Circular Economy for the Built Environment (BRI Research Series) [1 ed.] 1032573759, 9781032573755

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Circular Economy for the Built Environment

This book provides an overview of the circular economy in the built environment, presenting a fusion of insights from esteemed researchers and seasoned practition‑ ers. The chapters cover pivotal themes, including the transformative concept of buildings as material banks, innovative design approaches, and the potential of digitalization for a circular built environment. Beyond these foundational themes, this book critically addresses the integration of low‑tech solutions and some prin‑ ciples of sobriety in the built environment. It also takes an informed look at the role of standardization, providing nuanced insights into its driving influence on circular practices and the associated challenges and opportunities. This book adopts a trans‑scalar perspective by traversing the entire spectrum of building phases from initial programming to the recovery phase, as well as from the scale of materials to the scale of buildings, offering a profound examination of the intricate dynamics involved in the offer/demand for recovered materials. This book highlights the paramount need to harmonize research with practical applica‑ tions. By spotlighting effective circular practices and elucidating the challenges faced by practitioners, it identifies fertile grounds for further research. Moreover, this book extends its reach by offering practical ideas on how practitioners can seamlessly adopt a circular approach in both thought and realization. Circular Economy for the Built Environment: Research and Practice is a must‑read book for students, researchers, academics, and practitioners in the fields of architecture, planning, engineering, construction, and real estate. This book pro‑ vides a compelling narrative that bridges the theoretical and practical realms of the circular economy in the built environment. Dr Rabia Charef serves as a Research Associate at Lancaster University (UK) actively contributing to the establishment of a circular future. With an extensive 15 years of industry experience, she spent over a dozen years leading intricate architectural projects in the residential and healthcare sectors. Transitioning to aca‑ demia, she leverages her industry insights to fuel research closely tied to practition‑ ers’ needs and challenges, taking a bottom‑up approach.

In her research role, she explores how digitalizing the construction sector can ac‑ celerate the adoption of circular economy practices. Addressing the environmen‑ tal impact of constructions, she delves into finding the optimal balance between low‑tech and high‑tech solutions for a genuinely circular built environment. Her dedication to the environment, coupled with her expertise in digital technology and the circular economy, led her to collaborate with ECOS (Environmental Coali‑ tion on Standards). She represents them in the European standard for the circular economy.

BRI Research Series

New interdisciplinary and transdisciplinary approaches need a forum for ­information and discussion. This book series shares similar aims and scope to the journal, Building Research & ­Information, but allows for a deeper discussion, together with more practical material. SCOPE: This book series explores the linkages between the built, natural, social and economic environments, with an emphasis on the interactions between theory, policy and practice. Emphasis is on the performance, impacts, assessment, contri‑ butions, improvement and value of buildings, building stocks and related systems: i.e. ecologies, resources (water, energy, air, materials, building stocks, etc.), sus‑ tainable development (social, economic, environmental and natural capitals) and climate change (mitigation and adaptation). If you wish to contribute to the series then contact the series editor Stephen Emmitt at [email protected] with a short note about your ideas. Professionalism for the Built Environment Simon Foxell Sustainable Retrofit Building Professional Capabilities Sarah Sayce Building Health and Wellbeing Edited by Stephen Emmitt Circular Economy for the Built Environment Research and Practice Edited by Rabia Charef For more information about this series, please visit: www.routledge.com/Routledge-Handbooks-inReligion/book-series

Circular Economy for the Built Environment Research and Practice

Edited by Rabia Charef

First published 2024 by Routledge 4 Park Square, Milton Park, Abingdon, Oxon OX14 4RN and by Routledge 605 Third Avenue, New York, NY 10158 Routledge is an imprint of the Taylor & Francis Group, an informa business © 2024 selection and editorial matter, Rabia Charef; individual chapters, the contributors The right of Rabia Charef to be identified as the author of the editorial material, and of the authors for their individual chapters, has been asserted in accordance with sections 77 and 78 of the Copyright, Designs and Patents Act 1988. All rights reserved. No part of this book may be reprinted or reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying and recording, or in any information storage or retrieval system, without permission in writing from the publishers. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. British Library Cataloguing‑in‑Publication Data A catalogue record for this book is available from the British Library ISBN: 978‑1‑032‑57375‑5 (hbk) ISBN: 978‑1‑032‑58429‑4 (pbk) ISBN: 978‑1‑003‑45002‑3 (ebk) DOI: 10.1201/9781003450023 Typeset in Times New Roman by codeMantra

Contents

List of contributorsix Series Prefacexi Introduction

1

RABIA CHAREF

PART 1

Setting the foundation for circular construction5   1 The future of the circular built environment: interest of a “low‑tech” approach

7

RABIA CHAREF AND PHILIPPE BIHOUIX

  2 The reuse of building elements: touchstone of a circular construction economy

24

LIONEL DEVLIEGER AND ARNE VANDE CAPELLE

  3 Buildings as material mines: towards digitalization of resource cadasters for circular economy

46

MAUD LANAU, LEONARDO ROSADO, DANIELLE DENSLEY TINGLEY, AND HOLGER WALLBAUM

  4 Boosting construction waste material circularity: a sharing economy approach

69

WEISHENG LU

  5 The role of standardisation in circular economy for the construction sector MICHAEL NEAVES

88

viii  Contents PART 2

Practical strategies for circular construction: building and material levels113   6 How can we view buildings as material banks? Learning from the pre‑redevelopment process

115

KATHERINE TEBBATT ADAMS AND GILLI HOBBS

  7 The potential for reusing reinforced concrete beams: technical feasibility and environmental impact

129

AMBROISE LACHAT, TIFFANY DESBOIS, ADÉLAÏDE FERAILLE, AND ANNE‑SOPHIE COLAS

  8 Building together with the site materials: a practitioner’s perspective

153

LOUIS‑ANTOINE GRÉGO

  9 Towards a situated understanding of challenges in the design and construction of circular earth buildings: the case study of an office building in France

179

ANTOINE PELÉ‑PELTIER AND JEAN GOIZAUSKAS

PART 3

Fostering circular construction through digital transformation199 10 Digitalising the deconstruction process: towards a circular economy for the construction industry

201

ANNIE GUERRIERO, ELMA DURMISEVIC, CALIN BOJE AND NICO MACK

11 Accelerating material reuse in construction: two case studies: One life, multiple cycles, a longer life

231

ANA RUTE COSTA, RACHEL HOOLAHAN, AND MELANIE MARTIN

12 Additive manufacturing and circular economies

250

JENNIFER JOHNS, DANIEL EYERS, RICK LUPTON, ARIS SYNTETOS, AND JESSICA ROBINS

13 Conclusion

268

RABIA CHAREF

Index

275

Contributors

Katherine Tebbatt Adams, PhD, is Director at Reusefully Ltd., Bedfordshire, UK. Philippe Bihouix is CEO of AREP, Paris, France. Calin Boje is Research Associate at Luxembourg Institute of Science and Technol‑ ogy, Luxembourg. Arne Vande Capelle is scientific collaborator in the Department of Architecture and Urban Planning at Ghent University and project manager at Rotor vzw‑asbl, Brussels. Rabia Charef is Research Associate at Lancaster School of Architecture, Imagina‑ tion Lancaster, Lancaster University, UK. Anne‑Sophie Colas, is Professor at Université Gustave Eiffel, GERS‑RRO, 25, avenue François Mitterrand, Case24 Cité des mobilités F‑69675 Bron Cedex – France. Ana Rute Costa is Senior Lecturer at Lancaster School of Architecture, Imagina‑ tion Lancaster, Lancaster University, UK. Tiffany Desbois, is Researcher at Cerema, Direction Ouest, 5 rue Jules Vallès, F‑22000, Saint‑Brieuc, France. Lionel Devlieger is Associate Professor in the Department of Architecture and Ur‑ ban Planning at Ghent University and co‑founder of Rotor vzw‑asbl, Brussels. Elma Durmisevic is Assistant Professor at Laboratory for Green Transformable Buildings, 4D architects, the Netherlands. Stephen Emmitt is Professor in the Department of Architecture and Civil En‑ gineering Centre for Doctoral Training in Decarbonisation of the Built Envi‑ ronment (dCarb), Centre for Climate Adaptation and Environment Research (CAER), University of Bath, Bath, UK. Daniel Eyers is Reader at Cardiff Business School, Cardiff University, UK. Adélaïde Feraille, is Professor in the Laboratoire Navier, Ecole des Ponts Paris‑ Tech, F‑77455, Marne‑La‑Vallée, France.

x  Contributors Jean Goizauskas, is a PhD Student at the Centre de sociologie de l’innovation, Mines Paris, PSL Université  –  i3 CNRS, 60 boulevard Saint Michel, 75005 Paris, France. Louis‑Antoine Grégo is Architect at Studio Méditerranée, Nice, France. Annie Guerriero is Senior Researcher and Technology Associate at Luxembourg Institute of Science and Technology, Luxembourg. Gilli Hobbs is Associate Director of Reusefully Ltd., Bedfordshire, UK.
 Rachel Hoolahan is Architect at Orms Architects, London, UK. Jennifer Johns is Professor at the University of Bristol Business School, Univer‑ sity of Bristol, UK. Ambroise Lachat, is Researcher at BRGM, 3 Avenue Claude Guillemin, F‑45100, Orléans, France. Maud Lanau is Assistant Professor in the Department of Architecture and Civil Engineering at Chalmers University of Technology, Sweden. Weisheng Lu is Professor in the Department of Real Estate and Construction, Fac‑ ulty of Architecture, The University of Hong Kong, Pokfulam, Hong Kong. Rick Lupton is Senior Lecturer in the Department of Mechanical Engineering at the University of Bath, UK. Nico Mack is Senior Engineer at Luxembourg Institute of Science and Technol‑ ogy, Luxembourg. Melanie Martin is Associate Director of Orms Architects, London, UK. Michael Neaves is Independent, Sustainable built environment policy and stand‑ ards advocate, Brussels, Belgium. Antoine Pelé‑Peltier, is Researcher at École Nationale des Travaux publics de l’Etat: Vaulx en Velin, France. Jessica Robins is Research Assistant at the University of Bristol Business School, University of Bristol, UK. Leonardo Rosado is Associate Professor in the Department of Architecture and Civil Engineering at Chalmers University of Technology, Sweden. Aris Syntetos is Professor at Cardiff Business School, Cardiff University, UK. Danielle Densley Tingley is Senior Lecturer in the Department of Civil and Struc‑ tural Engineering at the University of Sheffield, UK. Holger Wallbaum is Professor in the Department of Architecture and Civil Engi‑ neering at Chalmers University of Technology, Sweden. Building Research & Information ‑ Research Series Series Editor: Stephen Emmitt ORCID: 0000‑0002‑8277‑3378

Series Preface

Building Research and Information (BRI) is a leading international refereed journal focused on the entire life cycle of buildings, from inception to designing, engineer‑ ing, construction, and assembly, through the building‑in‑use phase, to disassembly and recovery. Unique to BRI is a holistic and interdisciplinary approach to a sus‑ tainable built environment, centred on the building and its context. This book series shares the journal’s philosophy and commitment to high‑quality research, provid‑ ing the space for a more detailed and nuanced exploration of a particular theme. Each book in the series aims to explore the complex and inter‑related nature of our sustainable built environment, embracing what? why? how? and when? questions in relation to a specific research theme. The content of the journal, except for Special Issues, is very much determined by what is submitted to the journal for consideration; and what gets through a rigorous anonymous peer review process. Thus, the content is wonderfully varied, and individual Issues are rarely themed in the way that an edited book can be. The journal content does, however, often suggest the need for further enquiry and exploration that lends itself a little better to a research book format. This research book series is a mechanism that allows the curation of chapters as a themed anthol‑ ogy and builds on the content of the journal. Like any edited collection, difficult decisions must be made about what to include and what to exclude to create books that are integrated around a specific topic. The rationale is to provide unbiased peer‑reviewed content by expert authors, championed by the book editor and sup‑ ported by the book series editor. In this way, this book series aims to be fresh and engaging, and by design, not formulaic. We believe that these books will be a valuable starting point for early career academics and readers wanting to discover more about a specific topic. With this book series, we hope to further inform and stimulate rapid advances in the performance of our buildings. The circular economy (CE) is a subject that has gained momentum in recent years as attention has turned to the role of the built environment in addressing the climate emergency. CE has been explored in articles published within BRI, and it was the focus of a recent Special Issue (SI) that investigated the transition of the built environment to a circular economy (Volume 51, Issue 1). The SI highlighted the complexity surrounding circular practices from a variety of geographical

xii  Series Preface locations and stakeholder perspectives. This book, edited by Rabia Charef, further adds to our knowledge by providing original contributions to discrete aspects of the built environment, combining evidence from research and practice. This book is designed for practitioners and scholars, drawing on real‑life ex‑ amples and research findings. Presented in three sections, the chapters provide a comprehensive perspective on circular construction, covering the establishment of foundational principles, practical strategies for circular construction at both the building and material levels, and the integration of digital transformation to pro‑ mote circular construction. Chapters address topical issues that are fundamental to the realization of a Circular Economy for the Built Environment, providing a unique trans‑scalar and interdisciplinary view of the issues to be considered by all built environment stakeholders. This book highlights the need for collaboration and digitalization as a way to organize markets of second‑hand materials and accel‑ erate the reuse of recovered materials. A better alignment between research, prac‑ tice, and policy is essential. Although this book presents solutions using high‑tech approaches as drivers and facilitators for the implementation of CE, it also high‑ lights the low‑tech approach as an avenue to regeneration within the context of the climate emergency. In doing so the chapters raise questions about the behaviours, thinking, and actions required to meet the needs of a growing population in a re‑ sponsible way. This book offers readers access to the latest advances in CE for the built environment and makes a significant contribution to knowledge. Professor Stephen Emmitt Department of Architecture and Civil Engineering University of Bath, UK.

Introduction Rabia Charef

Over the past decade, the architecture, engineering, and construction (AEC) ­sector has gone through a digital transformation particularly through the use of Build‑ ing Information Modelling (BIM). The shift from a linear economy to a circular economy (CE) is the next change that the AEC sector must undertake. A paradigm shift is inevitable to address the environmental impact of the AEC sector, whether it be the amount of waste generated, material scarcity, the amount of raw material extraction, and/or the reduction of soil fertility. The transition to a CE has garnered priority status in numerous countries that have developed comprehensive transition plans. For example, Asian countries have set up plans to move towards a CE via the “comprehensive legal framework for moving towards a recycling‑based society” for Japan (Su et al., 2013) and the 11th Five‑Year Plan for China. The ISO/TC 323 Standard in the field of CE is under development and aims to provide frameworks, guidance, supporting tools, and re‑ quirements for the implementation of activities of all involved organisations, to maximise the contribution to sustainable development. In Europe, the European Commission has appealed to stakeholders to urgently tackle the economic depend‑ ency on natural resources by considering the current building stocks (European Commission, 2019). The “European Green Deal” will set up zero net emissions of greenhouse gases by the 2050 target. Many standards are being revised, and CEN/ TC 350/SC 1 is under development, aiming to focus on the CE in the construction sector. The primary objective of this book is to offer a comprehensive exploration of the CE within the built environment, offering insights from both researchers and practitioners. The content is structured around three core themes: Establishing the fundamental principles of circular construction, implementing practical strategies for circular construction at both the building and material levels, and advancing circular construction through the integration of digital transformation. The first part (Chapters 1–5) establishes the groundwork for circular construc‑ tion. Chapter 1 underscores the contrast between high‑tech and low‑tech ap‑ proaches and outlines the challenges and opportunities in circular construction. The digitalisation of the built environment has to be developed with discernment to support the transition to a true CE, not to support profit for the linear economy, as is the case in the dominant current practices. Moreover, the environmental and DOI: 10.1201/9781003450023-1

2  Rabia Charef societal costs of the digitalisation of the built environment have to be assessed and balanced with the economic benefits. Chapter 2 emphasises the importance of reus‑ ing building components within a circular construction economy, discussing its his‑ torical context and recent resurgence. It addresses obstacles to reuse adoption and presents innovative solutions. Chapter 3, which examines the concept of buildings as material mines, explores the digitalisation of resource cadasters and presents a technological perspective on circular construction. Chapter 4 introduces the idea of a construction waste material (CWM) sharing economy, creates a framework, and looks at it in the context of China’s Greater Bay Area. It reveals the challenges in certifying and matching CWM in order to share them. The research suggests that combining technical advancements from sharing economies with non‑technical el‑ ements, such as market development and secure CWM delivery through monitor‑ ing or blockchain technology, is essential for the success of this sharing economy, offering new insights for establishing a robust CWM sharing market. Chapter 5, on the other hand, emphasises the significance of standardisation for implement‑ ing CE practices in the construction sector. Combined, these chapters prepare the ground and set the foundation for circular construction. The second part of this book, titled “Practical Strategies for Circular Construc‑ tion: Building and Material Levels,” shifts from theory to practical implementa‑ tion. It offers insights from both researchers and practitioners, highlighting their collaborative roles in advancing circular construction. Researchers innovate, while practitioners apply these concepts in construction projects, bridging theory and practice. Chapter 6 explores practical aspects like viewing buildings as material banks and emphasising pre‑redevelopment processes. This section also delves into advanced technical considerations for reusing reinforced concrete beams, focusing on feasibility and environmental impact (Chapter 7). Real‑world examples dem‑ onstrate efficient on‑site resource reuse, address challenges, and provide ideas for future projects. Indeed, Chapter 8 discusses the use of site‑specific and reclaimed materials in construction. It emphasises the role of historical analysis in identify‑ ing materials and adapting to unexpected challenges like material shortages. The study also explores how local insights influenced material choices and how de‑ construction efforts led to a community‑focused material platform, aligned with a university‑like model for experimentation and reporting. Chapter 9, on the other hand, explores material choices for CE in construction, emphasising local earth materials. It delves into the challenges faced by modern earth‑based construction projects, like the Lyon office building, considering technical, economic, and socio‑­ cultural factors. The chapter outlines an analytical approach to derive lessons for future projects. The final part of this book focuses on improving circular construction through digital innovation. Chapter 10 explores the impact of digitising the deconstruction process in the construction industry to advance CE goals. The chapter explores emerging technologies, outlines a collaborative approach for defining reuse strate‑ gies, and presents a pilot case in Luxembourg using the Digital Deconstruction integrated platform. Digital tools and platforms are being developed to identify reusable materials and improve the deconstruction‑to‑reuse process. Chapter 11

Introduction 3 discusses two case studies that illustrate how close collaboration between the cli‑ ent and the design team, along with digitalisation, has expedited material reuse in construction. These case studies skilfully utilise Material Passports to champion CE principles, particularly emphasising material reuse. They serve as compelling examples of technology’s pivotal role in achieving circularity and offer valuable industry insights. Chapter 12 explores the role of additive manufacturing (3D print‑ ing) in advancing circular economies within the built environment. It discusses various printing technologies suitable for this purpose and outlines their current and potential future applications. The chapter highlights four key entry points for additive manufacturing in the CE: design, construction, post‑construction, and ma‑ terials development, offering contemporary examples and an assessment of its po‑ tential and challenges in the built environment. A short Conclusion brings together the themes running through this book to set out direction for future research and practice.

