclusion and Outlook

161

T I M BER PR ODUCTION

D 3.6

large timber contractors are currently ­moving in this direction and are assuming a pioneering role in prefabricated construction as such. In parallel, there also exists a strong craftsmanship-based tradition in small and very small companies across the entire timber value chain. Mediumsized businesses represent all possible ­gradients between these two extremes. It remains to be seen how small businesses will be able to continue offering the full

range of services for smaller construction tasks in the future, or if specialisation in the realm of planning, element production and assembly will play an even stronger role. The interfaces between the construction materials industry and businesses involved in execution are also in flux. The ­digitalisation of the construction site, however, is still in early stages. Yet, greater developments can be expected to take place here as well.

D 3.5 Prefabrication of a wall framing element: a integrated rotating device within a modular gantry system b mobile assembly cell of a modular gantry ­system c nail application to sheathing by a multi-­ functional assembly unit D 3.6 Production of a stud frame for a wall framing ­element along a framing station D 3.7 Production steps, example floor plan of a ­workshop or factory hall of a timber construction company

storage and mill heating and pressurised air

chippings and shavings

CNC milling machine

preparation and pre-fitting

storage

storage

planing machine

production line 1 structure

insulation

gantry crane

material sheathing

facade office

production line 2 special construction components

finishes

material

truck loading dock

exhaust system

production line 1

special construction components

window integration 1

loading

hall crane

pallets

hall crane

material delivery

CNC bridge

covered storage facility

window integration 2 storage area

material separation

flock station (blow-in insulation)

storage

terrace

staff room

covered storage facility D 3.7

162

Prefabrication Wolfgang Huß

D 4.1

Timber and wood-based materials are, due to simple workability, jointing options and, most of all, due to low transport weight of elements and room modules, particularly suitable for the prefabrication of large scale construction elements and building components.

Prefabrication and Uniqueness

D 4.1 Prefabrication of room modules, European school, Frankfurt am Main (DE) 2015, NKBAK D 4.2 Prefabrication of wall framing elements in a ­workshop D 4.3 Prefabrication of linear elements a  Schematic illustration b Office building in Augsburg (DE) 2015, ­lattkearchitekten D 4.4 Prefabrication of planar elements a  Schematic illustration b Office building LifeCycle Tower (LCT ONE), Dornbirn (AT) 2012, Architekten Hermann Kaufmann D 4.5 Prefabrication of room modules a  Schematic illustration b Hotel addition, Bezau (AT) 1998, Kaufmann 96

The common view of building prefabrication is still strongly informed by the architecture of the 1960s and most of all the 1970s, characterised by the use of serially prefabricated reinforced-concrete elements. From this perspective, prefabricated buildings embodied unimaginative design, monotony and a stubborn focus on joints. Prefabricated slab housing construction implemented on a large scale in former socialist countries of Eastern Europe were based on a technology completely contrary to the type of prefabrication used in timber construction. These buildings were efficient because of the large quantities of identical construction components. The formwork for prefabricated elements allowed repeated use. Structural analyses, which are costly and complex to establish, did not require adaptation. Modern timber construction manufacturing does not rely on this type of rigid formula. Modern software can automatically generate framing preparation and pre-fitting data, even for complex buildings (see “Planning”, p. 146ff. and “Timber Production”, p. 158ff.). When using CNC for preparation and prefitting, the cost and effort involved in manufacture is independent of the differentiation of workpieces. Only the cost and effort of planning and organisation increases with the number of different types of elements. Overall, automated manufacturing will likely become increasingly customised. In practice, this great freedom in construction is more problematic than any restrictions

imposed by prefabrication. Large timber buildings today usually have a prototype character and their structures, layers and joints are individually designed and optimised for each specific building. Developments in this area lead to innovations and high-quality solutions, yet details remain highly specific to particular projects. A higher degree of standardisation would greatly improve efficiency on several levels. Conventional construction in comparison Compared with industrial production, conventional construction does not seem highly optimised. Its dependence on weather conditions, the complex coordination of many separately commissioned trades, and inherently non-ergonomic working conditions on the building site render processes inef­ ficient. Problems are often identified and solved only on the building site and late changes to plans often further delay processes. The work of different successive trades occasionally leads to damages to the previously completed components by other contractors. Schedules often cannot be met and additional costs only become apparent during construction. The many worksteps required on site and necessary drying times can greatly prolong construction periods, while impacting users and the surroundings to equal degrees, especially in urban settings. Prefabricated timber construction can offer an alternative. The tradition of prefabrication Carpentry has always been closely connected to prefabrication. Historical log ­cabins and half-timbered buildings required, at the very least, the preparation and pre-­ fitting of individual linear timber members in the workshop. Traditional woodworking joints are geometrically complex and demand a high degree of precision, which is much easier to achieve under workshop conditions, protected from the weather. In such cases, organisation can also be

PR EFA B R ICA TION

163

D 4.2

optimised and heavy tools are always at hand. The preparation and pre-fitting of a structure in a workshop, beginning with full-scale tracing and including the manu­ facture, marking and trial assembly of members, minimises the need for corrections on the building site. It is also easier to develop more complex solutions for details and to test their assembly in advance in the workshop. Advantages in the construction process Shifting production steps into a workshop shortens assembly times on site (Fig. D 4.2), which offers two positive outcomes for the construction of timber buildings. For one,

building with wood, a material that is sensitive to moisture during the critical phase from assembly to the completion of the sealed building envelope, can take place in an extremely short amount of time. As a result, the dependency on weather conditions can be minimised. A sealed building envelope implies at least the temporary sealing of roof surfaces and exterior walls and the installation of sealed facade elem­ ents. Prefabrication reduces the risk of damage from moisture during the construction phase. As a result, the cost and effort involved in measures to protect structures from the weather is reduced. The second outcome relates to the construction period

as such. The degree to which building ­services technology, interior fittings and building envelope components are pre­ fabricated is decisive for reducing the time required for the completion of interiors. Shorter construction times have economic advantages that will have a varying impact, depending on each project. In the case of replacement buildings, the expensive downtime can be limited. The use of existing buildings can continue without interruption while construction measures take place – unthinkable in the case of conventional construction methods. For example, school buildings can be extended and renovated during holidays.

a

a

a

b

D 4.3

b

D 4.4

b

D 4.5

164

However, modern timber construction does not generally involve a shorter overall planning and execution process, because the planning phase is more complex and, thus, requires more time. Projects stay “virtual” for a long time. As a result, investment costs for execution are required comparatively late in the process and financing spans a shorter period of time. Protected workshop conditions, ideal for manufacture, lead to higher quality of execution and better process control. The ability to work independ­ ently of the weather, very short distances and the permanent availability of a complete assembly team, materials, and tools increase efficiency. In addition, the workbench is a much more ergonomic workplace than a scaffold. It is also easier to coordinate

ules, costs and quality. Prefabrication can make construction more complex and costly in smaller projects, which must be weighed up against its potential advantages. When working on existing buildings, prefabricated solutions require a comprehensive analysis of existing conditions and detailed measurements.

Disadvantages of prefabrication Prefabrication in construction requires very detailed planning (see “Planning”, p. 146ff.). Planners and clients must be ­prepared to make all necessary decisions in a timely manner, based on rigorous deliberation. Corrections on site usually have significant negative effects on sched-

From Linear Member to Room Module

Planar elements 2 D 2D 2D

Beyond the degree of prefabrication, the dimensions of prefabrication are generally distinguished according to linear members, planar elements and room modules (Fig. D 4.6). 3D Room module 3D 3D

Dimension of prefabrication horizontal level Dimension Dimension Dimension derder Vorfertigung der Vorfertigung Vorfertigung horizontale horizontale horizontale Elemente Elemente Elemente

Dimension of prefabrication vertical level Dimension Dimension Dimension derder Vorfertigung der Vorfertigung Vorfertigung vertiakle vertiakle vertiakle Elemente Elemente Elemente

1D Linear elements 1D 1D

and control other trades within a workshop, and the risk of damage to already completed components is much lower. Prefabrication can also help to conserve materials: the amount of waste wood can be minimised by computer control and waste material can be collected and processed in a more controlled way than on the building site.

D 4.6

PR EFA B R ICA TION

165

D 4.6 From linear element to room module – prefabrication steps D 4.7 Delivery of a room module by truck, European School, Frankfurt am Main (DE) 2015, NKBAK D 4.8 Transport dimensions and resulting measures D 4.7

windows. Compact transport is an advantage, working with simple lifting equipment an option, to certain degrees. If assembly takes place on the building site, minor ­simplification of structures can result. For traditional timber beam ceilings assembled on site, for example, doubling of beams required for installation along butt joints of adjoining prefabricated planar elements can be omitted. This can be relevant to vis­ ible ceiling undersides. The disadvantages of on-site assembly are, however, longer assembly times and loss of precision.

2.90 m

(Fig. D 4.4, p. 163). The construction grid elements are based on influences the design, because joints between elements remain visible, depending on the degree of prefabrication and design intentions. Compared to building with room modules, using planar elements offers a great degree of design freedom that allows the creation of any conceivable configuration of rooms. In the case of vertical elements such as exterior walls the degree of pos­ sible prefabrication is large (Fig. D 4.11, p. 167): typically, closed wall elements are prefabricated with sheathing on both sides, windows and door elements integrated in the workshop, as well as a substructure for facade cladding or siding. A maximum degree of prefabrication,

4.20 m

Planar elements Planar elements such as walls, ceilings and roofs are the most frequently pre­ fabricated parts in timber construction

3.10 m

Linear elements Prepared and pre-fitted linear elements represent the simplest level of prefabrication (Fig. D 4.3, p. 163). Correspondingly, the interdependencies between their design and prefabrication are limited. Prepared and pre-fitted linear members of the type used in traditional timber construction are still in use today. It can be advisable to assemble individual linear members of frame structures with long spans into loadbearing structures on site only or to combine them with planar elements. For modi­ fications of existing buildings, individual ­linear members find use if required by site logistics. This is the case, for instance, when new components can be introduced only through small openings, such as existing

2.55 m

3.00 m

3.50 m

4.00 m

4.20 m

4.50 m

5.50 m

Width (W) Height (H) Length (L)

W  2.55 m H  2.90 m L 13.50 m

W  3.00 m H  2.90 m L 30.00 m

W  3.50 m H  2.90 m L 12.50 m

W  4.00 m H  3.10 m L 12.50 m

W  4.20 m H  4.20 m L 12.50 m

W  4.50 m H  4.20 m L 12.50 m

W  5.50 m H  4.20 m L 12.50 m

Permit required

none

special permit required mostly perman­ ent permit ­available

Escort vehicle

individual permit application required for related transports

required for specific roads (German federal roads) along highways in AT, partially in DE / CH

Police escort Miscellaneous

escort vehicle required on highways, double escort in AT police escort in DE / CH

with police escort flat-bed trailer combinations D 4.8

166

a

b

D 4.9

including the facade cladding and the ­visible ­interior surface, is possible and advisable, depending on project specificity. A certain restriction is imposed by element joints, which, similar to fire safety encapsu­ lations, must often be completed on site. The degree of prefabrication is also related to the design of facades and especially to the way joints between elements are con­ figured. For instance, in the case of multistorey exterior walls with timber cladding, floor-by-floor interruptions in the form of ­horizontal sheet steel elements are often integrated in the back ventilation layer, due to reasons of fire protection. Such necessary visible joints can facilitate a maximum degree of prefabrication, including facade cladding. The prefabrication of ceiling elements takes place without the floor construction for numerous reasons. These types of structures often include loose infill that can, as a result, only be added subsequently. In the related layer, electrical and heating service lines are laid out horizontally across multiple elements, which is in contradiction to prefabrication. Floating screed types can be interconnected to create larger coherent areas only by subsequent installation. Joints in a flooring material considered unsatisfactory from a design and technical point of view can be avoided by installing the floor on site at a later point in time. Room modules Room modules overcome the limitations of planar elements. All surfaces and joints can be completely prefabricated in high quality, room module by room module, thereby reducing assembly times on site to a minimum (Fig. D 4.5, p. 163). This is particularly the case for closed room modules. Modules can also be delivered with various interior fittings, even built-in furniture. Technical building installations can also be largely preassembled. Pipes and cables can be connected to each other once modules are

c

D 4.10

set into position. The use of room modules requires a planning decision that should take place at the beginning of the design phase, because it significantly influences the design. This applies to the organisation of the floor plan as well as to the dimensions of rooms. The maximum dimensions of rooms depend on the circumstances of transport from the workshop to the building site. In housing development, the limiting factor is, most of all, the width of room modules. A standard truck can deliver ­ements up to about 13.50 metres long and 3.50 metres tall (Fig. D 4.7 and D 4.8, p. 165).

Fabrication Methods The shift of production from the construction site into the workshop also enables the use of new fabrication technologies that are tied to workshop-based production (see “Timber Production”, p. 158ff.). Professional profile of carpenters Production methods undergoing continuous change influence the professional profile of carpenters and woodworkers on mul­ tiple levels. In modern timber construction companies, this increasingly demands that staff possess additional skille. Most of all in large companies, requirements are shifting from a purely crafts­manshiporiented perspective to the use of computerbased production automation. In relation to the industrialisation and computerisation of processes, the result is, ­similar as in other types of business, a trend towards the need for highly qualified staff as well as personnel with a relatively low degree of qualification. This contrasts with traditional understandings of professional qualification based on comprehensively trained apprentices and masters. As a result, on the one hand, digital expertise is required at the interface between planning disciplines

as well as in-house workshop planning, logistics and production. On the other hand, a conveyor belt-oriented production type also offers fields of activity for staff without training to the level of traditional master and apprentice crafts­ people. The traditional in-depth knowledge of timber contractors related to ­craftsmanship, planning and process, ­however, is still highly relevant. Modern ­timber construction firms demand a broad range of skills. Prefabrication increasingly offers protected work conditions, automation and ergonomic human-machine interaction that reduces physical strain. This makes work easier against the background of advanced age or physical limitations, also making this future-oriented field of work more attractive to women. Craftsmanship versus industrialisation The degree and the dimensions of prefabrication in timber construction have reached a stage that is seemingly finite. However, very dynamic developments still take place in the type of prefabrication and, in par­ ticular, methods of production. On the one hand, the realisation of timber buildings in Central Europe is defined by many smaller and medium-size businesses. As a result, the craftsmanship-related character of this innovative field of business will continue to exist. On the other hand, as current developments show, the degree of automation in prefabrication is strongly increasing among many pioneering businesses. Today, the production of prefabricated houses in the detached to semi-detached two-unit residential property segment is already taking place on an industrial scale. Step by step, the field of multi-storey timber construction is gaining a continuously growing market foothold and currently establishing a farreaching degree of automation in production, with high demands placed on flexibility and customisation.

PR EFA B R ICA TION

167

D 4.9  Classroom interior with visible joints between room modules, European School, Frankfurt am Main (DE) 2015, NKBAK D 4.10 Connection methods for prefabricated elements and related joints a  element joints b  coupling elements c  separation into multiple layers D 4.11 Degrees of prefabrication, e.g. exterior wall ­element a  Low degree of prefabrication: open elements b Medium degree of prefabrication: closed ­elements with windows c High degree of prefabrication: elements with complete layer composition

The Influence of Prefabrication on Design and Construction Prefabrication influences construction just as much as structural engineering and building physics solutions. This becomes clear when looking at the simple example of a corner solution for a wall framing element. The detail does not exclusively articulate requirements of construction and building physics. The fact that two prefabricated and closed wall elements are to be joined must also be considered. This becomes even more clear when taking the influence of ­prefabrication on construction with room modules into account: the layers of two adjoining room modules consisting of floors, ceilings and wall enclosures are nearly completely developed with assembly considerations in mind. In prefabrication, two principally different kinds of design approaches exist. Based on

the system that results from the subdivision into prefabricated elements, planners can derive the spatial organisation and the design of interior surfaces, exterior facades, ceiling undersides and roof surfaces. This approach is generally conducive to a very high degree of prefabrication. At the same time and to a large degree, it is possible to approach design and spatial organisation independ­ ently of element joints and limit these to a technically required minimum. This can coincide with a slightly reduced degree of prefabrication. Both cases require comprehensive knowledge of the prefabrication process already during early design stages. When connecting horizontal and vertical planar elements, one particular conflict is typical within design development: on the one hand, elements are supposed to be joined with prefabricated exposed surfaces on both sides as far as possible. On the other hand, continuous construction com­

ponent layers need to be connected, for structural engineering, building physics and fire safety reasons. This conflict can be resolved by means of joint formation, by introducing subsequently installed connectors, or by dividing a structure into several prefabricated elements (e.g. exterior cladding, wall element and interior lining) (Fig. D 4.10). A combination of the two strategies served to attach wall framing elements and complete wall layers to previously erected frame columns in the Ölzbündt housing development project in Dornbirn (Fig. D 4.12 and D 4.13, p. 168). The elements were set into position from the outside and fixed in place with screw connectors from the inside. Their exterior connections are windproof, because each element is connected to a timber member with a butt joint. The resulting cavity within the joint was subsequently filled with thermal insulation from above. In

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a final step, panels with integrated sealing strips were attached to the inside, completing the airtight and vapour barrier layers. The example of two element joint alternatives in the case of a facade renovation ­project with wall framing elements in Fig. D 4.14 shows how assembly process and prefabrication influence the design of details. In the case of a residential building renovation in Augsburg (see p. 228ff.), floor-to-floor height elements were connected with screws and the timber frame structure was geometrically interlocked, which also led to minimising thermal bridges (Fig. D 4.14 a). In the renovation of a residential and office building in Munich, extensive metal cladding projecting beyond elem­ents did not permit this type of solution. The elements were set into position from above, stacked on top of each other, and connected by hardwood dowels (Fig. D 4.14 b). The structure was completed once the element was lifted into place. No further connection was necessary along the edges of the building structure.

Combinations of different prefabrication steps Similar to the simultaneous use of different timber construction types, the combi­ nation of different prefabrication steps offers potential that has, thus far, been scarcely exploited. Modular construction is a suit­ able method for room modules that are comparatively small and feature a high degree of technical installation and building services technology or complex equipment, such as kitchens, sanitary rooms or also access cores. In contrast, planar or linear elements demonstrate ideal suitability for flexible and open spatial structures with long spans. By intelligently combining systems, buildings become possible that can be assembled quickly with a high degree of flexibility and a maximum degree of ­prefabrication. Another application of this method is suitable for elegantly solving the central problem of renovating bathrooms in residential buildings, by adding replaceable modules that are accessible from the building exterior. There may also be great poten-

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tial for combining space-enclosing and planar elements when adding further storeys and horizontal extensions to buildings while they are still in use. Hybrid construction types It is both possible and probable that the combination of timber with other building materials, primarily concrete and reinforced concrete, will see further developments. Solutions are already available in the form of hybrid construction components, such as timber concrete composite ceilings that include shared prefabrication processes for both materials. Some construction types allow for intelligent combinations of elements prefabricated separately according to particular materials on the building site (see “Timber-Concrete Composite Ceilings”, p. 70f.), in response to the available, yet ­different options specific to construction companies and trades. The integration of different trades in the context of assembly has, thus far, not been practised exhaust­ ively. Building components made of mineral materials, such as firewalls or stiffening access cores, are typically built independently of timber construction, even where prefabricated reinforced concrete elements are used. This significantly slows down the construction process and increases the cost and complexity required for scaffolding. The reason for this lack of integration is less due to construction-related obstacles and more due to the typical contemporary separation of trades into one construction company carrying out execution for concrete and another for timber construction and the resulting organisation on the building site (e.g. crane use). In Central Europe, there is an ongoing trend of large firms serving as general contractor merging with timber construction companies with the aim of securing a share in the promising future timber construction market. As a result, there is a likelihood of the creation of companies underpinning hybrid construction

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D 4.12 Ölzbündt housing development, Dornbirn (AT) 1997, Architekten Hermann Kaufmann, Christian Lenz a  Prefabricated facade element on site b High degree of prefabrication, horizontal section, element joint, exterior wall, scale 1:20 D 4.13 Facade design revealing prefabrication, housing development in Dornbirn (AT) 1997, Architekten Hermann Kaufmann, Christian Lenz D 4.14 Facade modernisation through prefabrication, vertical cross section, element joint a Cladding allows for screw connections along front edge, renovation of a residential building, Augsburg (DE) 2012, lattkearchitekten b Cladding does not allow for screw connections along front edge, residential and office building, Munich (DE) 2016, Braun Krötsch Architekten D 4.15 Typology of room modules: interrelation room – module

types with a corresponding corporate ­structure, which then will significantly accel­ erate the construction process for hybrid buildings.

Maximum Prefabrication: Room Module Construction Types Room modules in timber construction have been realised in Germany since the 1970s. Initially only used for single-storey buildings, multi-storey timber room module buildings have been built since the 1990s, most of all, in the Vorarlberg state of Austria and in Switzerland. A maximum degree of prefabrication was employed for early projects by adding storeys to hotel structures with min­ imal permitted downtime (e.g. Hotel Fetz in the Bödele ski resort, by Leopold Kaufmann, 1997). The construction of the five-storey Hotel Ammerwald near Reutte in 2009 is considered a milestone in the development of timber room module construction types. With 96 modules, it constitutes an entirely new dimension of this construction type. From 2010 onward, projects exceeding high-rise limits were built all over the world. The market share of timber room module construction is currently increasing and plays a strong role in the range of different timber construction types. Design and typology Room module construction has a significant influence on the logic of spatial organisation (Fig. D 4.15). Transport and load-bearing characteristics are the most influential limiting factors. The typical application of room modules encompasses construction tasks for small, enclosed and repetitive functional units, such as apartments, senior care facil­ ities or hotels. In these cases, a degree of prefabrication of 100 % is possible. Modules are, under ideal circumstances, delivered to the construction site complete with

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furniture, locked entrance door and only to be opened after inspection. Beyond this typical field of application, there is a tendency towards utilising transport sizes as much as possible and organising entire apartments within a spatial module. Larger apartments can be created by connecting multiple room modules. In school construction in particular, large rooms, such as classrooms, are mostly assembled from three-room modules that allow individual transport (Fig. D 4.9, p. 166). In the case of these open room modules, the degree of prefabrication is somewhat lower. Flooring needs to be applied on site.

In structural terms, the application type occurring most often includes precisely stacked room modules with primary loadbearing capacity (Fig. D 4.17, p. 170). However, self-load-bearing room modules for placement within a primary structure are also available. In addition, combinations are possible: in the case of the residential timber high-rise building Treet in Bergen in Norway, already the world's tallest timber building during construction in 2015, four storeys of room modules were stacked on top of each other altogether three times and placed into a large-scale glued laminated timber exoskeleton (Fig. A 1.12, p. 11). This

module for a complete apartment

D 4.14

two open modules combined into e.g. an office room

module with ­sanitary room

multiple ­modules combined into e.g. classrooms

module = room D 4.15

170

D 4.16 Notches for transmission of stiffening loads in the lower module D 4.17 Typology of structural engineering hierarchy D 4.18 Room module variants, vertical section, element joint, scale 1:20 a Hybrid construction type with room modules open above, student housing, Heidelberg (DE) 2013, LiWood AG b Slender construction due to limited spans of cross-laminated timber ceilings, European School, Frankfurt am Main (DE) 2015, NKBAK c Solid cross-laminated timber ceiling also forms pavement, impact sound decoupling only between elements. Oskar Leo Kaufmann, Albert Rüf D 4.19 Shell construction of cross-laminated timber room modules D 4.16

allows transfer of strong wind loads. A ­typical combination of planar and threedimensional elements includes setting ceilings into structures above central corridors between room modules.

Timber construction From the viewpoint of construction, the difference between closed and open room modules is significant. In the case of closed modules, load-bearing generally takes place along the longitudinal module sides, lastabtragende Raummodule selbsttragende, eingestellte Raummodule meaning that the ceiling spans the shorter load-bearing room modules distance between walls. The closed module a comprises a stable system in structural engineering terms, consisting of six plates. If more than one plate is removed from this system, such as in the case of a central module of a classroom consisting of three modules, the module needs additional temporary stiffening, at least for transport and assembly, prior to its integration into the overall structure. This requires rotating the ceiling construction, Kombination: with the result that sekundär tragende Raummodule the module ceiling spans the longer disin Primärstruktur eingestellt selbsttragende, eingestellte Raummodule tance between walls. Alternatively, the loadbearing function of longitudinal walls can be self load-bearing integrated room modules stabtragende Raummodule selbsttragende, eingestellte performed Raummodule by downstand beams (Fig. D 4.9, b p. 166). For the construction of room modules, the entire range of timber construction solutions is available. Cross-laminated timber and timber wall framing solutions find use particularly often. This is related to constructionbased considerations and specificities of timber contractors: firms that already employ highly automated means of producKombination: sekundär tragende Raummodule tion for timber wall framing elements also in Primärstruktur eingestellt create room modules based on these eleKombination: ments, in order to increase corporate value sekundär tragende Raummodule in Primärstruktur eingestellt chains. Other firms benefit from the preced2D trägt 3D: 3D trägt 2D: eingestellte Raummodule in flächig timber panel Raummodule mit eingehängten ing work of cross-laminated aufgebauter Gebäudestruktur Deckenscheiben manufacturers and purchase completely prepared and pre-fitted cross-laminated combinations: timber elements. As a result, neither insecondary load-bearing room modules intehouse preparation and pre-fitting, nor extengrated into primary load-bearing structure sive machinery are required. Beyond that, c

D 4.17

hybrid construction types find use: filigree prefabricated reinforced concrete elements for floors comprise an interesting option in economic and building physics terms (Fig. D 4.18 a). In order to stiffen a building, modules are often connected to access cores consisting of reinforced concrete. The most simple ­variant features the placement of modules between two cores. As a result, only horizontal compressive forces are transmitted, which significantly simplifies connections. As an alternative, module walls themselves can be used to stiffen a building or can be reinforced by adequate measures. If soundproofing requirements need to be met, room modules can feature decoupled connections by use of elastomeric bearings, both horizontally as well as vertically. Aside from target conflicts of load transmission and decoupling for soundproofing purposes, the geometrically exact placement of successively stacked modules requires consideration during assembly. This is, for instance, achieved by use of notches, pegs or conical pins that enable self-positioning (Fig. D 4.16). Layers – envelope – equipment The principle of double layer cavity walls and ceilings enables effective sound­ proofing. This doubling of layers is also an advantage in terms of fire protection: if a module wall separates different functional units, the assumption is that fire loads will only occur on one side of a particular wall. The side of the wall facing the fire will ex­­ perience burnout by a few centimetres within cross-laminated timber recesses for elec­ trical sockets. This typically does not lead to the collapse of a wall plate. The load-bearing capacity (R) remains constant throughout the fire resistance time. The module wall on the other side of the fire provides smoke proofing and heat resistance (EI). In the case of the ceiling construction, it is an advantage in terms of fire protection if

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PR EFA B R ICA TION

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­ odule ceilings are not used for stiffening m a building. As a result, they do not become a component of the load-bearing structure and do not require protection in the case of a fire. Instead, they offer protection to the module floor above. For the facade construction, the continuity of construction component layers must be ensured across module joints. While prefabricated module walls constitute the airtight layer in the case of closed units, sealing off of thermal insulation, windproofing and facade cladding takes place after module assembly. If the facade cladding is also prefabricated, it must be connected sub­ sequently along module joints. Depending on the type of facade cladding, the joint between elements remains visible or is concealed, related to design intentions. Room modules are often set on top of a solid construction pedestal floor, if the spatial organisation of the ground floor differs from the organisation of modules. This is, for example, the case in hotel buildings, since the lobby, hotel restaurant, etc. typ­ ically require an open spatial arrangement. For a room module construction type purely based on modules, however, the foundation – especially in the case of permanent, non-temporary buildings – can consist of a planar reinforced concrete slab. The advantage is that ground floor modules do not need to deviate from the standard module type. This offers the opportunity to pour the foundation slab while modules are prefabricated. In the case of temporary buildings, however, strip or pad foundations are preferable. This enables ventilation beneath module floors. The connections between continuous layers of thermal insulation and windproofing requires particularly diligent planning. Handling during assembly is highly difficult, compared to freely accessible types of facade assembly. Flat-roof components are typically installed on site. It is possible to apply a pitched roof construction or to equip roof modules with

pitched roof components. In the case of modular buildings, the optimal service line layout in relation to construction process and maximisation of prefabrication consists in completing the installation within modules before establishing a successive connection to shafts and ducts outside of a module, for instance in a corridor, on site. As a result, entering modules for finishing or maintenance purposes is not required. Service lines outside of modules can be completed on site by plumbing contractors who are not involved in prefabrication.

struction site are reduced to a minimum. Aside from scheduling advantages, this procedure also allows responsible contractors to optimise construction types without impacting the overall process.

Process The production of timber constructionbased room modules is typically undertaken by teams within medium-size businesses under the direction of a timber contractor (Fig. D 4.1, p. 162 and D 4.19). For the production of modules, principal preconditions are adequate space and available conveyor systems in a workshop. The project duration for a room modulebased building is, compared to a prefabricated timber construction with planar elements or a conventional building based on solid construction, significantly shorter. Time savings should not be expected during the design phase, but instead, in the successive project phases. The reason is that awarding of bids, in the case of room module-based buildings, takes place almost always after conclusion of the design phase, on the basis of a functional tender, which requires much less advance planning than a detailed set of specifications. In such cases, the contractor, after being awarded the contract, is already involved in execution planning and typically capable of implementing it effectively and in a timely manner. The prefabrication of modules occurs in parallel with preparatory measures on the construction site. The assembly can take place quickly and with a capacity of 10 – 20 modules per crane per day. Interior finishes and remaining work on the con-

D 4.18

When is a room module-based construction type advised? The necessary basic preconditions for a room module-based construction type ­consist in the principal suitability of a project for timber construction, a programme that can be translated into room modules in a sensible manner, non-complex load transmission characteristics and the openness of all involved parties to engage in this ­construction type. Advantageous framework conditions beyond that include high demands on ecological quality, an interest in exposed timber surfaces, quantities of identical modules of more than 10 –15, a correspondence between functional unit and room module, a high degree of installations inside modules and the demand for cost security. Projects that are predestined for room modules include buildings with temporary or short-term characteristics or repeated use and those which prioritise short construction time, construction sites that produce low emissions and high quality of execution.

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Solutions for Modernising and Expanding Existing Buildings Frank Lattke

D 5.1

D 5.1 Installation of a facade element, renovation of the Grüntenstraße residential complex, Augsburg (DE) 2012, lattkearchitekten D 5.2 Parametric building model based on digital measurements, Grüntenstraße residential ­complex D 5.3 Comparison of survey methods D 5.4 Rooftop addition, Flachgasse, Vienna (AT) 2007, Dietrich Untertrifaller Architekten

A large share of the existing building stock in Germany is outdated: construction components have reached the end of their service life cycle, operation has become inadequate in terms of energy consumption and often no longer meets current functional requirements with regards to accessibility and comfort. Further, in some metropolitan areas, affordable housing and available land for building have become scarce. Modernisations and expansions of existing buildings and the creation of additional storeys are increasingly gaining importance. The comprehensive modernisation of building envelopes and building services technology, as well as programme changes, including accessible renovations, constitute important contemporary construction tasks. In particular, this refers to large structures, e.g. school, office and residential buildings that are remodelled and modernised while remaining in use, because there are no alternative facilities available, neither adequately dimensioned nor economically viable. Concepts and methods are called for that can be quickly and precisely implemented with as little disruption as possible. Long-term, cost-effective and environmentally sustainable solutions are in the focus of interest that, in ideal cases, transform an existing building into a future-proof one – energy-efficient, carbon-neutral and functionally appropriate for contem­porary needs. At the same time, the appeal of buildings and urban ensembles highly relevant to building culture can be maintained during such processes of change. Continued construction efforts also create opportunities for the redesign and upgrading of existing architecture. Most of all, the conservation of existing buildings and the embedded primary energy, as opposed to demolition and disposal of construction materials, offer significant ecological potential. The use of building products made of renewable raw materials also reduces the environmental impact of buildings. Wood and wood-based building

materials receive particular environmental relevance in the field of construction in the context of existing structures [1]. An intervention in the form of a comprehensive modernisation can involve addressing issues related to economy, building regulations and construction-based requirements, such as thermal insulation, fire safety and soundproofing, as well as structural stability and earthquake safety, which always changes the appearance of a building. This offers an opportunity to upgrade the interior and exterior situation of buildings in architectural and design terms and to improve and change their structure through constructionbased alterations. A new building envelope, in combination with the creation of additional storeys, can completely modify an existing building, giving it an entirely new architectural expression. Related design opportun­ ities are nearly unlimited. Timber construction, in particular in the context of modernising existing buildings, offers significant design potential. Triedand-tested wall structures can feature ­rendered surfaces or cladding based on a broad range of facade materials. The fact that they consist of timber must not be obvious to observers. In technical terms, the comparatively low weight of timber structures, compared to reinforced concrete or masonry, offers many advantages. Prefabricated timber wall framing elements or room modules are suitable for renovating facades, replacing or adding individual construction components, including extensions and added storeys (Fig. D 5.4). For this purpose, planners can draw from triedand-tested solutions specific to timber ­construction that can be applied to new construction projects. With widespread CNC (computerised numerical control) ­production technology, complex, threedimensional components can be created that are adapted to existing buildings. Prefabricated and highly thermally insulated construction components can be serially

S O L U T I O N S F O R M O D E R N I S I N G A N D E X P A N D I N G E X I STING B UILDINGS

Tacheometry Geometric conformity

Photogrammetry

3D laser scan

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Granularity

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Model integrity

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External disturbances

™­1)

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Interior spaces integration Analysis options

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++ very good   + acceptable   ™ incomplete or error-prone 1)  rated lower since method is impacted by vibrations and shaded facade areas D 5.2

produced for wall framing or room module construction types (Fig. D 5.2). The high degree of prefabrication and resulting fast construction processes based on precise planning and logistics can reduce any unnecessary nuisances related to construction work, especially in urban environments. Common transport and lifting technology allows for precise assembly of large-format, prefabricated wall elements or room modules, even in confined situations in existing buildings. Short assembly times mean that buildings can be better protected from precipitation and wetting during construction, which reduces the potential for damage due to the weather. Building survey In the case of the modernisation of an existing building or the addition of storeys, an ­in-depth survey and analysis of the building by architects and expert planners is indispensable in order to identify the requirements related to building code, fire protection, structural engineering, toxic substance management, functionality and building services technology. The more information can be gathered on the building, its load-bearing structure and the materials used, the better solutions can be developed and coordinated in the planning phase. A survey and anal­ ysis should not be limited to surfaces, but should also go beneath the surface, opening and drilling into construction components as required. In planning that is adequate to timber construction, aside from architectural considerations, a comprehensive analysis of a building and the related regulatory context, the size and geometry of construction elements, transport logistics and conditions of assembly all require consideration. The structural engineering and construction-based characteristics of an existing building are decisive for creating proper connections between old and new construction components and, in particular, to ensure that structural fire

D 5.3

safety, airtightness and soundproofing requirements are met. Joint and connection details that have been tried and tested for new buildings can meet the construction and building physics-related needs of timber structures. Cavity-free construction of components and joints is important in preventing uncontrollable convection and the spread of fire within a structure. An exact survey of the geometry of an existing building forms the basis for planning a new, prefabricated building envelope. Connections to the existing building must provide appropriate tolerances, in order to compensate for any irregularities and discrepancies in the structure. The new and the old should fit together like pieces of a puzzle. For this purpose, the following should be considered: the higher the degree of prefabrication of construction components, the more assembly tolerances can be reduced. Details of the floor plan and cross sections

based on existing plans or approximate measurements are usually sufficient for the architectural design and implementation planning. Exact digital measurements should ideally be provided by the timber contractor responsible for execution, as part of their production planning. The contractor bears responsibility for the subsequent dimensional accuracy of construction components. Contact-free measurement (e.g. photogrammetry, tacheometry or a 3D laser scan) leads to a three-dimensional digital building model that forms the basis for workshop planning in CAD. Defining all points of a building to be measured and documented and a shared interpretation of results in the planning team are the most important part of preparations. Precise measurements include building corners and edges, window openings, positions of inner and outer reveals and building projections and recesses. Surveyed raw data is transferred

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into 3D point clouds or 3D lines, in order to generate a digital model of the actual state of a building. If subsequent planning takes place on the basis of BIM (building information modelling) processes, the requirements placed on the model structure, the construction component information to be gathered and the responsibility for planning and execution are to be determined among involved parties beforehand. The choice of method depends on the desired result and technical options offered by the different measuring methods (Fig. D 5.3, p. 173).

Adding Storeys Most existing buildings possess sufficient structural redundancy to provide for the addition of one or several storeys. The add­ ition of further storeys constitutes a possible and appealing economic endeavour when

the production of new and attractive usable area serves to finance related construction measures. Timber construction offers the advantage of lightweight, prefabricated, rapid construction for the conversion or replacement of an existing attic or the add­ ition of one or more storeys. It also allows largely minimising nuisances to lower storeys during the construction phase. Protecting the structure has a high priority and a temporary roof, additional scaffolding or sealing of the topmost floor slab can shield it from potential damage caused by the weather (Fig. D 5.5). Rapid construction already greatly reduces the risk of wetting in the existing building. Adding storeys to existing buildings by use of lightweight structures offers numerous opportunities for spatial expansion. In such cases, continued construction means that designs aimed at subsequent use changes should be in line with the existing building structure from the the very beginning.