Part 1

Setting the foundation for circular construction

1

The future of the circular built environment Interest of a “low‑tech” approach Rabia Charef and Philippe Bihouix

Introduction The Intergovernmental Panel on Climate Change (IPCC) assessments of environ‑ mental damage over the past decades give evidence that governments, industry, and most people are in a “parallel reality” (IPCC, 2022, 2014). Despite numerous warnings from various sources (Meadows et al., 1972) and the Brundtland report, among others, the global linear economy is extracting and consuming more and more resources, severely impacting life on Earth (Brundtland, 1987). The growth of the economy without any sign of transition to a more sustainable economy is consistent with the conclusion made by the historian Fressoz in 2022. Fressoz stud‑ ied the history of energy and resource consumption in Europe, showing that the switch from wood to coal was not a replacement but an accumulation because much more timber was needed for equipping coal mines. He critiques the idea that technological advancements alone will solve environmental problems without fundamental changes in societal structures and consumption patterns. Moreover, Fressoz contends that the focus on “green growth” and technological fixes in con‑ temporary environmental discourse often fails to address the underlying issues of overconsumption and the pursuit of endless economic expansion. He calls for a more profound re‑evaluation of societal values, consumption habits, and economic structures to achieve genuine sustainability (Fressoz, 2022). Population growth and the resulting demand for housing and infrastructure are factors that are not going to decline in the next decades. Indeed, as presented in many reports, the population may reach 9.5 to 10 billion people by 2050, with a high concentration in urban areas (United Nations, 2018, 2017). This will increase housing needs and the materials required to build them. Therefore, the number of extracted resources is going to increase, potentially more than doubling (from 79 to 167 billion tons) between 2011 and 2060 (OECD, 2019). Population growth and its desire to maintain or develop high standards of living are also increasing the pressure on our planet. Some authors promote green growth, but others call for degrowth and sobriety (Bihouix and McMahon, 2020). Digitalization, particularly in the construction sector, is not the Holy Grail as many have claimed. Bihouix (2022) has highlighted the negative aspects of digital‑ ization and its high demand for high‑tech metals and extremely low recycling rates, DOI: 10.1201/9781003450023-3

8  Rabia Charef and Philippe Bihouix and hence its critical effect on the environment. Bihouix stressed the pollution im‑ pact of the activities required by the mining and metallurgical industries. Indeed, energy consumption and pollution are omnipresent throughout the lifecycle from extraction to end‑of‑life management, which is very complex. In addition to this environmental disaster, we will probably also discover some negative impacts of systematic digitalization on human health and questionable evolutions of cognitive patterns and human societies (Bihouix, 2022a). Similarly, the growing interest in the circular economy (CE) among researchers, practitioners, and governments requires acknowledgement and discussion, but CE should not be viewed as a simple solution to a complex challenge. Although some researchers analysed 114 definitions of the CE, and more recently 221, there are still amalgams made between recycling and the CE leading directly to greenwash‑ ing (Kirchherr et al., 2023, 2017; Willis et al., 2023). Precise definitions and clear statements of what the CE is, and just as importantly what it is not, in relation to the built environment are still required. The role of standardization is crucial, for the implementation of the CE at a large scale, and also for a common understanding (Charef et al., 2021b; Ottosen et al., 2021). Charef (2022) stressed the positive and negative aspects of digitalization and the CE in a brief article (Charef, 2022a). Other thinkers criticize the CE question‑ ing the virtues advocated by its defenders (Corvellec et al., 2022). In addition, the circularity gap report assesses that only approximately seven percent of the global economy is circular (Crowe et al., 2023). Cloud systems for instance, underlined by many players as being a kind of panacea for improving urban metabolism via data collecting and analysis, require a lot of materials to set them up, generate tons of E‑waste that increased by 21% over the last five years, and are poorly recyclable. Only 17% of E‑waste worldwide is recycled. Moreover, digital could refer to the sector itself or the tool altering other sectors by digitalizing their pro‑ cesses. A deep analysis needs to be done to ensure that digitalization is “part of the solution and not the problem” (Verne, 2021). Indeed, the rebound effect is now well‑documented and an attractive area of research (Font Vivanco et al., 2022; Galvin, 2015). This chapter aims to raise awareness of the risks of unrestrained development. It focuses on the paradigm shift needed to address the current challenges facing the construction sector. In doing so, the links to the chapters in this book are high‑ lighted to provide readers with the context for navigating the book’s contents. Is high‑tech the panacea? The current dominant high‑tech approaches and their consequences in the linear economy context

Faced with environmental challenges, we are counting on new technologies to re‑integrate within planetary limits: renewable energies, hydrogen, digital applica‑ tions, future smart cities optimized with shared autonomous vehicles, carbon cap‑ ture, and so on. However technological development creates its own challenges.

The future of the circular built environment  9 First, high‑tech consumes resources, metals, and fossil fuels. To date, there has been no real dematerialization of the economy. On the contrary, the IPCC reports point to the massive acceleration of extraction of various metals that is, and will be necessary in next decades, to fuel the energy transition based on renewable ener‑ gies, storage devices, electric mobility solutions, etc. Indeed, according to current and forecast data, the dematerialization of the economy is a distraction. We have never consumed so many resources, more than 90 billion tons per year (OECD, 2019; United Nations, n.d.). Similarly, the waste generated also increases, reaching record amounts, about 35 billion tons per year (Crowe et al., 2023). The logic of the CE can help to reduce this “extractive” pressure and recirculate the “waste” generated as much as possible as a valuable resource. However, it is not an easy task, particularly because the waste is coming from goods, materials, and components designed for the linear economy (Benachio et al., 2020). Simi‑ larly, accounting standards and principles are also designed for the linear economy and must be revised to be able to capture the value of the CE approach (Laundes Foundation, 2023). Indeed, when buildings or products are not designed by fol‑ lowing the principles of CE, they are difficult to deconstruct without damaging the components and without loss of functionality or quality (downcycling) (Corvellec et al., 2022). Moreover, the mixing of materials, the increasing complexity of ob‑ jects, and the use of very small quantities in miniaturized products and integrated electronics make recycling even more difficult. Some authors believe that reducing complexity is a key parameter for moving towards the CE, whether at the build‑ ing, systems, product, or material levels (Brancart et al., 2017; Desing and Blum, 2022). On a global scale, the end‑of‑life recycling rate (EOL‑RR) of half of the 60 or so metals is less than one percent (UNEP, 2011). As stressed by Michaux, we “don’t have enough minerals and materials in the Earth’s crust to develop a fully renewable economy”. According to Michaux, the only solution is to reduce our energy and material demands by living simpler, in line with what the authors call sobriety. Considering the time and cost parameters, reinforce the fact that it is not possible, one does not have enough resources, time, and money “to build the renewable non‑fossil fuels industrial system or satisfy long‑term demand in the current system” (Michaux, 2021). Therefore, for example, switching to electric cars is not going to solve the problem but will make it worse if global thinking on size and use of individual vehicles is not integrated. Second, if they are in a defined sector, when all sectors are combined the result is less clear. While some technologies may seem interesting, their real environmen‑ tal benefits are far from obvious. For example, future autonomous cars or smart city applications require the deployment of major digital infrastructures (5G or even 6G telecom networks, data centres, etc.). Before the environmental benefits resulting from transformed services or practices can be realized, a lot of electricity and re‑ sources will have to be consumed or mobilized. The global digital system (personal equipment, networks, data centres) already consumes more than 10% of electric‑ ity and emits around one billion tons of CO2 per year  –  significantly more than air transport before the COVID‑19 crisis. While the ecological applications of the smart city are still vague, the feedback on the first smart buildings, for example, is

10  Rabia Charef and Philippe Bihouix often disappointing, regarding actual performance in the long run, maintainability, costs, and user experience. Some of the main drawbacks of smart buildings are the high initial costs, the complexity and compatibility issues, the privacy and security concerns, the technology obsolescence, and the skills and knowledge gaps (Harper et al., 2021; Srividya, 2022). Third, technological efficiency is often, at least partially, annihilated by the re‑ bound effect, also known as the “Jevons paradox” (Jevons, 1865). Indeed, when each product or service is more environmentally efficient per “unit”, it is then less expensive, and therefore more readily consumed. Generally, environmental effi‑ ciency also results in an economic gain (less energy and/or resource incorporated or mobilized), leading to an increase in uses, and an increase in the environmental cost as a global result. This is the case in several sectors, such as the car industry (with more optimized engines but ever heavier vehicles), the digital sector (with volume of data increasing faster compared to the efficiency gains of data centres and radio access networks), the air transportation sector (turbojets consuming less kerosene, allowing the development of low‑cost players and additional commercial lines and passengers), the ground transportation sector (new high‑speed train lines that do not empty planes but cause or enable new trips), etc. Low prices inevitably stimulate demand and increase the production of any good or service (Ovaere and Proost, 2022). In the building sector, the built‑up areas and surfaces per inhabitant continue to increase, and thermal renovation is generally accompanied by “an improvement” in comfort in the form of an increase in setpoint temperatures (see later). Introduction to low‑tech concept

The term low‑tech is enough on its own to arouse skepticism or even rejection. Indeed, who would like to be treated in a low‑tech hospital, drive carefree in a low‑tech car, or depend on a low‑tech communications network? For decades, cus‑ tomers and users have become accustomed to the incredible efficiency of high technologies, to the rapid and numerous innovations, and to the phenomenal ad‑ vances in the performance of electronics and computing. However, it is crucial to specify that the low‑tech supporters do not fantasize about a return to troglodyte times. What if, on the contrary, far from being retrograde, an approach based on so‑ ber, agile, and resilient technologies was at the forefront of modernity? Indeed, the authors consider the low‑tech could be used as a reflection and a fruitful approach, applying to all activities, including the high‑tech sectors. Like the CE, the low‑tech approach should have several principles to guide practitioners. Based on semi‑structured interviews, Tanguy et al. came out with seven key principles. (i) decrease the resource consumption, (ii) service life ex‑ tension, (iii) appropriation of the approach by having a good understanding, (iv) develop collective networks, (v) return to basics, (vi) Limited external dependency, and (vii) consider the context and scale (Tanguy et al., 2023). For example, for the second principle related to the extension of the product duration, we need to rethink/redesign our goods and products to significantly increase their lifespan, by enabling their reuse, repair, remanufacture, and ultimately optimizing their proper

The future of the circular built environment  11 dismantling and resource recycling rates. Products need to be redesigned in a simple and robust way by using standardized elements, systems, and a modular approach, conducive to deconstruction. In the case of buildings, they also need to be resilient, flexible, and even adaptable to the evolving users’ needs (Watt et al., 2023). In ad‑ dition to the seven key principles, the adaptation of the approach to product types is also crucial. Indeed, the use of safe, chemical‑free components should be strictly adhered to, while non‑renewable, rare, and irreplaceable resources should be used sparingly (Bihouix, 2020). The last important principle could be to change con‑ sumption patterns. Emblematic examples are fast fashion or the mobile phone and IT industries: do we really need to change our mobile phone for a new one when our current phone still works well? In the construction industry, does every family need an extra spare bedroom that will be used a few times a year? Does the second home, vacant most of the time, make sense in a housing crisis context? These ques‑ tions raise social concerns that require a radical change in human behaviour and consumption. Sobriety before efficiency, a shift of paradigm

First, instead of dealing with the end‑of‑pipe issues, it seems more efficient to tackle the problem at the source by reducing needs and driving down the demand. In other words, sobriety before efficiency, notions that sometimes tend to be con‑ fused. For example, in the construction sector, the efficiency strategy is to insu‑ late buildings to invest less energy in heating/refreshing them less and thus reduce the “environmental bill”. However, the sobriety strategy will question the needs, whether in terms of comfort needs (which thermal comfort is really required, and which could be “given up”?) or occupation needs. For the moment, sobriety is of‑ ten forced by circumstances and temporary rather than organized and piloted action towards climate change mitigation and/or resilience. Indeed, in Europe, during the energy crisis following the war in Ukraine (2022–2023), the term “sobriety” has become commonplace and especially a language used by governments. Second, we need to aim for big milestones to expect big impacts. Governments are efficient for the most innocuous “small actions”, such as unplugging the Wifi box when leaving on vacation, turning off the sign’s lights at night, and closing the doors of air‑conditioned shops. However, although these small steps are symboli‑ cally important, big impacts will require the questioning of needs and injunctions to economic growth. We should question our ways of living and recognize our responsibility for the destruction of the biosphere. With good arguments, some ac‑ tions could be the object of a democratic consensus, like, for example, the removal of many disposable items, except some for medical use. The actions that are dif‑ ficult to implement are those that require the most effort with legal or regulatory adaptations, such as banning disposable packaging, encouraging reuse as much as possible, or reducing meat consumption. As the tension on resources may increase in the long term, the small steps will need to be followed with more complex, more “systemic” actions, more difficult to implement and get accepted, requiring a real holistic, societal, and socio‑technical approach.

12  Rabia Charef and Philippe Bihouix Techno‑discernment and limited automation and mechanization

Revisiting production methods will also be required by asking whether the race for productivity and the effect of upscaling in automatized, robotized giga‑factories should continue for all types of products. Would it be better to develop workshops and companies on a human scale, at least for specific types of production? Should we not review the role of humans and the sometimes unjustified degree of mechanization and robotization? Soon robots and artificial intelligence may replace humans in additional places, eliminating many jobs but engendering extra material needs. The objective is not to “de‑mechanise” all types of production. But we should think how we balance human labour on the one side, and consumption of resources and energy on the other. In the construction sector, the use of local and sustainable materials with a preference for reuse materials, components, and equipment, and the priority given to reno‑ vating and transforming buildings already produced, are both more intensive in human labour and, therefore, often more costly in the current economic system. Recovery networks could be developed and organized to enable repair, reuse, resale, and sharing activities, but their economic balance is for the moment far from being achieved. Thinking low‑tech is therefore much more than designing “fun” products such as a washing machine with pedals or the solar shower. It means collectively chang‑ ing the current production and consumption methods: craftsmen or small‑scale pro‑ duction workshops, shorter sale and distribution circuits, zero waste approaches, plants for reuse, repair, repurposing, remanufacturing, and recycling. It is also hav‑ ing a different design mindset, a systemic eco‑design, or using “design for” ap‑ proaches (Design for Deconstruction, Design for Disassembly, etc.) as clarified by (Charef et al., 2022). The alternative – and quite disruptive – model required has not yet been in‑ vented and tested. Bihouix qualifies it as a “post‑growth” economic system, ca‑ pable of offering people permanent jobs and promoting local development, that would be more resilient and respectful of ecosystems (Bihouix and McMahon, 2020). The originality of this system is to tackle the roots of the problem instead of using the end‑of‑pipe approach. For example, the prohibition of the most polluting productions, the policy of reducing mobility needs by better regional and city plan‑ ning, and the rational use of digital technologies (rather at the hospital to help the surgeon than at school to replace books and teachers). In the following sections, we will elaborate on the low‑tech approach to the building sector, which is one of the most impactful on the environment. The low‑tech approach applied to the construction sector Although some pitfalls need to be avoided, the low‑tech approach is quite easy to implement in the construction sector, compared to other sectors. Indeed, consider‑ ing a “low‑tech plane” or “low‑tech internet” appears more challenging compared to the idea of a “low‑tech house (or building)”.

The future of the circular built environment  13 Sobriety: intensification of the use of existing buildings

In the European construction sector, the need for new constructions could be re‑ duced by intensifying the use of existing buildings, concentrating technical and fi‑ nancial resources on rehabilitation, renovation, transformation, and refurbishment. Many analyses could be carried out to intensify the use of surfaces already built. This is why knowing the building stock and spaces available is crucial, as reported by many authors (Maury‑Ramirez et al., 2022). The under‑utilization can be ad‑ dressed not only in housing (vacancy rate, second homes, under‑occupation) but also in public buildings, industries, workshops and storage surfaces, offices, park‑ ing areas, etc. Vernacular vs low‑tech architecture

Low‑tech and vernacular are different, and confusion should be avoided. Relying on “old techniques” does not mean doing things the old‑fashioned way, but they could be used as sources of inspiration. The best of human experience, scientific and technical knowledge, could be applied to new contexts. Indeed, the old con‑ struction methods should be inspiring to find alternatives to the current use of steel and concrete which are recognized as an important generator of CO2 emissions (Belaïd, 2022). Geo‑sourced materials (stone and earth in all their diversity, etc.) and bio‑sourced materials (timber, thatch, straw, etc.) are preferable construction options to lower CO2 emissions from the construction sector (Martins et al., 2022). They also have the potential to provide natural ventilation and thermal comfort. Another aspect is the orientation of buildings and streets according to the climate (Giesekam et al., 2016; Pelé‑Peltier et al., 2022). Low‑tech architecture: an approach rather than a recipe

Low‑tech architecture is not a “friendly do it yourself” approach that could be used only for some emblematic buildings (Parisi, 2021). Instead, it should apply to all situations and scales, whether objects, buildings, neighbourhoods, cities, or even territories, as discussed by Detavernier and Le Bot (2022). Indeed, at the city level, over the next few decades, cities will have to evolve mainly due to the coming changes, such as new uses and consumption patterns, strategies for mitigating and adapting to climate change, etc. The low‑tech approach needs to start with the simple question: do we really need to build? Do we need to demolish? Would it be possible instead to rehabili‑ tate, transform, and adapt? How many square meters do we “really” need? These questions need to be answered during the programming phase, before starting the design, and with the end in mind, in terms of the use of resources, the material end‑of‑life management, and actual space usage. The organizational change and the importance of the programming phase are explained by some authors for the case of circular buildings. Charef (2022) provided a trans‑scaler framework to sup‑ port construction actors in their understanding of how to start a circular project

14  Rabia Charef and Philippe Bihouix (Charef, 2022b). Similarly, some authors, based on a literature review and the inter‑ views of the low‑tech players, have developed a seven‑principle framework aimed at clarifying the concept of low‑tech (Tanguy et al., 2023). The framework aims to support the understanding of the low‑tech approach and to be able to differentiate it from other sustainability concepts, including the CE. Indeed, low‑tech thinking is a counter‑model to the smart city, allowing other modes of operation and organiza‑ tion (Bihouix et al., 2022). A low‑tech approach is not intended to replace or include all previous sustain‑ ability concepts but should be considered as a posture and a state of mind, rather than as a “labelling logic” with several criteria to check (Lefrançois, 2020). Indeed, generally, the construction stakeholders limit their approach to sustainability by claiming to reduce the in‑use energy of the buildings. They increase the insula‑ tion for new constructions and for existing buildings. In the case of renovation of existing buildings that represent approximately 197 million households in the EU, around 75% of the building stock is energy inefficient with a very low renovation rate, between 0.4 and 1.2% per year (Firląg, 2018). This figure makes it neces‑ sary to address first the existing building challenges rather than designing “perfect” new buildings. However, reducing the in‑use energy of buildings is necessary but insufficient. We must move from the approach of “less bad”, which is not good enough to a “more good” approach (McDonough and Braungart, 2002; Simpson et al., 2022; Verberne, 2016). The low‑tech and the CE approaches appear to be more holistic with greater im‑ pacts. However, these approaches certainly come up against technical barriers but not only. Various other barriers, whether social, organizational, or economic, must be overcome. These issues were reported by several authors, for the CE approach (Charef et al., 2021a, 2021b; Hart et al., 2019). Regarding the low‑tech approach, it integrates three main generic assets. First, a low‑tech approach has straightforward implementation feasibility without delay. Indeed, once established the low‑tech actions will not face high‑tech barriers. For example, in the case of thermal renovation, reducing the comfort temperature of indoor air can be technically done immediately. In Europe, people could “easily” get into the habit of wearing appropriate clothing inside their accommodation. The complexity is not technical but social, cultural, and organizational. People need to be convinced to change their habits and behaviour (négaWatt, 2022). Similarly, for the use of reclaimed material, several authors point out several types of challenges, including social barriers (Charef and Lu, 2021; Pelé‑Peltier et al., 2022). The sec‑ ond main generic asset is that the assessment of the benefits is not necessary. In fact, the reduction of the comfort temperature of the rooms will have an immediate effect on the consumption of energy and a positive chain reaction to reduce the impacts (less transport, less pollution, etc.). Similarly, reusing reclaimed materials will, as a minimum, reduce the use of virgin materials and the energy required to manufacture them. The last generic asset is probably avoiding the rebound effect, by taking into account not only the technical aspects but also the behavioural and societal aspects of the consumption.