The more parts of an existing building are preserved, the more intensive the deliberation on planning for the existing structure will be, in order to identify constructionrelated opportunities and interrelations. The existing building and the available access and supply characteristics determine the structure of the rooftop additions. The range of timber construction elements that can be adapted to an existing building include prepared, pre-fitted individual timber components (e.g. roof beams, rafters and purlins, posts and columns, beams), prefabricated timber wall framing elements for walls and roofs and complete room modules. Combining a rooftop addition comprising one or more storeys with a new timber wall framing facade offers the advantage that the transition from the facade to the roof structure will feature no thermal bridges and a single trade will be responsible for interfaces with the building. Load transfer Aside from meeting building code requirements, the feasibility of adding storeys is mainly a question of the load-bearing capacity of the existing building. Adding one or more storeys will depend on the structural redundancy of existing foundations, columns, walls and ceilings. The low weight of timber structures compared to masonry or concrete results in comparatively lower additional loads transmitted into an existing load-bearing structure. In the event of an earthquake, the horizontal inertia resulting from the new addition will be relatively minor. If the existing structure no longer meets the more stringent structural stability requirements for the event of an earthquake, it must be upgraded and re­­ inforced by additional longitudinal and transverse stiffening measures. Loads from additional storeys are transferred either directly into existing construction components or into additional walls or columns, which can also be integrated into the plane

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of a newly added facade. The relatively low weight of a timber structure means that it is occasionally possible to concentrate load bearing at points within the existing building and situate load-bearing construction components in the building interior, in order to keep the facade free of load-bearing ­elements as far as possible, for purposes of greater design freedom regarding facade openings. This was the case in the storeys added to a former railway operations building and its conversion into a residential and commercial building in Zurich. The original two storeys above the ground floor pedestal were replaced, without additional reinforcement measures, by a four-storey addition [2]. Its timber frame walls and hollow box slabs reduce the structural dead weight by more than 50 % compared to solid structures built with mineral materials. As part of a modernisation or expansion project, it may become necessary to upgrade existing construction components. The topmost floor slabs, especially in buildings erected in the 1950s and 1960s, are of limited thickness and possess no add­ itional structural redundancy [3]. In such cases, reinforcement will be necessary if the load-bearing capacity, soundproofing or stiffening of the existing structure have to be upgraded. For this purpose, the following construction options exist (Fig. D 5.7): • Reinforcing the shear strength of the existing slab (e.g. through wood-based material panels with screw connections or creating a timber concrete composite slab) • Upgrading the load-bearing cross section (e.g. by adding a layer of joists or crosslaminated timber panels) • Replacing the existing structure with a new timber slab.

Wood based material panel with screw connection Wood based material panel with screw connection Wood based material panel with screw connection

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D 5.5  Construction under a temporary roof, Treehouse Bebelallee, Hamburg (DE) 2010, blauraum ­Architekten D 5.6  Treehouse Bebelallee, timber construction ­rooftop addition D 5.7  Structural slab upgrading options: a reinforcing the shear stiffness of the original slab b upgrading the load-bearing cross section c replacing an existing structure with a new ­timber slab D 5.8  Timber construction elements follow the existing load-bearing structure of walls and ceilings D 5.9  Arrangement of timber construction elements Timberto concrete composite ceiling structure transverse the existing load-bearing D 5.10 Possible geometries of rooftop additions Timber concrete composite ceiling Timber concrete composite ceiling

a Reinforcement a Reinforcement a Reinforcement Added cross-laminated panel

Added beam layer

Added cross-laminated panel

Added beam layer

Added cross-laminated panel

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b retrofit b retrofit b retrofit New beam layer

New cross-laminated timber ceiling

New beam layer

New cross-laminated timber ceiling

New beam layer

New cross-laminated timber ceiling

c Replacement c Replacement

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c Replacement

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Dealing with existing buildings The simplest form of extension is the upgrade or replacement of the entire roof structure. Fig. D 5.10 shows possible geome­ tries for rooftop extensions. If one or more D 5.10

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storeys are added, the new room layout will be determined by the existing ­access patterns, the spatial arrangement of loadbearing walls and columns, as well as the supply shafts and ducts for building ­services equipment. Often, maintaining such existing elements contradicts the newly differentiated organisation of rooms, due to new functions or a desire for greater design freedom. Large-format timber frame wall ­elements and ceiling and roof structures with long spans, such as beam, dowel lamin­ ated timber, cross-laminated timber or hollow box ceilings, as well as room modules can be used in accordance with the pos­ ition of existing walls or columns (Fig. D 5.8, p. 175). Alternatively, the new load-bearing structure can be positioned transverse to the main direction of existing walls or ­columns (Fig. D 5.9, p. 175). For this purpose, it is not mandatory to adopt the existing room layout. The result can be a new

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D 5.11

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t­ypology of rooms that corresponds to the function envisioned. Deep beams, frame structures and rib construction types all ­enable spanning across rooms of greater depth, if load transmission from the new into the existing load-bearing structure is ensured. The rooftop expansion of the Berlin Metropolitan School was planned as a timber structure, based on low weight and simul­ taneous high load-bearing capacity. In 2020, the architects of Sauerbruch Hutton placed it on top of a reinforced concrete slab structure from 1987 (Fig. D 5.11). The school building was expanded while in use and the block border structure received two add­ itional storeys. The high degree of prefabrication of the timber frame elements and simple connections without requiring interventions in the existing foundations or the load-bearing structure of the existing slab building were advantageous to the construction process. Covering about 3,650 m2, a differentiated programme including audito­ rium, school library and rooms for shared activities, self-learning and group work was created. The prefabricated timber rooftop extension clad in copper panels is visually distinguishable from the tectonic structure of the existing building and its brick facade. Principles such as determining element sizes and joining different prefabricated construction systems remain legible along the facade. The reinforced concrete exterior walls continue to transfer only the loads of the existing slab building into its foundations. The primary load-bearing structure of the rooftop addition features partition walls consisting of cross-laminated timber set at a 90° angle to the exterior walls of the existing loadbearing structure. They transfer the loads of the hollow box roof structure into the stiffening walls of the slab building. Similar to the exterior walls and their foundations, they feature sufficient structural redundancy. The roof structure of the two-storey audito­

rium comprises an inclined, angular pinned frame beam construction spanning 16 m. The facade facing the block border is tilted outward, forms the recognisable roof perime­ ter and encloses the interior courtyard. The alternating slim and broad facade openings of the rooftop extension follow the logic of the new structure and its corresponding function. On the interior, the structure is vis­ ibly exposed. The timber surfaces with white glazed finish provide the rooms with a bright and friendly atmosphere. The orientation and the rotation of the new structural system compared to the old creates a high degree of flexibility for architectural and interior design. The exemplary superimposition of various types of functions is visible in the Wylerpark project in Bern by Rolf Mühlethaler (Fig. D 5.12) [4]. A three-storey timber residential rooftop addition was placed on top of a two-storey reinforced concrete office building with two

177

below-grade storage levels. The grid of the load-bearing structure, the type of access and the building services installations vary between the office and residential uses. A prefabricated ribbed concrete panel is set on top of a concrete column grid and cantilevers beyond the two-storey ground floor. A raised floor installed on this load-distributing platform serves to redirect ventilation and sanitary system installations from a limited D 5.11 Rooftop addition, Berlin Metropolitan School (DE) 2020, Sauerbruch Hutton a, b  The high degree of prefabrication permitted construction while the school was in use. c Visible laminated veneer lumber construction in the auditorium. d Roof construction with sheet copper exterior cladding. e The rooftop additions of the existing building consist of solid timber. A laminated veneer lumber construction serves as the roof of the new reinforced concrete addition. D 5.12 Rooftop addition, Wylerpark, Bern (CH) 2008, Rolf Mühlethaler

D 5.12

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D 5.13 Horizontal and vertical arrangement of facade elements D 5.14 Installation of facade elements a  set on top of an existing slab edge b  set on top of an additional foundation c appended d suspended D 5.15 Vertical loads transferred into foundations D 5.16 Vertical loads transferred into edge beam D 5.17 Vertical loads transferred into brackets

number of shafts for office use to several shafts for residential use. The three-storey residential rooftop addition made of timber wall framing bulkheads and timber ceilings follows its own logic in terms of structural grid and shaft layout. Access balconies serve to enter and exit the units of the residential floors. Increasing the height of the office building by three storeys was only possible due to the relatively low weight of the timber construction and by exploiting the structural redundancy of the below-grade levels and foundations without requiring additional upgrading. D 5.13

a

b

Building code and fire safety An attic conversion or added storeys can result in more stringent building code requirements placed on the structure if the building is assigned to a higher building class following modifications. Typically, heightened requirements are not placed on the topmost floor load-bearing components, as long as they do not serve special uses, for example, as a firewall. In such cases, planners need to determine early on which fire resistance duration requirements construction components need to meet and which results the flammability of building materials in relation to the change of building class entail for the building in its entirety. If necessary, the existing building may have to be upgraded and the timber structure may have to be built to be highly fire-resistant or fireproof (see “Fire Protection”, p. 78ff.).

Facades Highly insulated, prefabricated timber wall framing elements can be an interesting alternative to common methods of energyefficient refurbishment, such as composite thermal insulation systems and element facades consisting of aluminium or steel. Elements are added in front of an existing c

d

D 5.14

wall or used to replace the existing facade. Mostly, closed timber wall framing elements with members either of solid construction lumber, glued laminated timber or Å-joists in combination with structurally effective sheathing and infilled thermal insulation (e.g. cellulose or mineral fibre) and built-in windows find use. The facade cladding is a separate layer. Depending on building code requirements, the layer facing the timber wall framing element may have to be built using non-flammable building materials and the back ventilation layer may have to be interrupted floor by floor, for fire safety reasons. A range of different cladding materials (e.g. wood siding, wood panels, wood fibre panels, glass or metal) can be attached to the load-bearing structure of a timber wall framing element, offering a broad range of facade design options. Upgrading a building envelope offers an opportunity to reconfigure characteristics of design, structure and technology of an existing facade, depending on the original construction. The effort involved in changing openings in the building envelope depends largely on the existing exterior wall structure. The options for altering a load-bearing, monolithic brick structure are limited. A ­masonry window parapet can easily be ­demolished, but enlarging openings lat­ erally is a costly and complex undertaking, especially in a building that is still occupied. A steel/glass or reinforced concrete curtain wall facade can, in contrast, be dismantled and replaced by a new facade more easily. This offers an opportunity to completely redefine the architectural and technical characteristics of facades. In the case of a multilayered facade made of prefabricated re­­ inforced concrete elements, the outermost layer of which protects the structure from the weather, the opportunity exists to install an exterior prefabricated timber layer in front of an existing structure. As a result, the existing facade layers are retained, which im-

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proves the cost-effectiveness of the system. Cantilevering construction components, such as balconies or loggias, usually comprise major thermal bridges and need to be removed, because it is generally either impossible or too expensive to insulate them. Enclosing such construction components is a possible solution and can also serve to upgrade interiors by extending the living area outward and adding heated space to the building volume. In the modernisation of the Grüntenstraße residential complex in Augsburg, for example, the ­reinforced concrete balcony structure was retained and covered with prefabricated facade elements. This approach enabled balconies to be integrated into the heated building volume (Fig. D 5.19, p. 181 and project example p. 228ff.). Facade load transfer The additional horizontal and vertical loads caused by a new facade layer can be transferred into the load-bearing structure of the existing building or into separate, new foundations. The structural redundancy of the existing building must be precisely defined in planning to ensure that the additional dead load and wind, snow and seismic loads can be absorbed by the existing building through force-fit, friction-locked

D 5.15

connections. Before new construction components are installed, the existing structure may have to be upgraded. The structural effectiveness of load transfer connections must be verified and they must be adapted to the existing structure. Depending on the building geometry, horizontal floor-to-floor height or vertical building-height timber wall framing elements can be installed in front of an existing exterior wall (Fig. 5.13). Related to the type of load transfer, they can be installed in front of an existing load-bearing structure according to four different variants (Fig. 5.14): •  set on top of an existing slab edge (a) •  set on top of an additional foundation (b) •  appended (c) •  suspended (d) Horizontal and vertical loads can be transferred by the same support. If they are transferred separately, vertical dead loads are distributed through additional foundations or bearing brackets and horizontal loads are transferred by anchors into the existing slab structure. Vertical loads should ideally be directly transferred into the base area and into a pad foundation (Fig. D 5.15), cantilever beam (Fig. D 5.16) or bracket (Fig. D 5.17). Structural protection of the new timber wall

D 5.16

179

elements must be maintained and the base area must be permanently protected from moisture. Horizontal wind suction and wind pressure loads can be transferred floorby-floor using anchors, e.g. angled steel brackets mounted to the outer slab edge. A more efficient solution is to connect a circumferential edge beam to the outer slab edge. It can serve as an edge guide for facade elements during assembly and as support for horizontal load transfer. If a facade is installed in front of an existing exterior wall, a 6 to 8-cm-deep gap has proven to be effective in compensating ­unevenness in the wall surface. This compensating layer between the existing wall and the new facade must be cavity-free and filled with insulating material, either blow-in insulation flock or a mat attached to the back of the facade element, in order to prevent uncontrolled convection. As is the case with hybrid structures, the open joint between a fixed facade element and the floor slab must also be filled, e.g. with insulating material that can withstand temperatures in excess of 1,000 °C [5]. The inside of the facade element is constructed as an airtight layer and vapour barrier to protect the wall from moisture due to convection and diffusion. In buildings with different functional units, such as multi-storey

D 5.17

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D 5.18 Renovation of the Grüntenstraße residential complex, Augsburg (DE) 2012, lattkearchitekten a  firestop, sealing of window reveal, elevation b  window reveal, horizontal section, scale 1:20 c  window reveal, vertical section, scale 1:20 D 5.19 Grüntenstraße, facade after renovation a

residential buildings, it must be ensured that sound is not transferred through cavities in the compensating layer. Connection details that have been tried and tested for joining timber wall framing elements in new buildings can be used to seal exterior facade surfaces. If elements feature a high degree of prefabrication and facade cladding is already attached, it must be ensured that anchor points and joints are easily accessible. Experience shows that a form-fit, friction-locked mortise joint or tongue and groove joint simplifies the installation of individual construction components by functioning as a guide and allows elements to be horizontally anchored to the existing building without eccentricity.

b

Window installation Exact survey data and careful planning under consideration of necessary tolerances support the installation of window units complete with reveal, flashing and sunshading into facade elements during prefabrication in the workshop. This reduces related adjustment work on the construction site. Joining an inner window reveal to a timber wall framing facade installed in front of it constitutes a particular challenge. If the building is occupied, it is advisable to remove the old windows from the exterior. After facade elements are installed, the inner reveal is levelled and plastered or clad in a double layer of gypsum board. The window frame is placed on the interior edge of the timber wall framing element and features an ad­ hesive and airtight connection. This is a ­visibly homogeneous and smooth solution, but requires several worksteps inside apartments. A quicker alternative, especially suitable for buildings that are occupied, is to build window connections by use of a prefabricated reveal frame (for example, made of wood-based material panels), which can be pushed against the window frame from the inside (Figs. D 5.18 b and c). c

D 5.18

Particular attention must be paid to the planning of joints and sealing of a second water-bearing layer beneath the sill flashing, which draws moisture away from the building. Window frames must be covered with insulation from the outside to reduce thermal bridges in compliance with stan­ dard requirements. The covering and encapsulation of the ­window reveal and, in particular, the lintel area are relevant in terms of fire protection. Transitions between the wall and window opening, which result from a compensating gap, must be filled with at least 50-cmthick, circumferential strips of mineral wool (with a melting point > 1,000 °C) and must be sealed with a fire safety compliant construction. Non-flammable panels or cementbonded particle board in building materials classes A2-s1, d 0 can be used for this purpose (Fig. D 5.18 a). Building regulations and fire safety Exterior wall elements that are connected to a building in the course of a facade ­modernisation project and designed to exclusively transfer dead weight and wind loads are, in terms of fire safety regulations, regarded as non-load-bearing construction components [6]. This means that a ­fire-resistant construction type is sufficient, even for tall buildings. From a building code perspective, however, a new wall element will have a space-enclosing function (EI) if it serves to replace an existing facade. In any case, cavities must be avoided and connectors must correspond to the required fire resistance duration, in order to avoid any possible risk of large elements falling down in the event of a fire. Building services technology For the renovation and adaptation of building services technology in the context of a modernisation or expansion project of an existing building, in addition to the advice for planning and execution (see “Digitalisa-

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tion in Timber Construction”, p. 154ff.), the ­situation of existing equipment should receive particular consideration. If the extensive rearrangement of existing shafts and ducts and the resulting new layout of service lines are not required, the pos­ ition of shafts and ducts must receive consideration in planning and they must be extended as required. In the context of modernising facades, thought should be given to whether an interior renovation of service lines requiring high expenditure and effort can be avoided and whether service lines can be integrated into the facade construction. There are two important arguments against this approach: wet rooms or existing shafts are seldom located next to facades. In the case of an extensive remodelling project, the renovation of service lines only constitutes a minor aspect. In addition, particularly in existing building stock from the 1950s and 1960s, there is often a large number of old chimneys that are mostly located in positions suitable for their reuse. In the case of multi-storey buildings, shafts are more easily accessible than service lines led through facade structures. This is why it is appropriate to integrate individual components, such as exterior wall penetrations, decentral ventilation equipment or solaractive modules in the exterior cladding layer. They can already be integrated during prefabrication.

Notes: [1] König, Holger: Bauen mit Holz als aktiver Klima­ schutz. In: Kaufmann, Hermann; Nerdinger, Winfried: Bauen mit Holz – Wege in die Zukunft. Munich 2011 [2] Schihin, Yves: Brown land densification – Urbane Aufstockung in Zürich. In: Conference proceedings 18. Internationales Holzbau-Forum. GarmischPartenkirchen 2012 [3] Isopp, Anne: Belastungstest. Was ist dem Bestand zuzumuten? In: zuschnitt 42, 06/2011 – Obendrauf, p. 9 [4] Mooser, Marcus et al.: Aufstocken mit Holz – ­Verdichten, Sanieren, Dämmen. Basel 2014 [5] see note [3] [6] ibid. D 5.19

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Part E  Examples of Buildings in Detail

Residential complex in Jyväskylä (FI) 2015, OOPEAA

E1  Joinery in Detail

184

01  Acton Ostry Architects, Student Residence in Vancouver

190

02  Kaden Klingbeil Architekten, Residential and Office Building in Berlin

194

03  White Arkitekter, Cultural Centre and Hotel in Skellefteå

198

04  pool Architekten, Residential and Commercial Building in Zurich

204

05  OOPEAA, Residential Complex in Jyväskylä

208

06  Deppisch Architekten, Residential Complex in Ansbach

212

07 ARGE ArchitekturWerkstatt Vallentin, Johannes Kaufmann Architektur, Residential Complex in Munich

218

08  Florian Nagler Architekten, Residential Development in Munich

220

09  spillmann echsle architekten, Rooftop Extension in Zurich

224

10  lattkearchitekten, Renovation of a Residential Building in Augsburg

228

11  Rolf Mühlethaler, Residential Buildings in Zurich

232

12 Florian Nagler Architekten (System Development and Design), Kampa (Construction), Administration Building in Aalen

237

13  Architekten Hermann Kaufmann, Office Building in Vandans

240

14  architekturwerkstatt, Office Building in St. Johann in Tyrol

246

15  Michael Green Architecture, Research and Office Building in Prince George

250

16  Bruno Mader, Administrative Building in Clermont-Ferrand

254

17  Cukrowicz Nachbaur Architekten, Community Centre in St. Gerold

258

18 ARGE Diedorf – Architekten Hermann Kaufmann, Florian Nagler Architekten, Secondary School in Diedorf

262

19  NKBAK, European School in Frankfurt am Main

268

20  Agence R2K, School Complex in Limeil-Brévannes

272

21  Fink Thurnher, Agricultural Training Centre in Altmünster

276

22  Sauerbruch Hutton, Student Housing in Hamburg

280

23  SEILERLINHART Architekten, Office Building in Alpnach

284

24  Andy Senn Architekt, Agricultural Centre in Salez

288

25  Helen & Hard and SAAHA, Bank Headquarters in Stavanger

294

184

Joinery in Detail Stefan Krötsch

The opportunities to combine various loadbearing systems, the multilayered character of construction components, different types and degrees of prefabrication and continuously growing requirements placed on construction types result in very complex and specific detail manifestations. Self-explanatory, generally applicable – if possible, standardised – forms of execution are still the exception, rather than the rule in timber construction. When a load-bearing structure is designed to remain visible, technical aspects of joints that connect construction components are deeply entwined with design intentions. The connection between a ceiling slab and a load-bearing exterior wall displays the interdependencies of joining construction components in multi-storey timber buildings particularly well. The continuity of exterior wall layers belonging to the thermal building envelope and slab structures as separation between floors must be coordinated with the slab supports and the transfer of loads from floors above. These parameters are superimposed by specific principles resulting from prefabrication and construction processes. The taller a building is, the more decisive a standard detail that is repeated floor by floor will become to its structure. As an introduction to the documentation of projects, this chapter features a comparison

of slab support details along exterior walls of five very different timber buildings. The office building in Vandans and the community centre in St. Gerold comprise frame structures that could hardly be more different in terms of their functional requirements, slab structures and assembly processes. The load-bearing structures of the Woodie student housing project and the agricultural centre in Salez consist of cross-laminated timber wall and ceiling plates. They are, however, fundamentally different buildings: on the one hand, apartments were prefab­ ricated as room modules, on the other hand, boarding school rooms were built as conventional wall and ceiling elements. These examples are compared with a residential complex in Zurich comprising multi-storey structures with load-bearing wall framing elements. While the projects are described in detail and comprehensively illustrated in the project documentation section, one specific detail will be compared here – the connection between the ceiling and the exterior wall. Each of these joinery examples – similar to the key topics of Parts B, C and D of this Manual – is analysed in terms of prin­ ciples of load-bearing structure, structural engineering and construction process and discussed in the context of the overall system of each building.

J O INER Y IN DETA IL

Detail 1 Wall framing element – dowel laminated timber ceiling

Residential Buildings in Zurich Project documentation p. 232ff. Isometric illustrations, n.t.s. Vertical sections, scale  1:50

Structural engineering The load-bearing exterior walls consist of wall framing elements. An edge beam with L-shaped cross section is placed on top of studs and into a recess along the upper edge of the wall elements. It serves as a ­linear support for the dowel laminated ­timber slab elements. The wall elements feature neither top nor bottom plates, studs are continuous along the entire height of the wall element. Vertical loads are transferred through element joints, settlement-free and without transverse compression applied to timber components, from one stud end grain to the next stud end grain. Layer composition The wall framing elements feature two layers of insulation. The interior sheathing layer comprises adhesively bonded joints and includes the airtight layer. It is continued along and around the integrated ceiling ­elements and is adhesively bonded to the sheathing in the area of the floor construction. Short, projecting roof elements protect the timber facade and windows from weathering. The sound insulation and fire safety requirements of the ceiling slabs are met by a layer of floating screed above and a hung ceiling below. Prefabrication and assembly The panel elements were prefabricated including windows, sun protection devices, interior finishes, cladding substructure and window soffits as construction components allowing integration of four windows each. The prefabricated floor-height exterior wall cladding panels and projecting roof elements were mounted on site. After erecting wall elements, ceiling elements were placed on top with a timber batten as a guide along their top edge, serving to fit in the successive wall element equipped with a corresponding recess along its lower edge.

185

186

Detail 2 Wall framing element / frame construction – dowel laminated timber ceiling

Community Centre in St. Gerold Project documentation p. 258ff. Isometric illustration, n.t.s. Vertical sections, scale  1:50

Structural engineering Solid construction timber columns and beams integrated into the exterior and ­interior walls form a frame structure with ­columns that are visually present in the strip windows. Dowel laminated timber element ceilings are set on top of beams as linear support. The load-bearing frame and ad­­ ditional studs are integrated into the exterior wall framing elements, which are braced by diagonal sheathing. Four exterior walls and a cross-laminated timber panel elevator shaft stiffen the building. As a result, the dowel laminated timber ceilings do not comprise rigid plates. Layer composition The exterior wall framing elements are ­insulated and feature a second, exterior insulation layer, into which windows were positioned. The second layer is continued in front of the ceiling supports and the loadbearing structure. A layer of oiled paper serves as airtight layer between the interior timber sheathing and insulation layer. In the ceiling area, foil sheets are drawn along the slab edges, connecting the airtight layer of the wall elements above and below the slab. Floating screed above and a hung ceiling below meet the ceiling sound insu­ lation and fire safety requirements. Prefabrication and detail The exterior walls comprising buildingheight frame wall elements and the crosslaminated timber elevator core were erected first. Slots within the wall elements served to arrange dowel laminated timber ceiling elements. An inlaid film layer was connected to the airtight layer of walls. Interior walls, columns and beams were installed successively after mounting slabs. Following completion of the load-bearing structure, a second layer with insulation, windows, facade cladding, installation shafts, hung ceilings and floor construction was mounted on site.

J O INER Y IN DETA IL

Detail 3 Cross-laminated timber walls – cross-laminated timber ceilings

Agricultural Centre in Salez Project documentation p. 288ff. Isometric illustrations n.t.s. Vertical sections, scale  1:50

Structural engineering The double-layer cross-laminated timber walls between the dorm rooms serve as a load-bearing parallel shear wall construction. Cross-laminated timber panels span between them and feature a top layer of insitu concrete. The ceilings are set on top of the wall plates and constitute single span beams. The corridor walls stiffen the parallel shear walls and serve as supports for the ceilings above the corridor. The exterior walls consisting of frame wall elements are placed in front of the parallel shear walls and bear the loads of the cantilevering roof projection. Layer composition The exterior walls do not bear ceiling loads and, instead, are set in front of the loadbearing structure. As a result, the construction component layers are nearly without any interruptions. The suspended balcony layer consists of a water-permeable, weathered oak construction connected to the exterior facade along individual point supports, which are located behind the back ventilation layer along the sarking membrane. The cavity wall structure of the walls between the boarding school dorm rooms and the room-by-room separation of ceiling elements minimises sound transmission and flanking sound transfer. Prefabrication and assembly After erecting the pre-fit cross-laminated timber wall and ceiling panels, the buildingheight wall framing elements of the exterior walls, including insulation, sheathing and sarking membrane were installed. In the next step, in-situ concrete was poured on top of the ceiling panels, equipped with ­millings. Projecting panels were mounted after vapour barriers and the temporary roof seal were applied to the roof surface. Balcony suspension and decking, windows, facade cladding, floor construction and wall finishes were added subsequently.

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188

Detail 4 Cross-laminated timber walls /  cross-laminated timber ceilings in room modules

Student Housing in Hamburg Project documentation p. 280ff. Isometric illustrations, n.t.s. Vertical sections, scale  1:50

Structural engineering The six-storey timber structure is set on top of a reinforced concrete platform and comprises a parallel shear wall construction with load-bearing cross-laminated timber walls and ceilings. The ceiling elements consisting of asymmetrical layers are not placed on top of the wall panels, but instead, mounted between them. This leads to end grain butt joints between lower and upper wall panels that are separated by elastomeric bearings and produce no transverse timber compression. The corridors feature prefabricated reinforced concrete elements that provide horizontal stiffening. Layer composition A visually exposed cross-laminated timber panel on the interior side of the exterior wall constitutes the airtight layer. The joints between modules are covered in airtight adhesive seals. The windows are situated in the double insulation layer with substructure, which is sealed by use of a sarking layer on its exterior. The back-ventilated facade cladding consists of closed timber boards with relief and sheet metal panels. The cavity wall and ceiling construction type resulting from the use of room modules, in combination with decoupled supports, provides adequate soundproofing. Prefabrication and assembly The logic of prefabrication guiding the production of modules determined all aspects of the assembly process. The acoustic decoup­ ling of the stacked room modules is provided by the load-bearing structure, while cavity walls and ceilings enhance soundproofing measures. The exterior wall joints were insulated and sealed on site. The assembly of the facade cladding took place on site as well and served to cover lateral module joints. The modules were completely prefabricated, with the exception of the facade cladding. The installations were c ­ onnected and finishes applied from within the corridors.

J O INER Y IN DETA IL

Detail 5 Frame construction – timber concrete ­composite ceilings

Office Building in Vandans Project documentation p. 240ff. Isometric illustrations n.t.s. Vertical sections, scale  1:50

Structural engineering Columns within the longitudinal facades and their counterparts placed at double intervals in the interior of the building, together with the primary beams, constitute the primary load-bearing structure. Timber concrete composite ceilings span between the primary beams. The edge beams of the prefabricated ceiling elements and the top layer of ceilings consist of concrete, serving as primary beams. The columns of the floor above are set on top of these beams and loads from the floors above are transferred without transverse timber compression from the ­column end grain into the concrete beam. Layer composition The exterior wall consists of wall framing elements with window strips and enclosed parapets with a double insulation layer. The load-bearing columns and edge beams are located in the interior insulation layer. The exterior insulation layer matches the window layer and is free of thermal bridges. The interior sheathing of parapets comprises an airtight layer that is led around ceiling elements and exposed c ­ olumns and is connected to the window frames. The projecting roofs on each floor protect the wood window frames and the facade from weathering and sunlight. Prefabrication and assembly The timber concrete composite ceilings comprise elements with four timber beams each, concrete edge beams and a top cover layer. They are prefabricated and feature embedded sleeves that connect elements to pegs at the tops of beams. This allows elements to be fixed in place. Pouring concrete into joints provides moisture protection during construction. A parapet section and three columns together constitute a prefabricated element. This allows prefabrication of all connections between c ­ olumns and wall framing elements in the workshop. Windows, facade cladding and projecting roofs were installed on site.

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190

Student Residence Vancouver, CA 2017

Architects: Acton Ostry Architects, Vancouver Structural engineering: Fast + Epp, Vancouver

Text: Hermann Kaufmann

Concept The University of British Columbia is the ­client of one of the most ambitious timber construction projects to date. At the time of its completion in 2017 the 53-m tall ­dormitory for 400 students was the world’s tallest solid timber building. Its 18 storeys are accessible via two stairwells and re­­ inforced concrete elevator cores. The project was developed within the “Tall Wood Demonstration Initiative” supported by the Canadian government. Its aim is to utilise the potential of solid timber construction and modular prefabrication as alternatives to conventional timber frame construction and to promote them in cooperation with the country’s construction industry. The 18-storey timber building is located on the Brock Commons campus and features about 15,000 square metres of floor space. It demonstrates how efficient wood can be as a construction material. To allow for taller timber buildings, local authorities raised the maximum permissible number of storeys from four to six back in 2009. ­Further, the Canadian Building Code allows variants under a “site-specific regulation”. In addition to that, the campus has a sepa­ rate building authority. These factors ulti­ mately allowed the university to erect a ­timber building of these dimensions while complying with stringent requirements.

Construction The vertical construction elements consist of glued laminated timber columns measuring 26 ≈ 26 cm and two concrete staircase ­towers for stiffening purposes that were continuously poured on site by use of sliding formwork. The column grid measures 2.85 ≈ 4.00 metres. Five-layer cross-laminated ­timber (CLT) ceiling slabs with a total thickness of 16.6 cm are placed on top of them. The staggered two and three-field panels with biaxial span enable creating ceilings

S T U D E N T R E S I D E N CE IN VA NCOUVER

without downstand beams. They support quick assembly and simple instal­lation of building services equipment. The shear bond between the individual CLT panels is provided by a recessed threelayer panel. Together with the individual panels, they form a structurally effective plate. Steel ties transfer all horizontal forces (due to wind or earthquake) from the plate into the concrete cores. In the case of tall buildings, load transfer from column to column is particularly challenging. This challenge was addressed using specifically

developed steel components, which also allowed for quick assembly. The building was erected in a very short time, two storeys were completed every week.

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

Fire Safety To increase fire resistance of the timber construction, wood components feature gypsum board encapsulation to enable a fire resistance duration of 120 minutes. Timber remains visible only on the topmost floor, serving as a recreation room b

9

8

8

8

8

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b b 9

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9 8 8 Standard 2nd –18th floor 8

a a

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a

3

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a Ground floor Floor plans • Sections Scale 1:400

a 1 Entrance 2 Community space 3 Kitchen

4 Work area 5 Building utilities 6 Waste room

7 Laundry service 8 1-room apartment 9 Shared apartment

aa

191

18 15,115 m2 approx. EUR 35 million approx. 2 months 17 months

192

Load-bearing structure, concrete

for students and offering a demonstrative look at the timber construction of the highrise building. The fire safety concept is based on the assumption that any fire will extinguish itself after 90 minutes prior to the structure contributing to the fire load, due to the encapsulation and the beam thickness. In addition, a sprinkler system was integrated and a redundant system supplies the main system with water and electricity if the connection to the public grid is interrupted.

Facade The facades comprise a steel frame structure typical of construction in Canada and are clad in high-pressure laminate (HPL) panels consisting of wood and paper. The large format HPL panels alternate with floorto-ceiling windows. Corners are glazed continuously. The appearance of the building harmonises with the restrained architectural language prevalent on campus. The facade elements were prefabricated including windows and mounted floor by floor to steel angles previously installed along the ceiling slabs. This enabled the structure to be quickly protected from the weather – essential in Vancouver’s rainy climate. Aside from demonstrating the state of the art in modern timber hybrid construction, the project helped achieve ambitious sustainability goals: the building received LEED Gold certification and is intended to comply with the ASHRAE 90.1-2010 standard (Energy Standard for Buildings Except LowRise Residential Buildings). Compared to a building of a conventional construction type, the student housing project is required to save 25 % of grey energy and consumption during operation. The client already made an important contribution to protecting the environment by selecting the construction material: the solid timber structure helped avoid consuming an equivalent of 2,650 m3 or about 500 tonnes of CO2.

Load-bearing structure, timber

Building services

S T U D E N T R E S I D E N CE IN VA NCOUVER

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Cross-laminated ceilings and columns with steel connector

bb c section c Vertical Horizontal section, facade 1 Scale 1:20 4 1 Aluminium window with double insulation glazing 2 Connector for facade elements 7 Sealant 2 3 Prefabricated facade: High-pressure laminate (HPL) 8 mm 6 5 Battens 25 mm 3Steel substructure, thermally separated, inlaid thermal insulation 50 mm Vapour-permeable liquid sealant Gypsum board 13 mm Steel substructure, inlaid glass fibre thermal ­insulation 152 mm On-site assembly: Vapour barrier Gypsum board 16 mm Painted finish 3 1

4 Wood windowsill 5 Continuous steel angle, installed after facade ­assembly, anchored within sealing layer to prevent water and screed penetration during 7 ­construction 6 Ceiling construction: Flooring 8 Screed 40 mm 9 Separation layer Cross-laminated timber ceiling 169 mm Moisture-resistant gypsum board 16 mm Hung ceiling, steel fasteners 38 mm Steel substructure 19 mm Gypsum board 2≈ 16 mm Painted finish 7 Glued laminated timber column (standard size 265 ≈ 265 mm on 2.85 ≈ 4.00 m basic grid) Three-layer gypsum board cladding 8 Threaded rod Ø 16 mm 9 Steel plug connector

Partial cladding of elements during construction

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Finished construction

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194

Residential and Office Building Berlin, DE 2014

Architects: Kaden Klingbeil Architekten, Berlin Timber structural engineering: Pirmin Jung, Rain

Text: Stefan Krötsch

Concept The residential and office building c 13 is situated on a formerly vacant plot between Wilhelmian-era block border buildings in Berlin’s Prenzlauer Berg district. It consists of a seven-storey building wing facing the street and a five-storey rear wing following the six-storey firewall of the neighbouring ­building bordering the entire depth of the 46-m deep plot. A gap separates the building from its eastern neighbour, offering a view of the block interior and the vertical access system comprised of two freestanding staircases. The rear wing is distanced from the firewall by three interior courtyards which allow southern and eastern daylight to enter along the entire depth of the building, while providing diligently staged views into, out of and through the building. Despite the rigorous discipline in construction, necessary for an economically feasible implementation as a timber building, an extraordinary degree of spatial diversity is apparent across all storeys, indicative of the broad range of functions that the building accommodates – including bistro, meeting point, childcare centre, family centre, doctors’ practices, offices and apartments. The frame construction with its long spans and the independent access system following the entire length of the building provide for a high degree of flexibility, which was already demonstrated during the planning phase since the functional concept required repeated changes.

Fire Safety Berlin’s building code prohibits the combustibility of essential structural parts in buildings with a top floor higher than 13 m above the finished ground floor level. Although the top floor elevation measures 19.50 m, the wood structure was approved based on an individual fire protection concept, the essential elements of which are

R E S I D E N T I A L A N D O F F I C E B U I LDING IN B ER LIN

Site plan Scale 1:3,000 Section • Floor plans Scale 1:500 1 Play area 2 Courtyard 3 Daycare facility

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

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The hybrid frame structure comprises steel beams flush with ceilings set on top of concrete columns on the ground floor and on top of laminated veneer and glued lamin­ated

4th floor

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7 4,673 m2 approx. EUR 4.7 million 5 months 15 months

Structural Engineering and Prefabrication

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 4 Kitchen  5 Office  6 Hall  7 Bistro   8 Entrance to underground car park  9 Void 10 Terrace 11 Apartment

similar to its predecessor building e 3 (Fig. A 1.8, p. 10), which was the first seven-storey timber building in Germany in 2008. The decision to create open staircases and set them at a distance to the building proper, hence providing an exterior means of access to functional units on all floors, is the result of the architectural and urban design concept of a vertically interlinked and multifunctional urban building type. In terms of fire safety, it offers the particular advantage that each functional unit features a direct emergency exit, while the open design guarantees that the emergency staircase remains smoke-free. The timber structure of the walls and columns was encapsulated with gypsum fibreboard to provide fire resistance for at least 90 minutes. The undersides of the dowel laminated timber ceilings feature a transparent, flame-retardant protective coating and the soffits of the steel beams are clad with gypsum fibreboard strips that delineate the structure.

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66 B 1 Thermal insulation composite system with mineral render 110 mm Gypsum board 18 mm Vapour barrier Solid cross-laminated timber wall 140 mm Gypsum fibreboard 2≈ 18 mm 2 Residential floor construction: Parquet flooring 16 mm Heating screed 74 mm, Separation layer Impact soundproofing 30 mm Sealant Reinforced concrete top layer 120 mm Dowel laminated timber ceiling with fire-retardant coating (B1) 140 mm 3 Ceiling construction, projecting window (without roofing): Single-layer plastic sealant EPS insulation to falls, on average 135 mm Reinforced concrete top layer 120 mm Dowel laminated timber ceiling with fire-retardant coating (B1) 140 mm 4 Steel Å beam 220 mm Gypsum board (fire prevention cladding) 25 mm Gypsum fibreboard 15 mm 5 Timber window, spruce with insulating glazing 6 Composite thermal insulation system with mineral render 150 mm Gypsum board 18 mm, Vapour barrier Solid cross-laminated timber wall 100 mm Gypsum fibreboard 2≈ 18 mm 7 Reinforced concrete column 300/300 mm 8 Composite thermal insulation system with mineral render 70 mm Gypsum fibreboard 18 mm Frame wall construction 60/180 mm Inlaid mineral fibre thermal insulation 180 mm Gypsum fibreboard 18 mm Vapour barrier Gypsum fibreboard 18 mm 9 Laminated veneer lumber (LVL) edge beam

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A Vertical section, front building (north facade) Scale 1:20 B Vertical section, rear building (south facade) Scale 1:20 C Load-bearing system D Shear connection E Moment reversal, support area, due to cantilevering ceiling Vertical section, exterior ceiling projection, 4th floor Rear building  Scale  1:10

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a a The cross-laminated timber wall with horizontal ceiling layer functions as a wall-height beam. The position and size of windows are coordinated with the loadbearing effect of the wall. b The concrete bridge of the stairwell is set on top of the wall. c The wall spans from column to column. d Cross-laminated timber wall with shear millings on the underside. The cross-laminated timber wall is set on top of steel columns, not the floor slab. e Pouring the concrete top layer of the timber concrete composite ceiling results in shear connections, due to millings within the wall.

C

timber columns on the upper floors. The structure partitions ceilings into nearly identical composite construction elements spanning 5 m and comprised of dowel ­laminated timber panels with an in-situ top layer of ­concrete. The 14-cm thick stacked boards are exposed on their underside and are placed on top of the lower flange of the steel Å beams of the primary structure. The 12-cm thick in-situ concrete top layer is flush with the top beam flange. The stiffening walls of the five-storey rear wing consist of wall framing elements, into which the supports of the frame structure are partially ­integrated. The stiffening walls of the seven-

storey street wing feature cross-laminated timber (CLT) with columns set in front of the walls. During assembly of the structure, CLT elements with millings were set on top of the steel beams. The millings were filled with insitu concrete when the top concrete layer was poured, creating shear-resistant connections with the timber concrete composite ceiling in a very simple manner. The CLT elements of the western exterior wall serve to stiffen the structure as wall-height beams, both sides of which are set on top of the steel girders, and hence, the columns, to which the stairwell is connected via the access balconies.

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10 Exterior ceiling projection: Parquet flooring 16 mm, cement screed 80 mm Impact soundproofing 30 mm, sealant Reinforced concrete top layer 120 mm Dowel laminated timber ceiling 140 mm Vapour barrier, metal connector Inlaid thermal insulation 100 mm, render 10 mm 11 Steel reinforcement 12 Swelling grouting mortar 13 Steel Å beam 220 mm 14 Composite thermal insulation system 70 mm Gypsum fibreboard 18 mm, timber frame wall ­construction, inlaid thermal insulation 180 mm Gypsum fibreboard 18 mm, vapour barrier Gypsum fibreboard 18 mm

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The projecting windows along the street facade and the fourth floor of the rear wing are held in place by cantilevering ceiling belements. Timber concrete composite ceilings are typically unsuitable for use as continuous beams or cantilevers, due to the reversal of compression and tension zones. a However, by enhancing the reinforcement layer through recesses in the steel beams, the concrete top layer was converted into the tension zone c of a cantilever beam. The pressure-resistant connection of the dowel laminated timber ceiling to the steel beam via swelling mortar creates an effective pressure zone (see Fig. E).

198

Cultural Centre and Hotel Skellefteå, SE 2021

Architects: White Arkitekter, Stockholm Robert Schmitz, Oskar Norelius Structural engineering: TK Botnia, Burträsk

Text: Stefan Krötsch

Concept The Swedish city of Skellefteå, home to about 35,000 residents, is 770 km north of Stockholm on the Gulf of Bothnia. With a floor area of roughly 28,000 m2, a height of approximately 82 m and a footprint of 60 ≈ 160 m, the Sara Cultural Center, named after the Swedish author Sara Lidman, con­ stitutes one of the world's largest timber buildings. The building complex unites ­different cultural functions and, thus, com­ prises the new centre of the city. It houses multiple theatre stages and public event spaces, a concert hall, an art museum, an

art gallery, studios for dance and ballet, the municipal library, as well as a hotel with conference centre. The building geom­ etry, an addition of multiple volumes, sculp­ turally represents the functional hetero­ geneity. The hotel, a slender high-rise struc­ ture, towers above the cultural centre and offers a panoramic view of the Nordic forest landscape beyond the city limits. Along the facade and in the interiors, the surfaces consist almost exclusively of timber. This creates a comfortable atmosphere most of all during the long, dark subarctic winters. The extensively glazed foyer in the south­ west of the building and the exhibition

spaces offering views to the interior in the north-east provide transparency and con­ nect spaces inside the building with the ­surrounding environment. The galleries and the grand staircase with its sitting steps pro­ vide the foyer with a character resembling a market place. The execution of a building ensemble of this size and complexity almost exclusively as a timber structure is, for one, indebted to the ecological aspirations of both the client and the planners. In addition, it reflects local building traditions and serves to integrate the timber processing industry, important to the region, within the project.

C U L T U R A L C E N T R E A N D H O T EL IN SK ELLEFTE�

10 Ventilation centre 11 Store / library 12 Storage rooms 13 Studio 14 Carpentry 15 Smithy 16 Theatre hall (small) 17 Auditorium 18 Foyer 19 Theatre hall (large) 20 Concert hall 21 Upper foyer 22 Kitchen 23 Exhibition space 24 Hotel room

Site plan Scale 1:3,000 Floor plans Scale 1:750 1 Library 2 Main foyer with “cultural staircase” 3 Cloakroom 4 Matinee stage 5 Hotel lobby 6 Reception 7 Hotel kitchen 8 Hotel auxiliary room 9 Building services centre

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Structural Engineering

timber top chords and king posts, cre­ ating a vivid impression of depth along the tall ceilings. The theatre hall walls feature a cavity wall construction type that acoustically de­ couples the surrounding spaces. They ­consist of a combination of glued laminated timber beams and cross-laminated timber walls that stiffen each other. Beneath the hotel floors, the small-scale column grid of the hotel structure is redirected by roomheight steel truss girders into three-ply block-glued laminated timber columns in order to span across the entire publicly ­accessible foyer below.

The basic structure of the multifaceted ­load-bearing system is a skeleton com­ prised of columns and beams consisting of glued laminated timber, complemented by load-bearing and stiffening cross-­ laminated timber walls and ceilings. In rooms that require large spans, such as the  concert hall, glued laminated timber truss ­girders find use. In the public foyer, an exposed timber and steel hybrid ­construction defines the character of the space. Slender steel rods serve as bottom chords and diagonals in combination with

Hotel Tower Construction Thirteen of the altogether 15 hotel tower ­storeys are situated above a structural floor and comprise stacked, load-bearing prefabricated room modules. The small scale and serial character of the hotel rooms, as well as the soundproofing require­ ments for partition walls and ceilings, are conducive to selecting this construction type. The decisive aspect was, however, that this enabled a reduction in the costintensive assembly time on-site. The walls of room modules contain glued laminated timber columns that transfer loads via end

Section Scale 1:750

12

  1 Main foyer with “cultural staircase”  2 Cloakroom   3 Matinee stage   4 Concert hall   5 Theatre hall (large)   6 Theatre hall (small)   7 Practice space /dance studio  8 Restaurant   9 Hotel building services centre 10 Hotel room 11 Restaurant /skybar 12 Hotel wellness area

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C U L T U R A L C E N T R E A N D H O T EL IN SK ELLEFTE� 13

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13 Roof construction: Bituminous sealant EPS insulation to falls 250 – 50 mm EPS thermal insulation 180 mm Vapour barrier Spruce cross-laminated timber 160 mm 14 Spruce glued laminated timber beam 500/220 mm 15 Spruce glued laminated timber downstand beam 300/350 mm 16 Interior sun protection 17 Glued laminated timber 90/345 mm 18 Triple insulation glazing in aluminium frame 19 Spruce glued laminated timber crossbar 225/280 mm 20 Facade construction:

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East facade /studio Vertical section • Horizontal section Scale 1:20

Spruce siding, pressure-treated, 22/145 mm Battens 28/70 mm Counterbattens / back ventilation 34 mm Vapour barrier Wood stud frame Inlaid three-layer thermal insulation 260 mm Spruce cross-laminated timber 120 mm 21 Glued laminated timber lamellae 90/225 mm 22 Floor construction: Spruce floorboards 25 mm Particle board 22 mm Gypsum board 12.5 mm Impact soundproofing 2≈ 20 mm PE film Reinforced concrete 300 mm 23 Pedestal construction: Terrazzo panel facade cladding 20 mm Back ventilation, thermal insulation 100 mm Vapour barrier, reinforced concrete 280 mm 24 Glued laminated timber column 320/220 mm

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grain butt joints into the columns of the floors below, which enables the modules to be connected in a skeleton frame structure. In order to enable effective soundproofing between individual floors, elastomeric bear­ ings were set into the butt joints between columns at each storey. The ceilings of the room modules are connected horizontally by i­ndividual steel flanges and, thus, form a stiff ceiling plate that minimises horizontal sound transmission. The two staircase cores, between which the individual room modules are set, pro­ vide the actual stiffening of the hotel tower. Due to their placement along the narrow sides of the tower, only minimal horizon­ tal forces impact the room modules. The

cores consist of four-storey, 40-cm thick walls with two or three adhesively bonded cross-laminated timber panels. In order to calculate these components, the structural engineers developed their own software. The wall elements are connected by bolted steel plates, which allowed a building height of approx. 82 m. The structural engineers originally had planned to build the altogether 20-storeys tall hotel tower purely as a timber struc­ ture. During the planning and construc­ tion process, however, additional mass in the form of a concrete layer was poured on top of the roof construction of the two topmost floors in order to reduce potential vibrations due to wind loads.

Fire Safety The cultural centre and hotel exceeds the high-rise barrier. The fire safety concept ­permitted building a timber structure with a major degree of exposed timber surfaces. The Swedish building code generally fea­ tures no provisions for limitations on com­ bustibility for elements of the load-bearing structure, for emergency exits or for sur­ faces. Even the staircases of the hotel tower are comprised entirely of cross-laminated timber dimensioned according to burnout. In addition, walls and ceilings were, in part, clad with gypsum fibreboard or received a fireproof coating in order to reduce possible fire loads. A sprinkler system was integrated into the fire safety concept as well.

C U L T U R A L C E N T R E A N D H O T EL IN SK ELLEFTE�

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20 28,000 m2 approx. EUR 103 million 13 months 31 months Hotel facade Vertical section • Horizontal section Scale 1:20

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1 Laminated safety glass 2≈ 10 mm in steel frame 2 Aluminium ventilation element 3 Aluminium ventilation slats 4 Plywood 22 mm 5 Facade construction: Glued laminated timber 19 mm with fireproof coating Thermal insulation 70 mm Vapour barrier Cross-laminated timber column 215/405 mm 6 Textile sun protection 7 Triple glazing in aluminium frame

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  8 Floor construction: Carpet flooring 8 mm Cement-bonded particle board 22 mm Gypsum board 2≈ 12.5 mm Impact soundproofing 2≈ 20 mm Glued laminated timber 140 mm Thermal insulation 100 mm inlaid between Room modules   9 Glued laminated timber column 215/405 mm 10 Room partition wall: Cross-laminated timber 120 mm Air layer 15 mm (module joint) Thermal insulation 120 mm Cross-laminated timber 120 mm 11 Cross-laminated timber 32 mm as glazed Facade shading element

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Residential and Commercial Building Zurich, CH 2010 Architects: pool Architekten, Zurich Structural engineering: Henauer Gugler, Zurich Timber structural engineering: Ingenieurbüro SJB.Kempter.Fitze, Herisau

Text: Anne Niemann

Concept The residential and office building on busy Badenerstraße is the first structure in Zurich to be developed in strict accordance with the criteria of the 2000-Watt Society. Its goal is for every resident to reduce their medium-term energy use to 2,000 watts and their carbon emissions to one tonne of CO2 per year by 2050. Timber construction is particularly well-suited to meet these high standards. Six building volumes offset from each other, each with four to six residential storeys, are placed on top of a supermarket. Recesses and projections allow optimal daylight intake in the apartments, which are up to 24 m deep. Due to the busy street to the north, the windows face east and west – and southward, oriented towards the park, thus providing required noise protection for the apartments. Inside the 54 apartments, the linear sequence of rooms allows for contin­ uous views that create an impression of space, despite the limited size of the two and three-room units. The facade structure emphasises the urban character of the building and refers to rusticated block designs used for upper-class townhouses of the Wilhelmian era, without concealing the structure of the curtain wall facade.

Structural Engineering The ground floor pedestal and the access cores consist of reinforced concrete, for reasons of fire safety and to stiffen the building. The offset residential floors above are comprised of timber. The simple parallel shear wall construction type remains con-

Section • Floor plan Scale 1:750 1 Supermarket 2 Living room 3 Kitchen

4 Room 5 Balcony 6 Roof terrace

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Vertical section  Scale  1:20

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  7 Roof construction: Round gravel 80 mm, protective layer 10 mm 2-ply bituminous sealant (root-proof top layer) Mineral wool insulation to falls 150 – 250 mm (roof edge near parapet: PUR rigid thermal ­insulation with aluminium laminate 130 mm) EVA sealant 3.5 mm, OSB 10 mm Dowel laminated timber ceiling 200 mm Airtight film, substructure with spring clips 27 mm Gypsum fibreboard (fire protection) 18 mm White render finish 5 mm   8 Sun protection, exterior blinds   9 Floor construction: Parquet flooring 10 mm Cement screed with underfloor heating 70 mm PE film separation layer Mineral wool thermal insulation / impact soundproofing 30 mm Hollow box element (total 240 mm): Three-layer panel 40 mm, timber ribs 160 mm Crushed gravel fill approx. 50 mm Three-layer panel 40 mm Substructure with spring clips 27 mm Gypsum fibreboard (fire protection) 18 mm White render finish 5 mm 10 Floor duct with steel plate 80 ≈ 150 mm, screw connection to gypsum fibreboard 11 Floor construction, roof terrace: Solid larch grating, glazed finish Battens 35 mm, separation layer /roof film 8 mm 2-ply bituminous sealant PUR rigid insulation to falls with aluminium laminate, pressure-resistant 60 −100 mm, vapour barrier Gypsum fibreboard 15 mm Dowel laminated timber ceiling 200 mm, airtight film Substructure with spring clips 27 mm Gypsum fibreboard (fire protection) 18 mm White render finish 5 mm 12 Facade construction: Glass fibre-reinforced concrete facade cladding element 70 mm Timber substructure / back ventilation 30 mm Wind paper, mineral wool thermal insulation 160 mm Dowel laminated timber wall 100 mm Mineral wool thermal insulation 80 mm Substructure 30 mm, felt layer Gypsum fibreboard 2≈ 12.5 mm White render finish, spackling compound 5 mm Glass fabric 13 Apartment partition: Glass fabric White render finish, spackling compound 5 mm Gypsum fibreboard 2≈ 12.5 mm, felt layer Substructure 30 mm Timber plank 100 mm Thermal insulation, mineral wool 40 mm Wood stud 100 mm, substructure 30 mm, felt layer Gypsum fibreboard 2≈ 12.5 mm White render finish, spackling compound 5 mm Glass fabric

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Axonometric illustration, plug-in connection Wall – ceiling – wall Assembly steps for timber structure above ground floor (supermarket) ceiling: For the first time, a newly developed solid wood ­system using floor-height spruce studs was used in this residential and office building project. Scale 1:10

R E S I D E N T I A L A N D C O M M E R C I A L B U I LDING IN ZUR ICH

sistent on all floors and enables econom­ ically feasible construction. On the retail floor, walls are dissolved into individual rows of columns. For the exterior walls and apartment partition walls, a newly developed solid timber system was used for the first time: a series of ceiling height ­vertical boards measuring 100 ≈ 195 mm were connected to a bottom plate using hardwood and with no need for machinery. Along their centre, they were aligned with transverse dowels. Shorter boards were used above and beneath the windows. A two-person team was able to complete one such storey per day. The top and bottom plates are made of birch plywood. Based on the large share of vertically aligned timber, problems due to transverse compression were avoided. Prefabricated ceiling elements consisting of box girders were placed on top of the walls featuring a horizontal flange to align them. The elements form a plate that stiffens the building and transmits horizontal forces into the solid staircase cores. Cinder fill in the cavities between the ribs provides excellent soundproofing. The timber surfaces feature gyp1

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sum board cladding for fire safety reasons and are, therefore, concealed.

Sustainability and Building ­Services The wall boards are connected to each other and to other components only by wooden dowels. Thus, individual components can be removed from the structure and reused. The curtain wall made of glass fibre-reinforced concrete elements can be easily replaced as well. The extruded sections are particularly stable due to their angular shape – this made it possible to increase the spacing between battens, which helped reduce material consumption. The ventilation of apartments features decentralised control by use of individual room fans with heat recovery integrated in the windows. This made it possible to do without ventilation ducts, their complex assembly and fire safety cladding. A control unit measures the CO2 content of the exhaust air and regulates the airflow. Heat is generated by using a geothermal heat pump and the waste heat from

207

the refrigeration units of the ground floor supermarket. Electricity for heat recovery, ventilation units and the operation of building services equipment is generated on the roof.

Building parameters Number of storeys Gross floor area Construction costs Construction time timber Construction time total

7 13,876 m2 EUR 33.5 million approx. 2.5 months 18 months

Horizontal section, window Scale 1:10 1 2 3

Glass fibre-reinforced concrete element 70 mm Timber substructure / back ventilation 30 mm Wind paper Thermal insulation 160 mm Dowel laminated timber wall 100 mm Mineral wool thermal insulation 80 mm Substructure 30 mm Felt layer Gypsum fibreboard 2≈ 12.5 mm Glass fabric Wood-metal window with double insulation glazing Ventilation element

208

Residential Complex Jyväskylä, FI 2015 (building 1), 2017 (building 2), 2018 (building 3)

Architects: OOPEAA, Helsinki / Seinäjoki Timber structural engineering: SWECO, Helsinki

Text: Wolfgang Huß

Concept Finland’s first eight-storey timber residential building was erected on the outskirts of Jyväskylä, a city with 143,000 inhabitants, 270 km north of Helsinki. Set on top of a concrete pedestal that houses parking spaces and storage rooms, 150 apartments in three stand-alone buildings with folded facades and slightly sloping pitched roofs were created in multiple phases, as agreed with the city planning authority. The aim of this pilot project is to offer high-quality, ­ecologically sound and affordable housing. Residents provide a modest down payment and become owners after 20 years of successive payments in instalments. The land use plan was specifically adapted to allow for the high density of the project. The amount of land covered by the building on the hilly plot was reduced as far as possible, in order to preserve a small grove of trees on the west side and, thus, create a high-quality outdoor area. The property is otherwise surrounded by wide streets. The buildings respond to the site in terms of shape and material: on the “green” side, partially glazed loggias or balconies project from the facade, creating a lively impression and, at the same time, enlarging the ­living rooms of the smaller apartments. In these areas, the facade consists of untreated larch, while the spruce siding facing the streets features a dark painted finish. The building volumes are highly compact. This is achieved by exclusively orienting apartments eastward or westward and by arranging a central corridor with interestingly designed and illuminated voids reaching from bottom to top of the buildings.

Structural Engineering and Prefabrication The project is characterised by its innovative use of room modules: each apartment contains one module housing a bedroom,

R E S I D E N T I A L C O M P LEX IN JYVÄ SK YLÄ

l­iving room and loggia that borders the facade and a second, interior module containing bathroom, kitchen and, if required, further rooms. The corridor ceilings resemble bridges set between apartment modules. Installations are integrated into walls oriented towards the corridor, allowing ­independent maintenance without having to enter apartments. The room modules consist of spruce crosslaminated timber and bear both vertical and horizontal loads. In the pedestal area, reinforced concrete hollow box ceiling ­elements span across the parking spaces. The prefabricated modules were delivered

to the site complete with interior fittings and windproof facade layer composition. Prefabricated timber siding elements were mounted subsequently. The first construction phase took only six months, an essential advantage in Finland’s climate.

209

cross-laminated timber of the load-bearing structure reappears as ­material used for flooring and treads. A sprinkler system is part of the fire safety concept.

Building parameters Number of storeys Gross floor area (GFA) 1st – 8th floor Below-grade level and parking Construction costs Construction time timber: Production of modules Assembly on site Construction time total

Fire Safety The apartment and staircase walls are clad in gypsum board. The timber ceiling undersides remain exposed in the apartments and also characterise the staircases, otherwise predominantly white. Here, the

8 5,335 m2 1,495 m2 approx. EUR 11 mill. 5 months 2 months 6 months

Site plan Scale 1:2,500 Section • Floor plans Scale 1:500 1 Entrance 2 Hallway 3 Void 4 Living

5 Kitchen 6 Bathroom 7 Rooms 8 Loggia

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  1 Floor construction: Oak parquet flooring 15 mm, screed 40 mm Impact soundproofing with underfloor heating 30 mm Cross-laminated timber panel 140 mm Glass wool cavity insulation 50 mm Cavity 77 mm, cross-laminated timber panel 80 mm   2 Facade construction: Spruce siding, painted finish/larch siding, untreated 28 mm Timber substructure with back ventilation 50 mm Glued laminated timber 100 mm   3 Parapet element: aluminium frame with glazing   4 Aluminium sliding window   5 Wood sliding window with triple glazing, flush with floor   6 Floor construction, loggia: Sealant, plywood panel to falls, wedge battens Cross-laminated timber panel 140 mm Glass wool cavity insulation 50 mm Cross-laminated timber panel 80 mm   7 Sealed room module joint   8 Ceiling above basement: Oak parquet flooring 15 mm, screed 40 mm Impact soundproofing with underfloor heating 30 mm Cross laminated timber panel 140 mm Cavity insulation 100/50 mm, cavity Prefabricated concrete hollow core slab   9 Roof construction: Bituminous sealant, OSB 18 mm Battens with rear ventilation Blow-in thermal insulation 450 mm Cross-laminated timber 80 mm 10 Ceiling above underground garage: Oak parquet flooring 15 mm, screed 40 mm Impact soundproofing with underfloor heating 30 mm Cross-laminated timber panel 140 mm Cavity insulation 100/50 mm, cavity Reinforced concrete slab 800 mm

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R E S I D E N T I A L C O M P LEX IN JYVÄ SK YLÄ

Building structure and room modules

Apartment consisting of two room modules

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Residential Complex Ansbach, DE 2013

Architects: Deppisch Architekten, Freising Structural engineers: Planungsgesellschaft Dittrich, Munich

Text: Manfred Stieglmeier

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Concept

2,400 m2 of total residential area in 37 apartments with eight different layout variations. A simple load-bearing structure and central sanitary cores enable high flexibility based on adaptable interior partitions. All publicly accessible functions are located on the ground floor and face the courtyard. The apartments on the upper floors either span the entire building width or are corner apartments and, thus, receive daylight from at least two directions. The lintel-free windows and bright reveal cladding ensure maximum daylight intake. The degree of fenestration of facades is based on energy optimisation. The interior kitchens receive daylight

Situated in a very heterogeneous context, two juxtaposed buildings with residential and auxiliary spaces constitute an enclosed, rectangular complex with a quiet central courtyard. The differentiated height of the buildings responds to the context and accentuates the ensemble. The residential complex is the result of a competition and, as energy-efficient housing, received dedicated subsidies. Both 16-m deep, very compact and clearly structured residential buildings feature no levels below grade and comprise around

through windows facing the stairwell ­covered by a glazed roof. Due to the ­compact building volume in combination with the highly insulated, homogeneous building envelope, the project meets ­KfW-40 Efficiency House standards.

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber (including facade) Construction time total

4 3,667 m2 EUR 4.34 mill. 4 months 13 months

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Section • Floor plans scale 1:500  1 Courtyard  2 Sandpit  3 Bench   4 Arbour (to be turned into a common area)  5 Heating   6 Pellet storage   7 Electrical room   8 Bicycle storage   9 Bin room 10 Vestibule 11 Laundry room 12 Pram storage 13 Storage rooms 14 Platform lift 15 Lift (optional) 16 Void

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Structural Engineering The load-bearing structure comprises spruce cross-laminated timber walls and ceilings. The ceiling elements project beyond the building envelope longitudi­ nally, resulting in a very simple continuous balcony construction. Due to the building physics characteristics of timber, there is no risk of condensate forming. A groove on the underside of ceiling panels prevents moisture intrusion from the exterior to the interior and reduces thermal bridges. This also facilitates creation of the required airtight layer connections. The outer walls contain prefabricated timber frame elements with 28-cm thick mineral wool cavity insulation. The windows and the facade cladding, comprising of pre-weathered and, thus, maintenance-free, horizontal, local silver fir siding, were installed on site. The three upper floors are set on top of a robust pedestal consisting of sand-blasted exposed concrete that envelops the ground floor level of the ensemble. In the interior, walls are clad in gypsum fibreboard with a white painted finish, while doors and windows are made of spruce with a clear lacquer finish. The hollow-frame wood windows feature deep reveals, due to design-based intentions and weather-related concerns. They include triple glazing and an additional

exterior insulation layer along frames in order to prevent thermal bridges. The roof construction also features cross-­ laminated timber elements, exposed on the inside and covered by 32-cm thick ­rooftop insulation.

Fire Safety Due to the different heights of the two ­residential buildings, they belong to different building classes. Each features specific structural fire safety requirements that impact the selection of materials for the facade. At the time of construction, the Bavarian building code typically required fire-retardant exterior cladding from the fourth floor upward. In order for both buildings to receive the same type of timber cladding, the four-storey ­structure received a non-combustible ­concrete pedestal ground floor as a ­compensation measure. This limits the ­flammable surface to three storeys and reduces the risk of arson. Still, K260 ­encapsulation with highly fire-retardant ­insulation was required for the exterior walls. In addition, the ceiling panels for the bal­conies that pass through the longitudinal facades without interruption serve as a firestop by separating the exterior walls, floor by floor. Further, all ­windows feature

reveal cladding with a thickness of 6 cm. This provides for E 30 fire resistance, ­dimensioned according to burnout, which prevents the spread of fire from the interior into the back ventilation. This made it possible to omit sheet metal ­firestops along the lateral facades of the building. To compensate for the exposed cross-laminated timber ceilings – not permitted by the valid building code – a smoke alarm connected to a ­building-wide network was installed in each apartment. This is further supported by the small size of the residential units with a maximum area of 100 m2 each and the solid timber construction of the ceilings without any cavities.

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Vertical section  Scale  1:20 1 Photovoltaic system (60,000 kWh/a > in-house ­consumption) 2 Roof construction: sealing membrane with fleece underlay, EPS thermal insulation 50 –130 mm, EPS thermal i­nsulation 160 mm Temporary seal / vapour barrier Spruce cross-laminated timber panel 160 mm 3 Sheet metal drip edge, black-grey painted finish 4 Reveal: spruce three-layer panel, clear glazed finish 30 mm 5 French windows with spruce hollow frame, Clear glazed finish, self-regulating rebate ventilation, soundproof ­argon-filled triple glazing, Uf = 0.91 W/m2K, Ug = 0.50 W/m2K, flush with floor 6 Flat steel handrail 75/10 mm 7 Balustrade: pre-weathered silver fir, patinised 30 mm on steel SHS substructure, black-grey finish 40/40 mm 8 Balcony floor construction: larch, untreated 30 mm solid construction-grade timber, conical 60/100 –120 mm, protective mat, sealant layer EPS impact soundproofing 20 – 50 mm Elastomeric bitumen temporary seal Spruce cross-laminated timber panel 180 mm 9 Ceiling construction: Solid oak mosaic parquet, oiled finish 10 mm Heating screed 65 mm, PE film separation layer Mineral wool impact soundproofing 40 mm

Bonded crushed stone fill 80 mm Elastomeric bitumen temporary seal Cross-laminated timber panel, spruce 180 mm 10 Encapsulation (K230): Fire-resistant gypsum board 18 mm Spruce cross-laminated timber panel 90 mm Mineral wool thermal insulation 60 mm Spruce cross-laminated timber panel 90 mm Encapsulation (K230): Fire-resistant gypsum board 18 mm 11 Gypsum board cladding 12.5 mm 12 Non-flammable mineral wool fire protection strips: Airtight connections, insulated groove (underside of cross-laminated t­imber ceiling) 13 Facade construction: pre-weathered silver fir siding, patinised 20 mm, battens 40/50 mm Vapour sarking layer Prefabricated wood frame element Encapsulation (K260): fire-resistant gypsum board 2≈ 18 mm Mineral wool thermal insulation 2≈ 140 mm Solid construction-grade timber posts 60/280 mm OSB 15 mm, encapsulation (K260): fire-resistant gypsum board, 2≈ 18 mm (interior layer mounted on site) 14 Courtyard paving: asphalt, sand-coloured 15 Precast reinforced-concrete pedestal element, sandblasted 16 Rigid polystyrene foam perimeter insulation 100 mm

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Residential Complex Munich, DE 2020

Architects: ARGE ArchitekturWerkstatt Vallentin, Munich; Johannes Kaufmann Architektur, Dornbirn /Vienna Structural engineering: Reiser Tragwerksplanung, Munich

Text: Manfred Stieglmeier

Concept The two four­storey townhouses belong to an urban housing cluster on the site of the former Prinz Eugen Barracks in the north­east of Munich. On the southern part of the neighbourhood covering a total area of 29.9 ha, an ecological timber and timber­hybrid construction model hous­ ing development was created and struc­ tured into three separate construction sites. The urban design scheme of the south­ western site, where the townhouses are located, is defined by three combined build­ ing typology variants featuring altogether 36 apartments, community spaces and a shared roof garden. The varying individu­ alised floor plans of the residential units cover areas ranging from 56 to 120 m2. Narrow and semi­public walkways lead residents and visitors past the garden courtyard houses to a small plaza in the centre of the residential development. The southern perimeter of the cluster is defined by the two four­storey townhouses, each with two apartments per floor. The unifying design theme within the cluster are bands consist­ ing of weatherproof steel, serving as hori­ zontal firestops. They also structure the timber facades of the townhouses, accen­ tuate full­height windows and delineate the exterior spaces, their function resembling picture frames.

Structural Engineering Due to the complex requirements of creating high density, while simultane­ ously maintaining the privacy of residents and achieving the passive house stand­ ard, as well as using renewable raw materials as far as possible, the planners decided to employ timber wall framing for the building envelopes of all structures. The construction­grade solid timber columns of the townhouses with a cross section of 240 ≈ 80 mm are clad in gypsum fibre­

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Axonometric illustration Section • Floor plans Scale 1:500   1 Garden courtyard house   2 Private outdoor space   3 Atrium house   4 Bicycle storage   5 Village square   6 Community kitchen   7 Bin store  8 Townhouse   9 Entrance to underground parking 10 Community room 11 Guest apartment 12 Shared roof terrace

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Fire Safety The two four-storey buildings belong to building class 4. Following the model tim­ ber construction directive (MHolzBauRL) on fire safety requirements placed on ­timber construction components and ­exterior wall cladding, construction com­ ponents with load-bearing and stiffening ­function and those which separate units are classified according to the fire resist­ ance class "highly fire-retardant" (REI 60, K260). This requirement corresponds to an implementation type featuring gypsum fibreboard cladding on both wall sur­ faces and non-combustible mineral wool insulation. Due to the steel bands projecting along each storey and serving as firestops, in order to prevent fire from spreading verti­ cally across cavities situated in the back ventilation layer, it was possible to clad exterior walls in a combustible material mounted to the encapsulated timber stud frame.

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board or OSB, depending on fire safety re­­ quirements. Load-bearing interior walls and ceilings comprise cross-laminated timber elements with a thickness of 220 mm. Due to soundproofing requirements, the staircase walls and the apartment party walls feature a cavity wall construction type clad in gypsum fibreboard. The ­apartment party walls consisting of crosslaminated timber and the exterior walls clad in gypsum fibreboard stiffen the ­buildings vertically. The wall plates feature shear connections that resist tensile and compressive forces along joints. The exposed cross-laminated timber ceilings function as horizontal plates. In order to avoid excessive thickness or depth of struc­ tural components, the exterior walls feature steel sections along large openings inte­ grated into ceilings in the form of in-plane upstand beams.

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Site plan Scale 1:7,000 Vertical section Scale 1:20 1 Green roof 80 mm, drainage mat 20 mm Thermal insulation 2 % to falls 275 mm PIR thermal insulation Vapour barrier, cross-laminated timber 160 mm 2 Firestop Weatherproof construction grade sheet steel 3 mm 3 Facade behind sliding shutter: Laminated panel 8 mm 4 Sliding shutter: Pre-weathered silver fir 24 mm in steel angle frame 4/40/40 mm or 5/60/40 mm 5 Fall protection: 2≈ toughened glass 8 mm 6 Pre-weathered silver fir 24 mm Counterbattens 24 mm Wood blocking 123/80 mm 7 Sliding door, triple glazing in wood /aluminium frame 8 Parquet flooring 15 mm, impact soundproofing 30 mm

Applications for variances to the building code faciliated the use of cross-laminated timber ceilings with visibly exposed under­ sides. For this purpose, the panel edges were adhesively bonded in order to prevent fire from spreading within the component.

Prefabrication All load-bearing wall and ceiling elements were industrially prefabricated. The integra­ tion of windows and the assembly of facade cladding consisting of pre-weathered silver fir took place on site. The application of sheathing to the interior sides of exterior walls and the manufacturing of non-loadbearing interior drywall construction took place during the interior finishing phase.

Building Ecology With the exception of the reinforced con­ crete below grade level and the upper-floor stair flights comprised of prefabricated re­inforced concrete elements, all construc­ tion components consist of timber. The ­staircase core walls feature cross-laminated timber and amount to the greatest share of timber used in the entire buildings. Certifica­ tion of building materials sourced from renewable raw materials applies to all wood-based materials used for the struc­ ture, as well as parquet flooring, wood win­ dows and interior doors. In summary, the townhouses reach a share of timber of approx. 220 kg per m2 of residential area.

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

4 (townhouses) 3 (atrium houses) 2 (garden apartment houses) 4,651 m2 (above grade) 2,374 m2 (below grade) approx. EUR 15.7 mill. 10 months 32 months

Perlite fill 90 mm, trickle protection fleece Cross-laminated timber 220 mm, visibly exposed surface   9 Steel channel support 220 mm 10 Parapet, nook window with integrated awning: Construction-grade steel frame 3 mm, with second insulation layer, back ventilation 85 mm PUR thermal insulation 120 mm, solid timber 80 mm 11 Pre-weathered silver fir with silicate coating 24 mm Battens 24 mm, back ventilation 40 mm 12 Prefabricated timber frame element: Wind barrier Gypsum fibreboard 2≈ 18 mm Beech laminated veneer lumber stud 240/80 mm Inlaid mineral wool thermal insulation 240 mm Gypsum fibreboard 2≈ 18 mm 13 Installation layer: Gypsum board 15 mm Steel channel 60 mm Inlaid mineral wool thermal insulation 60 mm Vapour barrier

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Residential Development Munich, DE 2016

Architects: Florian Nagler Architekten, Munich Timber structural engineering: Franz Mitter-Mang, Waldkraiburg Solid construction structural engineering: r.plan Büro für Bauplanung, Chemnitz

Text: Anne Niemann

Concept “We need more affordable housing – and fast!” This was the motivation behind developing a building above a car park next to the Dantebad public baths in Munich. Advantageous preconditions included the fact that the city of Munich owns the property, that the parking spaces were not ­permanently assigned, and that all those involved were interested in quickly realising a project that demonstrated appropriate quality standards. The result is a five-storey building with an open ground floor that maintains the

parking area while enabling construction above it. The more than 100-m long structure harmonises with the urban design ­context defined by large-format residential buildings and forms an improved backdrop for the existing open spaces. Staircases and access balconies lead ­residents and visitors to the apartments. In front of every third apartment, the access balcony increases in width and a small niche offers room for furniture, serving as a meeting point for residents. Of the 100 units, 86 are studio apartments, while

the remaining 14 units feature two and a half rooms. The apartments were built for eligible households of different income levels and officially recognised refugees, who encounter particular difficulties finding affordable apartments on the high-priced Munich housing market. As an additional offer, residents can use shared areas, a laundry café and a ­rooftop terrace with play areas, deckchairs and space to grow vegetables and herbs.

R E S I D E N T I A L D E V E L O PM ENT IN M UNICH

Load-bearing Structure In order to maintain the majority of existing parking spaces, a structure comprised of reinforced concrete columns and beams was erected first. The actual residential housing was built as a timber structure on top of it. The building is connected to the ground level via two staircases and the ­narrow front segments housing building ­services, storage and bin stores. The ­load-bearing interior walls and ceilings consist of cross-laminated timber elements spanning the entire depth of an apartment. The ceilings remain exposed in the interiors,

while the walls are clad in two layers of ­gypsum board in order to provide necessary soundproofing. The exterior walls ­consist of timber wall framing elements with 20-cm thick mineral fibre insulation that meet 2016 Energy Saving Ordinance requirements. The building exterior clearly refers to the timber structure behind it: the differentiated design of facades with their roughsawn ­timber frames and panels makes the construction process transparent, while their repet­itive patterns provide the building with a calm rhythm. The colourful facades effortlessly blend in with the urban context.

Building parameters Number of storeys Gross floor area Construction costs Construction time timber Construction time total

5 4,630 m2 (a) 722 m2 (b) 192 m2 (c) approx. EUR 8.4 million 2 months 7 months

Site plan  Scale  1:2,000 Sections • Floor plans  Scale  1:750 1 2 3 4 5 6 7

Access balcony Studio apartment Sanitary unit, prefabricated Common areas Storage area 2.5-room apartment Accessible apartments

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Prefabrication The reinforced concrete structure of the building was cast on site, while the timber structure features a high degree of pre­ fabrication. After the exterior walls and apartment partition walls were installed, the prefabricated bathrooms, protected against the weather, were lowered into the residential units by use of a crane. ­Timber ceiling panels were then placed on top of the units. After mounting the pre­ fabricated concrete access balcony ele­ ments onto the structure, the respective ­storey was complete and work could

Floor plan of the two apartment types  Scale  1:100

begin on the next storey above it. The method of construction, in addition to installing fully equipped bathroom modules on site, reduced the assembly time on site to a minimum. This allowed completion of the project within the short planning and construction timeframe between April and December.

Fire Safety The residential development belongs to building class 4, which requires a fire ­resistance of 60 minutes in upper storeys. The reinforced concrete platform above

the car parking area comprises a 90-minute fire resistance duration, in order to protect the residential floors above from the fire load of the cars parked below. The access balconies also consist of nonflammable materials. The two s ­ taircases provide two structurally independent escape routes. The staircase cores and the lift shaft consist of ­reinforced c ­ oncrete on the ground floor and solid ­timber on the upper floors. They feature cladding on both sides and are, thus, ­classified as substitute firewalls with a fire resistance duration of 60 minutes.