The future of the circular built environment  15 The advantages of the low‑tech approach in the construction sector

The low‑tech approach in construction refers to using simple and traditional meth‑ ods, materials, and technologies to build. It emphasizes sustainable practices, reduced energy consumption, and a focus on human labour rather than relying heavily on complex machinery and advanced technologies. The first key advantage of the low‑tech approach in the construction sector could be cost‑effectiveness. Indeed, low‑tech construction methods often involve the use of locally available and affordable materials, reducing overall construction costs. Traditional techniques and local craftsmanship can also minimize labour expenses compared to high‑tech construction methods that rely on expensive machinery and specialized skills. However, the cost advantage may depend on local labour costs and be more achievable in emerging countries rather than developed countries. The second advantage is the reduction of environmental impact. Low‑tech con‑ struction promotes sustainable practices by utilizing natural and renewable resources, minimizing waste generation, and reducing energy consumption. It often involves strategies such as passive design, natural ventilation, daylighting, and the use of eco‑friendly and/or highly recyclable materials. This approach aligns with the princi‑ ples of ecological balance and reduces the carbon footprint of construction projects. Moreover, low‑tech construction methods are often characterized by their simplic‑ ity and ease of implementation. Buildings built using these methods tend to be more adaptable and resilient, making them suitable for various contexts and climates. They can be more easily repaired, modified, or dismantled, reducing the environmental im‑ pact, and facilitating future adaptability. The local empowerment and community en‑ gagement are also important benefits associated with the low‑tech approach. Low‑tech construction methods often involve the participation of local communities and skilled craftsmen, promoting local knowledge and empowering individuals with construc‑ tion skills. It can contribute to local economic development and cultural preserva‑ tion, maintaining the connection between people and their built environment. Also, low‑tech construction methods can be more accessible and inclusive, allowing for the participation of individuals (and future users) with varying skill levels and resources. It reduces the dependence on advanced machinery and technology, making construction practices more accessible to communities with limited resources or in remote areas. Finally, low‑tech construction has undeniable aesthetic value and potential for preserving cultural heritage. Indeed, low‑tech construction often celebrates tradi‑ tional architectural styles and craftsmanship, creating aesthetically pleasing struc‑ tures that reflect the cultural heritage of a region. By using local materials and techniques, it helps preserve local architectural traditions and materials consistency and contributes to the cultural identity of a place. While the low‑tech approach in construction has several advantages, it may not always be suitable for every project or context. Modern technologies and tech‑ niques can offer benefits in terms of speed, precision, and specialized functionality. Therefore, a balanced approach that combines low‑tech methods with appropriate high‑tech interventions can be beneficial, depending on the project requirements and sustainability goals.

16  Rabia Charef and Philippe Bihouix Existing buildings: the case of the thermal renovation In the building sector, in‑use energy “sobriety” is one tool used to fight against cli‑ mate change. Part of the European Green Deal, the “Renovation Wave of Europe” aims to pursue the ambition of energy gains and economic growth. The goal set up by the European Commission is to double the annual energy renovation rate in the next decade. The first buildings that require to be insulated are the worst‑­ performing buildings, known as “thermal sieves” (buildings ranked F and G in the Energy Performance Certificate scheme). The other target is the decarbonization of heating and cooling by moving away from fuel and gas. The expected impacts are the reduction of CO2 emissions, the improvement of the users’ quality of life, and the creation of green jobs. The shortcomings of the current approach

Despite this strong willingness of the European Commission, several signals may bring doubts about the effectiveness of this renovation strategy, and the actual ca‑ pacities of the European countries to implement the renovation program at the right pace. For instance, in France, the “national carbon strategy” (SNBC, Stratégie Nationale Bas‑Carbone), a French energy transition law established in 2015, has set up a plan enabling France to respect the international carbon neutrality commit‑ ments by 2050. For the building sector (residential and tertiary), a 40% reduction in energy consumption is expected between 2015 and 2050 (SNBC, 2020) while a recent decree targets to reduce consumption by 40% by 2030 and 60% by 2050 for the renovation of the tertiary sector (2015 as the reference year). Despite the ambitions of the construction sector and public authorities, the first expected “performance jump” has been postponed because the implementation of the renovation wave was encountering some challenges, mainly a lower rate of renovation and a lower impact than expected. Indeed, the first carbon budget from the SNBC (2015–2018 period) was exceeded by 11% for the building sector. Con‑ sequently, for the following periods, the objectives have been revised (revision of the second carbon budget and its sectoral distribution) (Ministère de la Transition écologique et solidaire, 2020). The first issue is the difficulties in the implementation of renovation operations. On the demand side, mobilizing owners and co‑owners is proving tough and re‑ quires financial support and incentives (tax credits, energy‑saving certificates, etc.). On the supply side, enough trained and skilled companies and craftspeople are needed. Drastically increasing the renovations carried out is a real industrial, so‑ cial, and human challenge, with no guarantee to date for its reachability. Indeed, this challenge needs to be carried out in parallel with other large‑scale programs, such as the deployment of renewable energies, the potential “revival” of nuclear power, and the adaptation of electrical transport networks, among others. The second issue is that a significant part of the expected efficiency (calculated by the technicians) is lost by the rebound effect. Indeed, when buildings are better insulated, the inhabitants tend to modify their uses, to increase the temperature in

The future of the circular built environment  17 their homes. In Germany for instance, the real estate federation GdW noted that if 340 billion euros were invested in housing thermal renovation from 2010 to 2018, the average energy consumption only decreased from 132 to 130 kWh per square‑meter per year (Appunn, 2020). Even if this observation should be further analysed, all players involved in operational renovation recognize the importance of this effect. Insulating buildings is insufficient without addressing references of internal thermal comfort and changing habits (ADEME, 2021). Toward a low‑tech renovation: redefining the thermal comfort standard

Another approach could be to adopt a less industrial and standardized approach, better involving end‑users. It could be necessary to extend the analysis of the use of heat, even question the historical approach to comfort to consider a “techno‑­ discernment approach” for the renovation program, as stressed by several authors (Bihouix, 2022b; OID and CentraleSupelec, 2021). It may appear as a more artisanal approach, but it could also be faster and adapt‑ able to a diversity of situations, whether single‑family or multi‑unit dwellings or types of construction and uses. Obviously, the low‑tech approach is not about re‑ nouncing all comfort, but it is a question of moderation and change of habits. As brought by Olivier Rey (2014), our modern societies are victims of “hubris”, ex‑ cessiveness, and immoderation, and should find ways to stick back to the “right measure” (Rey, 2014). Thermal comfort inside buildings is not that old. In the second half of the 19th century, central heating appeared and developed, pushing people to leave their flannel and woolen clothes and use coats and mantles to go outside (Chansigaud, 2020). In the energy abundance of the “Glorious Thirties” (circa 1945–1975), com‑ fort became widespread, and the set temperature rose, at home and in the labour places (offices, workshops, some factories…), to reach today 22 or 23°C. Lowering the temperature would be a quick, free, and effective lever compared to the insula‑ tion of buildings. In line with this, the French strategy is counting on a voluntary drop in the heating temperature of 1°C on average by 2050. The strategy and public actions are not known yet as the actual practices of French users. A lead could be given by Japan history. Indeed, after Fukushima and the rapid shutdown of all the nuclear power plants, Japanese ministers wore a sweater in winter and encouraged people to wear light clothing in summer to avoid the use of air conditioning, (Cor‑ day, 2022). It could also be possible to draw inspiration from old techniques which made it possible to achieve a certain thermal comfort, using an extremely limited en‑ ergy resource (“Low Tech Magazine”, n.d.). Thermal comfort is not only linked to heating: it is the result of a complex equation that depends, of course, on the temperature of the room, but also on the relative humidity, the characteristics of the walls and the floors’ materials, the way of diffusing the heat, the way people are dressed and the activity they are engaged in (De Decker and Collett, 2015). Hence a low‑tech thermal renovation should question the uses before focusing on the right techniques, materials, and processes to implement. The aim is to achieve the “best”

18  Rabia Charef and Philippe Bihouix thermal comfort, as environmentally friendly as possible. Could the constraints that the electricity grid may experience in the 2030s or 2040s be an opportunity to ques‑ tion uses and put in place habits (or laws?) requiring citizens to wear appropriate clothes for each season? Conclusion In the construction sector, the low‑tech approach can theoretically offer several (theoretically quite) simple solutions to help overcome the coming challenges in the industry. Low‑tech does not imply a low level of thinking. On the contrary, it often necessitates a higher level or more complex level of thinking to embrace a consistent holistic approach to the challenges. The low‑tech approach applied to the construction sector provides several bene‑ fits, and has the potential to be implemented straightforwardly, quite easily, without delay, and without facing high‑tech barriers. Accessibility and inclusivity are also key benefits allowing individual involvement and reducing technology depend‑ ence. The low‑tech approach should also be less sensitive to rebound effect, and the benefits do not require to be precisely assessed, because of their obviousness. The potential cost‑effectiveness of a sobriety‑based design and construction method is also a key aspect to consider. The low‑tech approach has the potential to empower local economic development and the commitment of communities. Lastly, it ena‑ bles the preservation of cultural heritage. Efforts required from governments and local authorities

To foster the implementation of low‑tech approaches, a coordinated effort involv‑ ing various stakeholders, including public authorities is required. Indeed, the pub‑ lic authorities at all levels could promote and implement this transition towards a low‑resource system. Currently, initiatives having the potential to promote and support the adoption of low‑tech solutions are popping up everywhere and have the potential to be multiplied, amplified, and generalized. Some regulations or tax measures may be considered technocratic or liberticidal and target vulnerable pop‑ ulations. However, used with fairness and exemplarity, they remain effective tools. Governments and local authorities have prescriptive and local support powers. They could use normative and regulatory levers to support and assist the imple‑ mentation of a low‑tech approach and push the specifications in the direction of sustainability. For instance, each municipality could open repair, reconditioning, and recycling centres. Additionally, highly polluting products and services need to be prohibited or their use should be strictly controlled. Likewise, waste should be “punished” (taxed more). “Zero waste” initiatives could be launched or amplified, and many disposable products could be banned. By taking these following steps, public authorities can provide a supportive environment for the implementation of low‑tech approaches and encourage their adoption in various sectors including the construction sector, leading to sustainable and resilient solutions for environmental and societal challenges. Indeed, public au‑ thorities can play a crucial role in creating awareness about the benefits of low‑tech

The future of the circular built environment  19 approaches among the public, businesses, and other relevant stakeholders. This can be done through campaigns, workshops, conferences, and educational programs to highlight successful low‑tech projects and demonstrate their effectiveness to the public and potential adopters. They can also collaborate with academic institutions, research centres, and in‑ dustry experts to ensure the technology transfer from academia to industry. Edu‑ cational resources and training programs on low‑tech solutions are also required. Public authorities can invest in research and development activities related to low‑tech approaches by allocating funding and providing financial support for pilot projects, innovation grants, and public‑private partnerships. They can also estab‑ lish standards and certifications for low‑tech products and services to ensure qual‑ ity and reliability, which can boost consumer confidence and market demand. In the construction sector, the second‑hand market needs to be organized locally to reduce the transport of goods. At the same time, border adjustment mechanisms should be implemented, to allow the economic sustainability of local production. Relocations need to be avoided as much as possible because they are counter‑productive for the environment. Tax system and other incentives

Another way where public authorities could play a key role is by developing policies and regulations that incentivize and support the adoption of low‑tech ap‑ proaches. This can include tax breaks, subsidies, grants, and other financial incen‑ tives for businesses and individuals implementing low‑tech solutions. Using a tax system and having a productivity‑driven strategy is costly in resources and energy and generates all kinds of pollution. Rising carbon, energy, and resource prices coupled with reducing the human la‑ bour cost and incentives promoting human labour and the local economy could be a strategy. Having human employment at the core will have beneficial impacts on the environment. Also, the taxation on the consumption of resources, the artificializa‑ tion of soils, and the production of hazardous or non‑hazardous waste remain very low. We should also enter a dynamic process of trying to save resources and make things more and more repairable and durable. In that respect, reuse, repair, recy‑ cling, and job‑driven activities would be favoured, to the detriment of machines or management software hosted in data centres. In the management of end‑of‑life activities of buildings, deconstruction needs to replace the current demolition. As deconstruction is a meticulous activity, it is time‑consuming and must be done manually, thus having the potential to create jobs. Craft trade, small businesses, renovation, reuse, short circuits, all more intensive in human work, creators of social ties, anchored in the territories, would find a new breath. Innovation and new technologies: caution

Additionally, innovation, such as artificial intelligence and blockchain, needs to be considered carefully. The environmental impacts of the use of new technolo‑ gies should be assessed and avoid aberrations such as the ultra‑connected trend.

20  Rabia Charef and Philippe Bihouix Similarly, while automation and manufacturing have the potential to bring nu‑ merous benefits to the construction sector, there are also some drawbacks and challenges associated with their implementation. Additive manufacturing, also known as 3D printing, associated with the CE approach has some advantages, such as enabling localized production, providing design flexibility, and reduc‑ ing waste compared to traditional manufacturing. Although it could have simi‑ lar advantages in a low‑tech approach, some limitations must be considered. Indeed, 3D printers require certain infrastructure and resources to function effectively (internet connection, raw materials, etc.). Overall, while additive manufacturing can offer advantages in low‑tech approaches, its implementation should be carefully evaluated based on the specific context, resources, and goals of the project. Transitioning from conventional construction practices to low‑tech methods requires careful planning, collaboration, and adaptation to ensure a smooth and successful transformation. Indeed, shifting from high‑tech to low‑tech approaches may require upskilling and retraining the existing workforce. Moreover, the in‑ frastructure and supply chain must be adapted to adjust to new demand, such as locally sourced materials and traditional construction products. Implementing a low‑tech solution might require upfront investments in new equipment or changes in project management. Also, policies and regulations need to be aligned to accom‑ modate sustainable and low‑tech construction practices. A gradual (but rapid if possible!) shift needs to be targeted to provide time for market acceptance and consumer education. As low‑tech solutions gain recognition for their sustainability benefits, demand for such construction methods is likely to grow. While a gradual approach is beneficial, it is crucial to maintain a sense of urgency and a commitment to continuous improvement. Regularly revisiting and reassessing the progress and goals can help construction companies stay on track and make the necessary adjustments for a successful transition to a low‑tech ap‑ proach in the construction sector. The low‑tech approach can closely align with and be integrated into the prin‑ ciples of the CE. Both concepts share common goals and strategies aiming at pro‑ moting sustainability, resource efficiency, and reducing environmental impact. By integrating the principles of the CE into the low‑tech approach, the construction industry can enhance its sustainability and environmental responsibility while pro‑ moting economic viability and social well‑being. Together, they contribute to a more resilient and resource‑efficient built environment. References ADEME, 2021. Transition(s) 2050. Choisir maintenant, agir pour le climat. Appunn, K., 2020. Rebound effect undoing decade of Germany’s home efficiency ­investments ‑ housing companies [WWW Document]. Clean Energy Wire. https://www. cleanenergywire.org/news/rebound‑effect‑undoing‑decade‑germanys‑home‑efficiency‑ investments‑housing‑companies Belaïd, F., 2022. How does concrete and cement industry transformation contribute to miti‑ gating climate change challenges? Resour. Conserv. Recycl. Adv. 15, 200084. https://doi. org/10.1016/j.rcradv.2022.200084

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The future of the circular built environment  23 Ottosen, L.M., Jensen, L.B., Astrup, T.F., McAloone, T.C., Ryberg, M., Thuesen, C., Lütken, S., Christiansen, S., Damø, A.J., Odgaard, M.H., 2021. Implementation stage for circular economy in the danish building and construction sector. Detritus 16, 26–30. https://doi. org/10.31025/2611‑4135/2021.15110 Ovaere, M., Proost, S., 2022. Cost‑effective reduction of fossil energy use in the European transport sector: An assessment of the Fit for 55 Package. Energy Policy 168, 113085. https://doi.org/10.1016/j.enpol.2022.113085 Parisi, M., 2021. Rénover Low‑tech c’est tout naturel, Profeel, Agence Qualité Construction. Pelé‑Peltier, A., Charef, R., Morel, J.‑C., 2022. Factors affecting the use of earth material in mainstream construction: A critical review. https://doi.org/10.1080/09613218.2022.2070 719 51, 119–137. https://doi.org/10.1080/09613218.2022.2070719 Rey, O., 2014. Une question de taille, Stock. ed. Simpson, E., Whiting, K., Carmona, L.G., 2022. Re‑envisioning innovation for sustain‑ ability, in: EcoMechatronics: Challenges Fpr Evolution, Deelopment and Sustainability. Springer, pp. 13–28. https://doi.org/10.1007/978‑3‑031‑07555‑1_2 SNBC, 2020. Stratégie nationale bas‑carbone ‑ La transition écologique et solidaire vers la neutralité carbone. Srividya, P., 2022. Smart Buildings Automation System. Chapter 3, In Smart Buildings Digi‑ talization. CRC Press, Taylor & Francis Group, 29‑38. Tanguy, A., Carrière, L., Laforest, V., 2023. Low‑tech approaches for sustainability: Key principles from the literature and practice. Sustain. Sci. Pract. Policy 19. https://doi.org/ 10.1080/15487733.2023.2170143 UNEP, 2011. Recycling Rates of Metals: A status Report, UNEP. United Nations, 2018. World Urbanization Prospects: The 2018 Revision e c t s: The 2018 Revision. United Nations, 2017. World Population Prospects ‑ Key findings and advance tables. United Nations, n.d. Goal 12: Sustainable consumption and production [WWW Docu‑ ment]. https://www.un.org/sustainabledevelopment/sustainable‑consumption‑production/ (accessed 4.24.23). Verberne, J., 2016. Building Circularity Indicators – An approach for measuring circularity of a building. Eindhoven University of Technology. Verne, X., 2021. Questioning the digital reflex. F. Actions Sci. Rep., the journal of field ac‑ tions, (Special Issue 23), 50‑53 Watt, H., Davison, B., Hodgson, P., Kitching, C., Tingley, D.D., Watt, H., Davison, B., Hodgson, P., Kitching, C., Tingley, D.D., 2023. What should an adaptable building look like? Resour. Conserv. Recycl. Adv. 200158. https://doi.org/10.1016/j.rcradv.2023.200158 Willis, J., Bofiliou, T., Manili, A., Reynolds, I., Kozlowski, N., 2023. The Greenwashing HYDRA, Planet Tracker, https://planet‑tracker.org/the‑greenwashing‑hydra/.