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  1 Roof construction: Extensive green roof or gravel surface Drainage element 40 mm, protective mat 6 mm 2-ply bituminous sealant, EPS insulation to falls 20 – 200 mm PU thermal insulation 60 mm, latex-bonded crushed stone fill 60 mm Vapour barrier (temporary seal), cross-laminated timber ceiling 140 mm   2 Larch siding, texture-planed, dark blue painted finish 19 mm Horizontal battens 35 ≈ 80 mm, vertical battens 16 ≈ 80 mm Cross-laminated timber 100 mm   3 Triple insulation glazing in wood frame   4 Standard ceiling construction: Linoleum flooring 2.5 mm, spackle primer 2 mm, cement screed 55 mm PE film separation layer 2≈ 0.2 mm, mineral fibre impact soundproofing 40 mm Latex-bonded crushed stone fill 100 mm Cross-laminated timber ceiling, exposed industrial grade 140 mm   5 Galvanised sheet steel coping, rough-cut larch element frame 100 ≈ 100 mm   6 Larch joint trim, texture-planed, dark blue painted finish 19 mm   7 Rough-sawn larch fascia, red painted finish 210 ≈ 40 mm   8 Roller shutter housing, plastic slats   9 Ceiling above 1st floor: Linoleum flooring 2.5 mm, spackle primer 2 mm, cement screed 55 mm PE film separation layer 2≈ 0.2 mm Mineral fibre impact soundproofing 20 mm EPS thermal insulation 40 mm, vapour barrier EPS thermal insulation 120 mm, reinforced concrete slab 250 mm 10 Pavers 50 mm, crushed stone bed 30 mm, supporting layer 182 mm Drainage element 40 mm, protective mat 6 mm, 2-ply bituminous sealant EPS insulation to falls 20 – 200 mm, PU thermal insulation 60 mm Latex-bonded crushed stone 60 mm, vapour barrier (temporary seal) Cross-laminated timber ceiling 140 mm 11 Galvanised steel baluster 12 Prefabricated reinforced concrete element 13 Prefabricated reinforced concrete element, PMMA coating 140 – 210 mm 14 Glued laminated timber 200/160 mm 15 Insulation strip 16 Hung thermal insulation 120 mm Lightweight wood wool panel, non-flammable 15 mm

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Rooftop Addition Zurich, CH 2015

Architects: spillmann echsle architekten, Zurich Structural engineering: Haag + Partner, Küsnacht

Text: Manfred Stieglmeier

Concept The “Rauti-Huus” is a production facility for a ventilation equipment manufacturer, built in 1948 and located in the Albisrieden neighbourhood of Zurich along a busy street. Together with its neighbouring building, it forms an ensemble that is represent­ ative of building in the era of its origin. On top of the structure, previously used as an office and laboratory with four full floors and a recessed top floor, the architects created a three-­storey rooftop addition comprised of a timber structure with 17 new residential units. This activated the remaining 30 % of

the entire permitted usable floor area. The lowest level of the rooftop addition is concealed behind the reconstructed fourthfloor facade. The two-storey addition, visible from the exterior, constitutes an interplay of rect­angular shapes enclosing extensive loft spaces which are maisonette apartments with private roof terraces. All apartments are accessed by an interior corridor on the fourth floor, comparable to a “rue intérieure”. Depending on apartment type, residents access them through a living kitchen and an interior staircase leading upstairs or downstairs into the further living spaces that extend across the entire width

of the building, along the respective floors. This creates interior spaces separated from the street noise and exterior spaces with adjacent terraces for every apartment. The individual apartments are entwined floor by floor in order to create differentiated apartment sizes.

Structural Engineering The existing building had already received two rooftop additions in the past. Due to this fact, the load-bearing structure had reached the limits of its capacity. In addition, the existing building substance of the recessed

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aa Site plan Scale 1:5,000 Sections • Floor plans Scale 1:750 Axonometric illustration apartment typology

Building parameters Number of storeys (timber) Gross floor area (GFA) Construction costs Construction time timber Construction time total

3 5,630 m2 approx. EUR 12.2 mill. 10 days 16 months

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rooftop floor displayed significant flaws that made a further solid rooftop addition impossible. The desired extension of the building was, however, enabled by demolishing the two upper existing floors and replacing them with three new storeys comprised of a prefabricated timber structure of lighter weight. The utilisation of the existing concrete structure required homogeneous load transmission into the existing 70-cm wide columns. Due to the entwined floor plans of the new apartments, this wasn't possible in all locations. An existing, central downstand beam on the third floor running along the middle of the entire 60-m long building was

used to distribute loads. The poor concrete quality of this construction component, however, required upgrading it with glass fibre reinforcement and a new top layer consistb ing of a special concrete type. A steel grid structure was placed between the concrete columns of the facade and the downstand beam. It is set on top of neoprene bearings along the exterior wall in order to homogeneously distribute transferred loads as far as possible into the 12 ≈ 20-cm concrete facade columns. This structure, in return, supports the new three-storey timber construction consisting of both timber wall framing and solid timber elements and featuring

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Prefabrication The advantages of the timber construction were its low weight and prefabrication-related short construction time. Timber wall framing components and solid timber walls were prefabricated in the workshop and delivered on

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site as elements. The integration of windows and facade elements took place on site. Due to transport circumstances, the hollowbox ceiling elements had a maximum size of 2.50 ≈ 13.00 m. They were prefabricated including fire protection cladding, insulation and integrated cement pavers. Work on the rooftop addition took place while the storeys below were occupied.

Fire Safety The building belongs to building class 5. During planning, load-bearing and stiffening construction components that partition

spaces required a fire resistance duration of REI 60 / EI 30 (non-combustible), meaning they need to maintain their load-bearing and thermal insulation capacity over 60 minutes of exposure to fire. In addition, construction component surfaces must remain ignitionresistant for 30 minutes. These requirements were met by comprehensively cladding the timber structure in two layers of EI 60 (noncombustible) gypsum board on the interior and, due to the design intent of selecting a material for the addition that corresponds to the existing building, fibre cement panels on the exterior. Each apartment constitutes an independent fire compartment.

Plan detail, load distribution grid, carbon fibrereinforced polymer (CFRP) enhancement of ceilings and central beam, n.t.s. Section, wall to beam connection  Scale  1:10   1 New steel beam   2 Existing ceiling structure   3 CFRP lamellae to ceiling   4 CFRP lamellae to central beam underside   5 CFRP strap as central beam casing   6 Gypsum board 2≈ 15 mm, metal stud Inlaid glass wool soundproofing 30 mm   7 Timber wall framing element: OSB sheathing 15 mm, wood blocking 80/160 mm Inlaid thermal insulation 160 mm, OSB 15 mm   8 Flush baseboard   9 Gypsum fibreboard 2≈ 12.5 mm 10 Load-bearing cross-laminated timber wall plate 120 mm 11 Welded flat steel 100/180/10 mm 6

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12 Extensive green roof, substrate 70 mm Storage mat 35 mm, drainage /protection mat 20 mm Sealant, separation layer Rigid insulation 60 –163 mm, PE film Vapour barrier, three-layer panel 27 mm Glued laminated timber member 60/216 mm Inlaid mineral fibre insulation Three-layer panel 27 mm 13 Gypsum board 2≈ 12.5 mm Spring clip / insulation 30 mm 14 Fibre cement fascia 16 mm 15 Aluminium substructure 16 Triple glazing in wood /aluminium-frame 17 Larch floorboards 20 mm Substructure 30 mm Point support 13 – 40 mm, sealant Rigid insulation 50 – 80 mm, vapour barrier Three-layer panel 27 mm Glued laminated timber member 60/180 mm Inlaid mineral fibre insulation 140 mm Concrete paver for soundproofing purposes 40 mm Three-layer panel 27 mm 18 2-ply colourless PU sealant Epoxy resin primer, calcium sulphate liquid screed Integrated underfloor heating 60 mm 3-ply impact soundproofing 50 mm Three-layer panel 27 mm Glued laminated timber rib 60/216 mm Inlaid mineral fibre insulation 160 mm Concrete paver for soundproofing purposes 50 mm Three-layer panel 27 mm 19 New cornice 20 Double render layer, brick 190/125 mm Thermal insulation 315 mm Gypsum board 2≈ 12.5 mm 21 Masonry brick wall (existing) 22 Timber post 100/200 mm 23 IPE 300 steel beam on neoprene bearing

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Renovation of a ­Residential Building Augsburg, DE 2012 Architects: lattkearchitekten, Augsburg Structural engineering: bauart Konstruktions GmbH, Munich

Text: Frank Lattke

Concept As one of the nine sites in the Bavarian Supreme Building Authority’s model project “e% Energy-efficient Housing”, the 60-units building on Augsburg’s Grüntenstraße was to be modernised without residents having to move out. The aim of the model project was to achieve levels 40 % lower than required by the 2009 Energy Saving Ordinance while also providing b ­ arrier-free access. The construction phase was supposed to proceed as quickly and smoothly as ­possible for the tenants. Thus, the focus of attention was on a related construction

process, given that the construction efforts included not only the building envelope, but the complete renovation of bathrooms and the kitchen water supply. Appropriate information management and coordination with residents, thus, were essential. The buildings received a new envelope consisting of prefabricated timber wall framing elements with rough-sawn timber siding and painted finish. The existing balconies were converted into enclosed conservatories that extend the living space outward, serve as a climate buffer and offer protection from noise coming from the main street along the southern building perimeter. The high degree of prefabrication of the new

building envelope enabled construction time to be reduced to a minimum. The six-­ storey building was not barrier-free prior to modernisation. The entrance was situated half a storey lower than the ground floor level, while the lift only served mezzanine floors. As part of the modernisation, the site was raised to street level, creating an accessible forecourt. A new lift now serves the access balconies on each floor.

Structural Engineering The facade construction features large-­ format, prefabricated, insulated and selfsupporting timber wall framing elements

RENOVATION OF A R ­ E S I D E N T I A L B U I L D I NG IN A UGSB UR G

Sections • Floor plans Scale 1:500

Building parameters Number of storeys 6 Gross floor area (GFA) 7,124 m2 (before) 7,730 m2 (after) Construction costs EUR 5.9 mill. Construction time timber 5 months Construction time total 14 months

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set in front of an existing exterior brick wall. Dead-weight vertical loads are led directly into a concrete strip footing set in front of the basement wall. The horizontal stress resulting from wind suction and pressure is transferred into the existing reinforced ­concrete ceiling floor by floor. To achieve this, a continuous timber plate was fixed by use of heavy-duty dowels to the front edge of the ceiling slab and the facade ­elements were mounted to it with bolted connections. The windows were replaced from the interior to the exterior. First, the masonry window reveals received notches and were partially demolished in order to lift window frames out of the facade. The new windows were set flush with the interior timber frame wall elements and connected to the shell opening. A new inner reveal consisting of two gypsum board ­layers was created and the new frame was provided with an airtight connection to the first gypsum board layer. The reinforced concrete balconies of the existing structure comprising cantilevered ceiling slabs and lateral walls embedded into the masonry facade led to the formation of significant thermal bridges. Key to the renovation ­concept was preserving the balconies and repurposing them by removing parapet walls and part of the lateral walls, in order to create enclosed conservatories with large ­sliding glass doors. As a result, the apartments gain both space and light. At the same time, benefits arise in terms of energy consumption: all cantilevering construction components are now covered by the building envelope. In addition, the conservatories serve as a climate buffer. Air intake through vent openings in walls during winter can lead to an increase of fresh, cold air temperatures before air enters apartments through upper window frame rebate ventilation elements and is exhausted via kitchens and bathrooms. Due to new timber loggias set between the conservatories, the residents also still have balconies.

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Fire Safety For fire safety purposes, a distinction was made between the existing load-bearing ­primary structure and the new, non-loadbearing building envelope. The existing structure of masonry and reinforced concrete walls and ceilings meets REI 90 and REI 90 M requirements. The new facade elements used for the energy upgrade of the building are considered non-loadbearing exterior walls. They neither serve to stiffen the building, nor to transfer loads from other construction components. As a result, the only requirement to be met is

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a fire resistance duration of construction components of W 30 B. This allowed the use of timber for wall framing studs and for cladding, even for a six-storey structure. The prefabricated facade elem­ents received a 15-mm layer of gypsum fibreboard along their exterior and their element joints. To prevent fire from spreading through the structure in the area of w ­ indow connections, window reveals ­feature a solid timber frame measuring 60/200 mm and are clad in gypsum fibreboard along all sides. The cavity between the timber wall framing elements and the existing masonry wall was completely filled with blow-in cellulose fibre insulation, in order to prevent uncontrollable convection and spread of fire. The building was clad in back-ventilated shiplap siding of normal combustibility, while complying with fire safety goals: boards are 24-mm thick, millings permit a 20-mm overlap and screws are driven into framing battens more than 20 mm deep. Sheet steel firestops were set into horizontal joints between elements to prevent fire from spreading from floor to floor through the facade back ventilation layer. The 1.5-mm thick steel firestops are tightly mounted to the gypsum fibreboard with screw connections to the wall frame substructure in 300-mm intervals.

Horizontal section • Vertical sections  Scale  1:20   1 Rough-sawn spruce shiplap siding, visible screws, white-painted finish 28 mm, timber substructure with back ventilation 30 mm, OSB strip counterbattens 10/120 mm, vapour-permeable sarking layer Gypsum fibreboard 15 mm, spruce solid ­Construction-grade timber 60/200 mm Inlaid cellulose fibre thermal insulation 200 mm OSB 10 mm, levelling layer 50 mm Existing: render 10 mm, masonry 365 mm   2 Render 10 mm, substrate panel 60 mm Construction-grade timber 60/160 mm Inlaid cellulose fibre thermal insulation 160 mm OSB 10 mm, installation layer 50 mm Existing: render 10 mm, masonry 365 mm Render 10 mm   3 Exterior wall air vent   4 Wood /aluminium window including flush-mounted sunblind box with triple insulation glazing   5 PVC window (demolished)   6 Wood window with rebate ventilation element and ­triple insulation glazing   7 Roof construction: single-layer bituminous sealant 5 mm Existing: single-layer bituminous sealant 5 mm PUR insulation 120 mm, reinforced concrete 170 mm   8 Galvanised steel sheet parapet coping 1.5 mm   9 Existing ceiling slab 10 Loggia: linoleum 5 mm, spackle primer 5 mm Existing: tiles 10 mm, cement screed 75 mm Bituminous layer, reinforced concrete 160 –120 mm 11 Steel SHS fall protection 12 Spruce shiplap siding 24 mm, spruce substructure 30/50 mm, counterbattens, OSB panel 12 mm Sarking layer 0.5 mm, gypsum fibreboard 15 mm Solid construction-grade spruce 120 mm, OSB 10 mm 13 Larch grating, untreated, gradient compensation 40 – 60 mm, plastic sealant layer 5 mm Glued laminated timber, exposed quality 51 mm 14 Canted sheet steel firestop 1.5 mm 15 In-situ concrete foundation with shear connector

RENOVATION OF A R ­ E S I D E N T I A L B U I L D I NG IN A UGSB UR G

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Residential Buildings Zurich, CH 2016

Architect: Rolf Mühlethaler, Bern Timber structural engineers: Indermühle Bauingenieure, Thun Solid construction structural engineers: Ingenta Ingenieure + Planer, Bern

A B C

Text: Stefan Krötsch

Concept On the site of the former customs warehouse in Albisrieden in Zurich, a new ­residential district comprising around 190 apartments was built. The units were distributed across three high-rise buildings comprising solid reinforced concrete construction and three longitudinal, six-­ storey timber building volumes. Continuous balconies provide the timber buildings with a strong horizontal structure that mediates between the urban design scale of the ensemble and the small-scale character of the apartment facades. The width of windows and the depth of bal­ conies vary depending on cardinal direction and are designed in accordance with

an ambitious energy concept (Minergie-Peco). The deep balconies offer weather ­protection for the timber facade consisting of pressure-treated spruce, while creating differentiated outdoor areas. Staircase cores spanning the entire building depth and comprised of reinforced concrete provide access to two apartments on each level – a principle that is repeated on every storey. The apartments of the two northern longitudinal buildings (A + B) consist of sequences of rooms that are functionally indeterminate and feature a large entrance hall as circulation space instead of corridors. In the southern longitudinal building (B) apartments are accessed via a continuous kitchen /dining / living area.

Structural Engineering The clarity and consistency of both floor plan variants correspond to the respective loadbearing structure. The ceilings of buildings A and B are set on top of the longitudinal facades and on two interior walls parallel with the facades. The ceilings of building C span across the longitudinal facades and are set on top of interior parallel shear walls. In both cases, the ceilings consist of dowel laminated timber elements, while OSB panels provide stiffening. Although the buildings feature six storeys, vertical loads are transferred via interior and exterior walls consisting of prefabricated timber wall framing elements. In order to prevent settlement adjacent to the stiffening concrete staircase cores, the timber

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R E S I D E N T I A L B U I L DINGS IN ZUR ICH

Site plan Scale 1:5,000 Axonometric illustrations, load bearing structure comparison Section • Floor plans Scale 1:500 1 Living / dining / kitchen 2 Room 3 Entrance 4 Bathroom 5 Building services 6 Circulation 7 Vestibule 8 Basement car park ­access 9 Bicycle store Buildings A + B

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panel elements are designed without a top plate or a bottom plate. The studs of the ceiling-height elements feature end grain butt joints, thus preventing transverse compression. Beams with an L-shaped cross section form the linear supports of the ceilings, which are inserted into notches milled into the studs.

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Assembly Process The timber structure was assembled after the reinforced concrete staircases were completed. Load-bearing and non-loadbearing walls and the ceilings set on top were installed floor by floor. The timber wall framing elements of the exterior walls were prefabricated including interior cladding, windows, facade substructure and exterior lintel covers. The facade cladding consists of prefabricated elements that were installed on site, similar to the dowel laminated timber ceilings including OSB stiffening panels. The floor construction and hung ceiling were also installed on site.

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R E S I D E N T I A L B U I L DINGS IN ZUR ICH

Vertical sections, longitudinal facade with balcony Buildings A, B and C Scale 1:20

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  1 Roof construction: Extensive green roof fill 128 – 328 mm Protection /drainage / filter layer 20 mm Plastic sealant layer EPS thermal insulation to falls 10 –190 mm EPS thermal insulation 140 mm, dividing strip Mineral wool, vapour barrier, loose layout Rib ceiling: adhesively bonded OSB ribs 22 mm (a = 650 mm) 80/220 mm Cavity for installations / ventilation 68 mm Hung cavity insulation with spring clips for acoustic decoupling 50 mm Gypsum board, painted finish 15 mm   2 Sun protection, patio: Textile awning element (one per apartment) Hand crank with lateral guide cables   3 Downstand beam silver fir fascia, pressure-treated, double-oiled finish 24 mm Glued laminated silver fir beam, pressure-treated, double-oiled finish 140 mm   4 Sun protection, compact venetian blinds with slats and lateral guide rails   5 Spruce window with triple insulation glazing, ­protective stain, brown, Ug = 0.6 W/m2K   6 Glued laminated silver fir facade posts, pressuretreated, double-oiled finish, different dimensions: Ground floor � 160 mm /1st – 4th floor � 140 mm / 5th floor � 120 mm Steel plate and steel CHS connector, rustproof 5 mm inserted into downstand beam   7 Silver fir patio partition wall, pressure-treated, oiled finish   8 Aluminium drip edge, dark brown painted finish Rough-cut silver fir fascia, pressure-treated, oiled finish 24 mm   9 Patio construction, 2nd – 5th floor: Silver fir decking, pressure-treated, planed /sanded 27 mm, battens 27 mm Mitred blocking 51– 81 mm Elastomeric bearing (impact sound) 20 mm Plastic sealant layer, mechanically fastened Glued laminated board 1.5 % to falls Soffits, gloss-stained 94 mm 10 Floor construction, upper storeys: Vertical solid oak parquet flooring 15 mm Screed with underfloor heating 53 mm Separation layer, impact soundproofing with kraft paper 27 mm, bonded fill (installation level) 30 mm OSB as stiffening ceiling plate 15 mm, Dowel laminated timber ceiling 180 mm Gypsum fibreboard (fire protection) 18 mm Cavity for installations / ventilation 50 mm Hung cavity insulation, spring clips (soundproofing) 50 mm Gypsum board, painted finish 15 mm 11 Ground floor construction: Vertical solid oak parquet flooring, untreated 15 mm, screed with underfloor heating 53 mm Separation layer, impact soundproofing 27 mm Bonded fill (installation level) 30 mm Reinforced concrete 250 mm EPS thermal insulation with cement bonded ­Wood-wool acoustic panel 200 mm 12 Silver fir fascia above cassette and timber window, pressure-treated, oiled finish 27 mm 13 Steel rod balusters, powder-coated Ø 15 mm 14 Facade (no installations in exterior walls): Silver fir siding, pressure-treated (tongue and groove) 22 mm, set into solid silver fir frame, ­pressure-treated, oiled finish 50 ≈ 50 mm Back ventilation 33 mm Polyester fleece facade membrane Gypsum fibreboard 15 mm Wood studs, inlaid mineral wool thermal Insulation 360 mm OSB (airtight layer), adhesively sealed joints 15 mm Gypsum fibreboard 18 mm Render painted white 1 mm

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Building parameters Building A Number of storeys 6 Gross floor area (GFA) 9,500 m2 Construction time timber 11.5 months (including fabrication) Construction time total 36 months Building C Number of storeys 6 Gross floor area (GFA) 10,554 m2 Construction time timber 12 months (including fabrication) Construction time total 36 months

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Buildings A, B and C Construction investment volume approx. EUR 330 mill.

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Horizontal sections, corner detail Element joint, apartment partition wall (non-load-bearing) Scale 1:10 1 Facade (no installations in exterior walls): Silver fir siding, pressure-treated (tongue and groove) 22 mm set into solid silver fir frame, ­pressure-treated, oiled finish 50 ≈ 50 mm Back ventilation 33 mm Polyester fleece facade membrane Gypsum fibreboard 15 mm Wood studs, inlaid mineral wool thermal insulation, 360 mm OSB (airtight layer) 15 mm, adhesively sealed joints Gypsum fibreboard 18 mm

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Render painted white 1 mm 2 Spruce window, painted finish, with triple insulation glazing Ug = 0.7 W/m2K, Uf = 1.1 W/m2K 3 Apartment partition wall (non-load-bearing): Gypsum fibreboard 12.5 mm Gypsum fibreboard 10 mm Metal stud frame 75/0.6 mm Cavity insulation 70 mm Cavity 20 mm Cavity insulation 70 mm Metal stud frame 75/0.6 mm Gypsum fibreboard 10 mm Gypsum fibreboard 12.5 mm 4 Electrical outlets in airtight gypsum board enclosures 2≈ 12.5 mm

A D M I N I S T R A T I O N B U ILDING IN A A LEN

Administration Building Aalen, DE 2014

System development and design: Florian Nagler Architekten, Munich Construction: Kampa, Aalen Josef Haas, Johann Wellner Structural engineering, fire safety planning and building physics: bauart Konstruktions GmbH, Lauterbach

Text: Wolfgang Huß

Concept The headquarters of a prefabricated housing manufacturer – similar to its products – was designed as a prototype for an adaptive construction system. The system allows for geometric variations of a defined building type and is suitable for five to eight­storey buildings. The construction grid ­varies between 2.50 and 3.20 m, while the depth of a building can range from 12 to 13.50 m. The seven-storey building constructed has a depth of 12.50 m, based on a 2.50 m grid. The below-grade level is occupied by the substantial building ­services equipment. The ground floor ­comprises a spacious foyer, a conference room and a cafeteria. The five storeys above feature areas for exhibiting products and samples and also house the company offices and meeting rooms.

Structural Engineering The load-bearing structure of the admin­ istration building is a purely timber construction placed on top of a reinforced ­concrete basement. The building is essentially designed as a frame structure comprised of glued laminated timber. Singlespan beams are transversely set into notches milled into studs. The remaining stud cross section is sufficient to directly transfer vertical loads from top stud to ­bottom stud. The stiff ceiling plates, the roof, the sanitary cores and access cores all consist of cross-laminated timber. The cores enable load transfer and longi­ tudinal stiffening of the building. Transverse stiffening is provided by four crosslamin­ated timber wall plates. Tensile anchors are integrated into the eight ­columns that are connected to these wall plates and serve to bear strong wind loads. To min­imise the required amount of such complex connections, the studs are three storeys tall.

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Building parameters Number of storeys 7 Gross floor area (GFA) 3,386 m2 (plus basement) Total construction costs approx. EUR 6 million Construction time timber 6 months (including interior finishes) Construction time total 10 months

Fire Safety The load-bearing timber components of the building are dimensioned for a 90-minute fire resistance duration before burnout. Small smoke and fire compartments and short escape routes to the two staircases increase safety in the event of a fire, making it possible to omit installing either a sprinkler system or encapsulating load-bearing components. Only the staircases are clad in gypsum fibreboard, while the stair treads and landings consist of prefabricated reinforced concrete elements. The fire safety certificate was based on the 2010 building code of the German 6 6 state of Baden-Württemberg. Following the 5 4

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2015 amendment of the state building code, timber structures in Baden-Württemberg must be planned to comply with building class 5.

Building Services Beneath the load-bearing ceilings, multifunctional ceiling sails span from beam to beam, structurally independent and, thus, acoustically decoupled. Supported by a timber substructure, gypsum board panels perforated along their underside are mounted flush with downstand beams. These prefabricated elements with integrated service lines (electrical, heating, cooling) also ensure good room acoustics.

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The building features an envelope that corresponds to the passive house standard, north-south orientation, controlled ventilation with 75 % heat recovery, seasonal ice storage with 685 m3 capacity in combination with heat pumps for heating and cooling, as well as a rooftop photovoltaic system, all of which provide energy gains while the building is in operation.

Lift The lift shaft features a cavity wall construction with an exterior layer consisting of cross-laminated timber walls with 2≈ 18 mm special gypsum board cladding on both

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The structural engineering concept can be employed unchanged for variable building structures with construction grids measuring 2.50 to 3.20 m. Basic floor plan dimensions: 38.75 ≈ 12.50 m, transverse grid 2.50 m. a

Floor plans • Section Scale 1:400 1 Reception / foyer 2 Conference room

3 Cafeteria 4 Exhibition area 5 Office 6 Meeting room

A D M I N I S T R A T I O N B U ILDING IN A A LEN 7

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sides. The acoustically decoupled interior layer consists of 10-cm thick cross-laminated timber without cladding. The shaft was prefabricated in three parts as a multi-storey module. In terms of construction, it is largely independent of the outer shell and set on top of the reinforced concrete basement foundation slab. Floor plan, lift shaft Scale 1:50 Vertical section, connection between exterior wall – interior wall Scale 1:10 7 Facade construction: Timber siding 25 mm with cover moulding in different sizes (35/44 mm and 47/44 mm)

15 Ceiling: Carpet flooring 10 mm Screed 23 mm, separation layer Impact soundproofing 10 mm Glued laminated timber 150 mm Gypsum board 25 mm (fire protection class A1) Cavity 360 mm, hung ceiling substructure Gypsum board 2≈ 12.5 mm 16 Mineral fibre insulation strips for acoustic decoupling 17 Load-bearing structure, cross-laminated timber 140 mm 18 Transverse tension tie, bolts 6≈ 120 mm 19 Gypsum board strips (fire protection class A1) 30 ≈ 125 mm 20 Plywood tongue F 20/10 27 mm 21 Horizontally crossed bolt pair 22 Elastomeric bearing for acoustic decoupling 23 Wood blocking 80/160 mm Bolted connection Gypsum board strip encapsulation (fire protection class A1) 30 mm

Battens 40/60 mm Gypsum board (fire protection class A1) 15 mm Wood blocking 80/300 mm Infilled mineral wool thermal insulation 300 mm   8 Load-bearing structure: Cross-laminated timber 140 mm 2-ply gypsum board encapsulation 2≈ 18 mm on both sides (fire protection class A1)   9 Lift shaft: Cross-laminated timber 100 mm Prefabricated as three-storey room module without additional cladding 10 Interior wall: Facing shell 25 mm Mineral fibre soundproofing 110 mm Gypsum board 2≈ 18 mm Cross-laminated timber 160 mm 11 Steel angle connector (two per element) 12 Slotted plate 13 Gypsum board, horizontal, continuous 25 mm 14 OSB as stiffening plate 22 mm

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Office Building Vandans, AT 2013

Architects: Architekten Hermann Kaufmann, Schwarzach Structural engineering: merz kley partner, Dornbirn

Text: Hermann Kaufmann

Concept The Illwerke Zentrum Montafon (IZM) in Vandans is the new administration building for Austrian power company Illwerke and has 10,000 m2 of usable floor area. The load-bearing structure of the construction system comprising prefabricated rib slabs and the intention of creating workplaces of comparable quality for all 270 staff members were the decisive guiding aspects of the building design. This limited the building width and, in return, contributed to its length of 120 m. One third of the clearly delineated timber building projects out over the adjacent lake. The building code permitted this design approach, thanks to the artificial character of the body of water. The floor plan concept responds to the site by placing the staff ­cafeteria and visitor centre in this special location. The building forms the backdrop of the adjacent park and presents its longitudinal facade to approaching visitors. A generously dimensioned canopy highlights the entrance. The facade is structured into horizontal layers consisting of parapets, horizontal strip windows and ­canopies that prevent fire from spreading between floors. The building length and construction grid become guiding images of its design.

Construction To stiffen the building horizontally, it features two access cores consisting of insitu concrete – also for fire safety reasons. Based on the fact that the building is situated in the lake, particular earthquake safety measures became necessary. As a result, building the entire ground floor and the ceiling above the ground floor as an ­in-situ concrete structure became economically feasible. The upper floor slabs consist of 3-m wide and 8.10-m long prefabricated timber concrete composite T-beam elements. The concrete slab is reduced to a thickness

O F F I C E B U I L DING IN VA NDA NS

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 1 Foyer  2 Office   3 Copy centre   4 Lecture hall  5 Kitchen  6 Cafeteria   7 Open plan office   8 Meeting room   9 Think tank 10 Single office 11 Copy / printer room 12 Kitchenette (open) 13 Break room

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of 8 cm, meeting the necessary sound insulation and fire safety requirements (REI 90), while displaying vibration behaviour in line with the standard. Following assembly, the individual elements were combined into ­friction-locked reinforced ceiling plates by use of joint sealing compound and, in part, screw connections. The pinned facade ­columns comprise double cross sections measuring 2≈ 24 x 24 cm. A reinforced ­concrete edge beam is integrated into the ceiling element and enables direct load transfer from timber top column end grain to bottom column end grain, without requiring elaborate connectors.

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Assembly The entire timber structure, including the prefabricated facades with unfinished oak siding and the roof elements, was assembled in just six weeks. The prefabricated oak windows were installed simultaneously. This minimised the risk of wetting the structure during assembly and, in turn, the necessary weatherproofing of the structure.

Fire Safety The entire structure remains exposed and meets REI 90 fire classification require-

ments. A sprinkler system was installed as compensation. This enabled all abovegrade storeys to be combined into a single fire compartment, which was divided into several smoke compartments.

Energy The building has primary energy consumption of less than 30 kWh/m2a and heating needs of 14 kWh/m2a (passive house standard). Supply is generated entirely by the power plant waste-heat system, while cold water from the surrounding reservoirs provides cooling energy.

O F F I C E B U I L DING IN VA NDA NS

A Building assembly sequence B LCT system (LifeCycle Tower One, Dornbirn (AT) 2011, predecessor and first eight-storey timber building in Austria) C IZM system D Assembly sequence in detail E Isometric illustration, load-bearing system F Timber concrete composite rib ceiling, vertical ­section, span 8.50 m, element width 2.70 – 3.00 m

1 Wall element consisting of three column pairs with parapet 2 Timber concrete composite rib ceiling 3 Window module 4 Canopy 5 Glued laminated timber columns 2≈ 240 ≈ 240 mm 6 Polypropylene fibre reinforced concrete C 30/37, thickness = 80 mm 7 Timber ribs, depth = 860 mm

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

5 11,497 m2 EUR 26 mill. (net) 6 weeks 17 months

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  1 Toughened glass, enamel coating 6 mm Back ventilation 46 mm Cement-bonded particle board 16 mm Mineral wool thermal insulation 130 mm OSB 18 mm Spruce glued laminated timber column 2≈ 240 ≈ 240 mm   2 Fixed timber window, solid oak with triple glazing   3 Timber window, solid oak with triple glazing Ug = 0.5 W/m2K   4 Å-beam canopy console 140 mm   5 Oak shiplap siding, untreated 27 mm Horizontal battens 40/60 mm Vertical battens 40/60 mm Cement-bonded particle board with Adhesively sealed joints 16 mm Glued laminated timber frame construction 59/340 mm Inlaid mineral wool thermal insulation 340 mm Airtight layer, vapour barrier OSB with adhesively sealed joints (vapour barrier) 18 mm Mineral wool thermal insulation (installation level) 77 mm Cabinetry, particle board with oak veneer 19 mm   6 Roof construction: Extensive green roof 100 mm Roof sealant, EPS thermal insulation 2≈ 140 mm Insulation to falls 0 –140 mm, vapour barrier Timber concrete composite rib ceiling: Reinforced concrete 80 mm Spruce glued laminated timber rib 240/280 mm Hung ceiling: heating and cooling panel Perforated sheet metal with laminated acoustic fleece, textured lacquer finish   7 Sheet copper parapet coping Timber sheathing 27 mm Battens 40/40 mm, counterbattens 40/40 mm Wind paper, gypsum fibreboard 16 mm Timber frame / mineral wool thermal insulation 170 mm, vapour barrier OSB 18 mm, roof sealant   8 Canopy: sheet copper 0.6 mm 3-ply bituminous sealant, particle board 24 mm Wood blocking 120/60 mm, oak soffit 20 mm   9 Sun protection blinds 10 Particle board, oak veneer 24 mm 11 Ceiling: carpet with acoustic underlay Fibre-reinforced mineral based panel 38 mm Installation layer 125 mm Infilled mineral fibre cavity insulation 30 mm Timber concrete composite rib ceiling: Reinforced concrete 80 mm Spruce glued laminated timber rib 240/280 mm Hung ceiling: soundproofing 50 mm Fibre mat, silver fir slats 30/40 mm

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Office Building St. Johann in Tyrol, AT 2015

Architects: architekturWERKSTATT, Breitenbach am Inn Structural engineers: dibral, Alfred R. Brunnsteiner, Natters

Text: Anne Niemann

Concept The winning design concept submitted to the competition for a series of buildings for wood-based material manufacturer Fritz Egger was to use client-produced OSB with maximum dimensions of 2.80 ≈ 11.40 m, the size of which determined the construction grid of the buildings and the prefabricated ceiling and wall elements. As a result, the spacing between the columns and wall height corresponds to a board width of 2.80 m.

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The new company headquarters in St. Johann consists of two parallel four-storey structures, connected and accessed by a covered atrium. The tripartite design of the structure is not discernible from the ­outside. Floor by floor, circumferential projecting roofs with offset larch slats visually tie the buildings together. The complex is distinguished by the rigorous and precise implementation of the construction system in combination with a high degree of design-based individuality – an eye-catcher against the Alpine backdrop.

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Structural Engineering The below-grade level houses a parking garage, a gym and auxiliary rooms. It ­consists of in-situ concrete to the top of the floor slab above. Prestressed beams span the entire grid module of 11.40 m. All above-grade storeys, comprising the foyer, cafeteria, seminar and office spaces, are constructed purely of timber. The ceilings – box elements filled with crushed stone and featuring glued ­laminated timber ribs and OSB adhesively bonded to the top and bottom of ­elements, with integrated service lines ­(ventilation, heating, cooling) – rest on glued laminated timber column point ­supports. Only the edge elements on the longitudinal building sides are partially set

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Sections • Floor plan Scale 1:500 1 Entrance 2 Reception 3 Atrium 4 Staircase / emergency exit 5 Training / seminar area

 6 Office   7 Storage / building services  8 Kitchen   9 Break area 10 Cafeteria 11 Scullery 12 Dining room

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

4 9,940 m2 n/a 5 months 12 months

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on top of stiffening, prefabricated timber frame wall elements, also with integrated service lines. This structure requires no downstand beams. The five-storey lift shaft, the connecting bridges in the atrium and the projecting staircases consist of five to seven layers of nail press-glued OSB elements. The load-bearing OSB ­surfaces have a white-glazed finish and remain exposed inside the building. The company’s own products were used nearly exclusively for the building construction and finishes.

Fire Safety Perfectly coordinated design and fire safety planning allowed for exposed ­timber surfaces inside the building as well as the central timber staircase in the atrium. Several compensation measures play a key role: three staircases in and around the atrium reduce the length of escape routes to just 25 metres. The entire building is divided into four fire c ­ ompartments: the below-grade level, the ground floor including the atrium and the combined upper floors of each building wing. For this purpose, the ceiling above the ground floor received a double layer of gypsum fibreboard with an REI 90 fire resistance class. The circumferential projection above the ground floor serves as a firestop. On the upper floors, the projections are for design reasons or for cleaning ­purposes. Horizontal spread of fire from floor to floor between wings is prevented by a water curtain created by a sprinkler system integrated into the cantilevering ­ceiling panels above the atrium. A fully ­integrated fire alarm system guarantees early fire detection and rapid notification of the fire service. The fire safety concept is supplemented by the atrium finishes’ reduced fire loads and the office wings’ transparence, thanks to the use of glass partitions and height l­imits for furniture.