2

The reuse of building elements Touchstone of a circular construction economy Lionel Devlieger and Arne Vande Capelle

Introduction This chapter covers the topic of building component reuse. This subject needs to be distinguished from the reuse, after refurbishment or adaptation, of entire buildings, as in ‘adaptive reuse’. As has been rightly pointed out by (Stricker et al., 2022) the question of correct terminology is crucial. Building component reuse, sometimes building element reuse or ‘piece‑wise reuse’, refers to the practice of salvaging components from a building with the aim of reusing them, usually with the same or a similar function, in a new building or renovation project. From the moment a component is unhinged from the original assemblage, to be reintegrated in another assemblage, this is called component reuse. That reuse can happen on the same building site (for instance, on‑site reuse of bricks, or in masonry that is taken down, then rebuilt in another configuration) or on another building site (off‑site reuse). Building materials or components reuse is also to be distinguished from recy‑ cling practices, as the latter implies the thorough transformation of the original element or material through mechanised crushing or melting. In reuse, the origi‑ nal shape and properties of the component are not or only slightly altered. This does not mean there is no handling involved. A typical sequence implies careful dismantling, packaging, cleaning, refurbishing or repairing, sorting, labelling, and re‑installation in a new project, with phases of packaging, transport, and storage in between. Usually, multiple actors are involved, and often one or several changes of ownership. Reuse is not new: a long history of component reuse in the building sector can be traced (see the next section), but its (re)discovery as a key circular strategy in the building sector is relatively recent. The Delft Ladder, a refinement of the 1979 Lad‑ der of Lansink, or hierarchy for preferred waste management strategies introduced by Dutch politician Ad Lansink, defines the following sequence: Prevention, Ob‑ ject renovation, Element reuse, Material reuse, Useful application, Immobilisation with useful application, Immobilisation, Incineration with energy recovery, and Incineration (te Dorsthorst et al., 2000). Element reuse stands high in the hierarchy, immediately after the renovation of the ‘object’, the initial building. Since the establishment of the Delft Ladder, studies have confirmed the envi‑ ronmental gains obtained from building component reuse, establishing its viability DOI: 10.1201/9781003450023-4

The reuse of building elements  25 as a practice in circular buildings. The numbers indicate that the CO2 emissions from reused components range from 0.8% to 15% compared to the production of an equivalent component from virgin raw materials (Stricker et al., 2022). An increasing amount of data in terms of LCA data becomes available, but the idea of the environmental logic of component reuse is simple: compared to a newly manu‑ factured element, a salvaged equivalent causes no depletion of finite raw material resources, no impacts due to transport of raw materials and manufacturing, and it reduces waste production. The remaining impacts are limited to the ones caused by transportation and limited remanufacturing or refurbishing operations. But, apart from the environmental gains, one can point to other gains as well: a positive social impact, as dismantling and refurbishing operations create low entry‑level jobs that cannot be delocalised, direly needed, especially in metropolitan areas (Friedhoff et al., 2010). On the other hand, component reuse also makes sense from a herit‑ age point of view, as it preserves not only the use value of a component but also its value as a testimony of past craftsmanship and industrial skills. A short history of reuse in construction Long tradition

For ages, reuse practices were ubiquitous in the construction sector. In an economy where the major power sources were human or animal muscles, it made sense from an economic and energetic point of view to use materials available at hand. Bal‑ ancing the effort of extracting, transporting, and processing raw materials with the facility of dismantling nearby and ready‑to‑be‑used elements was usually a no‑brainer. The proofs in architectural history are omnipresent. Archaeological literature describing the material economy of ancient cities is filled with examples of reuse of all sorts (Bernardi et al., 2019). Evidence of the many lives of materials comes in the form of old engravings in the back of ash‑ lar masonry or statue bases, dug‑out walls with clear traces of dismantled lay‑ ers of tiles and bricks, remains of workshops with specialised tools to recondition reclaimed elements, the creative combinations of columns of different types and dimensions into one structural system, and so on. The city of Rome is especially well documented on this front. Its republican and imperial material economy came very close to the contemporary idea of the urban mine, with a large and versatile ecosystem of actors active in reuse. In architectural history, such examples of reuse have for a long time been observed through the lens of the notion of the spolia, a term introduced retrospectively, in the 16th century, by Giorgio Vasari to label architectural remains that had been ‘plundered’ from earlier buildings, an example being the Arch of Constantine, built by the 3–4th C AD Emperor with dismantled architectural fragments from earlier periods. That narrative of reuse as plunder, joining modern notions of progress, dominated the 19th and 20th century approach to architectural reuse, and contributed to its poor reputation (Meier, 2020). Only in the past decades has new scholarship drawn attention to the more pragmatic motivations for historic building component reuse, and for the sophisticated supply

26  Lionel Devlieger and Arne Vande Capelle chains, infrastructures, and regulations that underpinned it (Barker and Marano, 2017; Barker, 2018). Evidence about more recent reuse ecosystems exists as well. High‑profile rec‑ lamation operations remained the norm until the early 20th century. Newspaper announcements testify to the practice of holding yard sales of building materials when modest structures, such as homes, were taken down. In the case of more important demolition works, projects were auctioned off to the highest bidder. Indeed, until the late 19th century, contractors most often paid to take buildings down, as the sale of the salvaged materials yielded values superior to the cost of dismantling them. An impressive case is the demolition of the Palais des Tuileries in Paris, by the contractor Achille Picart in 1882. Picart succeeded in dismantling this symbol of the monarchy, damaged by the 1872 Commune, in just six months. The contractor, leading a well‑coordinated army of workers using hand tools and horse‑drawn carts, was able to disperse the reclaimed materials over his wide net‑ work of customers. Important for Picart’s way of functioning was his centrally located warehouse, which served as a temporary storage, workshop, and signboard for his practice (Ghyoot et al., 2018). Industrialisation of demolition and construction practices.

Solidly established reuse practices for virtually all components of a building (from bricks and roof tiles to windows with intact glass panes and finishing materials) started crumbling in the first half of the 20th century. Experts agree that the trend was inaugurated in New York, where real‑estate prices evolved quickly, as did construction and demolition techniques. A decisive moment was the demolition of the Gillender building, in 1910: a 22‑level state‑of‑the‑art office tower built 13 years earlier, to be replaced by a far taller building. Contractor Jacob Volk finished the job in a stunning 45 days, using a state‑of‑the‑art steam shovel, an army of trucks, and barges to haul demolition debris into the East River. In 1920, New York demolition contractors still bid against each other for demolition sites. In 1928, the practice was over with, and contractors started demanding large sums of money to demolish at an ever‑quicker pace. The supply of reclaimed materials dropped so quickly that a New York Times article mentions new bricks being delivered to construction sites, still hot from the oven (Byles, 2005). Manufacturers of new ma‑ terials had to work at unprecedented rates to fill the gap. From then on, wrecking, instead of dismantling, became the dominant practice in Manhattan. The concatenation of causes is simple: optimised, industrial construction tech‑ niques allow for increasingly tall buildings, causing an inflation in real estate value. This, in turn, leads to increased time pressure for the completion of new projects. Keeping old structures on site becomes untenable from a financial standpoint. Prof‑ its from real estate operations explode and dwarf the gains from selling reclaimed materials. Speed becomes a determining factor in demolition: mechanised tools al‑ low for quick destruction and site clearing. In parallel, the real estate sector lobbies successfully for a change of fiscality. The depreciation period for buildings, once seen as everlasting assets, is generally reduced to a couple of decades. Beyond that

The reuse of building elements  27 term, buildings become useless from a fiscal point of view: architecture becomes a consumer product; obsolescence is the inevitable fate of a building (Abramson, 2016). Quickly, the first signs of this logic started to appear in Europe as well. The first half of the 20th century is characterised by the coexistence of careful reuse operations and swift demolitions. Reuse is no longer a given, but a practice whose economic viability must be studied on a case‑by‑case basis, by comparing the gains from the sale of reclaimed materials to the cost of the ‘delays it entails’. In the post‑war period, the industrialisation of building production strides on. The widespread adoption of concrete technology, cement‑based (instead of tradi‑ tional, lime‑based) mortars, and the increased use of glues, synthetic sealants, and other irreversible joining materials make the recovery of components more compli‑ cated. Demolition equipment becomes ever more mechanised, efficient, and fast. The high cost of these machines means indebted contractors focus on having them operate as much as possible. Outdated buildings are regularly reduced to a pile of rubble in no time. The environmental worries coming up in the 1970s (concerns about resource depletion and waste production) would eventually lead to meas‑ ures compatible with industrialised waste management: the recycling of construc‑ tion and demolition (C&D) waste. If (largely mechanised) recycling allows for the recovery of some precious molecules, such as metals, and some valorisation for streams such as the wood or plastic fraction. It offers only a poor outcome for the most important fraction: inert materials. Still today, the recycling industry reduces demolished masonry, natural stones, concrete, etc. into certified debris, for which the best possible use is backfill in road construction; in the terminology of the Delft Ladder: immobilisation. The reclamation sector: marginalised but ready to grow again

Today, the practice of component reuse is largely forgotten. Few people know it was once widespread. As for other man‑made products, people have grown accus‑ tomed to considering buildings (except for a few ones with heritage status) as dis‑ posable goods. We entered an age of fast real estate, in analogy with fast fashion. In all big cities around the world, the demolition of a building that is less than 30 years old has become a familiar reality. In this context, reuse practices still exist but have become marginal. A 2007 study on the situation in the UK concluded that 1% of all materials in circulation are reclaimed (CRWP and Salvo, 2007). Much of this stream passes through the hands of a group of operators which, until recently, received scant attention: the professional resellers of second‑hand building materials. As these businesses will be the nexus of a future, reinvigorated supply chain of second‑hand building mate‑ rials, it is worth briefly discussing them here. The sector is still largely uncharted in Europe, except for a few countries in which two entities (Salvo for UK and Ireland), and Opalis (Benelux and France) have done important mapping work. Based on that mapping, a recent study esti‑ mated that, for the countries under consideration, the sector represents an economic

28  Lionel Devlieger and Arne Vande Capelle volume of 511,3 million Euros in turnover, employs 6 940 Full‑Time Employees, and involves the storage of 615.900 tonnes of materials (Bougrain and Doutreleau, 2021). Beyond the numbers, the following observations can be made, based on the sample in New‑West Europe (territory covered by Opalis.eu and Salvoweb.com). Despite offering environmentally relevant services, most of them are unsubsidised, and survive economically, solely on the income they generate. For a branch that is space‑consuming and relies a lot on manpower, contemporary economic conditions are hard. High real estate prices force these businesses to move far out of urban ag‑ glomerations to afford the warehousing space they need; they also stay small, with a huge majority of businesses (85%) employing less than 10 people (Bougrain and Doutreleau, 2021). The bulk of income (between 75 and 87%) comes from the re‑ sale of second‑hand materials, but most of them also offer supplementary services, such as repair, refurbishment, cleaning, or the sale of new materials to complement the second‑hand ones. Modes of acquisition are often varied and range from demo‑ litions to deposits, from third parties to sales. These companies are not immune to globalisation: materials with high added value may be sold all over the world, and some might import from overseas, thus cancelling out the possible environmental advantage of salvage. Occasional cases have been documented of imports of sal‑ vaged materials causing heritage destruction in donor countries from the global south (Devlieger et al., 2014). These businesses offer a wide range of salvaged materials for sale, but these can nevertheless be divided into two categories. Those that can compete within a given framework with their counterparts made from virgin resources, and those that feature an added value beyond their pure use value, for which people are will‑ ing to pay more. The first category varies strongly from place to place: in the US a lot of cheap second‑hand wood is available for do‑it‑yourself builders; in the Neth‑ erlands, you might easily find ventilation units for pig stables on the second‑hand market, or many other forms of cheap technical industrial equipment. This second category was dominant for many Western European businesses founded in the 1970s, specialising in architectural antiques. Such ‘antique’ archi‑ tectural elements are characterised by durable materials, generous dimensions, vis‑ ible craftsmanship or industrial refinement, and often picturesque traces of wear on their surfaces (patina). Nineteenth‑century fireplaces, centuries‑old oak or natu‑ ral stone flooring, or cast‑iron fencing are examples of these almost exclusively pre‑war and usually very expensive materials (not infrequently shipped over long distances) for which there exists simply no new alternative (Vande Capelle and Cortés Garcia, 2021). In the 1970s and 1980s, at the time these businesses started, there were close contacts between these resellers and demolition contractors, which were approach‑ able figures, running small‑scale operations. One would see resellers on a demoli‑ tion site point at the parts they were interested in, negotiate a price on the spot, and hand cash money to the wrecker once the elements were ready to be hauled away on flatbed trucks. In the last decades, the gap has started to widen. Demolitions of ancient farm buildings or 19th‑century mansions, the typical stocks for antique materials, scarcely occur anymore. Contemporary demolition companies are huge,

The reuse of building elements  29 hard‑to‑approach businesses that function in a highly regulated environment; visi‑ tors on their demolition project are usually a no‑go. A sizable number of resellers in architectural antiques are now approaching retirement age; most of them struggle to find candidates to take over their businesses. Yet, despite the slow decline of the architectural antiques market, some tradi‑ tional materials yield very high and steady turnover rates. Examples are bricks, roof tiles, pavement blocks in natural stone, and natural stone slabs. These materials are modular, relatively easy to dismantle, compact, easy to store in the open air, and still present in great quantities in urban mines. The companies reselling these and offering the related services are specialised and knowledgeable. Interestingly, a siz‑ able portion of these have started using the environmental argument commercially.

Figure 2.1 Dismantling phase: Dismantling of a 1930s ceramic tile floor by a team of Rotor DC, Institut du Génie Civil, Liège, 2014.

30  Lionel Devlieger and Arne Vande Capelle In effect, this means that, beyond the two rough categories listed above (materi‑ als that are cheap, or materials that contain stored, crafty work), a third, and often overlapping quality is appreciated and sought after: sustainability. A series of new operators have emerged in the past decades that are betting on this and putting environmental arguments explicitly to the fore, often reselling very recent building components, more attuned to current demolitions. Möbius and Incomex in the Paris region are specialised in second‑hand raised office floors; TK Hergebruik, Rotor DC, Orak, in, respectively, the Amsterdam, Brussels, and Paris region sell other reclaimed office furnishing materials. Yet, in practice, in the current economic cli‑ mate, the environmental argument never completely supersedes the economics of a project, meaning profit margins remain thin (Figure 2.1). Challenges for reuse in contrast with contemporary logics In a free‑market economy with little to no other incentives to make reuse happen, economic feasibility is the main hindering factor for reuse. The decline of this feasibility is due to several interrelated factors brought about by the 20th century ‘modernisation’ of the construction sector sketched above. Two decades into the 21st century, most of these factors still weigh. Challenges related to cost High cost of reclamation and speed imperative

The first barrier anyone motivated to reuse will be confronted with today is that materials have become very expensive to reclaim (Gielen, 2021). As stated above, in the first instance, it was not the dismantling of materials that got more expensive in the US in the 1920s, it was the rising profitability of real estate operations that started to leave less and less room for reclamation. The lack of time was the first crack in the omnipresence of reuse practices within construction. Additionally, speed being the new imperative on a demolition site, this quickly initiated all sorts of logistical and technological ‘innovation’. Hand‑operated wheel‑ barrows, shovels, pickaxes, and crowbars, which, for ages, had been the tools of both demolition and dismantling, had to make place for mechanised equipment. Hand tools were first replaced by their mechanised counterparts, such as pneumatic ham‑ mers, but it would not take long for the bulldozers, dynamite, and wrecking balls to arrive (Byles, 2005). And with them, critical health and security hazards, which in turn meant increasing insurance costs and costs linked to new safety measures (Ghy‑ oot et al., 2018). In a couple of decades, demolition sites changed from beehives, buzzing with activity, to fenced‑off zones forbidden for unauthorised personnel. Speed did not only become increasingly important for demolition by the way. Construction had to happen increasingly fast as well, leading to another set of innova‑ tions, to decrease the amount of time necessary for the installation of materials. The quicker and the stronger things could be glued together, the better. A famous example of this development took place in brick architecture, where older, often lime‑based mortar types, got replaced by cement‑based mortar. Cement sets faster and sticks

The reuse of building elements  31 harder, thus increasing a mason’s productivity, but it also makes the dismantling and cleaning of the bricks virtually impossible. New construction methods in the second half of the 20th century are characterised by general negligence for revers‑ ible installation. But since reuse was disappearing, nobody advocated in its favour. Driven mostly by big contractors and the sector producing new building materials and elements, whose profit model is based on maximising sellable output, construc‑ tion technology innovations were by definition not inclined to favour salvageability. Additionally, increasing worker productivity (in more economic activities than just construction) meant increasing wages. The booming economy of ‘les Trentes Glorieusess’ led to the welfare state as we know it today, with increased taxes as well, to provide states with enough money to finance programs such as health care or pensions, and to continue to provide the infrastructural framework for further modernisation. Today, the salary of workers involved in dismantling and reprocess‑ ing is often by far the largest share of the total cost of a dismantling operation. Cheaper new materials: cost efficiency of linear supply chains

The extraction of virgin resources and their subsequent transformation into building materials respond very well to the linear paradigm of industrialisation and upscal‑ ing. Raw material can often be found concentrated in large quantities in certain geo‑ logical areas, inviting big investments resulting in bigger returns. The remnants of colonial power structures in combination with the globalisation of the market econ‑ omy have made these material supplies available to multinational corporations, no matter where these are located geographically. Aided by cheap and easy transport on a planetary scale, resource extraction, and material production each happen where they are cheapest and/or least bound by constraints on the negative production ex‑ ternalities, before being shipped to markets of the rich world. The cost efficiency of these supply chains, after decades of optimisation, has reached an economic opti‑ mum, resulting in rock‑bottom prices, which only logistic accidents, soaring energy prices, or the depletion of the considered natural resources can thwart. Challenges related to linear protocols and project organisation Linear protocols

The different frameworks that guide construction processes today were estab‑ lished, for the most part, in the course of the 20th century. They have been shaped by the same market forces that are responsible for our bias towards linear materi‑ als, and hence, rarely take into account the specificities of working with reuse. The highly codified and bureaucratic construction sector as we know it today answers to pre‑occupations such as the transparency of building costs, the identification of liabilities, and our increasing need for data to make sustainability claims, but it leaves no room for the, often sensory know‑how linked to judging the fitness for reuse of a material, the shifting availability of specific products on the market, and the resulting, reciprocal design and construction processes (Vande Capelle and Cortés Garcia, 2021).

32  Lionel Devlieger and Arne Vande Capelle Separation of design and construction

The separation between design and construction started with the definition of the role of the architect as opposed to that of the contractor, which mostly happened in the interbellum. In most Western countries, practicing the profession of archi‑ tecture is deemed incompatible with the profession of contractor, since the former is supposed to control the work of the latter, and hence be independent. It is the culmination of the general historical narrative of a growing distance between de‑ sign and construction, which took off in the Renaissance, one we urgently need a counter‑history for (Ghyoot and Guichard, 2022). Almost a century after this principle has been established by law, the communication tools that we have today, to mediate between both professions, and the way we use them, have pushed this division to its limits. A design is consolidated in tendering documents that define the result in its utmost detail. The contemporary adoption of digital twins such as in BIM, in the design phase, is the logical continuation of that tendency. Our current tendering culture leaves no room for discussion whatsoever, fixing each and every component’s performance beforehand. And, of course, this is completely justified in a lot of cases. But making the (ultimately arbitrary) decision that a floor needs to be white, or that all tiles need to measure exactly 20 by 40 cm, heavily limits pos‑ sibilities for reuse. Finding a large enough batch of tiles on the reclamation market with exactly these properties becomes a virtually impossible task, even though a batch of freshly reclaimed grey tiles measuring 30 by 30 could be available just around the corner. Challenges related to End‑of‑Life (EoL) activities and reclaimed materials Processing and reconditioning reclaimed materials

One step further down the line, at the stage of processing and reconditioning reclaimed materials, the consequences are the same. An incoming flow at a recla‑ mation yard will never consist of the exact same product in dimensions, weight, and technical characteristics. For one thing, the technical and dimensional error margin was often simply bigger in previous decades. In addition, it’s often not even possible for a single dealer to rely on just one product to keep his business going. And lastly, materials change over the years, under the influence of wear and tear, and consecutive adaptations and appropriations; no reclaimed wooden beam will have nails on exactly the same spot, and no plank will be worn in the same manner. All of this combined makes the reconditioning of reclaimed materials a largely manual task, executed by human workers, limited by their physical capacities. Obviously, they do not stand a chance against the efficiency of factories producing the exact same product for decades on a stretch. The indus‑ trial mindset does not match with reuse (Ghyoot and Topalov, 2022). Moreover, material recovery facilities are lacking and not well developed, although many governments support their establishment (Azizuddin and Shamsuzzoha, 2021) (Figure 2.2).

The reuse of building elements  33

Figure 2.2  Refurbishing phase: Cleaning of the mortar from the ceramic tiles. Lack of understanding: reuse is different from recycling

On another level, the way in which the destination of evacuated building materials is recorded all too often makes no distinction between recycling and reuse. Be it a state’s administration that needs the numbers for their annual follow‑up on the state of the building sector, or a consultant feeding the numbers into a sustainability labelling scheme such as LEED, BREEAM, or more local examples, results will always be very optimistic. Recycling is, after all, a very developed economic activ‑ ity in most Western countries. Crushing materials to their granular level and using these as resources for new materials has been making sense on an economic level for a long time. Contrary to reuse, recycling is very compatible with our current economic logic of upscaling, but also contrary to reuse, it is very energy intensive. But it all too often still happens to materials that are in the first place perfectly reus‑ able. As long as these two, in essence, very different economic activities, are not

34  Lionel Devlieger and Arne Vande Capelle divided in the state’s statistics, or treated separately in sustainable rating systems, our high recycling rates do not generate any sense of urgency. A corollary of the poor understanding of the different economic implications of reuse vs. recycling is the confusion around the oft‑used metaphor of the ‘urban mine’. Most people seize the idea of dormant resources that the metaphor entails but fail to realise that, unlike ‘real mines’, the urban mine does not lend itself well to mechanised extraction. It consists of buildings of all sizes, owned by a vari‑ ety of different actors. They are of different ages and have been constructed and maintained in different ways. In each building, up for renovation or demolition, batches of materials are often small and heterogeneous. Vice versa, the same type of building element is often dispersed over multiple buildings with multiple own‑ ers, making the exploitation of the urban mine very different from the exploitation of a geological mine (Ghyoot et al., 2018; Vande Capelle and Cortés Garcia, 2021). At the end of the closed-loop that the circular economy promises us, one must deal with all the contingencies accumulated on a given material over its lifespan up to that point. Unsuitable economies with inappropriate policies

In the Western world, massive amounts of materials are discarded as waste, even those that require virtually no treatment to make reuse possible. The combination of expensive labour and cheap material extraction downgrades most materials im‑ mediately to the category of unreclaimable. This is illustrative of economies in which the use of raw materials is not taxed, while labour is, and heavily so, despite the fact that human labour has no environmental impact, while the mechanised extraction, transformation, transport of raw materials and all the related emissions cause considerable negative externalities. Concrete pavers are very telling in this regard. Installed in a bed of sand without mortar, and often discarded long before the end of their lifespan, these mundane but serviceable elements are almost with‑ out exception downcycled into rubble and replaced by new, very similar ones. New concrete pavers are simply too cheap for anyone to invest in the infrastructure needed to bring salvaged pavers to the market (Gielen, 2021). And the same goes for a lot of (energy‑intensive) materials. Society acceptance

The societal ignorance of lifecycle thinking is another barrier that needs to be over‑ come to see the development of the circular economy and the reuse of reclaimed materials. Our current ‘consumer society’ is used to thinking in a linear economy and shows a lack of acceptance of reclaimed materials, expressing distrust of the quality of salvaged and used items (Charef et al., 2021b). Construction practi‑ tioners all too often identify the circular economy as an ‘unrealistic assumption’, ­‘improbable’, and ‘utopian’ (Charef et al., 2022). Whenever confronted with the price of a reclamation operation due to its largely manual nature, and hence, a reclaimed material, the price of its new counterpart will

The reuse of building elements  35 suddenly appear incredibly cheap in comparison. Not only did reuse become more ex‑ pensive, but at the same time, new materials became actively cheaper from the 1950s onwards. Combined with the low societal acceptance of second‑hand materials, the regulatory framework that is largely prohibitive of reuse, and the difficult search for material recovery facilities, it’s not hard to imagine that in the contemporary construc‑ tion sector, the window of opportunity for salvage and reuse is very small. Overcoming the hurdles Several types of hurdles: several ways of overcoming them

The above‑mentioned hurdles are very real, and unfortunately, not easy to overcome, considering how complex and inert the building sector in industrial societies is. It is first important that some of these hurdles are not the result of human oversight or for‑ getfulness: they have been consciously designed into the building sector by the stake‑ holders of the linear economy. Overcoming these, hence, does not just equal solving a complex puzzle in logistics, engineering, or process optimisation. It implies being able to analyse the situation in different aspects (economical, political, juridical, …), to un‑ derstand the actions of the protagonists involved, and to bend the current situation into a more sustainable or circular one (Condotta and Zatta, 2021). The number mentioned above, that an estimated 1% of all building components are currently reused, shows how operative the hurdles are, and how much bending still needs to be done. On a hopeful note, the situation seems a little less dire as we write this chapter, com‑ pared to 15 years ago, if not on the building sites, at least in people’s minds. The topic

Figure 2.3  Logistic phase: Batches of refurbished ceramic tiles.

36  Lionel Devlieger and Arne Vande Capelle has been raised and has caught the attention of the building sector and policymakers (European Commission, 2020; IPCC, 2023). A first exploration of the implications for architectural design is on its way; the topic is being taught in the most progressive architecture schools. New academic research on the topic, if not always relevant, is booming, and many companies are exploring novel ways of functioning (Figure 2.3). Product legislation and standardisation

Some immediate hurdles have been overcome, at least for the European context, such as the potential confusion about whether salvaged building components fall under waste or product legislation: if a building component has not hit the bottom of a waste container, and is treated as waste, it remains under the product legisla‑ tion. Other issues, still for the European context, are less murky than they appeared before, such as the question of whether salvaged building components should, or not, bear a CE marking (Condotta and Zatta, 2021; Seys, 2017). Currently, much of the environmental cost of manufacturing new building prod‑ ucts is still not internalised. Upcoming European legislation, such as the Carbon border adjustment mechanisms (CBAM), will help to redress some of the totally skewed realities brought about by the globalisation of the building product trade, and reduce the cost gap between new and reclaimed building products, but there is probably still a long way to go. Ongoing standardisation efforts, still slow but potentially impactful, should be carefully observed. At the international level, the ISO/TC 323 on Circular Econ‑ omy aims to standardise the field of circular economy for the whole world and all sectors by providing some basis. At the European level, the sub‑commission CEN/TC 350 SC1 is focusing on the Circular Economy for the construction sector. Standards to be issued by these bodies aim to support the transition towards the Circular Economy, but it remains to be seen how these standardisation measures will affect the reuse of construction elements. Nevertheless, past experiences have already shown that authorities can play an important role by facilitating access to incoming streams of recoverable materi‑ als. A direct example is legislation that would forbid the destruction by recycling materials that have proven to be easily recoverable, forcing demolition operators to divert these streams to the local reuse sector. Portland (Oregon) has put in place a regulation obliging the dismantling (instead of demolition) of all structures built before 1916. One could also imagine regulations forbidding the recycling of cer‑ tain recoverable brick types, or of standard‑sized raised floor panels from office interiors, etc., or regulations obliging a modest percentage, for instance, 5% in weight, of all demolition materials to be diverted to reuse (Gobbo et al., 2021). Organising the reclamation sector: visibility of the reuse actors

The reuse economy of the future will only be made if the supply chains for recov‑ ery and redistribution of used components are reinvigorated. This will be a matter of inventing new professions and new types of businesses. But it will also pass by a

The reuse of building elements  37 better understanding of the existing reclamation sector. The companies in question are a repository of important know‑how on questions as crucial as dismantling, re‑ conditioning, evaluating fitness for reuse, and marketing strategies. After decades of bending to the needs of the linear economy players, the construction ecosystem should try to facilitate or support their activities. Such an effort requires first that the already existing sector be well‑known and understood, which is hardly the case now. We mentioned before Salvo, which is mapping the professional resellers of salvaged elements in the UK and Ireland, and Opalis, which is doing the same for Western Europe. Apart from the companies in question, it is important that landmark projects, integrating reclaimed materials in ways that are remarkable (because of the quality, amount, and nature of integrated elements) receive more attention. Recent books, catering to a public interested in contemporary architecture, have been drawing attention to some of the most interesting projects, such as K118 in Winterthur (Stricker et al., 2022), or Multi in Brussels (Ooms, 2022); textbooks on element reuse usually contain several interesting examples; a recent list of detailed pilot projects is part of the FCRBE outputs, but no published, international atlases of exemplary element reuse exist yet. We hope it will change soon. Overcoming the cost of dismantling: fiscality changes and process optimisation

The current economic climate, surfing on earlier reflexes, still incentivises the re‑ placement of costly labour by supposedly cheap energy, pushing the construction sector to the use of energy‑gobbling tools of production. Useful inspiration to help reframe things and counter this evolution can be found in writings dating back to the first energy crisis of the 1970s. In a seminal text of 1976, Geneviève Reday‑­ Mulvey and Walter Stahel identified extraction and the production of materials such as steel, concrete, and glass, as far more energy‑consuming as the final trans‑ formation of these materials into finished products, yet these imply comparatively a higher amount of human labour (Stahel and Reday‑Mulvey, 1976). Recovery operations, similar to transformation, hence, amount to substituting manpower for energy. In the context of the climate crisis and global effort to counter the un‑ necessary consumption of (fossil) energy, manpower is to be identified squarely as virtuous rather than sinful (economically). Such an inversion of the perception of manpower, from bad to good, is obviously facilitated by peaking energy prices, caused, for example, by the war in Ukraine (Figure 2.4). In general, beyond the fluctuating prices on the international markets of fossil fuels, overcoming the high cost of labour in rich countries, in comparison with work done by machines, might seem to reach beyond the agency of private or public actors. One method to overcome this would be to change the fiscality of the sale of salvaged goods, which, in most countries, are still taxed as much as newly produced goods. Such actions are easily accessible, as they need to be taken on the highest political levels (Gobbo et al., 2021). At a lower level of action, resorting to the social economy is a strategy that is often followed. In the US, most companies active in building element recovery are

38  Lionel Devlieger and Arne Vande Capelle

Figure 2.4 Documentation phase: Photography of a salvaged Carrara marble tile before it was put on sale online.

non‑profit organisations, benefiting from that special status in virtue of US‑specific fiscal regulations which make the donation of not yet dismantled building com‑ ponents to a charity deductible. Companies are also offering training programs for unskilled workers (Ghyoot et al., 2018). Several companies recently char‑ tered in Europe similarly offer low‑entry level job opportunities and are therefore state‑supported (opalis.eu, n.d.). Another means of lowering labour costs in dismantling and recovery activities is of course by optimising processes. A natural tendency that can be observed in the young companies mapped by Salvo and Opalis (see section above: The reclama‑ tion sector: marginalised but ready to grow again), is that of specialisation in cer‑ tain types of elements, whose workflow can be optimised by innovation. Applied academic research and public funding can play an important role in these forms of process optimisation, improving work conditions for the employees, while raising the prospects of profitability for the businesses in question. Overcoming the competition with virgin materials

In the linear economy, producers of construction elements from virgin raw mate‑ rials, sometimes supplemented with a share of recycled content, control produc‑ tion lines that operate almost continuously, in which quality control is automated.

The reuse of building elements  39 The performances of the end product are fixed, controlled and can be shared in the technical documentation. There are usually no issues either with future avail‑ ability, as produced quantities can be anticipated in advance. As we have seen, it is impossible to make similar predictions about the availability of important quantities of recovered materials featuring specific performances (Koutamanis et al., 2018; Vande Capelle and Cortés Garcia, 2021). This is a fact of reuse that is not easy to overcome. There are several things to do to try to answer it (Figure 2.5): – Commissioners and the design team may adopt a more flexible approach to the idea of total control over the final design, by allowing a wider range of finishes. In the Zinneke project in Brussels, the final design of a facade was left open dur‑ ing the tendering phase, depending on the type of second‑hand window profiles that would be available on the market. – If possible (providing available funds and storage facilities), commissioners may purchase second‑hand items in advance, or describe them in detail in the tender documents, allowing the tenderer to give a detailed price estimate in ad‑ vance (Geerts et al., 2022). – Finally, one could resort to the use of second‑hand construction materials of suf‑ ficient quantities. These materials are increasingly well known; in some cases, the technical sheets for these have been written as part of publicly funded re‑ search (Rotor, 2021).

Figure 2.5 Reinstallation phase: In‑situ reinstallation of refurbished ceramic tiles, Tivoli Greencity, Brussels, 2019.

40  Lionel Devlieger and Arne Vande Capelle Protocols that were designed for linear materials

Currently, a wide range of protocols governing the establishment of construction projects are ill‑prepared to accommodate reused components. The question of the CE marking was mentioned earlier in the section ‘Product legislation and stand‑ ardization’. It is revealing that the European legislator, imposing CE marking on all construction products entering the European market, did not anticipate the question ‹What about reused elements, do they need a CE marking too?’ (Seys, 2017). Initially, labelling schemes measuring the environmental performance of a building did not properly take reused materials into consideration. Schemes such as BREAAM (set up in 1990 in the UK by the British Research Establishment) or LEED (set up in 1993 in the US by the US Green Building Council), used to assess the environmental performance of a building, initially included only indirect means of rating the environmental advantage of their use. Increased understanding of the issue of embodied carbon has, however, led to improvements. The last version of LEED, v4, offers better rewards for reuse. In 2018, Dutch researchers suggested ad‑ ditional indicators to BREEAM to better assess circularity, for an improved Dutch version of BREEAM that could also extend internationally (Kubbinga et al., 2018). For environmental comparisons between different materialisation options that would incorporate a wider range of environmental impacts, also over time, the LCA tool (Life Cycle Analysis) is often used. Specialised design offices, research centres, and university departments have access to proprietary software (e.g., Simapro) capable of generating certified LCA comparisons. This software uses da‑ tabases containing information on the various impacts (CO2 emissions, resource depletion, ocean acidification, etc.) of all stages of the production processes of building elements as they were declared in the context of the Environmental Prod‑ uct Declaration (EPD). An EPD is a document that transparently communicates the environmental impact of a material/product over its lifetime. EPDs for building materials are generated according to the relevant standards (ISO 14040/14044, ISO 14025, EN 15804, or ISO 21930), usually by independent and certified consultan‑ cies. The procedure is costly, and only justified for construction products manufac‑ tured in large quantities. Resellers of reclaimed materials could, in principle, also obtain an EPD, to promote its environmental advantages, but they do not. The cost is prohibitive in comparison to the recovered batches, which are generally small. Only two reclaimed materials, to the knowledge of the authors, have obtained an EPD: the bricks marketed by the Danish reclamation dealer Gamle Mursten, and the raised floor tiles marketed by the French company Möbius (Gobbo, 2021). Since there are no EPDs available for reused products, they do not appear in the databases and are therefore less likely to be included in software‑generated com‑ parisons, which becomes a block. A workaround, in this case, would be for public authorities or publicly funded research institutes to invest in covering the cost of generating EPDs for some of the best‑performing products currently circulating in the recovery market, based on data obtained from the reclamation actors on their recovery, transport, and refurbishment operations. We mentioned above the tricky problem of obtaining data for the environmental performance of a salvaged product, but the same is true for the overall physical

The reuse of building elements  41 performances of a product, and the resulting trouble to certify it in the eyes of, for example, stability engineers or insurances. Indeed, it was reported in several studies that the digitalisation of the construction sector will help to overcome the lack of data on reclaimed materials. For example, some authors stressed the poten‑ tial of BIM for the management of the End‑of‑Life activities of assets (Won and Cheng, 2017). Others have identified, based on interviews with practitioners, seven specific uses of BIM for the Circular Economy, including the data checking BIM use N‑BU04 (Charef and Emmitt, 2021). More recently, Charef (2022) presented the three BIM models developed throughout the asset lifecycle in the context of circular economy and stressed the importance of data quality and updates. The author also defined the content of the deconstruction information model (DIM) and proposed the 8th dimension associated with End‑of‑Life activities, including reuse, remanufacturing, and recycling (Charef, 2022). Conclusion: the steps to take The current impossibility of scaling up reuse in the construction sector is a test of the capacity of our industrial system to effectively make a sustainable transition. If public authorities take the challenge seriously, making changes that enable reuse will serve an exemplary function. Among the many deliverables from the Interreg NWE FCRBE project is a roadmap, intended to provide public authorities with ‘guidelines on how to foster the reuse of building materials and elements in their area’ (Gobbo, 2021). The roadmap was drafted based on a review of the literature but also on feedback from the field. It is based, among other things, on the experience acquired since the start of the project, the development of a series of practical tools (such as a Recla‑ mation Audit Method, or Guidebook on Procurement Strategies for second‑hand building elements), and feedback 36 concrete and well‑documented pilot opera‑ tions in which many of these tools have been tested. The roadmap eventually comes up with 36 different possible actions, which are classified into different categories. While this roadmap is drafted for the specificities of the situation in North‑Western Europe, the authors believe the recommendations are valid beyond these borders. The roadmap sees the following areas of action: – Better actions at the level of the recipient buildings. Fostering the demand for reusing building materials. Among the recommendations here are feature meas‑ ures such as setting reuse objectives in public tenders or encouraging and sup‑ porting specifiers and contractors to adopt reuse practices. – Better actions at the level of the donor buildings. Efforts made to promote the ap‑ propriate reclamation of reusable building materials. The extraction of reusable building materials from obsolete buildings, which are now lost to lower‑quality construction waste management strategies. Possible recommendations include the establishment of lists of protected materials or the inventory of reusable materials in renovation and demolition projects.

42  Lionel Devlieger and Arne Vande Capelle – At the level of the connection between demand and supply of reclaimed ele‑ ments. Reclamation dealers play a key role here. Among the many measures recommended here are, for instance, ‘documenting the reclamation trade’ and ‘analyzing existing reuse practices’, as well as ‘fostering urban salvage yards and facilitating access to land and storage spaces’. – At the level of the protocols there is a great need to establish a support frame‑ work. Recommendations here include integrating reusing into green building rating systems, developing labels for reclaimed products, or internalising the environmental costs of new products. – Finally, a last cluster of action concerns the quantification of reuse rates: Moni‑ toring of evolutions. It is important to know if we are heading in the right di‑ rection, for instance looking at the reclamation trade or monitoring reuse in building projects (Figure 2.6). As emerges from the foregoing, there is no lack of possible action courses on be‑ half of the authorities. But the private sector equally has a crucial role to play. – Commissioners of large and small‑scale construction projects should know that, even with modest ambitions, such as substituting only a few weight per cent of the incoming stream of new materials to their project, with reclaimed materials, they can kickstart a whole new local economy. Circular consultancies can help them in achieving that goal.

Figure 2.6 A new project completed with salvaged components: Office refurbishment (Ypres, 2020).

The reuse of building elements  43 – Designers are currently discovering the power, economically, functionally, and aesthetically, of combining new with reclaimed materials. A growing pool of exemplary projects is there to inspire and encourage them. – Contractors, in a crucial position because they are present both on dismantling and construction sites, must discover new ways of doing things by familiarising themselves with recirculating building elements. – They rely on a network of increasingly professional reclamation dealers, ready to make the link between supply and demand and to offer additional services and guarantees. – Finally, the manufacturers of new building materials must be ready, as some have already done, to open a new range in their assortment: that of products of their own brand, which have been reclaimed and refurbished and for which they can offer the same types of guarantees as if they were new. References Abramson, D. M., 2016. Obsolescence: An architectural history. Chicago: The University of Chicago Press. Azizuddin, M., Shamsuzzoha, A., 2021. Influence of circular economy phenomenon to fulfil global sustainable development goal: Perspective from Bangladesh. Sustain. 13, 11455. Barker, S. J., 2018. The demolition, salvage, and recycling industry in Imperial Rome. Ae‑ dificare, 4, 37–88. Barker, S. J., Marano, Y. A., 2017. Demolition laws in an archaeological context. Thiasos Monografie, 9, 833–850. Bernardi, P., Carvais, R., Nègre, V. (Eds.), 2019. Recyclage et remploi: La seconde vie des matériaux de construction. Ædificare Revue internationale d’histoire de la construction, 2(4). https://doi.org/10.15122/isbn.978‑2‑406‑09276‑6 Bougrain, F., Doutreleau, M., 2021. Statistical analysis of the building elements reclamation trade in the Benelux, France, the UK and Ireland. Interreg NWE FCRBE. https://opalis. eu/sites/default/files/2022‑02/FCRBE‑en‑statistical‑analysis.pdf Byles, J., 2005. Rubble: Unearthing the history of demolition (1st ed.). New York: Harmony Books. Charef, R., 2022. The use of building information modelling in the circular economy con‑ text: Several models and a new dimension of BIM (8D). Clean. Eng. Technol. 7, 100414. https://doi.org/10.1016/j.clet.2022.100414 Charef, R., Emmitt, S., 2021. Uses of building information modelling for overcoming barriers to a circular economy. J. Clean. Prod. 285, 124854. https://doi.org/10.1016/ j.jclepro.2020.124854 Charef, R., Ganjian, E., Emmitt, S., 2021a. Socio‑economic and environmental barriers for a holistic asset lifecycle approach to achieve circular economy: A pattern‑matching method. Technol. Forecast. Soc. Change, 170. https://doi.org/10.1016/j.techfore.2021. 120798 Charef, R., Lu, W., Hall, D., 2022. The transition to the circular economy of the construction industry: Insights into sustainable approaches to improve the understanding. J. Clean. Prod., 364, 132421. https://doi.org/10.1016/j.jclepro.2022.132421 Charef, R., Morel, J. C., Rakhshan, K., 2021b. Barriers to implementing the circular econ‑ omy in the construction sector: A critical review. Sustain., 13(23), 12989.