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Modular System On the occasion of a competition in 2008, the wood-based material manufacturer developed a sustainable modular t­imber construction system that was intended to allow flexibility of use despite a strict ­construction grid, while enabling central manufacture. Buildings of this type have previously been built in Romania, Austria and Germany. Adaptations are possible in geometric terms and in order to meet ­architectural, functional, building physics and building code requirements, although there are limitations on adapting to narrow sites, given the relatively large-format ­construction grid. The modularity allows large quantities of identical ­elements to be produced on an industrial scale. To achieve this, the cross sections of the elements were designed for maximum load-bearing effect. Efficient production is intended to compensate for the resulting partial overdimensioning. In order to principally avoid the need for special lengths and components, the atrium and the office wings of the building in St. Johann are based on the same module grid. Vertical section  Scale  1:20 1 Roof construction: EPDM sealant, mechanically fastened Mineral wool thermal insulation 2≈ 140 mm Vapour barrier, bituminous membrane Aluminium laminate 4 mm Prefabricated roof construction: OSB 22 mm on wedge battens OSB airtight panel, nail press-glued 6≈ 30 mm Glued laminated timber beam 530/200 mm Installation lines in cavity OSB airtight panel, white-glazed finish 30 mm 2 Canopy: EPDM sealant OSB panel 22 mm on wedge battens OSB airtight panel, nail press-glued 5≈ 30 mm Glued laminated timber beam 500/100 mm OSB airtight panel, clear-glazed finish 30 mm

3 Wood /aluminium windows with triple glazing Laminated safety glass 12 + cavity 14 + toughened glass 6 + cavity 14 + toughened glass 8 mm 4 Ceiling above ground floor: Laminate flooring with impact soundproofing 10 mm OSB panel, tongue and groove 18 mm Wood fibre insulation panel, tongue and groove 32 mm OSB airtight panel 30 mm laminated to glued laminated timber beam 200/520 mm Installation lines in cavity, crushed stone fill 60 mm OSB airtight panel 30 mm, gypsum board 2≈ 20 mm Hung ceiling connector / installation lines 500 mm OSB airtight panel, white-glazed finish 18 mm 5 Heater outlet 6 Fire safety measures, ground to top floor: Larch grating, untreated EPDM plastic sealant layer 1.8 mm OSB 30 mm laminated to glued laminated timber beam 100/300 – 320 mm

OSB airtight panel, nail press-glued, underside with clear glazed finish 4≈ 30 mm 7 Sheet copper fascia, sealant layer, OSB 30 mm 8 Facade: Vertical larch battens 85/44 mm Rhomboid larch battens, planed 85/44 mm Facade membrane breathable wind paper Wood fibre insulation panel (fire-resistant), tongue and groove 32 mm, timber beams 60/280 mm Inlaid mineral wool thermal insulation 2≈ 140 mm OSB airtight panel, white-glazed finish 22 mm 9 Floor construction: Laminate flooring with impact soundproofing 10 mm OSB 22 mm, OSB 30 mm Single laminated vapour barrier Battens 60/140 mm Inlaid mineral wool thermal insulation Levelling layer approx. 30 mm Reinforced concrete slab 300 mm

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Research and Office Building Prince George, CA 2014

Architects: Michael Green Architecture, Vancouver Structural engineering: Equilibrium Consulting, Vancouver

Text: Hermann Kaufmann

Concept

organ­isations in the forestry and timber ­sector. The architect’s goal was “to celebrate wood as a building material, to make it tangible everywhere and to show its beauty both externally and internally”. The intention was to develop a prototype for an innovative, yet very simple and repli­ cable construction system for tall buildings that would inspire new developments in ­timber construction.

The Wood Innovation and Design Centre of the University of North British Columbia at Prince George is a pilot project for multistorey timber construction in Canada. Covering nearly 5,000 square metres of floor space, it is considered a high-rise, because the topmost floor elevation is above the high-rise threshold of 22 m. The building serves as a centre for researchers, scientists, engineers and architects who are invested in the topic of modern timber construction. It was built as part of Canada’s Tall Wood programme, a government-led initiative to promote large and tall timber structures. The lower three floors of the seven-storey and nearly 30-m tall building are occupied by the university and its ­timber construction Master’s programme. The upper floors provide office space for the timber industry and for governmental b 5

Structural Engineering The construction system features a skele­ ton frame structure based on a square grid measuring about 8 ≈ 8 m and stiffened by a central access core. The entire load-bearing structure including the core consists exclusively of different Canadian softwood species. Composite constructions were avoided to allow for easy ­demo­lition and end-of-life recycling. The

exposed primary beams, between 60 and 100-cm deep depending on loads, are connected to the glued laminated ­timber columns (36 ≈ 36 cm on the lower floors and 30 ≈ 30 cm on the upper floors), also exposed. Loads are transferred from the upper ­column directly into the lower ­column, thus preventing transverse compression and settlement. Two layers of ­alternating, offset and exposed cross-­ laminated timber elements, 10 or 17-cm thick and about 120 to 160-cm wide, are set on top of the primary beams. The ­resulting cavities are used as installation zones and are effectively acoustically closed at the ceiling. Impact sound insulation is provided by carpet flooring on a soft substrate layer. Canadian regulations allow omitting specific measures for airborne soundproofing, with the exception of gypsum board hung in the lower instal­ lation zone.

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5 Auditorium 6 Laboratory 7 Office 8 Electrical room

  9 Building services 10 Waste and recycling room

11 Delivery 12 Bike store 13 Office (tenant fit-out)

R E S E A R C H A N D O F F I C E B U I L D I N G I N PR INCE GEOR GE

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Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

7 4,820 m2 EUR 11.4 million 5 months 15 months

Fire Safety Thanks to a specifically developed fire pro­ tection concept, the entire construction remained exposed throughout the interior and encapsulation was not required. It is dimensioned to withstand 60 minutes of fire before burnout. Sprinklers offer additional protection. The timber post-and-beam facade is mostly glazed, alternating with opaque elements consisting of natural or charred vertical siding. External sun blinds were omitted.

Prefabrication The degree of prefabrication of the building was not very high, due to the limited experience of Canadian timber construction companies in this field. First, the ­structure was erected and then the facades were built. As a result, extensive weather protection measures were required during the construction phase. The building is an important contribution to the field of large-scale structures made entirely of wood, based on dry ­construction methods, and it impresses ­visitors with its unique atmosphere achieved through meticulous attention to detail.

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  1 Roof construction: 2-ply bituminous sealant Mineral wool thermal insulation Bituminous coating 100 mm PIR thermal insulation 2≈ 50 mm EPS insulation to falls approx. 100 –140 mm Vapour barrier, plywood panel 25 mm Plywood panel 19 mm 7-ply cross-laminated timber 239 mm   2 Battens with spacing 19/40 mm, acoustic mat Soundproofing 24 mm   3 Glued laminated timber beam 320/500 mm   4 Glued laminated timber column 320/320 mm   5 Glare protection: timber slats (horizontal)   6 Sheet aluminium curtain-wall facade Mineral wool thermal insulation 80 mm  7 Wood /aluminium post-beam facade with triple glazing   8 Heating and supply duct   9 Installation space: plywood panel 2≈ 13 mm Service lines Glass fibre soundproofing panel 2≈ 25 mm 10 Typical floor construction: Carpet flooring 9 mm Impact soundproofing 7 mm 3-ply cross-laminated timber 99 mm 5-ply cross-laminated timber 169 mm 11 Glued laminated timber beams 220/500 mm 12 Facade: Cedar siding, heat-treated, flamed or untreated ­surface, different widths 30 mm Substructure, plywood slats, weatherproof 13 mm Horizontal timber slat 10 mm, vapour barrier Wood fibreboard 13 mm, thermal insulation 165 mm wood fibreboard 18 mm, gypsum board 16 mm 13 Installation space: Wood blocking 89/40 mm Hollow metal rail, spring-mounted Gypsum board 2≈ 16 mm Glass fibre soundproofing panel 50 mm 14 Sprinkler 15 Reinforced concrete slab, polished 16 Pedestal: Rigid foam thermal insulation with latex modified ­concrete coating Steel angle fixed to base slab, sealant

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Administrative Building Clermont-Ferrand, FR 2014 Site plan Scale 1:3,000 Floor plans Scale 1:750

Architect: Bruno Mader, Paris Construction management: Atelier 4, Clermont-Ferrand Timber structural engineering: Sylva-Conseil, Clermont Ferrand Solid construction structural engineers: Sibat, Paris

1 Foyer 2 Reception 3 Cloakroom 4 Catering 5 Break room 6 Storage 7 Office 8 Open plan office 9 Green courtyard

Text: Anne Niemann

Concept The five-storey administrative centre in Clermont-Ferrand with its representative character and 18,000 m2 of usable area ­features a polygonal form that allows it to fit in precisely with the urban context. The reticular facade structure emphasises its sculptural appearance, while the different degrees of public access to the building are represented by different building materials. The two concrete pedestal storeys house public facilities, including the entrance hall, the assembly hall and spaces for citizen services. Above it, three storeys consisting of timber contain offices and various agencies that are not open to the public. The main building access leads past three green ­interior courtyards, naturally ventilated and covered by glazing, and towards which office spaces are oriented. The project is a showcase for sustainable construction in the region. It is highly energy-efficient and, due to the use of renewable materials, also resource-efficient. The load-bearing structure ­consists of Douglas fir from the Auvergne region, where this species has been planted in a targeted manner since the 1950s. Additional benefits include redu­ cing CO2 emissions through short transport routes and providing added value to local businesses.

Load-bearing Structure A three-storey timber frame structure is set on top of a two-storey concrete pedestal and remains visible behind a protective glass curtain wall facade. Glued laminated Douglas fir columns arranged within a 2.50-m grid extend across three storeys. The exposed beams are connected to the columns through slotted steel plates. The building is stiffened by diagonal members in the facade layer and by its concrete core, containing auxiliary rooms, stairs and elevators. In the area of the courtyards,

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10 Meeting room 11 Assembly room 12 Control room, ­interpreter booth 13 Mailroom 14 Copy room 15 Delivery 16 Changing room 17 Pre-archiving 18 Archive 19 Documentation 20 Press room 21 Parliamentarian ­reception area 22 Guest room

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­ olumns are placed behind the building c envelope – in contrast to the facades of the building exterior, where structural members are set between the insulating layer and the exterior glazed surface, visibly apparent as design features. As a result, the primary beams penetrate the thermal envelope of the building, which remains condensate-free, due to the properties of timber. The interior walls comprise wall framing elements. The ceilings are set on top of the primary beams and consist of 14.60-cm thick, continuous cross-laminated timber elements that were prefabricated and assembled including parapets. The individual panels contain bolted shear connections, functioning as plates that bear horizontal forces. Horizontal loads are transferred into the concrete cores via dowelled edge beams. The entire load-bearing structure achieves a fire-resistance rating of 60 minutes.

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The ventilated double facade serves as a climate and acoustic buffer. In winter, it remains closed and reduces heat losses. When outdoor temperatures rise above 26 °C, the glass slats are opened to prevent overheating. Powered blinds for sun protection purposes are located along the three facades exposed to sunlight. The interior courtyards are covered in glazing and also serve as a thermal buffer. In winter, this results in intermediate temperatures. In summer, evaporation from plants supports natural cooling, along with fresh air flowing through the opened glass slats along the facade and the roof openings. The glass slats are controlled centrally, based on changes in temperature, but can also be operated independently and directly from the offices. The southern facades of the atrium spaces are shaded by plants and translucent photovoltaic modules within the glass roof.

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Vertical section, street facade Scale 1:100 Vertical section, courtyard facade Scale 1:20

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  1 Sealant, thermal insulation 60 mm Douglas fir glued laminated timber beam 138/765 mm   2 Insulation glazing: Toughened glass 6 mm + cavity 16 mm + 2≈ 5 mm laminated safety glass Steel Å-beam frame 100 mm Glued laminated timber beam 2≈ 90/360 mm   3 Steel Å-beam 200 mm   4 Steel tension rod stiffener Ø 34 mm   5 Sheet steel facade cladding 1.5 mm Vapour barrier Douglas fir glued laminated timber edge beam 138/1035 mm   6 Douglas fir glued laminated timber column 250/264 mm (F 60), connected to reinforced concrete slab via steel console   7 Wood /aluminium window with insulation glazing: Toughened glass 6 mm + cavity 14 mm + toughened glass 4 mm  8 Ceiling: Carpet flooring 10 mm Gypsum board 3≈ 12.5 mm Impact soundproofing 15 mm Thermal insulation with honeycomb structure 30 mm 5-ply cross-laminated timber ceiling 146 mm (fire resistance 60 minutes)   9 Sheet steel facade cladding 1.5 mm Vapour barrier, OSB 10 mm Wood studs 46/155 mm, inlaid thermal insulation 155 mm, vapour barrier Thermal insulation 60 mm Laminated veneer lumber panel facade stiffener 22 mm, 2.50 m off centre (per column line) 10 Wood blocking horizontal stiffener 60/155 mm 11 Douglas fir glued laminated timber beam 112/355 mm, steel bracket connector to masonry wall, 2.50 off centre 12 Glued laminated timber lateral beam 138/225 mm 13 Douglas fir glued laminated timber edge beam 185/495 mm

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Community Centre St. Gerold, AT 2009

Architects: Cukrowicz Nachbaur Architekten, Bregenz Structural engineers: M+G Ingenieure, Feldkirch

Text: Stefan Krötsch

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C O M M U N I T Y C E N T RE IN ST. GER OLD

Site plan Scale 1:2,000 Sections • Floor plans Scale 1:400 1 Group room 2 Office 3 Storage 4 Kitchenette

 5 Cloakroom  6 Entrance   7 Building services  8 Archive  9 Shop 10 Exercise room 11 Council room 12 Mayor’s office

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including an outdoor area at the foot of the retaining wall. With the exception of the foundation slab and retaining wall, the fourstorey building consists entirely of timber. The structure, facade clad12 load-bearing 2 ding, interior fittings and furnishings comprised of fir constitute a uniform entity, in which every detail consists of wood, up to 1 and including the ventilation ducts.

Located on a steep southern slope above the collegiate church of Sankt Gerold in the Great Walser Valley, the community centre 11 accommodates various public functions of 5 the small town. A high retaining wall along the road delineates an antespace, from which 1 two storeys of the building are prominently 2 visible. The ground floor houses a village shop and a multi-purpose room, while the floor Structural Engineering 3 4 above is home to the local administration. The two storeys below the entrance take 5 The four-storey building6 features a skeleton advantage of the steep hillside, with a frame with columns that remain visible along ­kindergarten and a children’s playgroup the horizontal strip windows facing the

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mountain and the valley. The primary beams are set along four axes on top of the exterior walls parallel to the slope and within the two interior walls bordering the lift. b Dowel laminated timber ceiling elements span between these beams. The solid ­timber columns and beams were intec 9 the load-bearing 10 grated into layer of athe a exterior wall structure already during the prefabrication of the floor-height wall 3 4 5 framing elements. The cross-laminated ­timber lift shaft and the exterior walls d 6 stiffen the building. The roof consists of a beam ceiling. b

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Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber (shell construction) Construction time total

Environmental Concept The Sankt Gerold community centre is a model of environmentally conscious ­construction. The building materials are sourced from the forests of the Great ­Walser Valley and were processed by local carpenters. Except for the lift shaft, solid timber is the exclusive construction material employed for the building; glued woodbased materials were omitted. Wood fibre and sheep wool were used as insulation. Although panel materials were largely avoided, the structure is based on the ­principles of modern timber buildings: diagonal sheathing replaces stiffening panel

4 773 m2 EUR 1.9 mill. (net) 2 weeks 10 months

materials in the walls and dowel laminated timber ceilings serve as adhesive-free solid timber ceilings. Operating energy needs were reduced to a minimum. With its highly insulated building envelope and ventilation featuring heat recovery, the building meets the passive house standard. The exterior walls feature a double layer of insulation – one in the same level as the load-bearing structure and a continuous outer layer that covers the ceiling edges. The roof structure contains three layers of insulation and was designed as a ventilated flat roof. Residual heat is provided by a ­geothermal heat pump.

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C O M M U N I T Y C E N T RE IN ST. GER OLD

1 Roof construction: 2-ply bituminous layer, granular slate surface 5 mm Spruce sheathing, tongue and groove 27/100 mm Timber frame, back ventilation 500 mm PE film temporary roof seal 2 mm Spruce sheathing, butt joints 27/100 mm Blocking to falls 40 – 230 mm, inlaid wood fibre thermal insulation Spruce blocking 180/100 mm Infilled wood fibre thermal insulation Timber beam 220/100 mm Infilled wood fibre thermal insulation Spruce sheathing, tongue and groove 27/100 mm PE film vapour barrier, installation level 110 mm Sheep wool soundproofing 30 mm Trickle protection membrane, black Silver fir battens, untreated 40/36 mm 2  Silver fir window, sanded with triple insulation glazing: Float glass 6 + cavity 16 + float glass 6 + cavity 14 + laminated safety glass 2≈ 6 mm, Ug = 0.6 W/m2K 3 Solid silver fir windowsill, planed

4 Facade: Rough-sawn silver fir siding 30/50 –120 mm Spruce battens, black painted finish 30/50 mm Spruce counterbattens / back ventilation 30/50 mm Wind paper, black Prefabricated element: Diagonal spruce sheathing, tongue and groove 25/80 –150 mm Spruce post 125/60 mm Infilled wood fibre thermal insulation Prefabricated element: diagonal spruce sheathing, tongue and groove 25/80 –150 mm Spruce post 200/60 mm Infilled wood fibre thermal insulation Diagonal spruce sheathing, tongue and groove 25/80 –150 mm, PE film vapour barrier Spruce battens, installation level 40/50 mm, infilled sheep wool thermal insulation, silver fir interior cladding, tongue and groove 5 20/50 –120 mm

5 Floor: Rough-sawn silver fir floorboards, nailed, tongue and groove 27/80 –100 mm Timber stringers 62 mm Infilled loam construction panels Wood fibre impact soundproofing 30 mm Dowel laminated timber 180 mm Installation level Sheep wool soundproofing 40 mm Gypsum fibreboard 15 mm 4 Installation level 36 mm Sheep wool soundproofing 30 mm Trickle protection membrane, black Silver fir slats, untreated 40/35 mm dispersed4 6 Oak grating, untreated 30 mm Stainless steel SHS frame 25/25 mm Plastic pad to falls, black 5 – 25 mm 2-ply bituminous membrane, torched 10 mm Foam glass insulation 120 mm Vapour barrier Dowel laminated timber 100 mm

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Secondary School Diedorf, DE 2015

Architects: ARGE Diedorf – Architekten Hermann ­Kaufmann, Schwarzach; Florian Nagler Architekten, Munich Structural engineers: merz kley partner, Dornbirn

Text: Hermann Kaufmann

Concept The new building for the Schmuttertal secondary school in Diedorf and its roughly 1,000 students is a research and pilot project funded by the German Federal Environmental Foundation. Four buildings – two for classrooms, one for central functions and one for the gym – encircle a courtyard. The timber clad volumes with their slightly sloping roofs and integrated photovoltaic systems refer to the regional agricultural structures and fit in with the sensitive landscape of the Schmuttertal valley, bordering a nature reserve known as the Augsburg Western Woods. The ambitious goals in terms of sustainability and education were

achieved by employing intrinsically architectural means: open spaces for various uses provide room for self-learning and shared learning and, thus, correspond to the new pedagogical concept of learning landscapes. Specifically selected building materials ensure a low-pollution learning environment, while bright rooms with exposed timber structure create a pleasant atmosphere.

Structural Engineering The clear structure of the skeleton frame allows flexible responses to new pedagogical concepts. Columns, beams and rafters ­consist of glued laminated timber with a

white-glazed finish in all buildings and display a uniform appearance. Column rows in 2.70-m intervals create spaces resembling a basilica. As a result, spaces with long spans require no specific solutions. Large glued laminated beams are arranged in a uniform rhythm and span the auditorium and the gym. The purlins of the simple, visible roof structure are set on top of them. The ceilings and the entire building envelope, which meet the passive house standard, were prefabricated as large elements with a length of up to 12 m. The structural top layer of concrete for the timber concrete composite ceilings was poured on site. Installations are laid out vertically within the deep corridor walls bordering the classrooms.

S E C O N D A R Y S C HOOL IN DIEDOR F

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

3 16,046 m2 EUR 35.44 mill. 6 months 24 months

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1 Entrance  /  vestibule 2 Auditorium 3 Stage 4 Library 5 Cafeteria 6 Kitchen 7 Music room 8 Art room

  9 Storage /archive 10 Craft room 11 Physics 12 Biology 13 Chemistry 14 Assembly room 15 Gym 16 Equipment 17 Schoolyard

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Fire Safety and Energy Concept The selected construction type led to minimal clear floor heights. As a result, the buildings belong to building class 3, requiring a fire resistance duration of only 30 minutes. The basis of the zero-energy concept, which also includes user-induced energy consumption, are the passive house concept and a photovoltaic system with more than 1,600 modules and 440-kWp yield, integrated into the large roof surfaces. Two pellet boilers and two buffer tanks holding 7,500 litres each supply sufficient heat. Heat distribution and cooling is pro-

vided by underfloor heating and cooling. A sophisticated concept for daylight use in combination with LEDs and fluorescent lamps limits electric energy consumption. Ventilation losses are minimised by a ventilation system with heat recovery. Only building materials free of pollutants were selected (see “Indoor Air Quality”, p. 32ff.). Lightweight wood-wool acoustic panels alternating with visible timber surfaces characterise the interiors. The achievement of the ambitious project goals was evaluated by the Federal Environmental Foundation in order to apply the model to other school projects as well.

S E C O N D A R Y S C HOOL IN DIEDOR F

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1 Vegetation mat 20 mm, extensive substrate 80 mm Drainage mat filled with substrate 40 mm, storage fleece 10 mm EPDM membrane, root-proof, parallel to parapet 1.3 mm Mineral wool renovation board 20 mm Wood battens 100/60 mm to secure EPDM membrane, infilled rigid mineral wool thermal insulation 60 mm Rigid mineral wool thermal insulation 160 mm Wood battens fastened to rafters 100/160 mm, infilled mineral wool thermal insulation 160 mm Laminated vapour barrier, bituminous separation layer membrane, nailed, laminated veneer lumber plate in edge and column area 51 mm 2 Spruce glued laminated timber rafters, white-glazed finish 100/320 mm 3 Primary beams 240/2000 mm 4 Facade element: spruce vertical siding 30 mm, offset layout, different width (120, 160, 200 mm) Horizontal wood battens 30/50 mm 5 Construction element: vertical wood siding 100/60 mm Wind paper, adhesively bonded joints diffusion-permeable wood fibreboard, hydrophobic treatment 16 mm Wood blocking 60/120 Mineral wool thermal insulation 120 mm Wood studs 60/240, mineral wool thermal insulation OSB (vapour barrier) 18 mm (sd ≥ 20 m) 6 Interior finishes, wainscoting: Perforated birch plywood panel 18 mm Glass fibre protective fabric, acoustic trickle protection fleece, soundproofing Galvanised steel SHS 40 mm and 100/30/2 mm structure, bolted connections Galvanised steel SHS 40/30/2 mm, Galvanised steel angle 35/50/35/3.0 mm mounted to OSB with nail sealing tape 7 Prefabricated parquet 15 mm (5 mm top wear layer) Plywood panel 9 mm, plywood panel 12 mm, PE film separation layer 0.4 mm Plywood strip bed 18 mm, plywood strip bed 18 mm Timber floor joists, elastic bearing 125 mm, underlayment 18 mm Thermal insulation / underfloor heating 100 mm Sealant layer 5 mm, primer Reinforced concrete slab (waterproof) 200 mm XPS thermal insulation 80 mm Levelling layer 50 mm, anti-capillary gravel layer 400 mm

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Vertical section, interior and facades Scale 1:20 1 Roof construction: Extensive green roof substrate 40 mm Drainage filled with substrate 40 mm Storage fleece EPDM sealant, root-proof 10 mm Mineral wool thermal insulation 20 mm Wood battens, infilled rigid mineral wool ­Thermal insulation 60 mm Rigid mineral wool thermal insulation 160 mm Wood battens 100/160 mm Infilled rigid mineral wool thermal insulation 160 mm Prefabricated roof element: Sealant layer Bituminous layer Lightweight wood wool panels in edge and column area 50 mm (otherwise spruce ­three-layer panel) Spruce glued laminated timber rafters, white-glazed finish 100/360 mm 2 Interior gutter 3 Sun protection: aluminium flat slats, white 4 Spruce window, white-glazed finish with triple insulation glazing: 4 mm float glass + 18 mm cavity + 4 mm float glass + 18 mm cavity + 4 mm toughened glass, heat soak-tested

  5 Exterior aluminium windowsill   6 Curtain wall facade element: Spruce vertical siding 30 mm, offset layout, ­different width Wood battens, 40 ≈ 40 mm Exterior wall element: Wood battens, horizontal 40 mm Wood battens, vertical 110 mm Wind paper Diffusion-permeable wood fibreboard, hydrophobic treatment 16 mm Spruce frame Infilled mineral wool thermal insulation 140 mm Spruce frame Infilled mineral wool thermal insulation 220 mm OSB (vapour barrier), adhesively sealed joints 18 mm   7 Interior windowsill, three-layer panel, white-glazed finish   8 Interior ventilation, displacement diffuser   9 Built-in shelving, spruce three-layer panel, white-glazed finish 42 mm 10 Interior wall: Gypsum fibreboard 12.5 mm OSB 18 mm Spruce frame 80/60 mm Infilled mineral wool thermal insulation 80 mm

OSB 18 mm, gypsum fibreboard 12.5 mm 11 Ceiling: Mineral-based coating 5 mm Heating screed, perforated plate 85 mm PE film separation layer Impact soundproofing 30 mm Levelling insulation 50 mm 2-ply PE film separation layer Reinforced concrete 98 –120 mm Ceiling element: OSB sheathing 22 mm Joists 2≈ 180/320 mm Infilled acoustic element: mineral wool thermal ­insulation 40 mm Magnesite-bonded wood wool acoustic panel 12 Fixed glazing, laminated safety glass, 2≈ 12 mm float glass 13 Glued laminated timber edge beams 100/740 mm 14 Floor Mineral based coating 5 mm Heating screed, perforated plate 85 mm PE film separation layer Impact soundproofing 30 mm Levelling insulation 50 mm 2-ply PE film separation layer Reinforced concrete 250 mm Thermal insulation 80 mm 15 Ventilation duct

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European School

Site plan Scale 1:5,000 Section • Floor plans Scale 1:500

Frankfurt am Main, DE 2015 3

Architects: NKBAK, Frankfurt am Main Structural engineers: Bollinger + Grohmann, Frankfurt am Main merz kley partner, Dornbirn

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Text: Wolfgang Huß

Concept In Frankfurt, as in all growing German cities, there is currently a great need for classrooms. With the expansion of the European Central Bank, the European School also reached the limits of its capacity, and the required additional space had to be obtained quickly. The new structure received approval as a temporary building and had to be realised within 17 months – from planning application to occupation. The extension offers room for 400 children ages 3 to 8, who receive supervision within a separate

preschool and a primary school. The room module construction type made it possible to adhere to the very ambitious schedule and meet the key requirement for reuse at a later date. The architects took advantage of the spatial potential of this construction type and combined room modules with corridor ceiling elements and glass facades into differentiated sequences of spaces with alternating single and double-loaded corridors and manifold connections to ex­ terior spaces. The design envisions a future extension of the elementary school on its northern side.

  1 Main building  2 Gym   3 Sports field   4 Container classrooms   5 Primary school and preschool   6 Main entrance  7 Classrooms   8 Staff room   9 Supply room 10 Cafeteria 11 Warming kitchen 12 Storage 13 Exercise room 14 Preschool group room 15 Play hallway

Structural Engineering and Prefabrication The building is defined by module sizes of 3 ≈ 9 m that correspond to the depth of the classrooms. The load-bearing walls of the modules are made of cross-laminated timber, while the ceiling slabs of the corridors are hung between the modules or placed on top of glued laminated timber frame structures. Each classroom consists of three modules, with high performance beech ­lam­inated veneer lumber downstand beams measuring 550 ≈ 220 mm spanning

E U R O P E A N S C H O O L I N F R A NK FUR T A M M A IN

Building parameters Number of storeys Gross floor area (GFA) Construction costs Construction time timber Construction time total

3 1,215 m2 approx. EUR 1.9 mill. (net) 3 months 8 months

them longitudinally. Cross-laminated timber ­ceilings and floors span 3 m transversely. The use of beech LVL beams saved 8 cm of room height per storey ­compared to conventional spruce glued laminated timber. The rigorous use of room modules made it possible to finish the weatherproof shell construction in just three and a half weeks, starting from the foundation slab. The modules were prefabricated complete with interior finishes, windows and building services equipment. Only the floor construction and the aluminium facade were assembled on site, in order to avoid unwanted joints and minimise the ­necessary protective measures for transport. The timber structure took a total of three months to build after completing the foundation slab.

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Fire Safety The three-storey building required a certified fire resistance duration of 30 minutes. The outstanding escape route design with three staircases ensures that two independent escape routes exist at all times for each classroom. This also permitted building exposed timber wall surfaces. Wall surfaces only required a fire protection coating in the staircases. A coloured glazed finish was intended for these areas anyway, in order to meet a request for a little colour and to facilitate orientation in the building.

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Building Services The building services and the climate concept were deliberately kept simple. Code requirements regarding heat transmission are met by moderate thermal insulation and triple glazing. The windows provide ventilation. Facades receiving strong ­sunlight intake are equipped with exterior sun protection. The building is connected to the district heating network, and radiant heating systems are visibly mounted to the ceilings.

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cc Vertical sections • Horizontal section  Scale  1:20   1 Roof construction: Plastic sealant layer, EPS insulation to falls, min. 120 mm, vapour barrier, cross-laminated ­timber 80 mm, mineral wool thermal insulation 50 mm Wood wool acoustic panel 25 mm Beech laminated veneer lumber beam 360/220 mm   2 Sheet metal gutter   3 Sheet aluminium, lacquer finish 1 mm Wind paper, mineral wool thermal insulation 120 mm   4 Beech laminated veneer lumber beam 360/120 mm   5 Wood-aluminium window with fall protection ­integrated into frame   6 Classroom floor: Module 1: linoleum 2.5 mm, laminated particle board 2≈ 16 mm, impact soundproofing panel 25 mm Cross-laminated timber 80 mm, mineral wool thermal insulation 60 mm Module 2: cross-laminated timber 60 mm Mineral wool thermal insulation 60 mm Wood wool acoustic panel 25 mm Beech laminated veneer lumber beam 560/220 mm   7 Cross-laminated timber 100 mm Soundproofing 50 mm, perforated acoustic panel   8 Hallway floor: Linoleum 2.5 mm, laminated particle board 2≈ 16 mm Impact soundproofing panel 25 mm Cross-laminated timber 80 mm, installation space 265 mm, mineral wool thermal insulation 60 mm Wood wool acoustic panel 25 mm   9 Wood blocking 100/200 mm 10 Ground floor: Linoleum 2.5 mm, laminated particle board 2≈ 16 mm Impact soundproofing panel 25 mm Cross-laminated timber 80 mm Mineral wool thermal insulation 80 mm Reinforced concrete slab 300 mm

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Prefabricated module: 11 Wood/aluminium window with fall protection ­integrated into frame 12 Beech laminated veneer lumber column 120/360 mm 13 Cross-laminated timber, white glazed finish 80 mm 14 Beech laminated veneer lumber beam 360/220 mm 15 Ceiling radiator 16 Wood wool acoustic panel 25 mm Mineral wool thermal insulation 50 mm Cross-laminated timber 80 mm, vapour barrier 17 Laminated particle board 2≈ 16 mm Impact soundproofing panel 25 mm, Cross-laminated timber 80 mm Mineral wool thermal insulation 60 mm 18 Beech laminated veneer lumber beam 560/220 mm Construction on site: 19 Aluminium panel, lacquer finish 1 mm, wind paper Mineral wool thermal insulation 120 mm 20 Beech laminated veneer lumber cover panel 21 Plastic sealant layer EPS insulation to falls, min. 120 mm 22 Linoleum 2.5 mm

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School Complex Limeil-Brévannes, FR 2012

Architects: Agence R2K, Grenoble Structural engineers (timber): Holzbau Amann, Weilheim Structural engineers (solid construction): Gaujard Technologie, Avignon

Text: Anne Niemann

Concept The huge timber school complex in Grenoble covers 9,500 m2 of floor area with a cap­ acity of 1,000 children in 50 classes, as well as daycare groups. To provide each of the five institutions (three daycare centres, two elementary schools) with its own identity, each received its own playground, which the classrooms and daycare rooms can access directly. Open passageways illu­ minated from above connect the outdoor areas. The library and the school cafeteria, which also serves as a multi-purpose hall for the local community, are shared by all users. By taking advantage of the large, 4-metre elevation difference on site, the new buildings are limited to a height of three storeys, despite the considerable building density. The flat roofs of the buildings on the lower parts of the site serve as courtyards and open spaces. The only truly vertical building volume is the tall, triangular clock tower – the symbol of the school. The entire building complex was to be completed within a year, which led the planners to opt for a timber structure. Incidentally, this also allowed them to achieve the ambitious sustainability goals.

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Structural Engineering Aside from the lift shafts and construction components in touch with the ground, all of which consist of concrete, the building is built entirely of roughly 2,000 m3 of timber. The cross-laminated timber rib ceiling ­elements are placed on top of a system of timber frame wall elements, columns and glued laminated beams. CLT box elements were used for the roof. Different types of wood were employed for construction. ­Construction components on the interior consist of glued laminated spruce and cross-lamin­ated spruce, while the 20-cm deep exter­ior columns with round cross ­section are comprised of larch. For the

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Floor plan Scale 1:1,000 Section Scale 1:500 1 Schoolyard 2 Classrooms 3 Vestibule 4 Principal’s ­office 5 Staff room

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 6 Library   7 Multi-purpose room   8 Relaxation room   9 Interior courtyard 10 Exercise room 11 Locker room 12 Cafeteria 13 Kitchen 14 Delivery

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facade cladding, the larch battens received a serrated profile, giving the material a look and a feel. The terraces feature heat-treated beech.

Indoor Climate The buildings contain a mechanical venti­ lation system with heat recovery. One third of the windows in the classrooms can be opened manually. Projecting canopies and striking vertically arranged, perforated steel slats with a painted finish provide shade. They are featured only partially along the upper storeys and do not cover the entirety of glazed surfaces. A clerestory strip window remains free of shade and introduces daylight deep into the classrooms. To limit heat intake, the clerestory windows have

been equipped with sun protection glazing. According to simulations, this limits the occurrence of excess temperatures (above 28 °C) to less than 2 % of annual operating hours.

the workshop as well. A total of 108 trucks transported the prefabricated elements from Germany to France where they were installed on site according to a co-ordinated schedule.

Prefabrication and Assembly

Soundproofing and Acoustics

Meticulous planning and logistics were indispensable to maintain the tight schedule. The decisive factor was involving the timber construction company in the planning from the beginning. The CLT ceiling elements spanning up to 7 metres were factorysupplied with finished timber surfaces and built-in absorbers for room acoustics. As a result, on-site interior finishes between floor and ceiling were not required. Service lines were integrated into rib ceiling cavities in

Since some classrooms are located underneath the playgrounds, impact sound­ proofing received particular attention. First, the cavities within the ceiling elements were filled with crushed stone in order to dampen noise. The ceilings had already received acoustic profiles in the workshop, in order to improve indoor acoustics. Concealed behind a filigree layer of silver fir slats, wood fibre insulation serves to absorb sound. Vertical section Horizontal section Scale 1:20   1 Roof structure: Plastic sealant layer (polyolefin) OSB 22 mm Roof beam 200 – 320 mm (3 % to falls) Infilled thermal insulation 200 – 320 mm OSB 15 mm, vapour barrier Prefabricated cross-laminated timber box element 210 mm Cross-laminated timber acoustic panel with ­integrated wood fibre absorber 18 mm   2 Half-round larch battens, grey-glazed finish, highly fire-resistant 81–134 mm /44 – 63 mm counterbattens, wood stud wall 60/80 mm OSB 15 mm Plastic sealant layer (polyolefin)   3 Spruce three-layer panel 19 mm Glued laminated timber beam 180/320 mm,   4 Spruce glued laminated timber column 200 mm   5 Interior ceiling: Flooring (soft) 10 mm Anhydrite screed 50 mm Wood fibreboard 10 mm Cross-laminated timber 109 mm Cavity for ventilation and installations 719 mm Gypsum board 2≈ 12.5 mm   6 Exterior floor: Natural rubber 20 mm Concrete pavers 50 mm Height-adjustable raised floor pedestals Sealant layer OSB 22 mm Lateral roof rafters with three-layer panel 40 mm, spacing 625 mm off-centre Infilled cellulose thermal insulation to falls 260 mm OSB 15 mm Vapour barrier Cross-laminated timber rib element 435 mm Cross-laminated timber acoustic panel, silver fir, with integrated wood fibre absorber 18 mm   7 Fall protection: Steel bar 2≈ 8/100 mm, spacing 1.50 m off-centre Stainless steel wire mesh   8 Roof glazing: post-and-beam construction, laminated safety glass 2 mm Wood slat shade elements 60/100 mm   9 Glued laminated timber beam 180/800 mm 10 Glued laminated timber beam 180/580 mm 11 Ground floor: Flooring 5 mm Liquid screed 5 mm Reinforced concrete ceiling 200 mm Thermal insulation 100 mm 12 Beech decking, thermally treated 30 mm

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Agricultural Training Centre Altmünster, AT 2011

Architects: Fink Thurnher, Bregenz Structural engineers (timber): merz kley partner, Dornbirn Structural engineers (solid construction): Mader & Flatz, Bregenz

Text: Wolfgang Huß

Concept The scheme to provide young farmers with additional education in trade or tourismrelated professions in order to supplement their income took on a concrete form by merging the existing agricultural and housekeeping schools. The agricultural school, located in Altmünster in Upper Austria, was maintained as far as possible and expanded into a square building complex with a maximum length of 70 m and enclosing an interior courtyard. This building type, typical to the region, served to underpin the design concept of a rather introverted

‡  Existing buildings

structure, while at the same time linking and the impressive surrounding landscape of lakes and mountains. This aim was pursued also by creating the meandering access ­patterns, with alternating links to the courtyard and to the exterior. As a result, the monotonous character of an enclosed central hallway was avoided. Functions are layered horizontally. A belowgrade level with a corresponding courtyard contains workshops and rooms for vocational classes. The middle entrance level is reserved for public uses, such as an auditorium, cafeteria and a double-height gym. The upper level houses the school, including

classrooms, staff room, administration and the boarding school dormitory rooms.

Structural Engineering The load-bearing structure comprises a pragmatic mix of timber, steel and concrete. Due to the sloping site, the below-grade ­levels consist of reinforced concrete. The upper storeys feature a frame construction in areas with long spans: the exterior walls contain steel columns with a square cross section, while freestanding steel columns are filled with concrete, for fire safety purposes. Continuous steel beams connect the steel

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 9 Kitchen 10 Food storage 11 Teaching kitchen 12 Dormitory, double room 13 Dormitory, ­four-person room 14 Interior courtyard 15 Principal’s office  / administration 16 Library 17 IT room 18 Classrooms 19 Staff room

Site plan Scale 1:3,000 Floor plans Scale 1:750 1 Auditorium 2 Gym 3 Shop 4 Seminar area / trades 5 Central cloakroom 6 Cafeteria  / serving room 7 Dining area 8 Internet café

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columns. Timber c ­ oncrete composite ­ceilings cover spans ranging from 5 m to 8.50 m. The continuous 120-mm thick layer of concrete in combination with the primary steel beams has a composite load-bearing function. The dowel laminated timber layer below features varying thicknesses ranging from 120 to 240 mm. Cross-laminated ­timber wall plates stiffen the structure. In areas with smaller spans, such as the ­supplemental boarding school dormitory, a similar system finds use. Here, the same ceiling type is set directly on top of the walls, without a steel frame. The roof c­ontains steel primary beams and timber

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secondary beams, with stiffening three-layer panel sheathing on top.