44  Lionel Devlieger and Arne Vande Capelle Condotta, M., Zatta, E., 2021. Reuse of building elements in the architectural practice and the European regulatory context: Inconsistencies and possible improvements. J. Clean. Prod. 318, 128413. https://doi.org/10.1088/1755‑1315/225/1/012058 CRWP (Construction Resources and Waste Platform) and Salvo, 2007. BigREc Survey: a Survey of the UK Reclamation and Salvage Trade. CRWP, Watford, UK. te Dorsthorst, B. J. H., Kowalczyk, T., Hendriks, C. F., Kristinsson, J. 2001. From grave to cradle: Reincarnation of building materials. Int. Conf. Sustain. Build. 200, 65–78. https:// doi.org/10.14359/10572 Devlieger , L., Cahn, L., and Gielen, M., Eds, 2014. Behind the green door. A critical look at sustainable architecture through 600 objects. Oslo: Oslo Architecture Triennale. European Commission, 2020. A new circular economy action plan. For a cleaner and more competitive Europe, https://eur‑lex.europa.eu/legal‑content/EN/TXT/?qid=158393381 4386&uri=COM:2020:98:FIN Friedhoff, A., Wial, H., Wolman, H., 2010. The consequences of metropolitan manufac‑ turing decline: Testing conventional wisdom. Available at SSRN: https://ssrn.com/ abstract=3799717 or https://doi.org/10.2139/ssrn.3799717 Geerts, G., Ghyoot, M., Naval, S., Topalov, H., 2022. Reuse toolkit: Procurement strategies—Integrating reuse in large‑scale projects and public procurements. Interreg NWE FCRBE. https://opalis.eu/sites/default/files/2022‑04/wpt3_d_2_2_procurement_ strategies_20220208.pdf Ghyoot, M., Devlieger, L., Billiet, L., Warnier, A. 2018. Déconstruction et réemploi: Com‑ ment faire circuler les éléments de construction. Lausanne: Presses polytechniques et universitaires romandes. Ghyoot, M., Guichard, C., 2022. Les effets du réemploi sur la conception et vice versa. In P. Belli‑Riz (Ed.), Réemploi, architecture et construction: Méthodes, ressources, concep‑ tion, mise en oeuvre. Presses Universitaires de France, Antony Cedex: Editions du Mo‑ niteur, p. 139–149. Ghyoot, M., and Topalov, H., 2022. Quelle place pour les matériaux de réemploi dans un monde industrialisé ? construction21.org. https://www.construction21.org/france/ articles/h/quelle‑place‑pour‑les‑materiaux‑de‑reemploi‑dans‑un‑monde‑industrialise. html Gielen, M., 2021. Reuse economy. In I. Ruby & A. Ruby (Eds.), The materials book (2nd ed., pp. 161–168). Berlin: Ruby Press. Gobbo, E., Ghyoot, M., Bernair, C., Paduart, A., 2021. A roadmap to foster reuse practices in the construction sector—A collection of inspiring actions for public authorities. Inter‑ reg NWE FCRBE. https://opalis.eu/sites/default/files/2022‑02/FCRBE‑en‑roadmap_for_ public_policies.pdf IPCC, 2023. Synthesis report of the IPCC Sixth Assessment Report, https://report.ipcc.ch/ ar6syr/pdf/IPCC_AR6_SYR_SPM.pdf Koutamanis, A., van Reijn, B., van Bueren, E., 2018. Urban mining and buildings: A re‑ view of possibilities and limitations. Resources, Conservation and Recycling, 138, 32–39. https://doi.org/10.1016/j.resconrec.2018.06.024 Kubbinga, B., Bamberger, M., van Noort, E., van den Reek, D., Blok, M., Roemers, G., Hoek, J., Faes, K., 2018. A framework for circular buildings—Indicators for possible inclusions in BREEAM. https://assets.website‑files.com/5d26d80e8836af2d12ed1269/ 5dea6b3713854714c4a8b755_A‑Framework‑For‑Circular‑Buildings‑BREEAM‑­ report‑20181007‑1.pdf Meier, H.‑R., 2020. Spolien: Phänomene der Wiederverwendung in der Architektur. Berlin: Jovis.

The reuse of building elements  45 Ooms, T. (Ed.), 2022. Working with. MULTI ‑ Open debate, publice interior and circularity. A graphic documentary. Antwerp: CONIX RDBM Architects. opalis.eu, n.d., Building and renovating with reclaimed materials ‑ Professional dealers, common materials, examples of projects. Rotor. 2021. Material sheets—Reuse Toolkit. https://opalis.eu/sites/default/files/2022‑02/ FCRBE‑all_sheets_merged‑EN.pdf Salvo, n.d., accessed 11 January 2024, https://www.salvoweb.com/ Seys, S., 2017. Vers un dépassement des freins réglementaires au réemploi des éléments de construction Un meilleur cadre pour le réemploi de produits, pas d’obligation de marquage CE et un système d’évaluation ad hoc. Brussels Buildings as Sources of new Materials. https://www.bbsm.brussels/wp‑content/uploads/2018/01/Rotor‑WP7‑Rapport‑final‑1.pdf Reday‑Mulvey, G., and Stahel, W., 1976. The potential for substituting manpower for en‑ ergy, a report to the commission of the European communities. Geneva, Switzerland. Stricker, E., Brandi, G., Sonderegger, A., Angst, M., Buser, B., Massmünster, M., Koralek, D., et al., 2022. Reuse in construction: A compendium of circular architecture. Zürich: Park Books. Vande Capelle, A., Cortés Garcia, E., 2021. Urban mine incorporation. In D. Hebel & F. Heisel (Eds.), Urban Mining und kreislaufgerechtes Bauen: Die Stadt als Rohstofflager (pp. 79–89). Stuttgart: Fraunhofer IRB Verlag. Won, J., Cheng, J. C. P., 2017. Identifying potential opportunities of building information modeling for construction and demolition waste management and minimization. Autom. Constr. 79, 3–18.

3

Buildings as material mines Towards digitalization of resource cadasters for circular economy Maud Lanau, Leonardo Rosado, Danielle Densley Tingley, and Holger Wallbaum

Introduction Buildings and infrastructure contribute to human well‑being by providing key ser‑ vices such as shelter, mobility, or communication, but their development and main‑ tenance are tied to substantial environmental impacts. Krausmann et al. (2017) showed that resource extraction increased eleven‑fold (from 7 Gt/y to 78 Gt/y) in the last century, with more than half (in mass) accumulating in society as ma‑ terial stocks (MSs; i.e., long‑lived products) largely dominated by buildings and infrastructure. Resource extraction is reaching such scales that materials previously considered abundant are becoming scarce, e.g., riverbed sands (used as aggregate, a key component of concrete) (Cao and Masanet 2022). In conjunction, greenhouse gas (GHG) emissions from primary resource extraction, transport, and manufactur‑ ing of resources into construction materials and components (i.e., embodied car‑ bon) contribute 11% of global GHG emissions (World Green Building Council 2019). Meanwhile, construction and demolition waste make up the largest share of landfilled waste (more than a third in Europe), and contain carbon‑intensive materials such as metals, plastics, bricks, or concrete (Deloitte 2017; European Union 2018). The construction sector is thus a crucial player in the sustainability transition, but it remains off track for decarbonization by 2050 (UNEP 2022). In their 2022 global status report for buildings and construction, the United Nations clearly highlights the need for governments and cities to “implement policies that promote the shift to ‘circular material economies’” to decarbonize the industry (UNEP 2022). In developed economies, where the built environment represents an extensive res‑ ervoir of secondary resources, circularity strategies include lifespan extension of building materials and components through their reuse (here understood as an um‑ brella term for reuse as is, repair, refurbishing, remanufacturing, or repurposing) (Potting et al. 2017) or recycling. Such circularity strategies have frequently been demonstrated at a case‑project level (Leising et al. 2018; Minunno et al. 2020), and a small number of decentralized and rarely digitized urban resource centres (i.e., warehouses with salvaged materials being sold) have now appeared at the urban level (Agenda Partnership on Circular Economy 2019; Ordóñez et al. 2022). De‑ spite these activities, the intensification of the reuse of materials and components DOI: 10.1201/9781003450023-5

Buildings as material mines  47 remains dramatically low. Engineers, contractors, and architects are often those called to implement resource‑efficient strategies in their operations (UNEP 2022) but even for keen practitioners, the practicalities of such endeavor are difficult. Research on the barriers to CE adoption in the construction sector has focused on reasons why circularity has not gained more traction in the last few years. We restrain from listing all barriers here and instead direct the reader to the works of, e.g., Charef and Lu (2021); Frändberg and Nyqvist (2021); Hart et al. (2019); Rakhshan et  al. (2020). Broadly speaking, barriers can be categorized into five groups. Cultural and knowledge barriers are those “soft” barriers present in the construction sector, such as a lack of interest and knowledge in CE, skepticism and inertia, and lack of actor collaboration. Technical barriers include technical difficulties to disassemble sometimes heavy and voluminous materials, their trans‑ portation, and their storage. Fixed lengths of some building components (e.g., steel members) also hinder designers from incorporating reused components into their design. Regulatory barriers pertain to challenges to fulfill regulatory standards with reused materials potentially contaminated or obsolete – a concern worsened by the lack of quality assurance certification schemes for reused components. Financial barriers include a lack of economies of scale, and skepticism about the profitability of deconstruction and reuse as opposed to demolition and the purchase of new products. Market barriers include an unclear and disorganized market demand for secondary resources and concerns about the consistency of returned flows. Con‑ sidering such a variety of barriers, it is unsurprising that progress towards a wide‑ spread implementation of CE is still slow. Fortunately, understanding exactly what materials are stocked in our built en‑ vironment has received increasing attention in industrial ecology research in the last few years. Recent studies have successfully demonstrated the scale of sec‑ ondary resources stocked in buildings and infrastructures (see Table 3.1) and the relevance of buildings as material mines. Indeed, buildings contain a variety of materials – including carbon‑intensive ones – located above ground and therefore easier to access than e.g., underground pipes that could only be retrieved by dig‑ ging into roads. An increasing number of stock studies focus on developing maps of the type, quantity, and location of construction materials stored in a city or na‑ tion’s building stock. These so‑called resource cadasters have successfully pleaded the case for buildings as material mines (Arora et al. 2020; Kleemann et al. 2015; Lanau and Liu 2020). But, with results often expressed in mass of materials and lacking details needed by construction actors (e.g., dimension, quality, and number of components), resource cadasters currently remain too coarse to provide action‑ able knowledge for the construction industry. In this chapter, we investigate the status and prospects of resource cadasters as a tool to enable the implementation of resource circularity strategies in construction. We specifically aim to answer the following research questions: – RQ1 What is the research status on material cadasters for CE? – RQ2 What are the limitations of current resource cadasters for CE?

Location and year

Buildings studied

Inventory data

Results

References

kt/km2

t/cap

73 RB: 75 NRB: 37 Tot: 112 RB: 190 NRB: 70 Tot: 260 RB: 176 NRB: 75 Tot: 251 130 250

(Lanau and Liu 2020)

88 210

(Mao et al. 2020) (Kleemann et al. 2017)

National scale Japan, 2010 Grenada, 2014

All (undifferentiated) All, differentiated into seven structural types

Cadastral Cadastral + land use

Germany, 2018

All, differentiated into residential (two types) and nonresidential

Satellite data + Open Street Map

Residential

Cadastral + building registry

25 RB: 23 NRB: 12 Tot: 35 RB: 45 NRB: 16 Tot: 61 RB: 19 NRB: 8 Tot: 27 26

Cadastral

1262

Austria, 2018 Switzerland, 2015

City scale Odense city centre All, differentiated into residential (three (DK), 2017 types) and nonresidential (24 types) Beijing (CN), 2018 All, differentiated into 12 types Vienna (AT), 2013 All, differentiated into three types (residential, commercial, industrial) Padua (IT), 2007 All, differentiated between residential (three types), nonresidential, and other Chiclayo (PE), 2007 Residential Esch‑sur‑Alzette Residential (LU), 2010

Cadastral + web scraping 2134 Cadastral + land use + construction 927 age data and zoning Cadastral RB: 389 NRB: 75 Tot: 464 Census database + cadastral RB: 608 Cadastral + LiDAR RB: 240

(Tanikawa et al. 2015) (Symmes et al. 2019) (Haberl et al. 2021)

(Heeren and Hellweg 2016)

RB: 175 (Miatto et al. 2019) NRB: 34 Tot: 209 RB: 55 (Mesta et al. 2018) RB: 106 (Mastrucci et al. 2017)

48  Maud Lanau et al.

Table 3.1  Overview of studies using the bottom‑up approach and their results

Melbourne (AU), 2015 Paris (FR), 2013

All (differentiated into eight types)

Cadastral + land use

Residential, nonresidential

Neighbourhood scale Wakayama city All centre (JP), 2004 Salford Quays, All Manchester (GB), 2004 Philadelphia All (2.6 km2) (US), 2012 Braddon (Canberra Residential (five types) + mixed use) suburb, AU), 2015 Bochum (DE), n.d. Residential

904

256

Cadastral

(Stephan and Athanassiadis 2017) RB: 2972 RB: 156 (Augiseau and Kim NRB: 776 NRB: 41 2021) Tot: 3748 Tot: 197

Cadastral

887

218

Cadastral

299

79

Cadastral + Land use

1382

153

(Marcellus‑Zamora et al. 2016)

LiDAR satellite data

511

130

(Schandl et al. 2020)

Cadastral + on‑site investigation

530–590

208–231 (Oezdemir et al. 2017)

(Tanikawa and Hashimoto 2009) (Tanikawa and Hashimoto 2009)

Buildings as material mines  49

Acronyms: n.d. no data; NRB nonresidential buildings; RB residential buildings; Tot Total. Country codes: AT Austria; AU Australia; CN China; DE Germany; DK Denmark; FR France; GB United Kingdom; IT Italy; JP Japan; LU Luxembourg; PE Peru; US United States.

50  Maud Lanau et al. – RQ3 What would be an optimal resource cadaster to support the construction industry in transitioning to CE? The focus is on information needs and delivery. – RQ4 How can current research support the achievement of such optimal re‑ source cadasters? Secondary resources cadasters: state‑of‑the‑art Bottom‑up stock modelling

As of now, modelling of MSs has successfully achieved a rough understanding of the type and quantities of materials in buildings. This is accomplished through the bottom‑up approach that calls for two essential datasets (Equation 3.1). First, the inventory (INV) of buildings (i) within the studied geographic boundary, expressed in a unit reflecting the size of the building (e.g., square meter of floor area). Sec‑ ond, material intensity (MI) data, which represents the average material quantities per dimensional unit of building (e.g., kilogram of material per square meter floor area). The combination of inventory and MI data results in a (more or less coarse) modelling of both types and quantities of materials stocked in the building stock under study.

MS =

∑INV × MI  i

i

(Equation 3.1)

i

But building inventories are a heterogenous dataset made of buildings varying in size, construction age, structure, and construction techniques – all of which influ‑ ence the material composition of the building. Though MIs should ideally be cal‑ culated for each building, the endeavor is unrealistic under current MI calculation practices that require manual material takeoffs from available building documents. For older buildings, documents are usually stored in rarely digitized archives and consist of hand‑drawn plans with sparse building specifications, thus requiring the development of assumptions based on construction technique handbooks and ex‑ pert consultation. For newer buildings, manual takeoff is a strenuous endeavor due to the highly detailed building data (often PDFs exported from digital models). To reduce data and time intensiveness, buildings are classified into archetypes, i.e., typical buildings across construction ages, construction types, and/or building uses. Archetype classification effectively homogenizes inventory data into a few dozen archetypes, rendering MI data collection more manageable. Where building inventories are available in a geo‑located format, the bottom‑up approach can be integrated with Geographical Information System (GIS) to create a resource cadaster that provides information on the location, quantity, and type of materials stocked in buildings. Tanikawa and Hashimoto (2009) performed such GIS‑based bottom‑up study for the first time in two neighbourhoods (Wakayama city centre in Japan, and Salford Quays in Manchester, UK). The approach has since then been used, refined, and complemented in numerous case studies.

Buildings as material mines  51 Resource cadasters to support the circular economy Material quantities

As can be seen from Table 3.1, GIS‑based bottom‑up studies have been per‑ formed for many neighbourhoods, cities, and even a few countries. We note here that Table 3.1 only includes studies quantifying all (or most) construction materi‑ als, with spatially differentiated results. “Cadastral” refers to existing GIS data that includes – at least – information on building footprint and location. The type of building information contained in such cadastral data greatly varies. Extensive building information can be found in those developed by governmental bodies (e.g., tax purposes, or risk management), while those retrieved from mapping services may not have any useful attribute for stock modelling. In such cases, additional datasets (e.g., land use data, census data) can complement basic ca‑ dastral data. Results from studies in Table 3.1 show higher MS densities in urban areas than national averages (which includes rural areas with much less buildings). For ex‑ ample, national building MSs range from 25 kt/km2 (Japan) to 61 kt/km2 (Ger‑ many) (Haberl et al. 2021; Tanikawa et al. 2015). In urban areas, building MSs are considerably higher and ranging around 900–1200 kt/km2 in Vienna (AT), Odense (DK), and Melbourne (AU), and up 3748 kt/km2 in Paris city (FR) (Augiseau and Kim 2021; Kleemann et al. 2017; Lanau and Liu 2020; Stephan and Athanassi‑ adis 2017). Additionally, the few case studies that include non‑residential buildings found them to contain large shares of carbon‑intensive materials such as metals (e.g., malls, warehouses) and glass (e.g., greenhouses). Coupled to their short lifetime (shaped by the dynamics of the economy), the turnover of construction materials for nonresidential buildings is greater than for residential, making them relevant candidates as material mines (Ortlepp et al. 2015). Embodied carbon

Material quantities from resource cadasters can be drawn on to quantify carbon emissions embodied in a building stock. In their bottom‑up stock modelling of Bei‑ jing (CN, 16411 km2), Mao et al calculated that the 2270 Mt (138 kt/km2) of ma‑ terials stocked in the city’s buildings embody 993 Mt.CO2e (61 kt.CO2e/km2). In the case of Odense (DK, 304 km2), results showed that developing the municipal‑ ity’s building stock from scratch today would emit 10.7 Mt.CO2e (35 kt/km2) from raw material extraction, transport, and manufacturing of construction materials and components (Lanau et al. 2021). A bottom‑up stock study of the Canberra suburb of Braddon (AU, 1.4 km2) allowed the authors to calculate that 282 kt.CO2e was embodied in the neighbourhood’s buildings (Schandl et al. 2020). In their MS study of buildings in Melbourne (AU, 26.2 km2), Stephan and Athanassiadis (2017) used results to analyze embodied carbon emissions, but also embodied energy and wa‑ ter, showing that the 32 Mt (904 kt/km2) of construction materials stocked in Mel‑ bourne’s buildings embodied 24 Mt.CO2e (605 kt.CO2e/km2), 362 PJ (10 PJ/km2),

52  Maud Lanau et al. and 640 million m3 (18 million m3/km2) of water. Such results demonstrate the relevance of pushing for more reuse and high‑value recycling strategies in the con‑ struction industry to displace emissions linked to new materials. Future material outflows