Prefabrication The steel frame was assembled on top of the in-situ concrete below-grade level. The concrete layer on top of the ceilings was poured on site. The wall elements were prefabricated without cladding. The facade cladding partially extends across multiple floors. Like the hung ceilings, it was delivered in the form of elements. The interior finishes of walls were undertaken on site in a conventional manner. Almost all surfaces comprise local silver fir, mostly rough-sawn and untreated. GSEducationalVersion

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Fire Safety The reinforced concrete below-grade level meets REI 90 requirements. The load-bearing components of the two upper storeys correspond to REI 60 requirements. The roof is designed according to REI 30 standards. Two solid construction staircases serve as main escape routes. A 1,200 m2 fire compartment across three ­storeys made it possible to create a central open staircase near the main entrance. Neither encapsulated components, nor a sprinkler system were required.

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1 1 Reinforced concrete 120 mm 2 Shear stud Ø 19, double rows 3 Dowel laminated timber ceiling 200 mm 4 Steel Å-beam 320 mm 5 Steel angle, welded, bolted connection

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11 Facade: Silver fir siding 72/30 mm Battens and counterbattens 60 mm UV-resistant wind seal 7 mm Spruce sheathing 20 mm Wood stud wall 80/370 mm, 5 infilled cellulose thermal insulation 370 mm Spruce sheathing 20 mm Vapour barrier 0.3 mm Gypsum board 12.5 mm (school) Installation level 40 mm Gypsum board 2≈ 12.5 mm (dormitory) Silver fir panelling, untreated 20 mm (school) 12 Timber plate in frame wall 13 Perforated gypsum board ceiling 12.5 mm Sheep wool thermal insulation 50 m Hung ceiling, ceiling clips, clearance 457 mm 14 Roof construction: Extensive green roof, substrate 100 mm Drainage 10 mm Bituminous sealant 2≈ 5 mm Bituminous sealant, self-adhesive, with embedded glass fibre heat protection 3 mm EPS thermal insulation to falls 300 – 500 mm 19 Vapour barrier, laminated 3.8 mm Three-layer panel 40 mm Glued laminated timber beam 360 mm Installation level 290 mm: Sheep wool thermal insulation 30 mm Acoustic fleece 1 mm Hung ceiling, silver fir slats, untreated 30/30 mm 15 Powered sun protection, textile 16 Fixed glazing, wood window, fir, insulated triple glazing, double-sided aluminium clamps, vertical silicone joints 20 17 Upper floor: Silver fir floorboards, untreated 27 mm Timber sleepers Infilled EPS thermal insulation with Underfloor heating 30 mm Impact sound proofing 40 mm Expanded clay fill 53 mm Timber concrete composite ceiling: Reinforced concrete 120 mm with dowel laminated timber element 200 mm Timber substructure for hung ceiling 290 mm Sheep wool impact soundproofing 30 mm Acoustic fleece 1 mm Hung ceiling, silver fir slats, untreated 30 mm 18 Steel Å-beam 200 mm Welded steel angle for load transfer into timber frame wall 19 Ceiling above ground floor: Silver fir floorboards, untreated 27 mm Timber sleepers 12Infilled EPS thermal insulation with  underfloor heating 30 mm Impact sound proofing 40 mm Expanded clay fill 100 mm Reinforced concrete 330 mm Installation level 260 mm: Sheep wool impact soundproofing 30 mm 13 fleece 1 mm Acoustic Hung ceiling, silver fir slats, untreated 30/30 mm 20 Preparation for interior shades

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Student Housing Hamburg, DE 2017

Architects: Sauerbruch Hutton, Berlin Timber structural engineering: merz kley partner, Dornbirn Solid construction structural engineering: Wetzel & von Seht, Hamburg

Text: Stefan Krötsch, Wolfgang Huß

Concept The building, operated by a private investor, is located in Hamburg's Wilhelmsburg neighbourhood. Comprising 371 apartments, the student housing project “Woodie” is currently the largest residential structure consisting of timber room modules. The large number of identical apartments that are manufactured as individual modules renders this construction type economically efficient. The additional expenditure due to the double ceiling and wall structures benefits soundproofing between units and helps avoid other related measures. The main

access to the building consists of a heavily frequented walkway and cycle path. The top floors of the comb-like structure canti­ lever above it. An expressive reinforced concrete platform structure above the mostly open ground floor houses service functions and a café. The E-shaped floor plans of the six upper storeys are, with the exception of the short lateral hallways in the cantilevering areas, accessed by a central corridor. 20 % of rooms are accessible and the related modules are slightly longer than a standard module. The staircases consist of reinforced concrete in order to meet fire safety requirements and to stiffen the build-

ing structure. The corridors comprise pre­ fabricated reinforced concrete elements to which the modules are connected in order to transfer horizontal loads.

Structural Engineering The partition walls between apartments form a parallel shear wall construction type consisting of double cross-laminated timber panels that serve to transmit loads within the timber structure. The cross-laminated timber ceilings are suspended between the parallel shear walls, in order to enable load transfer from floor to floor without trans-

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verse compression in timber ceilings. All vertical loads are transferred from the upper walls to the lower walls via end grain joints of the vertically oriented panel layers. To improve soundproofing, joints are separated by elastomeric bearings.

Construction Process An assembly line with 17 stations served to complete four modules daily. A flat-bed truck transported two modules measuring 6.30 ≈ 3.30 m simultaneously from the production facility in Austria to Hamburg. Due to constrained conditions on site, modules

were delivered to the construction site on demand. Per day, twelve modules were integrated, including the prefabricated concrete components of the corridor structure. All modules were prefabricated complete with windows, doors, flooring, installations and interior finishes. Facade elements and interior corridor wall finishes were installed on site. Immediately following the integration of modules, joints were insulated and sealed, in order to ensure that the timber structure was protected against the weather at all times. Installation ducts were laid out along the corridors. The modules were connected to them from within the corridor without hav-

ing to enter rooms. On-site construction lasted ten months.

Fire Safety The structure belongs to building class 5 with exposed timber surfaces and required building code variants. The load-bearing structure of modules is dimensioned according to burnout as “fire-resistant” (REI 90). Firestops consisting of sheet metal aprons separate the back ventilation layer and extend far beyond the facade exterior, in order to prevent a spread of fire for at least 30 minutes.

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Cross / longitudinal section, timber module Horizontal section, timber module Scale 1:20 1 Natural rubber 0.4 mm Particle board 2≈ 19 mm Impact soundproofing 30 mm PE film, crushed stone fill 60 mm Cross-laminated timber panel 80 mm Mineral wool thermal insulation 70 mm, melting point > 1,000 °C Cross-laminated timber panel 60 mm 2 Elastomeric bearing 3 Natural rubber 0.4 mm Epoxy resin primer Cement screed 50 mm PE film, gypsum load distribution panel 10 mm PE film Levelling fill for installations 115 mm Prefabricated reinforced concrete ceiling element 160 mm 4 Prefabricated reinforced concrete column 20/35 mm 5 Pre-weathered larch facade panel 26 mm Timber substructure / back ventilation 60 mm Sarking layer 3

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Timber substructure  /  thermal i­nsulation 200 mm, melting point > 1,000 °C Cross-laminated timber panel 125 mm 6 Extensive green roof 80 mm Plastic sealant layer Insulation to falls 40-200 mm Thermal insulation 200 mm Bituminous temporary seal Prefabricated reinforced concrete ceiling element 160 mm 7 Sheet aluminium 2 mm Substructure, sarking layer Timber substructure / mineral wool thermal insulation 200 mm, melting point > 1,000 °C Cross-laminated timber panel 125 mm 8 Red Grandis timber window with triple insulation glazing, Ug = 0.6 W/m2K 9 Cross-laminated timber panel 125 mm Gypsum board 15 mm Mineral wool thermal insulation 50 mm, melting point > 1,000 °C gypsum board 15 mm Cross-laminated timber panel 125 mm 1

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Office Building Alpnach, CH 2020

Architects: SEILERLINHART Architekten, Lucerne Structural engineering: ZEO Ingenieurbüro, Alpnach

Text: Manfred Stieglmeier

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Site plan Scale 1:5,000 Floor plans • Sections Scale 1:400 1 Foyer 2 Office 3 Cafeteria 4 Building services 5 Void 6 Meeting room 7 Lounge 8 Exhibition 22 2

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The new administrative building of the Swiss timber construction company Küng is located in Alpnach in the Swiss canton of Obwalden near Lucerne. The building comprises four storeys on a rectangular plan (17.64 ≈ 15.24 m) and embodies the corporate philosophy of building simply with timber, without use of adhesives or compos­ ite materials. In terms of a manifest corpor­ ate identity, the building was erected using the company's own solid timber construc­ tion system. It offers room for 25 staff mem­ bers in single and double office spaces as

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well as meeting rooms, a ground floor ­cafeteria and an exhibition space on the top floor. The double-height entrance hall directs the gaze towards a central access core consisting of sandblasted concrete that houses staircases, lifts, sanitary areas as well as an integrated chimney. The material establishes an appealing contrast to the silver fir slats on the first floor and the beech grid structures of the ceiling under­ sides. The floors are also made of beech – with the exception of the ground floor. The solid timber walls were clad in silver fir with rough-sawn and sanded surfaces. On the exterior, the circumferential balconies, sus­

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pended by use of tension rods, distinguish the appearance of the building – a modern interpretation of the pergola, referring to ­traditional means of construction originating in central Switzerland.

Structural Engineering The construction system is based on a solid timber structure exclusively consisting of dowelled boards, without requiring insulation. Walls comprise two elements with six or seven board layers of 3-cm thickness each (comparable to cross-laminated timber), re­ sulting in an overall wall thickness of 42 cm.

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1 Vertical section • Horizontal section Scale 1:20 1 Roof construction: Canted sheet aluminium 3 mm Timber sheathing 27 mm Counterbattens 60 mm Sealant layer 5 mm Wood fibre thermal insulation 60 mm Wood fibre thermal insulation 120 mm 5-ply solid timber element 260 mm 2 Wall construction: Rough-sawn spruce siding 30 mm 6-ply solid timber element 180 mm 7-ply solid timber element 206 mm 3 Beech parquet 20 mm Grooved solid beech with millings for underfloor heating components 44 mm Wood fibre panel impact soundproofing 60 mm 3-ply spruce grating 150/36 mm Crushed limestone fill Grooved solid beech 60 mm 2-ply beech grating 150/36 mm 4 Access balcony construction: Oak decking 60/120 mm Solid oak beam 250 mm 5 Oak tension rod 100 mm, connected to beech dowels � 20 mm 6 Oak handrail 25/140 mm Steel rod baluster � 5 mm 7 Lime mortar 170 mm Mineral fibreboard 15 mm Dowel laminated timber ceiling 180 mm

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4 1,144 m2 approx. EUR 3.02 mill 36 months 36 months

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Individual board layers are neither adhe­ sively bonded nor feature nail or screw ­connections. Instead, beech dowels are used to join them. In order to counteract overconsumption of high-quality timber, for the inner layers, the construction system makes use of lower-quality spruce, which would otherwise serve as a basis for wood fibre products or for thermal energy recov­ ery. Irregularities in board dimensions do not play a role for creating these layers, since air pockets inside wall elements actu­ ally provide an advantage in terms of thermal insulation. Based on the thermal insulation effect and storage mass capacity of solid timber, thermal insulation is not r­ equired for exterior wall components. Facade cladding consists of rough-sawn spruce and forms a backdrop for the suspended oak struc­ ture of the circumferential balconies. Their filigree construction exclusively features ­dowels and woodworking joints. Only floor­ boards are connected by screws. The width of the access balconies varies depending on cardinal direction and generally increases from top to bottom. The oak tensile struc­ tural members resembling clamps corre­ spondingly feature a slight inclination along the roof edge. The access balconies serve to exit the interiors, as a form of structural timber protection for the facade and as complete sun protection. The roof structure is unique: three interlock­ ing grid load-bearing structures consisting of beech boards (150 ≈ 36 mm) are situ­ ated beneath the parquet flooring and a layer of beech floorboards (width = 44 mm). The grid structure cavities are filled with crushed limestone in order to improve sound­ proofing. Beneath this structure, a layer of grooved beech boards (width = 60 mm) serves as a substructure for a ceiling grid also comprised of beech and featuring lighting and acoustic fleece within its cav­ ities. The building is stiffened by the central reinforced concrete core.

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Agricultural Centre Salez, CH 2019

Architects: Andy Senn Architekt, St. Gallen Structural engineering: merz kley partner, Altenrhein

Text: Stefan Krötsch

Concept Salez, a village in the Rhine valley with a population of 830, is located only a few kilometres from the border between Switzerland and Liechtenstein. The Swiss canton St. Gallen has operated a training centre for agricultural professions here since the 1970s. The existing building ensemble housing administration and workshops was expanded by an L-shaped addition. The two-storey, longitudinal main wing contains rooms for education and training, while a three-storey wing comprises the boarding school dormitory and guest apartments.

As a result, an elongated courtyard was ­created between the new construction and the existing buildings. The two entrances to the new addition are located on the courtyard side at the interface between the education and dormitory wings and at the eastern end of the main longitudinal wing. In the interior, staircases and double-height rooms provide interruptions and changes in orientation to the otherwise strictly linear organisation of the building. Access ­bal­conies in front of the south and west facades provide structural sun protection. Together with the access balconies on the north side of the building, they vividly

express the rhythm of the load-bearing structure with its uninterrupted 2.14-m grid and define the appearance of the building. A central incision on the building volume’s southern side creates space for a covered and, in parts, two-storey terrace that offers gorgeous views towards the surrounding landscape of the Rhine Valley.

Structural Engineering The two-storey, longitudinal main education wing comprises a skeleton frame structure with spruce glued laminate timber columns and beams. Ceiling elements consisting of

A G R I C U L T U R A L C ENTR E IN SA LEZ

Site plan Scale 1:4000 Section • Floor plans Scale 1:750 1 Entrance / vestibule 2 Dining hall 3 Terrace 4 Recreation 5 Teaching kitchen 6 Training room

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 7 Fitness   8 Double room   9 Janitor’s apartment 10 First aid room 11 Cloakroom 12 Delivery 13 Kitchen 14 Food counter 15 Auditorium 16 Group room

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7 6 panels5are set into 4 6-cm thick three-layer this frame. Combined with a 10-cm bthick layer of in-situ concrete, they constitute a b timber-concrete composite construction. This composite construction forms a stiff ceiling plate and ensures necessary stiffness for ceilings spanning up to 8.50 m. The large concrete mass allows maintaining soundproofing requirements between floors of the education wing and also serves as thermal storage mass. The three-storey ­dormitory wing is based on the same construction grid as the main longitudinal wing. Due to the shorter spans, a parallel shear wall construction based on cross-laminated

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timber3 panels finds use, 2with the primary span oriented parallel to the longitudinal facades. For reasons of soundproofing, load-­bearing walls between dormitory rooms are built as cavity walls. As in the school facility, timber concrete composite ceilings featuring cross-laminated timber and in-situ concrete span from wall to wall. To prevent sound transmission between ­storeys, ceilings are separated by a gap, similar to the walls. To create a ceiling plate that stiffens the entire building, ceiling segments are connected by three steel flanges each placed between the cross-laminated timber and the concrete layer.

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Structural Timber Protection In order to ensure that the weathered access balconies remain functional as long as possible, all structural components consist of oak. In addition, the construction is suspended from a cross-laminated timber panel that projects from the roof, which prefents splash or surface water penetration. A steel edge beam ­enables ­linear distribution of point loads from the tensile oak glued laminated timber posts into the cantilevering panel. The oak decking is placed indirectly on top of beams, which feature slotted plate spacers as connectors

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Sarking layer MDF panel 16 mm Timber post 240/120 mm Inlaid mineral wool insulation 240 mm OSB 15 mm Horizontal silver fir siding 15 mm 3 Oak floorboards 120/80 mm Oak blocking 40/100 mm Polymer bearing Oak beam 100/160 mm 4 Upper floor construction: Silver fir floorboards 15 mm Screed 70 mm PE film separation layer Mineral wool soundproofing 20 mm Levelling layer 35 mm Timber concrete composite ceiling: Reinforced concrete 100 mm 5-ply spruce cross-laminated timber flat ceiling 120 mm

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11   5 Oak handrail 50/100 mm   6 Ground floor construction Silver fir floorboards 15 mm Screed 70 mm PE film separation layer Levelling layer 35 mm Thermal insulation 120 mm Bituminous barrier Reinforced concrete 300 mm Non-reinforced concrete ­Levelling layer 50 mm   7 Silver fir sliding shutter 40/40 mm   8 Silver fir fixed triple insulation glazing   9 Ventilation flap, manual ­operation 10 Insect screen 11 Glued laminated timber beam 180/200

12 Silver fir window, triple insulation glazing 13 School wing floor construction: Casein coating 5 mm Screed 70 mm PE film separation layer Mineral wool impact ­Soundproofing 20 mm Levelling insulation 35 mm Reinforced timber concrete composite ceiling 100 mm 3-ply spruce cross-laminated timber flat ceiling 60 mm 14 Acoustic ceiling: Silver fir battens, untreated, ­dispersed placement 18 mm Black fleece Spruce beam 60/150 mm Infilled mineral wool ­soundproofing 30 mm

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2 (school wing) 3 (dormitory wing) 5,730 m2 approx. EUR 29 million 5 months 28 months

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to the tensile posts and the facade. The decking extends laterally across beams and comprises grooved drip edges on its underside that protect beams, and most of all the dowel peg per­forations, from weathering and capillary moisture intrusion.

Low-tech Concept Intelligent building planning and the co­operation of the users in building operations enables reducing building services equipment as far as possible, while still meeting contemporary comfort standards.

Sun ­protection and ventilation are not ­automated, but instead, manually operated by users. The planners also omitted installing active cooling. All building services equipment components, such as heating pipes, radiators or cranks for ventilation flaps are mounted without enclosures to ­simplify the maintenance and replacement of parts. ­Circumferential balconies and robust wood sliding shutters provide sun protection. They offer shade on the longi­ tudinal facades, yet only up to a certain height per floor. A clerestory window remains permanently without cover to

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­ nable natural daylight intake as required. e The ventilation of classrooms is supported by thermal uplift alone. Ventilation shafts on the ground floor and ventilation flaps on the upper floor vent stale indoor air into a buffer zone beneath the roof, protected from rain. Ven­tilation flaps in the facades let fresh air stream into rooms. This, most of all, allows very effective nighttime ventilation. Primarily, screed and solid timber construction components serve as thermal storage mass. As the example shows, timber construction is not an obstacle to building a low tech structure.

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Bank Headquarters Stavanger, NO 2019

Architects: Helen & Hard, Stavanger; SAAHA, Oslo Structural engineering: Création Holz, Herisau; Degree of Freedom, Oslo

Text: Manfred Stieglmeier

Concept The new headquarters of a regional bank in the Norwegian city of Stavanger is one of the largest timber office buildings in Europe and a pioneering modern timber construction. The building volume features an A-shaped plan that is open towards the city centre and mediates between a public park with a concert hall and the traditional, smallscale architecture of neighbouring t­imber and brick buildings. The longitudinal facade with its tranquil design, accentuated by vertical glass fins for sun protection purposes, rises in height from three to seven storeys towards the tip of the building in the east direction. The floor plan is centred around an atrium that introduces light, air and green into the building. The more lively areas of the office functions are oriented towards the atrium, while the quiet workplaces are situated along the exterior facades. The building exterior is defined by a strictly triangular form. In the interior, however, meandering and overlapping timber ramps with organic shapes create a spectacular open staircase sculpture.

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Structural Engineering The timber hybrid building features multiple solid basement levels and four access cores consisting of reinforced concrete. From the ground floor upward, the structure comprises a timber frame with columns and beams resembling tongs that form multi-­ storey load-bearing elements with lateral beams that support cross-laminated timber ceilings. The columns and beams of the two lower floors are built of beech laminated veneer lumber, due to high loads. From the second floor upward, they consist of spruce glued laminated timber and cross-­ laminated timber. Columns and beams are arranged according to a 5.40-m construction grid, which permits flexibility of use. The glued laminated timber columns with

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Site plan Scale 1:2,500 Isometric illustration, construction A B C

Cross-laminated timber ceiling elements Spruce glued laminated timber or beech laminated veneer lumber columns, beams Reinforced concrete

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7 13,500 m2 (above grade) 9,000 m2 (below grade) approx. EUR 40 mill. 12 months 37 months

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Horizontal section Vertical section Scale 1:20   1 Laminated safety glass triple shed glazing 50 mm   2 Beech laminated veneer lumber 50 mm   3 Beech laminated veneer lumber roof edge beam 150/500 mm   4 Floor construction: 8 mm carpet Raised floor pedestals 100 mm Screed 40 mm Impact soundproofing 30 mm Spruce cross-laminated lumber 200 mm Fire protection insulation 100 mm Ash hung ceiling slats   5 Laminated safety glass fin 460/2 mm   6 Prefabricated gutter element Sheet aluminium coping  7 Triple insulation glazing, lacquer finish 50 mm   8 Beech laminated veneer lumber 12 mm   9 Triple insulation glazing 50 mm 10 Beech dowel connector Ø 80 mm 11 Spruce glued laminated timber column 380/500 mm 12 Spruce glued laminated timber beam 190/1045 mm 13 Beech laminated veneer lumber vertical member 105/120 mm 14 Beech laminated veneer lumber windowsill 50 mm 15 Beech laminated veneer lumber 11 14 edge beam 160/920 mm 16 Triple glazing, lacquer finish 50 mm thermal insulation 210 mm 4

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38 ≈ 50-cm cross sections reach from the second floor to the roof and, in part, measure more than 23 m in height. They ­feature recesses for glued laminated timber beams on both sides with bending-resistant connections via beech dowels (width = 8 cm). The spruce glued laminated timber beam tongs with a cross section of 54 ≈ 19 cm include three layers, with the central layer consisting of beech laminated veneer ­lumber in order to increase compressive strength. The organic shapes of joints with visible timber dowels follows the direction of forces and moments. The dowel joints as well as continuous beech LVL ring beams (92 ≈16 cm) serve to stiffen the timber ­structure. Together with the four reinforced concrete access cores and the cross-­ laminated timber ceiling plates (20 cm), they stiffen the building.

Prefabrication The frame structure was completely prefabricated in the workshop. The assembly on site required sufficient weather and moisture protection of the beech LVL construction components. The use of BIM throughout the entire planning process allowed the direct transfer of data sets from BIM modelling during the planning phase into CAM production.

Fire Safety The building corresponds to building class 5. Load-bearing and stiffening construction components that partition spaces require REI 90 fire resistance duration. Dimensioning according to burnout (fire protection certificate) leads to cross sections of construction components larger than required for structural engineering purposes, due to including a combustible layer. In the case of a fire, it guarantees that the remaining cross section, effective in load-bearing terms, meets the required fire resistance duration.

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Authors Hermann Kaufmann born 1955 Univ.-Prof. Dipl.-Ing. certified architect Studied architecture at the Technical University of ­Innsbruck and the Technical University of Vienna 1981–1983 Employed at firm Hiesmayr in Vienna Founded own architectural firm in Schwarzach, ­Vorarlberg in partnership with Christian Lenz, focus on sustainable building and the possibilities of modern (multi-storey) timber construction 1995 –1996 Guest lecturer for Timber Construction at the Liechtenstein Engineering School (LIS) 1998 Visiting professor at Graz University of Technology 2000 Visiting professor at the University of Ljubljana 2002 – 2021 Professorship of Architectural Design and Timber Construction at the Technical University of ­Munich (TUM) Director, hkarchitekten, Hermann Kaufmann + Partner, Schwarzach Stefan Krötsch born 1973 Dipl.-Ing. certified architect, Association of German ­Architects (BDA) 1994 – 2001 Studied architecture at the Technical ­University of Munich and the Wrocław University of ­Science and Technology in Wrocław, Poland 2001– 2003 Employed at bogevischs buero, Munich 2003 – 2005 Project manager at Söldner und Stender ­Architekten, Munich 2005 – 2013 Architekturbüro Stefan Krötsch in Munich 2008 – 2014 Academic councillor at the Chair of ­Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of ­Munich since 2009 Braun Krötsch Architekten in partnership with Florian Braun 2015 – 2018 Junior professor, head of the newly founded Department of Tectonics in Timber Construction, ­Faculty of Architecture at the Technical University of Kaiserslautern (TUK) since 2018 Professor for Building Construction and ­Design, University of Applied Sciences Konstanz 2020 Appointment to the Association of German Architects Bavaria, member of the state executive board and expert on climate-friendly construction since 2020 Klingelhöfer Krötsch Architekten in partnership with Ruth Klingelhöfer-Krötsch Stefan Winter born 1959 Univ.-Prof. Dr.-Ing. 1980 –1982 Apprenticeship in carpentry 1982 –1987 Studied civil engineering at the Technical University of Munich and the Technical University of Darmstadt 1987 –1990 Research assistant at the Institute of Steel Construction and Materials Mechanics and at the ­Institute of Concrete Construction at the Technical ­University of Darmstadt 1990 –1993 Director at the Institute of Carpenters, ­Darmstadt 1993 Founded engineering company bauart Kon­ struktions GmbH & Co. KG, with headquarters in Lauterbach and branches in Munich, Darmstadt and Berlin 1993 – 2003 Expert consultant for the information service Informationsdienst Holz in Hesse 1998 Doctorate at the Technical University of Darmstadt, topic: “Structural behaviour of steel-concrete com­ posite columns made of high tensile steel StE 460” since 2000 Publicly appointed and sworn expert for ­timber construction at the Gießen-Friedberg Chamber of Industry and Commerce (IHK) 2000 – 2003 Chair of Steel and Timber Construction, ­University of Leipzig

2001– 2010 Shareholder at MFPA Leipzig GmbH since 2003 Full professor of Timber Structures and ­Building Construction at the Technical University of Munich since 2006 Test engineer for structural analyses in ­timber construction, Bavaria 2009 – 2012 Finland Distinguished Professor (FiDiPro) at Aalto University, Helsinki since 2012 Chairman of the construction standards ­committee Department 04 “Timber Construction”, member of the DIN Standards Committee Building since 2014 Chairman of the European standards ­committee CEN TC 250 / SC 5 Eurocode 5 – Timber construction – Design and Execution Sonja Geier born 1973 Dr.-Ing. 1991– 2000 Studied architecture at Graz University of Technology 2006 Qualification in International Project Management at Vienna University of Economics and Business 1992 – 2008 Work and project management at various ­architectural and civil engineering firms 2008 – 2012 International and national research projects at AEE INTEC in the area of sustainable buildings and timber construction since 2012 International and national research projects at Lucerne University of Applied Sciences and Arts – Engineering and Architecture (HSLU T&A) in the area of timber construction and planning processes, BIM and circular economy 2018 Doctorate at Technical University of ­Munich in the topic of prefabricated timber construction at the Chair of Architectural Design and Timber Construction, Prof. Hermann Kaufmann since 2018 Deputy head of CC Typology and Planning in Architecture, HSLU T&A Annette Hafner born 1971 Prof. Dr.-Ing. certified architect 1990 –1997 Studied architecture at the Technical University of Munich and ETSAB Barcelona 1998 – 2004 Architect in London and Munich 2004 – 2014 Research assistant at the Chair of Timber Structures and Building Construction, Prof. Winter and head of Certification Body ZQ MPA BAU, Technical University of Munich 2012 Doctorate at the Department of Civil Engineering and Surveying, Technical University of Munich since 2014 Professor at the Chair of Resource-Efficient Building at Ruhr-University Bochum, Department of Civil and Environmental Engineering Wolfgang Huß born 1973 Prof. Dipl.-Ing. Architect 1994 – 2000 Studied architecture at the Technical Uni­ versity of Munich and ETSA Madrid, graduated 2000 2000 – 2007 Architect at SPP Munich 2007– 2016 Teaching and research assistant at the Chair of Architectural Design and Timber C ­ onstruction, Prof. Hermann Kaufmann, Technical U ­ niversity of ­Munich since 2013 HKS architekten (Huß Kühfuss Schühle) since 2016 Professor of Industrialised Construction and Production Technology, Faculty of Architecture and Civil Engineering, Augsburg University of Applied Sciences

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Holger König born 1951 Dipl.-Ing. certified architect, book author 1971–1977 Studied architecture at the Technical University of Munich Promoting environment and health issues in the building sector for over 30 years Maren Kohaus born 1975 Dipl.-Ing. certified architect 1994– 2000 Studied architecture at the Technical University of ­Dortmund, Technical University of Munich, ETSA ­Madrid 2001– 2008 Employed at Allmann Sattler Wappner ­Architekten GmbH, Munich 2008 – 2012 Member of the Executive Board at Allmann Sattler Wappner Architekten, Munich since 2012 Freelance architect, focus on timber construction consultancy since 2012 Research assistant / academic councillor at the Chair of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich (since 2021 Chair of Architecture and ­Timber Construction, Prof. Stephan Birk) 2015 – 2016 Lecturer at the Technical University of ­Munich since 2020 Lecturer at Rosenheim Technical University of Applied Sciences for the Master’s programme Timber Construction and Energy efficient Buildings, studies for professionals Collaboration in the research project dataholz.eu Frank Lattke born 1968 Dipl.-Ing. certified architect, Association of German ­Architects (BDA) Apprenticeship in carpentry, studied architecture at the Technical University of Munich and ETSA Madrid since 2003 own firm in Augsburg (Lattke Architekten) 2002 – 2014 Research assistant at the Chair of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich 2007– 2010 TES EnergyFacade (WoodWisdom ERA Net), from 2011 onward smart TES 2010 – 2014 Collaboration, E2ReBuild 2014 – 2017 Project partner in the leanWOOD research project Klaus Mindrup born 1985 Dr.-Ing. Civil Engineering 2002 – 2006 Apprenticeship and qualification as ­electrician 2008 – 2011 Studied Building Services Technology at the School of Applied Sciences Münster 2011– 2013 Studied Energy-Efficient and Sustainable Construction at the Technical University of Munich 2014 – 2019 Research assistant at the Chair of Timber Structures and Building Construction 2015 – 2020 Doctorate at the Technical University of ­Munich, topic: “Thermally activated solid timber ­elements” 2017– 2019 Team leader for expert planning in building services technology, engineering firm bauart Konstruktions GmbH & Co. KG since 2019 Executive partner, bauart TGA GmbH & Co. KG Lutz Müller born 1969 1989 –1992 Carpentry apprenticeship in Munich 1995 –1999 Studied architecture at Konstanz University of Applied Sciences

1999 – 2001 Employed at Prof. Wolfgang Lauber und Prof. Steidle + Partner, Munich 2001– 2005 Employed at RRP Architekten, Munich 2005 – 2014 Project manager at agmm Architekten, ­Munich 2007 Research assistant at the Chair of Building in the Tropics, Prof. Dr. Wolfgang Lauber, Konstanz University of Applied Sciences 2007– 2009 Graduate studies under Prof. Hans Kollhoff at the ETH Zurich 2011– 2014 Studied art history at Ludwig Maximilian ­University of Munich 2015 Employed at Henn Architekten, Munich since 2015 Assistant at the Chair of Architec­tural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich since 2016 Employed at Gassmann Architekten, Munich Anne Niemann born 1976 Dipl.-Ing. certified architect 1996 – 2002 Studied architecture at the Technical University of Munich, ETSA Madrid and Ben-Gurion University of the Negev 2003 – 2009 Partner at Niemann Ingrisch Architekten, Munich 2006 German Academy Rome Villa Massimo: Fellowship at Casa Baldi, Olevano Romano, Italy 2008 – 2014 Assistant at the Chair of Architec­tural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of Munich 2009 – 2013 Partner at m8architekten, Munich 2014 – 2019 Research assistant at the Chair of ­Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of ­Munich since 2017 Research assistant at the Chair of Architectural Design and Construction, Prof. Florian Nagler, Technical University of Munich Daniel Rüdisser born 1974 Dipl.-Ing. certified engineering physicists and building ­scientist 1994 – 2006 Founder, CARD EDV Entwicklungs- und ­Vertriebsgmbh 2004 – 2012 Founder, iuvaris Software GmbH, development of software for technical-scientific applications 2014 – 2017 Research project manager for heat, humidity and climate at the Laboratory for Building Physics, Graz University of Technology since 2013 Owner of engineering firm HTflux, which ­focuses primarily on developing building physics ­software since 2017 Senior Researcher at AEE – Institute for ­Sustainable Technologies for Buildings, research areas: building physics, solar radiation, thermal ­comfort, heat and moisture transport, building climate, simulations and numerical modelling, BIM Christian Schühle born 1971 Prof. Dipl.-Ing. certified architect 1995 – 2002 Studied architecture at the Technical Uni­ versity of Munich 2000 – 2005 Employed at Herzog & de Meuron in Munich and Basel since 2007 own architecture firm, since 2013 HKS ­architekten (Huß Kuehfuss Schühle) 2010 – 2020 Research assistant at the Chair of Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of ­Munich since 2020 Professor, Building Construction and Design, Munich University of Applied Sciences

Sandra Schuster born 1970 Dipl.-Ing. (FH) certified architect 1989 –1998 Studied at Augsburg University of Applied Sciences and postgraduate studies at the Academy of Fine Arts, master class Prof. Otto Steidle 1998 – 2001 Employed at Cepezed, Delft (NL) and ­Neutelings Riedijk, Rotterdam (NL) since 2000 Teaching activity at TU Delft, Academy of Fine Arts, Nuremberg Tech and Augsburg University of Applied Sciences since 2001 Freelance architect 2001– 2006 RingSchuster Architekten, Munich since 2006 SAS.Architekten, Munich since 2016 Research assistant at the Chair of ­Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of ­Munich (since 2021 Chair of Architecture and ­Timber Construction, Prof. Stephan Birk) since 2019 Director of the network for research and teaching TUMwood Manfred Stieglmeier born 1962 Prof. M Eng architect 1982 –1991 Studied architecture at the Academy of Fine Arts Munich, University of Applied Sciences Munich 1987–1998 Employed at various Munich-based architecture firms, including Auer + Weber, among others 1999 – 2000 Partner, Schmidhuber + Partner since 2000 Freelance architect, own firm in Munich, focus on timber construction (stieglmeier architekten) 2007– 2009 Graduate studies in timber construction for architects at the Rosenheim University of Applied Sciences 2009 – 2021 Research assistant at the Chair of ­Architectural Design and Timber Construction, Prof. Hermann Kaufmann, Technical University of ­Munich 2019 – 2020 Lecturer, Timber Technology and Timber Construction Programme, Salzburg University of ­Applied Sciences since 2021 Professor, Smart Building program, Department of Building Studies, Building Construction and Timber Construction Martin Teibinger born 1972 Dipl.-Ing. Dr. techn. 1992 –1999 Combined studies, Timber Economy, University for Soil Culture and Structural Engineering at the Technical University Vienna 2002 – 2004 Doctorate at TU Vienna 1996 – 2016 Collaboration, Construction Technology ­Department at Holzforschung Austria 2006 – 2016 Head of the Department of Building Physics; research, appraisal and publication activities in the fields of building physics, fire protection and multi-­ storey timber construction since 2016 Sworn and court-certified expert Lecturer, teaching in the fields of building physics, ­timber construction and fire protection at universities, schools of applied sciences, technical colleges Gerd Wegener born 1945 Prof. Dr. Dr. habil. Drs. h.c. TUM Emeritus of Excellence 1993 – 2010 Full professor of Wood Science and Wood Technology and Head of Wood Research Munich (HFM) at the Technical University of Munich More than 400 publications on forestry and wood ­science Visiting professor and expert reviewer around the world Numerous awards and distinctions

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Holzbau Deutschland-Institut e. V. (ed.); Schmidt, Daniel; Bühler, Jörg; Niedermeyer, Johannes; Dederich, Ludger; Niedermeyer, Johannes: Holzschutz – Bau­ liche Maßnahmen. Informationsdienst Holz. Holzbau Handbuch, Series 5 Holzschutz, Part 2 Vorbeugender baulicher Holzschutz, Volume 2. December 2015 Holzbau Deutschland – Verband Niedersächsischer ­Zimmermeister; Holzbau Deutschland Institut e. V. (ed.): Mehrgeschossiges Bauen und Nachverdichtung in der Stadt, Fachtagung Holzbau in Hannover. Informationsdienst Holz. June 2014 Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und pflanzliche Baustoffe. Heidelberg 2012 Hovestadt, Ludger; Hirschberg, Ute; Fritz, Oliver (eds.): Building Information Modeling (BIM). In: Atlas of Digital Architecture – Terminology, Concepts, Methods, Tools, Examples, Phenomena. Basel 2020, p. 507– 526 Isopp, Anne; Gutmann, Eva; Teibinger, Martin; proholz Austria (eds.). In: zuschnitt. Issue 54, Holzdecken. Vienna 2015 Jeska, Simone; Saleh Pascha, Khaled; Hascher, Rainer: Neue Holzbautechnologien. Materialien, Konstruktionen, Bautechnik, Projekte. Basel 2015 Kaufmann, Hermann; Nerdinger, Winfried et al.: Bauen mit Holz: Wege in die Zukunft. Munich 2011 Kelly, Burnham: The prefabrication of houses. A study by the Albert Farwell Bernis Foundation of the prefabrication industry in the United States. Massachussetts Institute of Technology. New York 1951 Keppler, Lars: Bewertung von Decken aus vorgefertigten flächigen Holzbausystemen beim Einsatz im Wohnungsbau unter Berücksichtigung des Kosten­ aspektes. Dissertation. Cottbus 2008 Knaack, Ulrich; Chung-Klatte, Sharon; Hasselbach, Reinhard: Systembau – Prinzipien der Konstruktion. Basel 2012 Knauf, Marcus; Hunkemöller, Raphael; Friedrich, Stefan; Borchert, Herbert; Bauer, Jürgen; Mai, Wolfgang: ­Cluster study, Forst, Holz und Papier in Bayern 2015. Freising 2016 Köhnke, Ernst Ulrich: Schallschutztechnische Aus­ führungsfehler an Holzdecken, Beitrag zum 4. ­HolzBau-Spezial: Akustik und Brandschutz im Holzund Innenausbau (ISB 2013) Bad Wörishofen 2013 Kolb, Josef: Holzbau mit System. Tragkonstruktion und Schichtaufbau der Bauteile, 3rd updated edition. Basel 2010 Kolb, Josef: Systembau mit Holz. Zurich 1992 König, Holger: Ökobilanz-Vergleich von Gebäuden in Holzbauweise im Vergleich zu Standard-Bauweisen bei Neubauten und bei Gebäudemodernisierung. In: Kaufmann, Hermann; Nerdinger, Winfried (eds.): Bauen mit Holz – Wege in die Zukunft. Ergänzung zum gleichnamigen Ausstellungskatalog. Munich 2015 Krieg, Oliver: Roboterfertigung: Entwicklungen und ­Tendenzen im Holzbau. 21. Internationales HolzbauForum 2015, Prolog II Fertigbau-Forum. HolzbauForum. Garmisch-Partenkirchen, 2 December 2015 Kristof, Kora; von Geibler, Justus (eds.): Zukunftsmärkte für das Bauen mit Holz. Leinfelden-Echterdingen 2008 Lückmann, Rudolf: Holzbau-Konstruktionen energie­ effizient, nachhaltig, praxisgerecht. Kissing 2011 Lückmann, Rudolf: Holzbau. Konstruktion – Bauphysik – Projekte. Kissing 2014 Lutze, Michael: LWF Merkblatt 7 – Verfahren der Rundholzlagerung. Bayerische Landesanstalt für Wald und Forstwirtschaft (ed.). Freising 2014 Marutzky, Rainer; Willeitner, Hubert; Radovic, Borimir et al.: Holzschutz – Praxiskommentar zu DIN 68 800 Parts 1 to 4. Berlin / Vienna / Zurich 2013 Meistermann, Alfred: Tragsysteme. Basel 2007 Menz, Sacha (ed.): Drei Bücher über den Bauprozess. Zurich 2014 Müller, Daniel; Eichenberger, Michael; Stenz, Michael: Holzbau vs. Massivbau – Ein umfassender Vergleich zweier Bauweisen im Zusammenhang mit dem SNBS Standard. Federal Office for the Environment FOEN,