Results of bottom‑up stock modelling can be used to predict when and how much construction materials will leave the stock (stock‑driven modelling). Such informa‑ tion is particularly interesting in a circular paradigm, where knowledge on future availability of secondary materials is critical to support the planning of reuse activ‑ ities. In stock‑driven modelling, average building lifetimes (i.e., the time between a building’s construction and its demolition) can be applied to bottom‑up stock results on the condition that building age is an available information. Probability distributions are then used to account for the fact that some buildings may last longer (or shorter) than their assigned lifetime. Here, it is the size of the building stock – made of thousands of items – that enables the use of probability distribu‑ tions to reflect the fraction of buildings living a building stock over time. For more details on the use of building lifetimes (and how those are calculated, i.e., mortal‑ ity/survival of building stocks), we refer the reader to the works of (Aksözen et al. 2016; Hashimoto et al. 2009; Miatto et al. 2017). Research gaps and methods Research gaps

Results of archetype‑based resource cadasters successfully demonstrate the scale, type, and location of construction materials stocked in a city/nation’s buildings. Before the development of such cadasters, the potential resource and environmen‑ tal savings offered by large‑scale reuse and recycling of building materials and components remained unclear. But several challenges subsist to the practical use‑ fulness of resource cadaster for stakeholders. First, the completeness of inventory information is a challenge for the develop‑ ment of resource cadasters. In data‑poor regions, the lack of inventory impedes any attempt to model a resource cadaster. But even where inventory is available, sev‑ eral challenges may arise. As inventory information drives archetype classification, poorly documented inventories challenge the development of clear and representa‑ tive archetypes. Only coarse archetypes can then be set, based on heavy assump‑ tions such as inference of a building’s structure based on its height. In contrast, a detailed building inventory (e.g., use type, age, structure, and height) allows for detailed archetype classification. The challenge then is to find a balance between representativeness of the building stock (the more archetypes, the better) and the challenges of data collection (the more archetypes, the more strenuous the data collection) (Ortlepp et al. 2018). Additionally, the accuracy of inventory informa‑ tion impacts the reliability of building‑level results. Erroneous inventory data (e.g., incorrect building type) would cause the building to be assigned to an archetype whose MI does not represent the actual building (Tanikawa et  al. 2015). Thus,

Buildings as material mines  53 developing a resource cadaster in areas that lack good quality inventory informa‑ tion is extremely challenging. Another limitation of resource cadasters is the presentation of results in total mass of construction material per building rather than differentiation of results at the component level. The focus on weight of building materials (rather than di‑ mensions, or count) may make results hardly fathomable to actors in the construc‑ tion industry. Worth noting here is the effort of Arora et al. (2019, 2020) in their bottom‑up stock study of public residential buildings of Singapore. The authors assessed the stock of nonmetallic minerals and steel, but also a select number of components (windows, doors, tiles, toilet accessories, lighting fixtures, and kitchen accessories). Rather than surveying material quantity in sample building plans, the authors surveyed the number of components. Such “component intensity”, ex‑ pressed in number of items per dwelling, was then scaled up to the city’s dwelling inventory. While successful in reaching a component level, the approach still relied on archetype classification and average component intensity, which involves un‑ certainties if a building differs from its assigned archetype. Indeed, though the archetype approach is sufficient to obtain reasonable rule‑of‑thumbs on quantities of stocked materials, the certainty of results varies de‑ pending on how much a building’s design deviates from its assigned archetype. This uncertainty is further exacerbated by the expression of material intensities in mass per floor area which fails to account for the geometry of buildings and thus may lead to incorrect results. For example, two buildings with the same floor area may have very different designs and material quantities, e.g., a one‑story building with intri‑ cate design (long external walls, no intermediate floor, and large roof) vs a two‑story square building (shorter external wall, intermediate floor, and smaller roof). A select number of studies thus went beyond building‑level modelling and towards elemen‑ tal modelling of buildings. For example, Stephan and Athanassiadis (2017) disag‑ gregated buildings into assemblies (e.g., roof, external wall) and calculated their material quantities. Using basic geometrical characteristics of buildings available in the inventory (e.g., building footprint, number of stories, and number of facades), the author successfully reached a more detailed material composition of buildings. A caveat to this method was the simplification of building shapes into rectangles. (Gontia et al. 2018) developed elemental material intensities (e.g., mass per square meter of basement, floor, and roof) that could be used with information on buildings’ floor area, number of stories, and perimeter. Using a similar line of thought, Lanau and Liu (2020) developed “block‑wise” material intensities by dividing a building into four building blocks. In each case, elemental material intensities may only be used with a detailed inventory that includes dimensional information for elements (e.g., height, perimeter, and type of roof). While elemental material intensities are a step towards more detailed modelling across buildings, a truly building‑specific cadaster with component‑level information has not been achieved. The limited amount of work performed so far towards component‑level stock modelling illustrates another important gap of resources cadaster: the lack of infor‑ mation about the location of each material and components within a building. Ma‑ terials in a building structure are likely to stay in place as long as the building, but many building components (e.g., windows, roofing) will be replaced several times

54  Maud Lanau et al. within a building’s lifetime. As stock research is increasingly focused on reaching a component‑level modelling, an additional gap emerges: the lack of understand‑ ing of time availability of materials and components. Currently, future material availability is modelled with average lifetimes of buildings, which may be valid for structural materials but does not account for the shorter service lifetimes of other building components (Brand 1994). The needs for higher modelling details within a building and for reaching component‑­level information are not yet met in resource cadaster. This may partly be explained by the relative youth of GIS‑based bottom‑up MS modelling kick‑ started by Tanikawa and Hashimoto (2009), and by the intensiveness of the model‑ ling approach in terms of data, labour and time; even before modelling details are added. But the development of truly informative resource cadasters is also hin‑ dered by the lack of clarity on which specific information would stakeholders need to enable wide‑scale reuse across the construction industry. General methodology

We use a qualitative research approach to answer all RQs. A selective literature review (whose results are presented in the section “Secondary resources cadasters: state‑of‑the‑art”) was used to investigate the status (RQ1) and limitations (RQ2) of material cadasters research. Lanau et al. (2019)’s critical review on built environ‑ ment stock research was used to populate a preliminary list of secondary cadasters developed until 2019. This was done by singling out all MS studies that used a GIS‑based bottom‑up approach, included building stocks, and quantified all (or most) construction materials. Relevant studies published after 2019 were retrieved through forward snowballing. We used an exploratory case study to envision an optimal resource cadaster (RQ3), focusing on stakeholders’ information needs. The exploratory case study consisted of a study visit to a school building commissioned for demolition. The components making up the interior of the school were documented through 3D pictures of the school (generated with a mobile application that uses LiDAR scan‑ ning and computer vision). These pictures were the basis for a workshop with 15 relevant stakeholders who were asked what types of components were interesting to reuse, what information would be needed, and what barriers could prevent the reuse. Findings from this workshop were further complemented with online sur‑ veys to Swedish stakeholders (real estate owners, architects and consultants, con‑ struction companies, demolition companies, recycling companies, private owners, and government) where similar questions were asked. To explore if and how such optimal cadaster could be achieved (RQ4), we inves‑ tigated recent research and advances in digital surveying of material or components in buildings such as digital solutions (e.g., building information modelling (BIM)) and remote sensing techniques. We limit the scope of literature to those studies that successfully generated valuable data for resource cadasters, such as information on buildings or components’ dimensions, or their material composition. Based on findings from RQ3 and RQ4, we then propose a workflow to start moving towards building‑specific and component‑level resource cadasters that

Buildings as material mines  55 would deliver actionable knowledge for industry actors to move towards circular‑ ity of resources in the built environment. We also reflect on the limitations of the resource cadaster concept and discuss implications for the construction industry. Results Envisioning an optimal resource cadaster: stakeholders’ information needs

Before presenting the results of the stakeholder workshop and survey, we would be remiss not to mention the work previously conducted by researchers on mate‑ rial passports, defined as “digital datasets [that] aim to catalogue and disseminate the CE characteristics of building materials, components, and products” (Heinrich and Lang 2019). We refer the reader to the European project Building as Material Banks (BAMB 2016), which produced a detailed overview of the types of mate‑ rial and product‑related information a building material passport should include (Heinrich and Lang 2019). On a related issue, Charef (2022) proposed a list of data required resulting from a set of semi‑structured interviews conducted within construction stakeholders (BIM and/or CE professionals). The author reflected on what the content of the Deconstruction Information Model (DIM) should be. Over‑ all, for construction sector stakeholders, an ideal data availability would include precise and reliable data on each building, such as its material composition at all levels (building, element, and component), as well as a whole host of information, e.g. material dimensions and properties. Results from the stakeholder workshop allowed us to further understand stake‑ holders’ information needs. When asked which existing building components are most attractive for reuse or recycling, the general agreement was that any product or component still functioning properly would be of interest. When asked to indi‑ cate specific materials or products, stakeholder’s responses varied depending on their role (e.g., private owners vs companies). Interestingly, 60% of the answers named doors and windows. The example of doors was then used to further identify information needed for stakeholders to reuse a specific product or element. Overall, the information needs identified during the workshop can be grouped into three broad categories. First, stakeholders require descriptive information such as door type, dimensions, fixings, material content, chemical content, and colour. Second, the door’s condition (e.g., functionality, fire class, acoustic qualities, aes‑ thetics) and reuse potential (e.g., reconditioning needs, and potential economic and environmental savings). Third, information pertaining to potential challenges that could prevent reuse, such as hazardous content, potential for quality disassembly, and possibility to transport and store the door until needed. The information needs highlighted in the workshop are significant, begging the question of how such information can be collected and processed into a detailed cadaster. The large amount of data involved in acquiring and displaying such a high‑resolution detailed inventory of the built environment may only be achievable digitally. Indeed, the rise of artificial intelligence and digital technology in indus‑ trial ecology research (Donati et al. 2022; Majeau‑Bettez et al. 2022) opens up a number of opportunities for data acquisition and visualization, including inputs to

56  Maud Lanau et al. building inventories and material and components recognition. In the next subsec‑ tion, we review recent works on the topic of building surveying – both physical size and material recognition. We refrain from limiting the scope to the field of MSs, and instead attempt to gain an overview of opportunities offered by digital technol‑ ogy for the development of resource cadasters. Diversification of data sources

The following sections outline the different artificial intelligence and digital tech‑ nologies that have been employed to assist with the development of resource ca‑ dasters or similar endeavors. Building Information Modelling. BIM files are 3D digital representation of a building that include all products, components, and materials that make up the build‑ ing. BIM software allows for automatic generation of material takeoffs that lists the count, dimensions, quantities, material types, and location (within the building) of building components. Though accuracy of BIM‑generated material takeoffs varies depending on the quality of the modelling (e.g., lack of construction details) (Kho‑ sakitchalert et al. 2019; Kim et al. 2019), they are still suitable source of data for resource cadasters. Their main limitation resides in the fact that BIM files are only available for new buildings (or renovated parts of older buildings). In the paradigm of buildings as material banks, the material composition of newer buildings might not be the most pertinent target since they will stay in use for a long time. Web scraping. In their study of Beijing’s (China) built environment stock, Mao et al. (2020) started with a base inventory including only footprint, number of sto‑ ries, and location and derived building type from land use data. They then used a web‑scraping approach to collect construction age of buildings. Web‑scraping consists of using bots (“scrapers”) to automatically extract specific data (here, construction age and location) from specific web pages (here, the largest real‑estate agency in China). Computer vision and machine learning. Computer vision is a field of artificial intelligence concerned with modelling and replicating human vision with comput‑ ers. Using digital images and machine learning, computers are trained to accurately identify and classify different objects. Such methods have been used by researchers to showcase automatized recognition of building attributes such as building height (Farella et al. 2021), buildings’ footprint (Huang et al. 2022), and the number and dimensions of doors, windows, façade, chimneys, and roofs (Arbabi et al. 2022; Dai et al. 2021; Sezen et al. 2022). Optical and radar satellite data. Earth observation products from optical sat‑ ellite data (Copernicus Sentinel‑2) and radar satellite data (Copernicus Sentinel‑1) are freely available at a 10‑meter resolution. Haberl et al. (2021) used this satellite data to derive spectral‑temporal metrics and model key information on built‑up areas, including the share of built‑up area in each 10 × 10 m cell (based on the variability of different parts of the electromagnetic spectrum over time), building height (based on morphological metrics and trained with a reference dataset), and building type (based on reflectance and backscatter characteristics of pixels’ sur‑ roundings). They complemented this building data with crowd‑sourced data from

Buildings as material mines  57 Open Street Map, as they calculated the area coverage of roads and railways (based on buffering the line data with width fitting the infrastructure type). The integration of these two large‑scale data sources proved effective in estimating MSs over large areas (national and international) at a spatial resolution of 10 m. Noteworthy is the replicability of the approach, enabling the calculation of MS levels anywhere in the world, provided MI data is available for the area under study. LiDAR satellite data. LiDAR data may be used for inventorying buildings’ external dimensions. LiDAR data consists of a “point cloud” of individual points. In practice, a LIDAR system includes a laser scanner that transmits pulses of light towards a target (e.g., the ground) and records the time for the light to travel to the target and back, thereby allowing to calculate the distance between the LiDAR system and the target. A GPS mounted on the LiDAR system allows to track its position, and an inertial navigation system records its orientation. LiDAR data thus consists of a point cloud of individual points. When scanning for ground elevation (and thus building heights), LiDAR vertical accuracy reaches 10 cm but the data may be costly to obtain and is often geographically limited to a small area. Schandl et al. (2020) used Light LiDAR point cloud data to create a 3D representation of the building stock of a Canberra suburb in Australia. They further derived a 2D build‑ ing inventory including information on each building’s footprint, volume, height, and roof type. Spectral imaging. Materials have their own spectral signature that can be ex‑ tracted by recording and analyzing the reflectance of light reflected from the mate‑ rial (Strauss et al. 2020). Because this reflectance is often in the electromagnetic spectrum (wider than the visible spectrum), specific technologies are required to capture information across the spectrum. Hyperspectral imaging records informa‑ tion continuously across the electromagnetic spectrum, while multispectral im‑ aging records several images of the same scene, with each image acquired at a specific wavelength range. Such technologies, first developed to locate minerals of interest for mining and geology, can identify several building materials. Ye et al. (2017) used hyperspectral remote sensing imagery to identify roof material and successfully developed a methodology to extract material information for roofs in coloured steel, clay, glazed tile, and asphalt concrete. Zahiri et al. (2021) used multispectral imagery and LiDAR intensity data to characterize building materi‑ als, aiming to support the life cycle analysis of existing buildings. Focusing on six brick types (with distinct colours and firing temperatures), three concrete types (with different water/cement ratio), and two mortar types, the authors achieved an average correct classification rate of 83%. Spectral imaging thus holds the potential to conduct in‑situ façade and roof material labelling in a non‑destructive manner. The diversity of techniques for capturing building‑specific data presents a con‑ siderable opportunity to reach a higher level of detail (LoD) and certainty in re‑ source cadasters. But this wide variety of data sources also poses challenges of data management, processing, and sharing. Additionally, with each data capture tech‑ nique focusing on precise building information, challenges of resource cadaster completeness arise. In the next section, we present a potential workflow for the development of a resource cadaster that takes such challenges into consideration.

58  Maud Lanau et al. A proposed workflow

According to Glaessgen and Stargel (2012), the concept of Digital Twin (DT) can be described as an integrated multi‑physical, multiscale probabilistic simulation of a com‑ plex object that uses physical, mathematical, simulative and other models to obtain the most accurate representation of the corresponding real object based on analysis of data from sensor networks and other sources. Based on this definition, Ivanov et al. (2020) define the concept of DT of a city as a system of interconnected digital twins, representing certain aspects of the functioning and development of the urban environment. These digital twins support fine‑tuning and synchronization with the real state of urban infra‑ structure through data from various sources in real‑time. A continuous flow of data generated by different sources in the digital infrastructure of a smart city is the key to the effective functioning of the city digital twin. Several initiatives have appeared to provide a platform for DT of cities. In Sweden, the Digital Twin Cities Centre is currently developing an open DT platform to facilitate the exchange and accessibility of relevant spatial, user, and quantitative data. This DT will serve as the basis for the development of tools and methods to support decision‑making processes, amongst which the development of circularity tools for reuse and recycling of existing building stocks. Although still in its in‑ fancy, the use of DT as host of material resource cadasters has potential to provide a platform for accessing information on candidates for reuse and recycling. Such a platform would also help raise awareness of actors on CE and its environmental and economic potentials and would facilitate collaboration. But achieving a DT of the built environment and its embedded construction ma‑ terials, in a form that fits the information needs of stakeholders, will be a data‑in‑ tense and time‑consuming endeavor. Based on such conclusions, we propose that complementing an existing traditional resource cadaster with any relevant addi‑ tional information captured from a variety of data sources may be the way forward. Such an approach resonates with the concept of LoD used in digital twins. LoDs indicate how comprehensively and accurately model features (e.g., a building) re‑ flect reality, ranging from LoD 0 (lowest LoD, building footprint with at least one height value) to LoD 3 (most detailed level of the building as seen from outside), with LoD 4 pertaining to adding internal structures (e.g., partition walls, doors) (Gröger and Plümer 2012). Typically, a model starts with low LoD, and methods are developed and integrated to enrich and increase the LoD over time. In our pro‑ posed approach, results of a traditional bottom‑up stock approach are comparable to a low LoD that needs to increase to higher accuracy and certainty. The LoD is then incrementally increased by developing modelling methodologies towards the component level and refining data completeness and quality through data capture

Buildings as material mines  59 solutions. Figure 3.1 illustrates a potential workflow that would theoretically result in a high LoD, i.e., a material passport for each building in a case study. First, a base resource cadaster is produced through the methodology described in the Section “Bottom‑up stock modelling” (low LoD). Here, elemental material intensities should be developed where possible to increase results’ reliability and differentiation (e.g., quantity of bricks in external walls, in internal walls, in base‑ ment). At this stage, results should be read with caution as they rely heavily on assumptions made during material takeoff, and on potentially faulty information in the inventory that would lead to a building being allocated to the wrong archetype. Still, this primary cadaster provides an overview of total material types and quanti‑ ties embodied in buildings. Any additional data source can then be used to improve and refine the cadaster (or parts of it). This includes digital solutions described in the Section “Diversifi‑ cation of data sources” but also any information already available for buildings in the form of environmental certifications, energy declarations, building safety bills, demolition audits, and more. We clarify here that not all information may be avail‑ able for each building, and that the improvement of the cadaster is a dynamic and systematic process relying on any new information being retrieved or created. We identify three broad categories of potential improvements, each linked to key data used in bottom‑up stock modelling. • The first set of improvements pertains to improving buildings’ geometrical in‑ formation in the inventory. Building shapes and locations may be extracted from satellite and aerial optical imaging, while satellite and aerial LiDAR data may be used to extract buildings’ heights. • A second set of improvements concerns the building attributes used to create ar‑ chetype categories. This includes building use (e.g., office, residential) that may be derived from land use data and web scraping (e.g., points of interest, which consist of the longitude and latitude of a place of interest such as malls, hotels, restaurants, and the like). Web scraping may also be used to retrieve additional building information, e.g., building age from real estate websites. Digitalizing and processing historical maps into GIS may also provide useful information on the presence or absence of a building at a specific time, thus helping derive the building’s age. • A third improvement pertains to capturing information on the materiality of the building and its components. Hyper‑ and multi‑spectral imaging may assist in assessing the materials of building’s facades and roofs. Computer vision and machine learning may help with the number of windows and doors in external walls, but also the potential presence of basement. LiDAR imagery and com‑ puter vision can also capture information inside buildings. These technologies, easily accessible to the public on smartphones and tablets, generate 3D models from which dimensions, materials, and colours of components can be derived. All newly generated building information is then compared against its relevant base counterpart. New dimensional inventory data is compared to the inventory

60  Maud Lanau et al.

Figure 3.1 Complementing resource cadaster with a variety of data capture and data mining. Figure developed by the authors.