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Forest Division (ed.). Aktionsplan Holz. Bern 2015 Paulitsch, Michael; Barbu, Marius C.: Holzwerkstoffe der Moderne. Leinfelden-Echterdingen 2015 Pryce, Will: Die Kunst der Holzarchitektur. Leipzig 2005 Radkau, Joachim: Holz. Wie ein Naturstoff Geschichte schreibt. Munich 2012 Rahm, Peter: Die Vorfabrikation mit Bauelementen – ein verkanntes Potenzial. In: Die Baustellen 10/2015, p. 32 – 36 Rosenberger, Michael; Weigl, Norbert (eds.): Über Nutzen und Würde von Wald und Holz. Überlegungen zur Verantwortung im Umgang mit einer zentralen ­Lebensgrundlage. Munich 2014 Rüter, Sebastian; Diederichs, Stefan: Ökobilanz-­ Basisdaten für Bauprodukte aus Holz. Arbeitsbericht aus dem Institut für Holztechnologie, No. 01/2012, Johann Heinrich von Thünen Institute. Hamburg 2012 Rüter, Sebastian: Projection of Net-Emissions from ­Harvested Wood Products in European Countries – For the period 2013 – 2020. Arbeitsbericht aus dem Institut für Holztechnologie und Holzbiologie No. 2015/1, Johann Heinrich von Thünen Institute. Hamburg 2015 Salthammer, Tunga; Marutzky, Rainer: Bauen und Leben mit Holz, Informationsdienst Holz – Special issue, March 2013 Sathre, Roger; O’Connor, Jennifer: Meta-analysis of greenhouse gas displacement factors of wood product substitution. In: Environmental Science & Policy 13, 2010, p. 104 –114 Schankula, Arthur: Vorgefertigtes Bauen mit Holz. In: Detail 06/2012, p. 662– 669 Scheer, Claus; Andresen, Kurt: Holzbau-Taschenbuch, vol. 1, Grundlagen, Entwurf, Bemessung und Konstruktionen. Berlin 1995 Scheer, Claus; Peter, Mandy: Holz Brandschutz Handbuch. Informationsdienst Holz and Deutsche Gesell­ schaft für Holzforschung e. V. Berlin 2009 Schindler, Christoph: Ein architektonisches Periodisie­ rungsmodell anhand fertigungstechnischer Kriterien dargestellt am Holzbau. Dissertation. ETH Zurich, 2009 Schittich, Christian: Vorfertigung – High-Tech und Handarbeit. In: Detail 06/2012, p. 588 – 593 Schmidt, Hans: Vom neuen Bauen: Industrialisierung des Bauens: aus der Wegleitung des Kunstgewerbemuseums der Stadt Zurich. In: Das Werk: Architektur und Kunst = L'oeuvre: architecture et art, 15th volume, 1928, p. 34 – 37. Accessible online at: www.e-periodica.ch/cntmng?pid=wbw-002:1928:15::808 Schulze, Dieter: Wohnbauten in Fertigteilbauweise ­(Baujahre 1958 –1990). Stuttgart 1995 Staib, Gerald, Dörrhöfer, Andreas, Rosenthal, Markus: Elemente + Systeme modulares Bauen: Entwurf, ­Konstruktion, neue Technologien. Munich 2008 Steiger, Ludwig: Basics Holzbau. Revised and updated new edition. Basel 2013 Stein, René et al.: Konstruktionskatalog Fassaden­ elemente für Hybridbauweisen. Technical University of Munich, 2016 (unpublished) Steurer, Anton: Entwicklung im Ingenieurholzbau. Der Schweizer Beitrag. Basel 2006 Studiengemeinschaft Holzleimbau e. V. (ed.); Mestek, Peter; Werther, Norman; Winter, Stefan: Bauen mit Brettsperrholz. Informationsdienst Holz. Holzbau Handbuch. Series 4, Part 6, Volume 1. April 2010 Technical University of Munich, Chair of timber con­ struction and structural design; Winter, Stefan; Merk, Michael et al.: Erarbeitung weiterführender ­Konstruktionsregeln /-details für mehrgeschossige Gebäude in Holzbauweise der Gebäudeklasse. 4 August 2014 Teibinger, Martin; Dolezal, Franz; Matzinger, Irmgard; Holzforschung Austria (eds.): Deckenkonstruktionen für den mehrgeschossigen Holzbau. Vienna 2014 Teibinger, Martin; Matzinger, Irmgard; Holzforschung Austria (eds.): Bauen mit Brettsperrholz im Geschoß­ bau – Fokus Bauphysik. Vienna 2013 Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz;

Holzforschung Austria (eds.): Bauen mit Brettsperrholz im Geschoßbau – Fokus Bauphysik. Planning brochure. 2nd revised edition. Vienna 2014 Teibinger, Martin; Matzinger, Irmgard; Dolezal, Franz; Holzforschung Austria (eds.): Holzrahmenbauweise im Geschossbau – Fokus Bauphysik. Planning brochure. Vienna 2014 The European Cement Association: CEMBUREAU, Cement & Concrete: Key facts & figures 2014 The International Aluminium Institute: Historical Aluminium Inventories (1973 – 2014). London 2014 Verband Holzfaser Dämmstoffe e. V. (ed.) Förster, F.; Mosch, M.; Wiegand, T.: Holzfaserdämmstoffe, Eigenschaften – Anforderungen – Anwendungen. Infor­ mationsdienst Holz. Holzbau Handbuch. Series 4 Baustoffe, Part 5 Dämmstoffe, Volume 2. December 2007 von Carlowitz, Hans Carl; Hamberger, Joachim (eds.): Sylvicultura oeconomica oder Haußwirthliche Nachricht und Naturmäßige Anweisung zur Wilden Baum-Zucht. Munich 2013 Wehrmann, Wiebke; Torno, Stefan: Laubholz für tragende Konstruktionen. Zusammenstellung zum Stand von Forschung und Entwicklung. Cluster-Initiative Forst und Holz in Bayern GmbH (eds.). Freising 2015 Westphal, Tim; Hermann, Eva Maria: BIM Building ­Information Modeling I Management – Methoden und Strategien für den Planungsprozess. Beispiele aus der Praxis. Munich 2015 Winter, Stefan; Merk, Michael: Verbundforschungs­ projekte Holzbau der Zukunft – Partial Project TP 02 – Brandsicherheit im mehrgeschossigen Holzbau. ­Technical University of Munich, Chair of Timber ­Construction and Structural Design. Munich 2009 Winter, Wolfgang: Wiederentdeckung des Holzbaues im urbanen Kontext – das Beispiel Wien. In: Standards der Zukunft. Wohnbau neu gedacht. Roland Burgard (ed.). Vienna 2008, p. 86 –103

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Glossary Acetylation Chemical modification of wood using acetic anhydride in order to prevent wood-destroying fungi or insect ­infestation, to reduce timber moisture absorption and to minimise swelling and shrinking. It increases the ­durability of timber areas exposed to weather and ­moisture. Airborne sound Sound transmitted by air. Airtight layer The airtight layer in a construction component (usu­ ally the building envelope) bordering different temper­ature levels serves to prevent air convection through and within the construction component. It prevents ­energy losses caused by warm interior air exiting the component and damage to the construction component from moisture due to the permeation of warm, moist interior air and condensation of moisture on cold surfaces. Airtight layers in interior construction ­components primarily have the function of preventing the transmission of airborne noise and obstructing smoke and fire. They are usually identical with the ­vapour barrier / vapour-retardant layer. Often made of airtight, composite wood-based panels that inhibit ­diffusion (OSB, three-layer panels or parallel strand ­lumber) with adhesive joints between panels to create an airtight surface. Airtightness Buildings must now demonstrate airtightness to prevent heat losses, damage due to moisture and sound transmission. The airtightness of a building should be tested during construction and /or renovation (with a blower door test and measures to locate leaks). A continuous airtight layer in the building envelope or between building sections will ensure airtightness. Anisotropy Directional dependency of certain physical properties. In timber construction, this usually refers to the varying characteristics of wood in relation to parallel or perpendicular fibre orientation. Annual heating requirement A measurement of the amount of heat in kilowatt-hours per square metre per year (kWh/m2a) required to ­maintain a pleasant interior temperature. It is based on a balance of heat gains and losses occurring in a building. Battens Defined in DIN 4074-1 as sawn timber up to 40-mm thick and up to 80-mm wide; for roof battens: 24/48, 30/50, 40/60 mm. Beam Horizontal linear element in a ceiling structure, typically within the layer of a frame, beams or joists. Individual beams or joists or primary parts of a frame structure are referred to as beams. Building Information Modelling (BIM) Method of optimising construction processes using a digital three-dimensional model of the building over its entire life cycle, from planning to demolition. Blower door test A test that measures the airtightness of building en­ velopes and identifies leaks by creating positive and ­negative pressure in a building. An important tool in ­determining the quality of a building. Board Sawn lumber up to 40-mm thick and more than 79-mm wide (DIN 4074-1). DIN 4070-1 specifies rough sawn board thicknesses of 16, 18, 22, 24, 28 and 38 mm.

Bottom plate Horizontal member at the bottom of a timber frame ­structure, stud frame or wall framing construction. Also a horizontally arranged bottom support beam in a timber structure. Usually squared solid wood or glulam, sometimes also hardwood or parallel strand lumber, when ­absorbing higher compressive loads is necessary (see also transverse compression). Box girder Beam or girder with a square, hollow cross section consisting of a top flange, a bottom flange and two webs. They can consist of boards, panel materials or glulam. Box slab / box slab element Ceiling structures consisting of box slab elements. The elements are made of slender ribs that follow the main span direction of the slab. Combined with edge beams, they form a frame structure to which sheathing is applied, making them structurally effective. From a structural engineering perspective, the individual components comprise a composite element, a box. Bracing Diagonally arranged linear member, installed by a ­carpenter to stabilise a frame structure. Set between a horizontal (beam, plate) and a vertical construction component (post, column, stud) at each storey (e.g. within a stud wall). A top diagonal brace is placed ­underneath a roof beam, while a bottom diagonal brace is set on top of a bottom plate. The installation of top ­diagonal braces is more common than bottom diagonal braces. Bulk density The proportion of mass to volume (g/cm3 or kg/m3) of wood at a specific temperature and humidity. Its density varies depending on the moisture content of wood. ­Normal density is determined at 20 °C and 65 % humid­ ity after storage, while kiln-dried wood is absolutely dry (0 % wood moisture content). CAD (Computer Aided Design) Computer-aided design and planning. CAM (Computer Aided Manufacturing) Computer-aided manufacturing. Carbon store Storage of carbon as a material. Timber products store carbon temporarily, because a tree absorbs carbon ­dioxide (CO2) from the atmosphere as it grows, storing it as carbon (C) until the wood is burnt, which releases carbon as CO2. Cellulose Cellulose is the main constituent of wood and, together with lignin and hemicellulose, forms the structural substance of cell walls and the raw material used for making paper. One frequent application of cellulose in timber construction is in cellulose insulation, which can be ­installed as blown-in insulation in the cavities of wall framing construction elements. It is an inexpensive and high-quality ecological material. Climate neutrality / climate-neutral Processes are described as “climate-neutral” when no gases that impact the climate are released or the amount of gas emitted is conserved elsewhere in the process, i.e. emissions do not change the atmospheric balance of gases. This evaluation is based on emissions of climaterelevant gases, especially CO2 (measured in GWP 100). CNC (Computerised Numerical Control) Electronic process used to control tooling machines, which are able to automatically process complex parts with high precision. Industrial looms were the precursors of today’s CNC machines.

CNC milling machines Tooling machines that use modern control technologies to automatically make parts, including complex forms, with great precision. Most milling machines can be fitted by means of tool changers with various milling machine tools, saw blades, drills and other special tools. Column Linear, vertical, load-bearing construction component, e.g. a vertical element in a frame structure or support for a beam. In timber construction, the term column is often used synonymously with post or pillar. Composite construction Construction component or construction element, the load-bearing capacity of which is based on the intrinsic interaction between various individual parts, e.g. a timber slab structure with a top layer of concrete as the tensile and compressive zone of a composite timber concrete slab, or the ribs and sheathing of a box slab ­element. Condensation Transition of material from a gaseous to a liquid state. In construction, condensation formation usually refers to the cooling of interior air in a construction component or along cool surfaces. Condensation forms when the temperature falls below the dew point, which can cause damage to a construction component and health problems (mould). Condensation usually results from leaks in the airtight layer of the building envelope or in and around thermal bridges. Construction component Prefabricated component of a construction element, e.g. of a wall framing construction element as part of an exterior wall, of a dowel laminated timber slab or panel element as part of a floor or ceiling slab, etc. Construction element Structural, geometrically self-contained part of a building, e.g. exterior and interior walls, floor and ceiling slabs, floor slab and roof. Construction components can be individual pieces or comprised of prefabricated construction components. Construction type Generalisable construction principle for the load-bearing structure of a building (e.g. frame, crosswall or parallel shear wall construction), materials (e.g. timber or hybrid construction), degree of prefabrication and assembly (e.g. wall framing or module construction) or structural use of materials (e.g. lightweight or solid construction). Convection The term generally refers to phenomena partial to flow processes. In construction, the term typically refers to the transport of heat and /or water vapour. Convection of interior air through a building envelope can result in considerable energy loss and produce large quantities of condensation within construction components. Water vapour convection can result in much larger amounts of condensation than water vapour diffusion. Counterbattens Battens installed perpendicular to the main support ­battens, making it possible to use horizontal battens to construct a continuous rear ventilation cavity. Cross-laminated timber – CLT Planar construction elements made of an odd number of layers of boards up to 40 cm thick that are laid out cross-wise and laminated. Various manufacturers supply different formats. Dew point Short for “dew point temperature”. Condensation can form in construction components when the temperature

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falls below this point. The dew point temperature depends on the ambient air temperature and humidity. Diffusion Physical process of complete mixing of various substances until their particles are evenly distributed. In construction, diffusion typically refers to the material transport of water vapour through an exterior construction component when interior air is moist and outside air is dry in winter. Condensation can form in construction components that are not properly built. The diffusion ­resistance of layers of exterior construction components should decrease from the inside towards the exterior. Dowel laminated timber Material used to create construction components consisting of boards or beams (squared timber) that are stacked, nailed or dowelled together (with hardwood dowels). Slabs made of horizontal dowel laminated timber ele­ ments are called glued dowel laminated timber slabs. Drying, artificial or technical Drying or curing under artificial climatic conditions, ­usually in a chamber kiln or flow channel. It can result in much lower final moisture levels and shorter drying times than natural or air drying. Drying, natural or air drying Drying or curing of wood without using artificially produced thermal energy or dehumidification. A gentle ­drying method carried out mainly in well-ventilated rooms or the exterior, protected from the weather. ­Usually used for pre-drying. Depending on the degree of drying required, this can take 6 months to 2 years. Effective storage mass Alternative term for areic effective thermal capacity (as defined in E DIN EN ISO 13 786:2015-06). It describes the ability of a construction component to absorb and ­release thermal energy as temperature fluctuates over a 24-hour cycle. This is especially relevant for thermal ­insulation in summer, when it can be used to reduce or prevent overheating. Elastic modulus (E-modulus) The measure of the resistance of a substance or object to elastic deformation under mechanical stress or loading in its elastic deformation range. Encapsulation Fire protection panelling with a protection period specified in minutes (capsule criterion, e.g. K2 30 or K2 60). ­Encapsulation limits the temperature on the side not ­directly exposed to fire to T ≤ 300 °C for the period specified, thereby preventing wood from burning and adding to the fire load. Encapsulating panelling should also prevent fire from penetrating into structures made of panel construction elements with insulated or uninsulated cavities. End grain wood Wood with a cut surface perpendicular to the direction of its fibres. End grain wood absorbs moisture very well through capillary action. It requires particular protection in construction components exposed to weathering. Compressive forces between construction components can be optimally transferred through joints in end grain wood surfaces without compression on crosspieces. Energy source, fossil Energy sources containing carbon, such as oil or brown coal, which formed in the Earth’s geological past. Energy source, renewable Renewable energy sources such as wood are continuously renewed (e.g. from forestry) when the energy source is used sustainably. As a result, they are per­ manently available.

Exposed surface quality Refers to the suitability of a construction element for use in its exposed form in the finished structure.

framing construction elements made of linear members (studs, bottom plate, top plate), box slab or box slab ­elements.

Facade, not ventilated Exterior wall structure, in which the facade surface is joined to the insulating layer without any gaps, e.g. a composite thermal insulation system or sandwich ele­ ment (DIN 68 800-2).

Frame construction Construction method, in which loads are supported by a load-bearing structure, i.e. a frame consisting of columns and beams. The building envelope and ­interior sheathing are independent of the load-bearing structure. They can be either created on the building site or comprise prefabricated, non-load-bearing wall ­elements.

Facade, back-ventilated Exterior wall structure, in which there is an uninterrupted vertical back ventilation cavity with an appropriate thickness (usually 2 cm; see DIN 68 800-2) between the insulating layer and the facade surface and through which large amounts of air can flow through openings with a suitable cross section (usually at least 50 % of the back ventilation cavity) along their top and bottom, based on the chimney effect. Facade, ventilated Exterior wall structure, in which there is an uninterrupted vertical back ventilation cavity with an appropriate thickness (usually 2 cm; see DIN 68 800-2) between the insulating layer and facade surface. Condensation can drain from the rear ventilation cavity and an exchange of air occurs through openings along the bottom. Finger joint Longitudinal joint between two solid wood or woodbased material construction components, a further ­development of the scarf joints used to join boards and beams since prehistoric times. A finger joint is ­usually also glued. Its tensile strength derives from the increased surface of the glued joint, which slopes slightly in the same direction as wood fibres. Fingerjointed construction components have relatively high flexural or bending strength. When they are created under optimum production and quality assurance conditions, they can almost achieve the load-bearing capacity of construction components made of solid timber grown naturally in one piece. Fire resistance Stipulated period during which a construction component so designated retains its load-bearing (R) and /or space-enclosing (E) and /or insulating (I) functions in the event of fire. Firestop Prevents the uncontrolled spread of a fire (e.g. in shafts, back ventilation cavities). Floorboards Boards at least 21– 50-mm thick and relatively wide (more than 80 mm). DIN EN 13 629 defines floorboards less than 40-mm thick as boards and thicker ones as planks. Footfall or impact sound Airborne sound caused by structure-borne impact sound in an adjoining space, e.g. when a slab vibrates, because of someone walking along or jumping on top of it. Formaldehyde Formaldehyde (systematic chemical name: methanal) is a gaseous substance at room temperature. Its low boiling point (-19 °C) means that, by definition, it does not belong to the group of VOCs, but to the group of V VOCs (very volatile organic compounds, which vaporise at a boiling point < 0 to 50 … 100 °C). Formaldehyde has been used to make and process industrial products for almost 150 years. In 2016, the EU classified it as carcinogenic in animal experiments (1B). Frame Structure made of linear construction elements, e.g. stud walls, frame structures, space frames and wall

Girder A linear, horizontal element laid on supports erected at various points that transfers vertical loads into columns or walls. Glued laminated timber /Glulam Linear cross sections consisting of glued boards (layers or veneers) laid out in the same direction, normally 40 mm thick and up to 30 cm wide. The depth of nonblock-glued cross sections is approx. 200 cm. Boards can be up to 65 metres long, depending on the manufacturer. The maximum radius of curved glulam beams depends on the thickness of their layers. Grey energy Energy used in the manufacture, storage, transport, ­installation and disposal of materials, construction components and buildings. Header Linear element for deflecting loads in frame structures, ribbed and box ceilings, in wall framing construction and in roof structures. Heartwood The inner core of a tree trunk that is surrounded by ­concentric rings of sapwood, often distinguished by its darker colour. Unlike sapwood, it does not transport water or nutrients. Hollow box Slab structure consisting of ribs and structurally effective sheathing (see box slab). Hybrid building Structures consisting of different construction materials can be combined within a single building, such as a ­reinforced concrete access core (for emergency exits, building stiffening) integrated into a timber building or a timber element facade on a reinforced concrete frame structure. Hybrid construction component Various materials are combined to create certain ­horizontal or vertical construction components. The ­best-known example is the timber concrete composite slab. Hybrid construction type Hybrid construction components or elements made of different materials can be systematically used within a single structure, e.g. steel beams in cross-laminated timber slab elements. Å-joist Beam with a typically Å-shaped cross section. Its geometry comprises a top flange, a bottom flange and a web. The bottom flange absorbs tensile forces and the top flange absorbs compressive forces resulting from the bending moment of the beam, while the web is mainly subject to shear forces. In-plane loading Loading or stress imposed on a planar construction component perpendicular to its plane.

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Indoor climate A term referring to all the conditions in a space that can impact the well-being and performance of its users. These conditions are influenced by air temperature, ­humidity and air velocity, the content of contaminants in the air, the temperatures of the surfaces of a room and its lighting situation.

Oriented strand board – OSB Structured board made of oriented, long, thin wood shavings (strands) usually with good load-bearing ­capacity, available in different thicknesses and vari­ ations (impregnated, with bevelled or tongue and groove edges). Originally made of by-products from the veneer and plywood industries.

Inhomogeneity The inhomogeneity of wood refers to the irregularity of its mechanical, structural and physical properties, due to factors such as knotholes, resin pockets, uneven fibre orientation and varying densities and strength. One of the goals in sorting solid wood and manufactured woodbased materials into types such as solid structural timber, dowel laminated timber elements, layered and veneered, fibre and chip and shaving materials is to ensure that the resulting timber product will be homogeneous.

Panelling Planar structures made of boards for cladding or sheathing timber structures.

Intumescent products Intumescent products foam up to close off any openings when they are subject to heat loads, thereby preventing smoke and toxic gases (fire safety) from passing through them.

Passive house, passive house standard Energy standard for buildings that can produce a ­comfortable indoor climate without a separate heating and air conditioning system. Annual heating requirement according to the PHPP (Passive House Planning Package) is max. 15 kWh/m2a; annual primary energy requirement (heating, hot water, household electricity) is max. 120 kWh/m2a. Demands on the building envelope: opaque exterior construction component with U  2 to 1,500 m) and vapour barriers (sd > 1,500 m). Solid construction-grade timber Finished timber that meets high demands in terms of its moisture content (15 % ± 3 %), cut type (free of heartwood or with heartwood separate) and surface finish (planed, bevelled). Solid structural timber can be fingerjointed (major inhomogeneities are eliminated) to make greater lengths available. Solid timber Wood with its structure unchanged as it has grown, in contrast to wood-based materials, which are made by reducing wood to small pieces that are bonded together. Solid timber construction Block or log construction types, or dowel laminated timber element structures made of large-format panel ma­ terials, such as cross-laminated timber or glulam, etc.

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Squared timber Lumber with a cross section at least 40 mm wide (b) and a depth (h) of b ≥ h ≥ 3 b (DIN 4074-1). Squared timber stock measures 60/60 mm to 160/180 mm. Structure-borne sound Sound created by the stimulation or excitation of solid bodies, partly emitted as airborne sound. Stud Vertical element running from the top plate to the bottom plate of a stud wall, frame wall or wall framing construction element. Mostly used as squared timber made of solid wood. Swelling and shrinking Wood is hygroscopic. It swells when it absorbs moisture and shrinks when it releases it. Its dimensions and form, thus, change. These changes are much greater perpendicular to the direction of its fibres than they are parallel to the direction of its fibres. Extensive swelling and shrinking can result in gaps, cracks, warps or bulges. Swelling / Shrinkage values Figures measuring the changes in length or volume of wood as caused by swelling or shrinking. They are ­expressed as percentages that describe the response of wood when it is in a dry state (and swells) or in a wet state (and shrinks). Swelling and shrinkage values are specified for three main cutting directions. Changes to length or in the direction of wood fibres are slight, while radial changes (in the direction of rays) are 10 to 20 times greater and tangential changes 15 to 30 times greater. Wood swells to its maximum, only when its fibres are completely saturated.

Timber preservation, physical The durability of wood and wood-based materials can be improved by means of e.g. thermal treatment. Timber preservation, structural Structural and geometric measures to keep wood and wood-based materials dry (e.g. covering wood with ­suitable panelling, protecting it from the weather with a roof overhang, keeping it away from areas exposed to splash water, mechanically separating it from moisture that could reach it through capillary action, by installing separating layers etc.). Examples of such structures are listed in the standards on structural timber preservation measures for buildings (DIN 68 800-2). Timber wall framing Variant of typical North American frame construction, ­re-imported to and further developed in Central Europe. Timber wall framing as a frame construction type resembles panel construction, but a conceptual distinction is made between the two construction types to avoid confusion with products of the prefabricated housing ­industry. Top plate Top horizontal member in a timber frame or wall framing construction element. It has the function of horizontally stiffening the structure, transferring horizontal shear ­forces through diagonal linear members and vertical forces through studs into the bottom plate or foundations. A top plate also supports the frame structure of joists and beams (as a support for rafters, it is also called a roof beam or purlin). Total energy balance A measurement of the amount of energy required for the construction, use and demolition of a building.

Thermal comfort Thermal comfort is a result of the interior air temperature, the temperatures of surfaces enclosing spaces, the transmission of heat by floor surfaces, air velocity and relative humidity of interior air. Individual users’ perception of comfort also depends on their activity, clothing, age, state of health and habits.

Total volatile organic compounds – TVOCs The total of all the VOCs measured in interior air.

Thermal energy storage capacity The amount of energy that a building material can store during a specific period. Wood has significant thermal energy storage capacity, because of its good ratio of thermal conductivity to density.

U-value The thermal transmission coefficient (U-value) describes the flow of heat through 1 m2 of a construction component that occurs at a temperature difference of 1° Kelvin. The physical unit is W/m2K.

Thermal uplift The different density of warm and cold air causes ­differences in pressure. In winter, this leads to growing internal pressure being exerted on a building envelope in relation to building height. This increases the risk of ­interior air penetrating the structure (e.g. around ceiling joints or windows) and causing condensation within ­construction components.

Vapour-retardant layer Layer in a construction component (usually the building envelope) between different temperature levels with a high sd value (> 2 m up to 1,500 m) to reduce water ­vapour diffusion through the component. Installed on the room side of thermal insulation to protect against damaging condensation in construction components and against moisture penetrating into thermal insulation and causing structural damage. Often made of airtight, diffusion-resistant wood-based material boards (OSB, three-layer panel or LVL) with adhesive joints between panels to make them airtight. The vapour barrier usually also serves as an airtight layer.

Timber framing A further development of the medieval half-timbered construction, with structures no longer braced by means of diagonal members or top or bottom diag­ onal braces, but instead, by sheathing mounted on a frame structure. Studs, the vertical, load-bearing ele­ ments of a frame structure, feature a square, slender cross section. Timber preservation, chemical Treating wood with biocides can help prevent it from being destroyed by fungi or insects. Use of these ­chemicals is regulated in the relevant standards (e.g. DIN 68 800-3). Chemical preservatives should be used as sparingly as possible, because disposing of such chemically treated timber can be costly, complex and detrimental to the environment.

Tube-in-tube system Load-bearing structure that consists of two concentric layers of load-bearing or stiffening walls joined by ­structural slabs.

Vapour-retardant layer, moisture-adaptive The vapour barrier diffusion resistance varies depending on the ambient humidity and material. In a dry ambient atmosphere (an interior in winter), it will have a higher sd value (up to sd = 10 m). When humidity levels are higher (e.g. in summer), its diffusion resistance will fall (to sd = 0.2 m). Vapour barrier (not permeable) Layer in a construction component (usually an exterior construction component) between different temperature levels with a very high sd value (>1,500 m) to

r­ educe vapour diffusion through the component. ­Installed on the room side of thermal insulation to protect against destructive condensation in components and against moisture from penetrating insulation and causing structural damage. Usually bituminous sheeting with a layer of aluminium. It also serves as an airtight layer. Veneer plywood Wood-based material consisting of multiple veneer ­layers that are laid out by rotating each layer by 90° and adhesively bonded with phenol-formaldehyde resin to form watertight panels. Volatile organic compounds – VOCs Volatile organic compounds is the collective term for ­organic substances containing carbon that vaporise easily and, thus, are volatile, meaning that they ­become gaseous at low temperatures, e.g. room temperature. Compounds consisting of natural raw mater­ ials are described as nVOC or natural volatile organic compounds. Water vapour diffusion resistance μ The resistance of a building material to penetration by water vapour in relation to the diffusion resistance of ­motionless air (μ = 1). Weathering Lignin is broken down by moisture and exposure to UV radiation. This changes the colour of wood, but does not destroy its substance. Moisture can turn a naturally aged timber facade grey or black, while it will darken to brown or black in strong sun and a dry climate. Windproofing A permeable layer (e.g. synthetic fleece, soft fibreboard panel or render) that is tightly glued or applied to the cold side of thermal insulation, preventing outside air from penetrating the insulation, cooling and causing heat loss. Windproofing also enhances the effect of an airtight layer by preventing excessive negative or positive pressure in the insulating layer, which can result in convection between interior air and the insulating layer. Windproof layers are often built as a second water bearing layer. Wood-based materials Materials that are produced by reducing wood to small pieces and bonding to form structured elements, usually through gluing or pressing. Wood fibreboard Planar wood-based material made of pressed, com­ pacted wood fibres of varying thicknesses and strengths. MDF board (medium density fibreboard) is the most commonly used soft fibre or hard fibreboard. Wood moisture Proportion of water in wood in relation to dry mass, ­expressed as a percentage. Wood is hygroscopic and reacts to fluctuations in humidity. Depending on wood thickness, it can take some time to reach a ­balanced state (sorption equilibrium). Wood should be dried before processing, to give it levels of moisture that approximate the levels in its subsequent ­surroundings. Thus, only periodic fluctuations in climate will affect the wood, and any changes in form due to swelling and shrinking will be kept to a min­ imum. Wood with a moisture content of more than 20 % is at risk of fungal infestation and must be protected from becoming too moist, mainly by implementing ­structural measures. Typical wood moisture content ­levels: newly harvested wood approx. 60 %, timber stored outside 15 –18 %, exterior cladding protected from the weather 15 – 20 %, exterior cladding not protected from the weather 18 – 24 %, unheated interiors 10 –12 %, heated interiors 6 – 8 %.

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DIN Standards The EU has passed directives on a number of products to ensure the safety and health of their users. These ­directives must be incorporated into binding laws and statutory regulations in Member States. The directives themselves do not contain any technical details, only fundamental binding specifications. The relevant tech­ nical values are specified in related technical rules and in harmonised European standards (EN standards). In general, technical rules provide practical guidance and instruments for everyday work. They are not legal regulations, but offer help in making decisions, form guidelines for correct technical procedure and /or render the contents of directives concrete. Anyone can apply technical rules in their work. They only become legally binding (e.g. in building law) when they are incorporated into laws, statutory regulations or codes – or when the binding character of specific standards between the parties is stipulated in a contract. Technical rules include DIN standards, VDI directives and works referred to as codes of practice (e.g. Technical Rules for Hazardous Substances – TRGS). Standards are divided into product, application and testing standards and often deal only with a specific group of materials or products. Standards are based on appropriate methods for testing and researching individual materials. The newest version of a standard, which should reflect the technological state of the art, is always the applicable one. A new or revised standard is made available for public discussion in the form of a draft standard before being adopted as standard. A standard’s title reveals its origins and scope. DIN plus a number (e.g. DIN 4108) is a standard of mainly national significance (drafts are prefixed with an E and pre-standards with a V). DIN EN plus a number (e.g. DIN EN 335) identifies the German edition of a European standard that has been adopted unchanged from the European standards organisation CEN. DIN EN ISO (e.g. DIN EN ISO 13 786) designates a national, European and worldwide scope. A European standard is drafted based on an ISO (International Standards Organisation) standard and then adopted as a DIN standard. DIN ISO (e.g. DIN ISO 2424) indicates the adoption of an ISO standard unchanged as a national standard. The following list is a selection of standards representing the state of the art (October 2021). Only standards specifications sheets with the latest date of issue from DIN (the German Institute for Standardisation) are binding. Voluntary agreements on strict compliance with standards that are not required in building law and additional features and requirements must be agreed on individual contracts. Statements made in contracts that all standards must be complied with are meaningless and can no longer be made in future contracts. To avoid inconsistencies, parties must definitively stipulate which standards must be complied with and which details of standards should apply in each requirements category. DIN 4074-1:2012-06 Strength grading of wood – Part 1: Coniferous sawn ­timber DIN 4074-5:2008-12 Strength grading of wood – Part 5: Sawn hard wood DIN 4102-1:1998-05 Fire behaviour of building materials and building ­components – Part 1: Building materials; concepts, requirements and tests DIN 4102-4:2016-05 Fire behaviour of building materials and building ­components – Part 4: Synopsis and application of classified building materials, components and special components 2016-05 DIN 4108 Amendment 2:2019-06 Thermal insulation and energy economy in buildings – Thermal bridges – Examples for planning and perform­ ance DIN 4108-2:2013-02 Thermal protection and energy economy in buildings – Part 2: Minimum requirements to thermal insulation

DIN 4108-3:2018-10 Thermal protection and energy economy in buildings – Part 3: Protection against moisture subject to climate conditions – Requirements and directions for design and construction DIN 4108-7:2011-01 Thermal insulation and energy economy in buildings – Part 7: Air tightness of buildings – Requirements, ­recommendations and examples for planning and ­performance DIN 4109 Amendment 2:1989-11 Sound insulation in buildings; guidelines for planning and execution; proposals for increased sound insulation; recommendations for sound insulation in personal living and working areas DIN 4109-1:2018-01 Sound insulation in buildings – Part 1: Minimum requirements DIN 20 000-1:2017-06 Application of construction products in structures – Part 1: Wood-based panels DIN 20 000-7:2021-06-Draft Application of construction products in structures – Part 7: Structural finger-jointed solid timber according to DIN EN 15 497:2014-07 DIN 68 800-1:20191-06 Wood preservation – Part 1: General DIN 68 800-2:2012-02 Wood preservation – Part 2: Preventive constructional measures in buildings DIN 68 800-3:2020-03 Wood preservation – Part 3: Preventive protection of wood with wood preservatives DIN 68 800-4:2020-12 Wood preservation – Part 4: Curative treatment of wood destroying fungi and insects and refurbishment DIN EN 300:2006-09 Oriented Strand Boards (OSB) – Definitions, ­classification and specifications; German version EN 300:2006 DIN EN 301:2018-01 Adhesives, phenolic and aminoplastic, for load-­ bearing timber structures – Classification and perfor­ mance requirements; German version EN 301:2017 DIN EN 312:2010-12 Particle boards – Specifications; German version EN 312:2010 DIN EN 316:2009-07 Wood fibreboards – Definition, classification and ­symbols; German version EN 316:2009 DIN EN 338:2016-07 Structural timber – Strength classes; German version EN 338:2016 DIN EN 350:2016-12 Durability of wood and wood-based products – Testing and classification of the durability to biological agents of wood and wood-based materials; German version EN 350:2016 DIN EN 622-4:2019-08 Fibreboards – Specifications – Part 4: Requirements for soft boards; German version EN 622-4:2019 DIN EN 622-5:2010-03 Fibreboards – Specifications – Part 5: Requirements for dry process boards (MDF); German version EN 622-5:2009 DIN EN 634-1:1995-04 Cement-bonded particle boards – Specifications – Part 1: General requirements; German version EN 634-1:1995 DIN EN 634-2:2007-05 Cement-bonded particle boards – Specifications – Part 2: Requirements for OPC bonded particle boards for use in dry, humid and exterior conditions; German version EN 634-2:2007 DIN EN 635-2:1995-08 Plywood – Classification by surface appearance – Part 2: Hardwood; German version EN 635-2:1995

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DIN EN 635-3:1995-08 Plywood – Classification by surface appearance – Part 3: Softwood; German version EN 635-3:1995 DIN EN 636:2015-05 Plywood – Specifications; German version EN 636:2012 + A1:2015 DIN EN 975-1:2011-08 Sawn timber – Appearance grading of hardwoods – Part 1: Oak and beech; German version EN 975-1:2009 + AC:2010 DIN EN 1611-1:2002-11 Sawn timber – Appearance grading of softwoods – Part 1: European spruces, firs, pines, Douglas firs and larches (including amendment 1:2002); German version EN 1611-1:1999 + A1:2002 DIN EN 1912:2013-10 Structural timber – Strength classes – Assignment of visual grades and species; German version EN 1912:2012 + AC:2013 DIN EN 1991-1-1:2010-12 Eurocode 1: Impact on structures – Part 1-1: General impact – Densities, dead weight, imposed loads for buildings; German version EN 1991-1-1:2002 + AC:2009 DIN EN 1991-1-1/ NA:2010-12 National Annex – Nationally determined parameters – Eurocode 1: Impact on structures – Part 1-1: General impact – Densities, dead weight, imposed loads for buildings DIN EN 1995-1-1:2010-12 Eurocode 5: Design of timber structures – Part 1-1: General – Common rules and rules for buildings; ­German version EN 1995-1-1:2004 + AC:2006 + A1:2008 DIN EN 1995-1-2:2010-12 Eurocode 5: Design of timber structures – Part 1-2: General – Structural fire design; German version EN 1995-1-2:2004 + AC:2009 DIN EN 1995-1-2/NA:2010-12 National Annex – Nationally determined parameters – Eurocode 5: Design of timber structures – Part 1-2: General – Structural fire design DIN EN 12 369-1:2001-04 Wood-based panels – Characteristic values for structural design – Part 1: OSB, particle boards and fibreboards; German version EN 12 369-1:2001 DIN EN 13 168:2015-04 Thermal insulation products for buildings – Factorymade wood wool (WW) products – Specification; ­German version EN 13 168:2012 + A1:2015 DIN EN 13 171:2015-04 Thermal insulation products for buildings – Factorymade wood fibre (WF) products – Specification; ­German version EN 13 171:2012 + A1:2015 DIN EN 13 353:2011-07 Solid wood panels (SWP) – Requirements; German version EN 13 353:2008 + A1:2011 DIN EN 13 501-1:2019-05 Fire classification of construction products and building elements – Part 1: Classification using data from reaction to fire tests; German version EN 13 501-1:2018 DIN EN 13 501-2:2016-12 Fire classification of construction products and building elements – Part 2: Classification using data from fire resistance tests, excluding ventilation services; German version EN 13 501-2:2016 DIN EN 13 986:2015-06 Wood-based panels for use in construction – Characteristics, evaluation of conformity and marking; German version EN 13 986:2004 + A1:2015 DIN EN 14 080:2013-09 Timber structures – Glued laminated timber and glued solid timber – Requirements; German version EN 14 080:2013 DIN EN 14 081-1:2019-10 Timber structures – Strength graded structural timber with rectangular cross section – Part 1: General requirements; German version EN 14 081-1:2016 + A1:2019

DIN EN 14 279:2009-07 Laminated Veneer Lumber (LVL) – Definitions, ­classification and specifications; German version EN 14 279:2004 + A1:2009 DIN EN 14 374:2016-07-Draft Timber structures – Laminated veneer lumber (LVL) – Requirements; German and English version prEN 14 374:2016 DIN EN 15 026:2007-07 Hygrothermal performance of building components and building elements – Assessment of moisture ­transfer by numerical simulation; German version EN 15 026:2007 DIN EN 15 251:2012-12 Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics; German version EN 15 251:2007 DIN EN 15 283-1:2009-12 Gypsum boards with fibrous reinforcement – Definitions, requirements and test methods – Part 1: Gypsum boards with fleece reinforcement; German version EN 15 283-1:2008 + A1:2009 DIN EN 15 425:2017-05 Adhesives – Single component polyurethane (PUR) for load-bearing timber structures – Classification and performance requirements; German version EN 15 425:2017 DIN EN 15 497:2014-07 Structural finger-jointed solid timber – Performance requirements and minimum production requirements; German version EN 15 497:2014 DIN EN 15 804:2020-03 Sustainability of construction works – Environmental product declarations – Core rules for the product ­category of construction products; German version EN 15 804:2012 + A2:2019 DIN EN 15 978:2012-10 Sustainability of construction works – Assessment of environmental performance of buildings – Calculation method; German version EN 15 978:2011 DIN EN 16 449:2014-06 Wood and wood-based products – Calculation of the biogenic carbon content of wood and conversion to carbon dioxide; German version EN 16 449:2014 DIN EN ISO 717-2:2021-05 Acoustics – Rating of sound insulation in buildings and of building elements – Part 2: Impact soundproofing (ISO 717-2:2020); German version EN ISO 717-2:2020 DIN EN ISO 10 456:2010-05 Building materials and products – Hygrothermal ­properties – Tabulated design values and procedures for determining declared and design thermal values (ISO 10 456:2007 + Cor. 1:2009); German version EN ISO 10 456:2007 + AC:2009 DIN EN ISO 14 044:2021-02 Environmental management – Life cycle assessment – Requirements and guidelines (ISO 14 044:2006); ­German and English version EN ISO 14 044:2006 + A1:2018 + A2:2020 SIA 102:2014-11; SN 50 8102:2014-11: Regulations governing architects’ services and fees SIA 112:2014; SN 50 9112:2014 Model construction planning – Agreed standards SIA 265:2012 Timber construction

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Image Credits The authors and publisher would like to sincerely thank everyone who contributed to the production of this book by providing images, granting permission to reproduce their work, or supplying other information. All the drawings and diagrams in this book were created especially for it. The authors and their staff created those graphics and tables for which no other source is credited. Photos for which no photographer is credited are architectural or work photos or originate from the archive of DETAIL magazine. Despite intensive efforts, we were unable to identify the copyright holders of some images, but their entitlement to claim copyright remains unaffected. In these cases, we would like to ask you to contact us. ­Figures refer to illustration numbers.

p. 4

Seraina Wirz

Part A Introduction p. 6

Christian Schittich

The Evolution of Multi-storey Timber Construction A 1.1 taken from: Weston, Richard: Utzon – Inspiration, Vision, Architektur. Kiel 2001, p. 48 A 1.2 HGPhotography A 1.3 mykyotomachia.com A 1.4 Sergio Somavilla A 1.5 Bernard Gagnon – own work, GNU Free ­Documentation License, https://commons. wikimedia.org/wiki/File:Ch%C3%A2teau_de_ Himeji02.jpg?uselang=de A 1.6 Neckar-Magazin, Esslingen / Neckar A 1.7 Peter Bonfig A 1.8 Bernd Borchardt A 1.9 Roland Pawlitschko A 1.10 TU Munich, Chair of Architectural Design and Timber Construction, Univ. Prof. DI Hermann ­Kaufmann A 1.11 Waugh-Thistleton Architects A 1.12 Artec Arkitekter A 1.13 cetus Baudevelopment/kito.at A 1.14 by Tilman 2007 – own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index. php?curid=87795952 A 1.15 �ke E:son Lindman A 1.16 a Jakob Schoof A 1.16 c Jacob Kanzleiter Wood as a Resource A 2.1 Friedrich Böhringer – own work, CCBY-SA 2.5, https://commons.wikimedia.org/wiki/ File:Mischwald_Herbst_Panorama.jpg A 2.2 Tourist Information Einbeck A 2.3 Munich Stadtmuseum, Graphics / Paintings collection A 2.4, 2.5 Gerd Wegener / Ralf Rosin, Wood Research Munich A 2.6 TU Munich, Chair of Architectural Design and Timber Construction, Univ. Prof. DI Hermann ­Kaufmann A 2.7, 2.8 Ralf Rosin, Wood Research Munich A 2.9 taken from: Kaufmann, Hermann; Nerdinger, ­Winfried (eds.): Bauen mit Holz – Wege in die Zukunft. Munich, London, New York 2012, p. 17 Solid Wood and Wood-based Products A 3.1a – d Hans-Joachim Heyer & Boris Miklautsch /Werk­ statt für Photographie, University of Stuttgart A 3.1e SWISS KRONO A 3.1f proHolz A 3.1g Holzabsatzfonds, Bonn A 3.1h Mathias Kestel A 3.1i – l Holzabsatzfonds, Bonn A 3.1m Mathias Kestel A 3.1n ARGE Holz, Düsseldorf

A 3.1o – q Holzabsatzfonds, Bonn A 3.1r Mathias Kestel Life Cycle Analysis A 4.1 paul ott photografiert A 4.2 taken from: Kaufmann, Hermann; Nerdinger, Winfried (eds.): Bauen mit Holz – Wege in die Zukunft. Munich, London, New York 2016, p. 52 A 4.3 Hafner, Annette et al.: Treibhausgasbilanzierung von Holzgebäuden – Umsetzung neuer Anforderungen an Ökobilanzen und Ermittlung empirischer Substitutionsfaktoren (THG-Holzbau). Bochum 2017 A 4.4 Annette Hafner A 4.5 taken from: Kaufmann, Hermann; Nerdinger, Winfried (eds.): Bauen mit Holz – Wege in die Zukunft. Munich, London, New York 2016, p. 47 A 4.6 Annette Hafner Indoor Air Quality – The Influence of Timber ­Construction A 5.1 David Schreyer A 5.2 according to: Leitwerte für TVOC in der ­Innenraumluft. Compiled by the ad-hoc ­working group under the auspices of the Federal E ­ nvironmental Agency. Dessau 2007 A 5.3 according to: Wikipedia A 5.4 taken from: Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und ­Pflanzliche Baustoffe. Wiesbaden 2012, p. 26 A 5.5 taken from: Bauen und Leben mit Holz. ­Informationsdienst Holz. March 2013, p. 23 A 5.6 taken from: Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und ­pflanzliche Baustoffe. Wiesbaden 2012, p. 33 A 5.7 TU Munich, Chair of Architectural Design and Timber Construction, Univ. Prof. DI Hermann ­Kaufmann A 5.8 according to: Thünen Institute and Holzmann, Gerhard; Wangelin, Matthias; Bruns, Rainer: Natürliche und pflanzliche Baustoffe. ­Wiesbaden 2012, p. 32 A 5.9 TU Munich, Chair of Architectural Design and Timber Construction, Univ. Prof. DI Hermann ­Kaufmann A 5.10 TU Munich, Chair of Architectural Design and Timber Construction, Univ. Prof. DI Hermann ­Kaufmann A 5.11 according to: Paulitsch, Michael; Barbu, ­Marius C.: Holzwerkstoffe der Moderne. ­Leinfelden-Echterdingen 2015, p. 418 A 5.12 Stefan Müller-Naumann A 5.13 taken from: König, Holger: Baustoffe – ­Lebenszyklusanalyse als Planungsinstrument. In: Djahanschah, Sabine; Kaufmann, Hermann; Nagler, Forian (eds.): SchmuttertalGymnasium. Architektur – Pädagogik – ­Ressourcen. DBU Bauband 1. Munich 2016, p. 84 A 5.14 according to: Raumluftqualität – Grundlagen und Massnahmen für gesundes Bauen. ­Published by Lignum. Zurich 2013, p. 27 A 5.15 a – c Brigida González A 5.16 David Schreyer

Part B Structural Systems p. 40

Eckhart Matthäus / lattkearchitekten

Structures and Load-bearing Systems B 1.1 Darko Todorovic B 1.7 a Architekten Hermann Kaufmann B 1.7 b, 1.10  Bernd Borchardt B 1.15 a proHolz Polaris B 1.15 b Bernd Borchard

tB 1.15 c Architekten Hermann Kaufmann B 1.17 ETH Zurich B 1.18 TU Munich, Chair of Architectural Design and Timber Construction, Univ. Prof. DI Hermann ­Kaufmann B 1.20 a Margherita Spiluttini, © Architekturzentrum ­Vienna, Collection B 1.20 a–c Roger Frei, Zürich B 1.21 a Marc Lins B 1.21 b, c Roland Wehinger Construction Components and Elements B 2.1, 2.2 Matthias Kestel B 2.8 STEICO SE B 2.16 proHolz Polaris B 2.22 Finnforrest B 2.27 Bernd Borchardt B 2.31, 2.37  Matthias Kestel B 2.42 Ökoberatung G. Bertsch B 2.49 Binderholz GmbH B 2.54 Peter Cheret B 2.61 Architekten Hermann Kaufmann

Part C Construction p. 76

ARTEC

Protective Functions C 1.1 abcmedia – Fotolia C 1.2 according to: MBO (2012) C 1.3 according to: DIN 4102-2 and DIN EN 13 501-2 C 1.4 according to: Deutsches Institut für Bau­ technik: Bauregelliste – Standards list A, B and C. Issue 2015/2 C 1.5, 1.6 Technical University of Munich C 1.7 according to: EN 1995-1-2 C 1.9 Stefan Winter C 1.10 Dianna Snape C 1.11 Emma Cross photographer C 1.16 a taken from: Zeumer, Martin; El Khouli, ­Sebastian; John, Viola: Nachhaltig ­konstruieren. Munich 2014 C 1.17 Huber & Sohn GmbH & Co. KG, Bachmehring C 1.18 Midroc, Photo: Martin Johansson C 1.19 a Photo: Bosch C 1.19 b Hilti, Kaufering C 1.20 David Borland C 1.21, 1.22  Stefan Winter C 1.23 Christian Schittich C 1.24 Stefan Winter C 1.25 Holzforschung Austria / Grüll C 1.26 Stein, René; Schneider, Patricia; Kleinhenz, Miriam et al.: Fassadenelemente für Hybridbauweisen – Vorgefertigte, integrale Fassaden­ elemente in Holzbauweise zur Anwen­dung im Neubau hybrider Stahlbetonhochbauwerke (unpublished). Chair of T ­ imber Construction and Structural Design, Chair of Energy-­ efficient and Sustainable Planning and ­Construction, Chair of Solid Construction. Technical University of Munich 2016 C 1.27 Thomas Madlener Thermal Insulation in Summer – A Question of ­Planning C 2.1 – 2.3 taken from: Ferk, Heinz; Rüdisser, Daniel et al., proholz Austria (eds.): ­Sommerlicher Wärmeschutz im Klima­wandel – Einfluss der Bauweise und weitere Faktoren. In: att.zuschnitt. Vienna 2016 C 2.4–2.10 Daniel Rüdisser The Layer Structure of Building Envelopes C 3.1 Bruno Klomfar C 3.2 Maren Kohaus, according to: Informations­ dienst Holz and dataholz.eu

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C 3.3 – 3.5 Maren Kohaus C 3.6 Maren Kohaus, according to: Winter, Stefan; Merk, ­Michael: Verbundforschungsprojekte ­Holzbau der Zukunft – Partial project TP 02 – Brandsicherheit im mehrgeschossigen ­Holzbau. Technical University of Munich, Chair of Timber Construction and Structural Design. Munich 2009 C 3.7 Huber & Sohn GmbH & Co. KG, Bachmehring C 3.8 according to: Muster-Richtlinie über brand­ schutztechnische Anforderungen an Bauteile und Außenwandbekleidungen in Holzbauweise (MHolzBauRL), October 2020 C 3.9 Photo: Claudia Fuchs, graphic: Maren K ­ ohaus C 3.10 Photo: Michael Meuter, graphic: Maren K ­ ohaus C 3.11 Photo: Bernd Borchardt, graphic: Maren ­Kohaus C 3.12 a –c Maren Kohaus C 3.13 a, b Maren Kohaus C 3.14 a, b Maren Kohaus C 3.15 b Architekten Hermann Kaufmann C 3.16 a Maren Kohaus, according to: DIN 68 800-2, A 7; following: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln / -details für mehr geschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 C 3.16 b Maren Kohaus, according to: DIN 68 800-2, A 4; following: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln / -details für mehr geschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 C 3.16 c Maren Kohaus C 3.17 a Maren Kohaus, according to: DIN 68 800-2, A 5; following: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln / -details für mehr geschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 C 3.17 b Maren Kohaus, according to: DIN 68 800-2, A 2; following: Merk, Michael et al.: Erarbeitung weiterführender Konstruktionsregeln / -details für mehr geschossige Gebäude in Holzbauweise der Gebäudeklasse 4. Stuttgart 2014 C 3.17 c Maren Kohaus C 3.18 Maren Kohaus C 3.19 a–c Maren Kohaus C 3.20 Bernd Borchardt C 3.21 Maren Kohaus C 3.22 Maren Kohaus, according to: DIN 68 800 and dataholz.eu C 3.24 – 3.30  Maren Kohaus C 3.31 a–c cf. dataholz.eu C 3.32 Maren Kohaus C 3.33 a paul ott photografiert C 3.33 b–d cf. dataholz.eu C 3.34 a–d RADON photography / Norman Radon C 3.35 a N11 Architekten GmbH C 3.35 b Maren Kohaus C 3.36 a Patrick Sun C 3.36 b Maren Kohaus C 3.37 a Jürgen Pollak C 3.37 b Maren Kohaus C 3.38 b Lanz, Schels, Pk Odessa C 3.38 c Maren Kohaus C 3.38 d Tilmann Jarmer C 3.38 e Maren Kohaus The Layer Structure of Interior Construction ­Components C 4.1 Ed White Photographics C 4.8 Köhnke, Ernst Ulrich: Schallschutztechnische Ausführungsfehler an Holzdecken, Contribution to 4th HolzBauSpezial: Akustik und Brandschutz im Holz- und Innenausbau (ISB 2013) Bad Wörishofen 2013 C 4.11 Giuseppe Micciché

Building Service Technology – Particularities of ­Timber Construction C 5.1 Kiefer Holzbau GmbH & Co. KG, Stockach C 5.2 b_solution b_box © binderholz C 5.3 Manfred Mühe C 5.6 Informationsdienst Holz, Düsseldorf C 5.7 Eisedicht, Dörentrup C 5.10 Kaiser GmbH & Co. KG, Schalksmühle C 5.11 Holzforschung Austria C 5.12 Informationsdienst Holz, Düsseldorf C 5.21 Hilti C 5.22 DEUTSCHE ROCKWOOL C 5.23 Stefan Winter C 5.24 Ernst Macho

Part D Process p. 144

courtesy of University of British Columbia

Planning D 1.1 TUM Chair of Architectural Design and ­Timber Con­struction D 1.2 Geier, Sonja; Keikut, Frank; Stieglmeier, ­Manfred: Book 3 – Part A and B: Ausbildung. In: leanWOOD 2017. Final Report Wood­ Wisdom-Net Projekt leanWOOD. Munich, ­Lucerne 2017 D 1.3 Geier, Sonja: leanWOOD. Planen und ­Kooperieren für den vorgefertigten Holzbau. Final documentation. Switzerland. Lucerne 2017. Available online: www.hslu.ch/de-ch/ hochschule-luzern/forschung/projekte/ detail/?pid=710 D 1.8 a merz kley partner D 1.8 b Architekten Hermann Kaufmann D 1.8 c Kaufmann Bausysteme Digitalisation in Timber Construction D 2.1 Gumpp & Maier, Binswangen D 2.2 a, b SAAHA AS D 2.4 BIM Levels in Bew-Richards BIM Maturity Model (Mark Bew and Mervyn Richards 2008) D 2.5 TUM, own illustration, Chair of Architectural Design and Timber Construction (BIMwood, 2021) Timber Production D 3.1 BDF / FingerHaus / Rolf Vennenbernd D 3.2, 3.3 Hans Hundegger AG D 3.5 a, b Eckhart Matthäus D 3.5 c, 3.6 WEINMANN Holzbausystemtechnik GmbH Prefabrication D 4.1 Kaufmann Bausysteme D 4.2 Huber & Sohn GmbH & Co. KG D 4.3 b lattkearchitekten D 4.4 b Darko Todorovic / Cree D 4.5 b Ignacio Martinez D 4.7 RADON photography / Norman Radon D 4.9 thomasmayerarchive.de D 4.11 b Vielstädte Holzbau GmbH & Co. KG D 4.11 d Stefan Müller-Naumann D 4.11 f Architekten Hermann Kaufmann D 4.12 a Architekten Hermann Kaufmann D 4.13 Ignacio Martinez D 4.16 Kaufmann Bausysteme D 4.19 Siegfried Mäser Solutions for Modernising and Expanding Existing Buildings D 5.1 lattkearchitekten D 5.2 Gumpp & Maier, Binswangen D 5.4 Bruno Klomfar D 5.5 Dominik Reipka D 5.6 Martin Lukas Kim

D 5.11 a, b Jens Rötzsch D 5.11 c, d Jan Bitter D 5.12 Alexander Gempeler, Bern D 5.19 Eckhart Matthäus / lattkearchitekten

Part E Examples of Buildings in Detail p. 182

Mikko Auerniitty

Joinery in Detail p. 185 Gataric Fotografie p. 186 Hanspeter Schiess p. 187 Seraina Wirz p. 188 Jan Bitter p. 189 Bruno Klomfar Project Examples p. 190 KK Law; naturally:wood p. 191 courtesy of Seagate Structures. Photographer: Pollux Chung p. 192 Steven Errico p. 193 left, centre Neil Taberner p. 193 right Steven Errico p. 194 –197 Bernd Borchardt p. 198, 200 left Patrick Degerman p. 200 right, 201 �ke E:son Lindman p. 202, 203 Jonas Westling p. 204 top Michael Meuter p. 204 bottom Jakob Schoof p. 205 Giuseppe Micciché p. 206, 207 top pool Architekten p. 207 bottom Giuseppe Micciché p. 208, 209, 211 Mikko Auerniitty p. 212 – 214 Sebastian Schels p. 215 Deppisch Architekten p. 216 Jacob Kanzleiter p. 218 Lukas Vallentin p. 220 top Eva Schönbrunner p. 220 bottom, 221, 222  Stefan Müller-Naumann p. 224 – 227 Roger Frei, Zürich p. 228 top, 229 lattkearchitekten p. 228 bottom Eckhart Matthäus p. 230 Guido Koeninger, Firma Keimfarben p. 232 – 236 Gataric Fotografie p. 237– 239 KAMPA GmbH p. 240, 241, 244 Bruno Klomfar p. 243 left, centre Thomas Giradelli p. 243 right Darko Todorovic p. 246 – 249 Christian Flatscher p. 250, 251, 253 Ed White Photographics p. 252 top photography by MAG (Michael Green Architecture, Vancouver) p. 252 top courtesy of Forestry Innovation ­Investment p. 254, 256, 257 photo.Abbadie.Herve p. 258, 259, 260 bottom, 261 top  Hanspeter Schiess p. 261 bottom Cukrowicz Nachbaur Architekten p. 262, 265 – 267 Carolin Hirschfeld p. 263, 264 Stefan Müller-Naumann p. 268, 270 thomasmayerarchive.de p. 271 RADON photography /  Norman Radon p. 272, 273 bottom, 274  Lignotrend, Weilheim-Bannholz / Fotografie Uwe Röder, Bischweier p. 273 top Antoine MERCUSOT p. 276, 277, 279 Walter Ebenhofer p. 278 Fink Thurnher Architekten p. 280, 283 Jan Bitter p. 281 Thomas Ebert p. 282 left Götz Wrage p. 282 right Kaufmann Bausysteme p. 284 – 287 Rasmus Norlander p. 288 – 293 Seraina Wirz p. 294, 295 left, 296 bottom, 297  Sindre Ellingsen p. 296 top Helen & Hard Architects p. 296 middle Moelven Limtre AS

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Project Partners Student Residence in Vancouver (CA) Architects: Acton Ostry Architects, Vancouver Russell Acton, Mark Ostry, Matthew Wood (project ­manager) Project team: Rafael Santa Ana, Andrew Weyrauch, Gjergj Hondro, Nebojsa Slijepcevic, Nathaniel Straathof, Warren Schmidt Structural engineering: Fast + Epp, Vancouver Timber construction consultant: Hermann Kaufmann, Christoph Dünser Residential and Office Building in Berlin (DE) Architects: Kaden Klingbeil Architekten, Berlin Project team: Tom Kaden (design), Tom Klingbeil, Kora Johanns, Malte Reimer, Fabio Verber Structural engineering (timber): Pirmin Jung, Rain Cultural Centre and Hotel in Skellefteå (SE) Architects: White Arkitekter, Stockholm Robert Schmitz, Oskar Norelius Project team: Maria Orvesten, Patrik Buchinger (project manager) Structural engineering: TK Botnia, Burträsk Greger Lindgren (project manager) Facade contractor: KG Constructions Group, Vilnius Residential and Commercial Building in Zurich (CH) Architects: pool Architekten, Zurich Mathias Heinz, David Leuthold Project team: Andreas Wipf, Jves Lauper Structural engineering: Henauer Gugler, Zurich Structural engineering (timber): SJB.Kempter.Fitze, ­Herisau Residential Complex in Jyväskylä (FI) Architects: OOPEAA, Helsinki /Seinäjoki Anssi Lassila (project manager) Project team: Jussi-Pekka Vesala, Lida Hedberg, Juha Pakkala Structural engineering, timber: SWECO, Helsinki Heikki Löytty, Lauri Lepikonmäki Residential Complex in Ansbach (DE) Architects: Deppisch Architekten, Freising Michael Deppisch Project team: Johannes Dantele, Simon Huber, Christian Klessinger, Andreas Kopp Structural engineering: Planungsgesellschaft Dittrich, Munich Building services engineering: Ingenieurbüro Vogt, ­Freising Residential Complex in Munich (DE) Architects: ARGE ArchitekturWerkstatt Vallentin, ­ Munich; Johannes Kaufmann Architektur, Dornbirn / Vienna Project team: Gernot Vallentin, Rena Vallentin, Margarita Lemoni, Moritz-Julius Pascher, Dania Soppelsa Structural engineering: Reiser Tragwerksplanung, ­Munich Residential Development in Munich (DE) Architects: Florian Nagler Architekten, Munich Project team: Tobias Pretscher, Patrick Fromme, ­Benedikt Rauh, Laura Kwanka Timber construction: Huber + Sohn, Bachmehring Structural engineering (timber): Franz Mitter-Mang, Waldkraiburg Structural engineering (solid construction): r.plan Büro für Bauplanung, Chemnitz Rooftop Extension in Zurich (CH) Architects: spillmann echsle architekten, Zurich Project team: Frank Keikut (project manager), Annette Spillmann, Harald Echsle, Tiago Matthes, Guillaume Chapallaz, Simone Retter Structural engineering: Haag + Partner, Küsnacht Timber construction: Timbatec Holzbauingenieure ­Schweiz, Zurich

Renovation of a Residential Building in Augsburg (DE) Architects: lattkearchitekten, Augsburg Frank Lattke Project team: Markus Hölzl, Esther Strahl Structural engineering: bauart Konstruktions GmbH, ­Munich

European School in Frankfurt am Main (DE) Architects: NKBAK, Frankfurt am Main Nicole Kerstin Berganski, Andreas Krawczyk Project team: Simon Bielmeier, Larissa Heller Structural engineering: Bollinger + Grohmann, Frankfurt am Main; merz kley partner, Dornbirn

Residential Buildings in Zurich (CH) Architects: Rolf Mühlethaler, Bern Project team: Thomas Moser (project manager), Chantal Amberg, Julia Grommas, Marion Heinzmann, Sandra Stein, Jonas von Wartburg, Simon Wiederkehr Structural engineering (solid construction): Ingenta ­Ingenieure + Planer, Bern Structural engineering (timber): Indermühle Bau­ ingenieure, Thun

School Complex in Limeil-Brévannes (FR) Architects: Agence R2K, Grenoble Véronique Klimine, Olavi Koponen Structural engineering (timber): Holzbau Amann, ­Weilheim Structural engineering (solid construction): Gaujard Technologie, Avignon

Administration Building in Aalen (DE) System development / design: Florian Nagler Architekten, Munich Execution: Kampa, Aalen; Josef Haas, Johann Wellner Structural engineering, fire safety planning and building physics: bauart Konstruktions GmbH, Lauterbach Office Building in Vandans (AT) Architects: Architekten Hermann Kaufmann, ­Schwarzach Project team: Christoph Dünser, Stefan Hiebeler, ­Thomas Fußenegger, Michael Laubender, Guillaume Weiss, Ann-Katrin Popp, Benjamin Baumgartl Structural engineering: merz kley partner, Dornbirn Office Building in St. Johann in Tyrol (AT) Architects: architekturwerkstatt, Breitenbach am Inn Project team: Bruno Moser, Florian Schmid, Thomas Schiegl Structural engineering: dibral, Alfred R. Brunnsteiner, Natters Timber construction: Holzbau Saurer, Höfen Research and Office Building in Prince George (CA) Architects: Michael Green Architecture, Vancouver Project team: Michael Green (project manager), ­Mingyuk Chen, Carla Smith, Seng Tsoi Design team: Kristalee Berger, Alfonso Bonilla, Jordan van Dijk, Guadalupe Font, Adrienne Gibbs, Jacqueline Green, Asher deGroot, Soo Han, Kristen Jamieson, Vuk Krcmar-Grkavac, Alexander Kobald, Sindhu Mahadevan, Maria Mora Structural engineering: Equilibrium Consulting, ­Vancouver Administrative Building in Clermont-Ferrand (FR) Architects: Bruno Mader, Paris Project team: M. Guzy, C. Grispello, E. Ranalletti, A. Veyssier, A. Bertrand, J. Varela Construction management: Atelier 4 Architekten, ­Clermont-Ferrand Structural engineering (timber): Sylva Conseil, ClermontFerrand Structural engineering (solid construction): Sibat, Paris Community Centre in St. Gerold (AT) Architects: Cukrowicz Nachbaur Architekten, Bregenz Andreas Cukrowicz, Anton Nachbaur-Sturm Project team: Stefan Abbrederis (project manager), ­Michael Abt, Christian Schmölz Structural engineering: M+G Ingenieure, Feldkirch Secondary School in Diedorf (DE) Architects: ARGE Diedorf – Architekten Hermann ­Kaufmann, Schwarzach; Florian Nagler Architekten, ­Munich Project management: Claudia Greußing, Stefan ­Lambertz Structural engineering: merz kley partner, Dornbirn

Agricultural Training Centre in Altmünster (AT) Architects: Fink Thurnher, Bregenz Project team: Josef Fink, Markus Thurnher, Sabine Leins, Carmen Schrötter-Lenzi Structural engineering (timber): merz kley partner, ­Dornbirn Structural engineering (solid construction): Mader & Flatz, Bregenz Student Housing in Hamburg (DE) Architects: Sauerbruch Hutton, Berlin Project team: Louisa Hutton, Matthias Sauerbruch, Juan Lucas Young, Jürgen Bartenschlag, Sibylle Bornefeld, Bettina Magistretti Structural engineering (timber): merz kley partner, ­Dornbirn Structural engineering (solid construction): Wetzel & von Seht, Hamburg Timber construction: Kaufmann Bausysteme, Reuthe Office Building in Alpnach (CH) Architects: SEILERLINHART Architekten, Lucerne Project team: Raphael Wiprächtiger (project manager) Structural engineering: ZEO Ingenieurbüro, Alpnach Timber construction: Küng Holzbau, Alpnach Agricultural Centre in Salez (CH) Architects: Andy Senn Architekt, St. Gallen Project team: Remo Wirth (project manager), Antje ­Wanner, Thomas Gerber, Anike Müller, Marlise Kuratli, Tobias Müller Structural engineering: merz kley partner, Altenrhein Building physics / energy planning: Lenum, Vaduz Bank Headquarters in Stavanger (NO) Architects: Helen & Hard, Stavanger; SAAHA, Oslo Structural engineering: Création Holz, Herisau; Degree of Freedom, Oslo Timber construction: Moelven Limtre, Moelv; Hess Timber, Kleinheubach; Pollmeier, Creuzburg

311

Subject Index  A acetylated timber  ∫ 91 airtightness  ∫ 103, 302 airtightness layer  ∫ 104, 302 anisotropy / anisotropic  ∫ 37, 302 antiquity  ∫ 8 B beam  ∫ 64, 302 BIM  ∫ 155, 302 bouwteam  ∫ 151 box ceiling  ∫ 66 building classes  ∫ 79, 102 building envelope   - airtightness  ∫ 103   - fire protection  ∫ 102, 107f.   - installations  ∫ 137ff.   - insulation  ∫ 99ff.   - layer composition  ∫ 98ff.   - prefabrication  ∫ 117f.   - renovation  ∫ 178ff.   - requirements  ∫ 98f.   - soundproofing  ∫ 106f.   - weatherproofing  ∫ 101f. building material classes  ∫ 84 building product  ∫ 33, 35 building services technology  ∫ 136ff. building simply  ∫ 118 building technology  ∫ 136ff.   - planning  ∫ 136   - renovation  ∫ 181 C carbon footprint  ∫ 29, 31 carbon sequestration capacity  ∫ 25, 27 carbon store / carbon sink  ∫ 24 cascading use  ∫ 28 ceiling elements  ∫ 73 ceiling slab / floor slab  ∫ 56ff. ceilings   - installations  ∫ 63ff., 75, 127f. CO2 efficiency  ∫ 27 CO2 equivalent  ∫ 25 comfort  ∫ 32 connections  ∫ 113, 133, 126, 184 construction component layers  ∫ 98, 106, 130, 134 construction components /construction   element  ∫ 56ff., 108, 114, 122ff. construction process  ∫ 163, 171 construction product regulation  ∫ 18 construction types in comparison  ∫ 29f., 49, 54, 72 cooling  ∫ 97 craft / craftsmanship  ∫ 166 cross-laminated timber ceiling  ∫ 68, 128, 187f. cross-laminated timber wall  ∫ 60, 187f. D data models  ∫ 156f.   - semantic  ∫ 155 decoupling  ∫ 134 demolition  ∫ 28, 121, 157 digitalisation  ∫ 154ff.   - CAM  ∫ 151 dowel laminated timber ceiling  ∫ 63 dowel laminated timber wall  ∫ 57 E ecological balance  ∫ 24ff. effective thermal mass  ∫ 95 emissions  ∫ 33ff. environmental product declaration  ∫ 24 expansion /extension  ∫ 172 F facade / exterior wall  ∫ 108 fire behaviour  ∫ 18ff., 80 fire protection / fire safety  ∫ 75, 78ff., 107, 126   - coatings  ∫ 84   - structural  ∫ 84

fire safety planning  ∫ 107 fire-resistance classes  ∫ 79 floor construction  ∫ 128 forest  ∫ 14f. formaldehyde  ∫ 21, 35 frame construction / skeleton frame construction   ∫ 43f., 58f., 72, 109, 185f. frame wall / wall framing element  ∫ 58f. functional layers  ∫ 113, 133 G global warming potential (GWP)  ∫ 18, 30 H half-timbered construction  ∫ 10 hardwood  ∫ 17, 18ff., 53f. heat protection / thermal insulation  ∫ 92, 97   - heat discharge / heat extraction  ∫ 97   - in summer / summertime  ∫ 93ff.   - in winter  ∫ 92   - shading  ∫ 96   - solar gains / solar radiation intake  ∫ 96 hybrid construction type  ∫ 45ff., 70, 168ff., 192 I indoor air emissions  ∫ 34, 36 indoor air quality  ∫ 32 indoor climate  ∫ 32ff., 108f. installations  ∫ 137ff., 140 insulation layer  ∫ 98 interior construction components  ∫ 126ff. interior walls  ∫ 133 J joinery  ∫ 113, 133 joints  ∫ 134f. L laminated veneer timber ceiling  ∫ 69 laminated veneer timber wall  ∫ 61 layer composition  ∫ 98   - building envelope  ∫ 98ff.   - functional  ∫ 100   - interiors  ∫ 126f. life cycle assessment  ∫ 24, 29 load-bearing structure / structural system  ∫ 41ff., 48 M material combinations  ∫ 37, 45ff. Middle Ages / medieval era  ∫ 8f. modernisation  ∫ 172ff. modernity / modern era  ∫ 10 moisture intrusion / moisture permeation  ∫ 87 moisture protection  ∫ 85ff. multi-storey timber construction   - development / history  ∫ 8   - height  ∫ 10f.   - structural systems  ∫ 42 P planning / planning process  ∫ 146ff., 153, 155 polyfunctionality  ∫ 99, 113 post / stud  ∫ 107, 160 post-in-ground construction  ∫ 9 prefabrication  ∫ 162 primary energy  ∫ 28 Prinz-Eugen-Park  ∫ 13, 28, 216ff. production  ∫ 158ff. production / manufacturing  ∫ 158ff. production methods  ∫ 166 protective functions  ∫ 78 R raw materials industry  ∫ 158 renovation / rehabilitation / modernisation   - building envelope  ∫ 178ff.   - building technology  ∫ 181   - construction code / building code  ∫ 181   - exterior wall  ∫ 180

  - facade  ∫ 178   - fire protection / fire safety  ∫ 178, 180 rib ceiling  ∫ 43 robustness  ∫ 87, 113, 119 roof construction  ∫ 103, 110ff.   - flat roof  ∫ 111   - installations  ∫ 139f.   - pitched roof  ∫ 113 rooftop addition  ∫ 174 room module construction type  ∫ 169f. room modules  ∫ 164ff., 169, 188 S shaft types  ∫ 140f. simply building  ∫ 118f. solar gains  ∫ 96 solid construction  ∫ 43, 108, 138, 143 solid timber products  ∫ 18ff., 158f. soundproofing  ∫ 88, 106, 126, 134 sprinkler system  ∫ 84 stiffening  ∫ 51ff. strength  ∫ 18, 50 structural system  ∫ 42ff. stud wall construction  ∫ 9f. substitution  ∫ 25f., 31 sun protection  ∫ 96f. T thermal effusivity  ∫ 33 timber / wood   - bulk density  ∫ 18   - carbon content  ∫ 18, 24, 27, 30   - fire behaviour  ∫ 18   - frame construction  ∫ 9   - global warming potential (GWP)  ∫ 18, 24   - stud wall construction  ∫ 9   - thermal conductivity  ∫ 18 timber concrete composite ceiling  ∫ 70, 128, 189 timber construction   - award models  ∫ 148   - companies / ­contractors  ∫ 151, 158ff.   - digitalisation  ∫ 154ff.   - elements  ∫ 72   - history  ∫ 8ff., 14ff.   - in comparison  ∫ 29f., 49, 54   - invitation to bid / invitation to tender  ∫ 151   - load-bearing structure  ∫ 42ff., 48   - planning / planning process  ∫ 146ff., 153, 155   - production chain  ∫ 158ff.   - thermal activation  ∫ 143 timber industry / timber economy  ∫ 15 timber preservation  ∫ 89ff. timber resources  ∫ 14 timber species / wood species  ∫ 15, 18, 53 timber use / use of timber  ∫ 15f. total contractor / full service general contractor  ∫ 150f. traditional craft / craftsmanship  ∫ 166 TVOC (total volatile organic compounds)  ∫ 32f., 35, 38 U urban timber construction  ∫ 12 V vapour barrier / vapour-retardant layer  ∫ 105ff. VOC (volatile organic compound)  ∫ 32, 36f. volatile materials  ∫ 32 W wall elements  ∫ 56, 72, 132 wet rooms / sanitary rooms  ∫ 141 windproof layers  ∫ 103 wood based materials  ∫ 18, 37, 159

The authors and the publisher wish to thank the following institutions for supporting the revised and expanded German edition:

www.stmelf.bayern.de

www.zimmerer-bayern.com

www. proholz.at