Buildings as material mines  61 used for the base cadaster, and new archetypical information is checked against that from the base inventory and base resource cadaster. Where new information is more reliable or accurate, it is uploaded to DT. We stress here the need for DT to disclose to users the quality of information and the relative level of certainty achieved. This disclosure may describe, for example, the data source and model‑ ling used, and a history of earlier results. The categorization of the DT resource cadaster across different LoD will also provide opportunities for multiple types of analysis and comparisons, all allowing for a richer understanding and purpose of the DT model. Results from a refined DT resource cadaster will also improve our understanding of uncertainties in traditional bottom‑up stock modelling through comparison of results (Figure 3.1). Discussion Limitations

We acknowledge the limited number of participants in the workshop (15 partici‑ pants), which we mitigated by conducting a broader survey (93 respondents). We thus believe the findings from the workshop and survey represent a good first un‑ derstanding of the interests, needs, and challenges that stakeholders face when questioned about the need for reusing and recycling existing building materials and components. We consider these to be enough to illustrate the need for increased details in cadasters. We also acknowledge the list of alternative data sources (in “Diversification of data sources”) to not be exhaustive. As digital solutions and artificial intelligence are increasingly integrated to the fields of geomatics and material science, the num‑ ber of case studies is too diverse and large to cover in this book chapter. This likely incompleteness of the list actually supports rather than challenges the conclusion that diversification of data sources is a way forward for improving both reliability and modelling details of resource cadasters. Any additional data source is indeed a welcome possibility to gather new data and improve existing ones. Additionally, we highlight the simplification of the workflow presented in Fig‑ ure 3.1 to increase clarity. In practice, the workflow would include process loops that return to previous steps and repeat (some of) the workflow path. For example, as archetypical information becomes increasingly diverse (e.g., additional infor‑ mation such as building construction type) and complete (i.e., available for a large part of the inventory), reworking the archetype classification would be desirable. A new archetype classification would then imply recalculating MIs across these new archetype categories. Finally, a limitation of the framework as an answer to stakeholders’ information needs is that some key information is likely to remain difficult to capture. This includes, for example, the potential contamination of materials and structural qual‑ ity of materials. Such information may only become available during demolition audits, a task hardly feasible for each building of a city. We note here the emerg‑ ing research topic on using machine learning to predict the presence of hazardous materials in buildings (Wu et al. 2021). Such methods could, in time, be integrated

62  Maud Lanau et al. into the workflow proposed in the former section of this chapter. For further discus‑ sion on the usefulness of potentially incomplete resource cadaster, see the Section “Form follows availability”. Challenges to data collection, processing, and sharing

The workflow’s reliance on digital solutions means that its implementation will require high processing power, especially if scaled up to cities or even countries. Solutions to minimize processing power should be implemented wherever possi‑ ble. In that aspect, the development of adaptive frameworks may help, as showed by Blaha et al. (2016) in their 3D reconstruction of Enschede (The Netherlands) at a resolution of 80 centimeters. The authors exploited the fact that large regions of the city did not actually need to be modelled as they did not contain buildings. They developed an adaptive method that refines the volumetric reconstruction only where necessary. Processing the dataset of images with the adaptive method re‑ quired only 28 gigabytes (40 hours on one computer), i.e., 6% of the memory needed without the adaptive method. Integrating, storing, and displaying results in the DT would also require significant processing power and data storage (Jones et al. 2020), and such technical require‑ ments should be considered when designing the DT’s data structure and visualization solutions. Further investigation is required on the balance to strike between techni‑ cal requirements and how data should be accessed and presented so the DT is both functional and useful as a tool supporting the “buildings as material banks” concept. A multi‑disciplinary and cross‑sectoral endeavor

Research interest is increasing on the topic of resource cadaster and stakeholders consulted for this chapter have also shown keen attraction in the concept. Much work remains to be done for resource cadasters to produce results on which build‑ ing designers can act. Collaboration with stakeholders across the construction value chain should continue (e.g., urban planner, building designer, developer, and waste managers), to identify which information is required by different stakeholders to upscale reuse operations. Engaging stakeholders can also prove fruitful for data collection as they may be keener on sharing useful data once involved in the pro‑ cess. Building designers and structural engineers are relevant stakeholders as they often work with BIM files. Demolition companies may have a good understanding of the type and quantities of materials expected from different buildings. Prop‑ erty management companies may hold building components’ lifetime information (a key data to model future availability of materials, see the Section “Resource cadasters to support the circular economy”), as this helps them to plan for timely renovation and refurbishment of their properties. As this chapter demonstrates, a wide array of disciplines is relevant to the devel‑ opment of a DT resource cadaster. Data capture and processing require disciplines such as computer science (machine learning, big data), geomatics (remote sens‑ ing), and those disciplines working with building data such as architecture and civil engineering. To optimize the value of a DT resource cadasters, potential end‑users

Buildings as material mines  63 ought to be involved in its development, including disciplines not mentioned so far in this chapter, e.g., construction management and logistic, urban planning, and contractors, but also practitioners and researchers in circular economy in the construction industry. It becomes clear that a DT resource cadaster can only be achieved through cross‑disciplinarity and high stakeholders’ engagement. Form follows availability

Today, planetary boundaries impose constraints that need to be urgently addressed. A new paradigm shift is needed in the construction, one where buildings are de‑ signed according to which materials are available for reuse. This paradigm of “form follows availability” (Gang 2010) would alter the long‑standing project de‑ livery process of the construction industry. In the case of nonstructural elements (e.g., cladding, windows, partition walls), designers can introduce flexibility in their process by “designing with blanks”. When it comes to structural design, how‑ ever, Brütting et al. (2019) showed that reuse of structural elements would imply a complete reversal of the design process, since mechanical and geometric properties of available elements have a major influence on the structural layout. In the “form follows availability” paradigm, a DT resource cadaster becomes a highly valuable tool – even if incomplete. Information on future available ma‑ terials and components can be consulted by city planners and building owners to decide which buildings should conduct pre‑demolition audits for a more precise inventory, including testing as needed to confirm material properties or check for contamination. Structural engineers may then consult such information to start de‑ signing bespoke structure made of reused materials, while building designers may fill their design blanks with future available materials and components. Here, the development of structured second‑hand market (including certification of salvaged products) would facilitate reuse operations, acting as a buffer between supply and demand, and as an inventory of reclaimed materials and components already avail‑ able. The DT resource cadaster would help answering the questions of where such markets should be located, and how big they ought to be to accommodate for the expected inflow of salvaged materials. Conclusion For construction stakeholders, ideal data availability on reusable materials and components would resemble that of current data for new products. This includes precise and reliable data on the quantity and availability of building products, and on their material composition, dimensions, and a whole host of properties (aes‑ thetic, acoustic, thermal, structural, and more). In this chapter, we present a work‑ flow to improve current resource cadaster though diversification of data sources, an endeavor increasingly enabled by the development of digital technologies. We also identify several prospects and challenges to the development of such DT resource cadaster to successfully support the vision of buildings as material mines. First, more research and collaboration with stakeholders is needed to not only gather their information needs but also better understand how such information can be

64  Maud Lanau et al. shared with them in a useful way (e.g., DT platform access, visualization). A better understanding of the time availability is also urgently needed. This warrants further research on the lifetime of building components and on the age of buildings and their components. We also recommend sustained research on various data sources to prove (or disprove) their value for added information, ideally through multi‑­ disciplinary research which often fosters creativity and out‑of‑the‑box thinking. It is worth highlighting that even with the hybrid approach of the workflow here presented, developing a DT resource cadaster is a significant undertaking that will take considerable time and investment. While it would increase accuracy, details, and completeness of information as compared to traditional resource ca‑ daster, achieving an optimal resource cadaster (as understood by stakeholders) may well remain an impossible task. The high LoDs currently required by stakeholders reflects the continued reliance on the linear economic model of the construction industry, where newly produced materials are systematically accompanied by all relevant documentation. Scaling up reuse of materials and components will require a paradigm shift to “design follows availability”, in which available knowledge on secondary resources, even if incomplete, is a valuable information that supports a new way of designing building within planetary boundaries. Acknowledgements ML, LR, and HW’s time was supported by the JPI Urban European ERA‑NET Cofund Urban Transformation Capacities project CREATE – Embedding advanced urban material stock methods within governance processes to enable circular econ‑ omy and cities resilience under the grant agreement No 875022, and by the Digital Twin Cities Centre supported by Sweden’s Innovation Agency Vinnova under the Grant No. 2019–00041. DDT’s time was funded by EPSRC grant EP/S029273/1. References Agenda Partnership on Circular Economy. 2019. Urban resource centres. http://www.un.org/ sustainabledevelopment/development‑. Aksözen, M., U. Hassler, M. Rivallain, and N. Kohler. 2016. Mortality analysis of an ur‑ ban building stock. Building Research & Information 0(0): 1–19. http://www.tandfonline. com/doi/abs/10.1080/09613218.2016.1152531. Arbabi, H., M. Lanau, X. Li, G. Meyers, M. Dai, M. Mayfield, and D. Densley Tingley. 2022. A scalable data collection, characterization, and accounting framework for urban material stocks. Journal of Industrial Ecology 26(1): 58–71. https://onlinelibrary.wiley. com/doi/10.1111/jiec.13198. Arora, M., F. Raspall, L. Cheah, and A. Silva. 2019. Residential building material stocks and component‑level circularity: The case of Singapore. Journal of Cleaner Production 216: 239–248. https://doi.org/10.1016/j.jclepro.2019.01.199. Arora, M., F. Raspall, L. Cheah, and A. Silva. 2020. Buildings and the circular economy: Es‑ timating urban mining, recovery and reuse potential of building components. Resources, Conservation and Recycling 154(November): 104581. https://linkinghub.elsevier.com/ retrieve/pii/S0921344919304872.

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4

Boosting construction waste material circularity A sharing economy approach Weisheng Lu

Introduction Construction waste, also called construction and demolition (C&D) waste, is the stream of solid waste generated from activities such as new construction, renovation, and demolition (Kofoworola and Gheewala, 2009; Bao and Lu, 2023). Its composi‑ tion varies across contexts. For example, the US Environmental Protection Agency (USEPA, 2022) refers to C&D debris such as steel, wood products, drywall and plaster, brick and clay tile, asphalt shingles, concrete, and asphalt concrete. Code 17 in the European Commission’s (EC’s, 2015) European Waste Catalogue (EWC) includes 10 sub‑codes for C&D waste such as concrete, bricks, tiles, and ceramics (17 01), and wood, glass, and plastic (17 02). In the UK, Hong Kong, and Australia, C&D waste is often categorised as either inert waste, comprising materials such as debris, rubble, earth, bitumen, and concrete; or non‑inert waste, including bamboo, plastics, glass, wood, paper, vegetation, and other organic materials (Lu et al., 2019). Generally, C&D waste management is guided by the ‘3Rs’, i.e., reduction, re‑ use, and recycling, arranged in a hierarchy according to desirability (Peng et al., 1997). Reduction is considered the most effective and efficient method of waste management as it can not only minimise the amount of construction waste gen‑ erated but also reduce the cost of waste transportation, disposal, and recycling (USEPA, 2022). Using the same material more than once, either for the same func‑ tion (e.g., formwork in construction) or in new‑life reuse for a different function (e.g., using cut‑corner steel bar for shelves; or stony fraction for road base mate‑ rial), is the next‑most desirable option because it minimises processing and energy use (HKEPD, 2023). When reduction and reuse become difficult, recycling offers a final option before disposal. More than 95% of C&D waste contains inert materi‑ als that can be repurposed for recovery and recycling (HKEPD, 2023), allowing a variety of new materials to be made. In this chapter, these inert materials are called construction waste materials (CWMs). Advocates of sharing such materials are emerging, especially with the growing success of the sharing economy around the globe. The Organisation for Economic Co‑operation and Development (OECD, 2016) defines the sharing economy as the use of underutilised assets and goods, whether in exchange for other resources (e.g., money, goods, services) or for free. Wosskow (2014) reports that sharing economy DOI: 10.1201/9781003450023-6

70  Weisheng Lu practices are often realised via the sharing of space, transport, time, and skills. The rapid growth of the sharing economy in the world is expected to continue, and pre‑ vious studies (Cohen and Munoz, 2016; OECD, 2016) pronounce its benefits, such as reducing adverse environmental impacts, strengthening communities, redistribut‑ ing resources, monetising illiquid underutilised assets, and accelerating sustainable consumption and economic development. It seems a natural fit to explain and inform CWM sharing through the sharing economy concept. However, to date, there appears to be no research investigating how a sharing economy of CWM can be cultivated. This research aims to analyse CWM sharing in order to boost its circularity from a sharing economy perspective. The chapter focuses on China’s Greater Bay Area (GBA), a highly interdependent city cluster with diverse socio‑economic‑­ demographical‑environmental profiles. We adopt a mixed‑method approach in‑ volving literature review, site visits, and interviews. Based on the literature review, a sharing economy analytic framework is developed to guide subsequent data col‑ lection and analyses. This research adds to global efforts to achieve a circular econ‑ omy by introducing an innovative analytic perspective and articulating the barriers and solutions to facilitating a CWM sharing economy. Literature review Boosting construction waste circularity

Construction waste is a stream of solid waste distinguished from municipal solid waste (MSW) and comprises surplus and waste materials from construction activi‑ ties. Three characteristics of CWM, namely, (a) voluminousness; (b) heterogeneous composition; and (c) relatively low reuse/recycling value, help to understand the urgency of CWM sharing. C&D waste generated in a region is often voluminous. In the UK, for example, construction generated 136.2 million tons of waste, account‑ ing for 61% of total UK solid waste in 2016 (DEFRA, 2018). The USEPA (2018) estimated that 548 million tons of construction waste were produced in 2015, more than twice the amount of MSW. Construction waste is not a heterogeneous sub‑ stance with a single composition. Rather, it comprises a range of materials such as metal, concrete, earth, bitumen, wood, cardboard, and so on. They require treatment with different technologies and have different economic considerations. However, this material has relatively low value for beneficial reuse or recycling, the business cases of which tend to be vulnerable to transportation and processing costs. A systems solution framework for tackling issues like climate change, resource scarcity, waste, and pollution (EMF, 2013), the circular economy is widely advo‑ cated as a means of meeting the grand challenge of managing CWM (Charef and Emmitt, 2021). It promotes replacing the current ‘take‑make‑waste’ linear econ‑ omy in production and consumption with a closed‑loop circularity (Abdelshafy and Walther, 2023). The application of circular economy principles in construc‑ tion, termed ‘circular construction’ or ‘construction circularity’ in this chapter, closes building material loops through resource recovery (e.g., the 3Rs) (Charef et al., 2022). Circular construction has been vigorously explored around the world. Numerous strategies have been developed from urban (e.g., urban metabolism,

Boosting construction waste material circularity  71 self‑sufficiency, and urban mining) to building level (e.g., green building, modular construction, building retrofit, deconstruction, and waste 3R). CWM cross‑border sharing is emerging from these campaigns. CWM cross‑border sharing

The idea of CWM cross‑jurisdictional sharing is not without precedent. In fact, for some categories of waste, such sharing has been conducted for decades. For example, a report published by Basel Action Network (2002) estimated that 50% to 80% of the huge amounts of E‑waste generated in the U.S. were being exported to Asian and African countries. In China’s Guangdong Province, Guiyu area is infa‑ mous for treating its imported E‑waste in an environmentally unsound manner and is heavily polluted as a result (Fu et al., 2008). The current pattern for cross‑border waste sharing involves waste production in developed countries and exportation to developing countries. The consciousness of the unfairness of this situation has increased over time, with some organisations and countries attempting to tackle the situation. For example, the Basel Convention ratified in 1989 prevents a country from dumping toxic waste in another. CWM is considered to be less damaging to the environment, and therefore more amenable for cross‑border sharing. However, such sharing is not yet widespread. Italy and Switzerland trade their aggregates and CWM, forming an international industrial symbiosis (Borbon‑Galvez et al., 2021). Singapore exports about 30% of its recyclable construction waste to Southeast Asian countries in 2018 (Mohan, 2019). CWM sharing between Hong Kong and China’s Guangdong Province com‑ menced in July 2007 and, as of May 2018, about 119 million tons of CWM had been delivered to Taishan in Guangdong forming an area of reclaimed land of over 660 hectares (HKCEDD, 2019). Unlike the transportation of toxic waste, sharing CWM between economies is a promising strategy for boosting CWM circularity. The sharing economy

The sharing economy has been variously referred to as the gig, collaborative, ac‑ cess, and Peer-to-Peer (P2P) economy. In the current literature, a variety of defini‑ tions have been proposed from different facets. Botsman and Roger (2010) define the sharing economy as a P2P‑based activity that involves obtaining, giving, or sharing access to goods and services among consumers. Hamari et al. (2016) of‑ fer a different perspective, considering the sharing economy as an integration of online collaboration, social commerce, online sharing, and consumer ideology. Notably, Richardson (2015) tries to describe the sharing economy with three clear defining features: a digital intermediary, P2P, and access based. Frenken and Schor (2017) provide three similar defining features for a sharing economy: consumer‑to‑­ consumer interaction, temporary access, and physical access. Sharing the idle capacity of goods is the essence of the sharing economy (Fren‑ ken and Schor, 2017). Uber and Didi share transport and cars in particular in a real‑time, location‑based manner. Digital platforms, such as Task Rabbit and Zaarly, share time by pairing users who have tasks to do with people who have

72  Weisheng Lu time to do them. Moreover, platforms such as Skillshare.com and Peer‑to‑Peer University, which aim to replace traditional educational institutions, facilitate the sharing of skills. Schor (2016) classifies sharing economy activities into four broad categories: i.e., increased utilisation of durable assets, exchange of services, sharing of productive assets, and recirculation of goods. From a broad understand‑ ing of the sharing economy, all under‑utilised goods are sharable. Therefore, the sharing economy has the potential to further permeate today’s social economic systems. The great success of Airbnb, Uber, and Didi has raised public interest in the sharing economy. It is estimated that the scale of the sharing economy will increase to 230 billion pounds by 2025, compared with 9 billion pounds in 2014 (Cadman, 2014). The OECD (2016) has also set out the benefits the sharing economy can bring, such as economic development from the new business models and redis‑ tribution of resources when accessing some goods and services at lower prices. Above all, it is desirable to foster the sharing economy in more disciplines to re‑ lieve the global concern of resource scarcity. Research method A sharing economy analytic framework

From the above discussion, it can be summarised that a sharing economy can be understood from the following aspects: 1. The sharing commodity, be it idle goods, space, transport, time, or skills, 2. The platform and its supporting technologies to facilitate the sharing economy,

Figure 4.1  An analytic framework of construction waste material sharing economy. Source: Adapted from Institute of Entrepreneurship Development (IED) (2018).

Boosting construction waste material circularity  73 3. Institutions designed to further support the sharing economy, and 4. Enforcement, education, and continuous improvement to sustain the sharing economy. An analytic framework of CWM sharing economy is developed, as shown in Figure 4.1. The focal area: the Greater Bay Area of China

The research focuses on China’s GBA, which is a ‘9+2’ megalopolis, composed of an alliance of nine cities from Guangdong province around the Pearl River Delta, i.e., Guangzhou, Shenzhen, as well as the two Special Administrative Regions (SARs) of Hong Kong and Macao (see Figure 6.2). It is one of the world’s largest city clusters, with 66.72 million people and a GDP of US$1.32 trillion created an‑ nually (Hui et al., 2020). Although it occupies less than 1% of China’s land area, the GBA contributes 12% of the national GDP (Cheung, 2019), making it one of the most economically vibrant regions in China (Figure 4.2). The promising economic outlook of the GBA has not only catalysed local con‑ struction industry growth in recent years but also raised the acute conundrum of construction circularity. It is estimated that over 1500 million m3 of solid waste is produced by construction activities in a typical year in the GBA (Lu et al., 2021a). In view of the situation, some regions have deployed response strategies. In 2006, for example, Hong Kong launched its construction waste disposal charging scheme, under which contractors are charged HK$71 to $200 per ton for waste mandato‑ rily disposed of at designated facilities. It aims to reduce, reuse, and recycle C&D waste in Hong Kong and achieve self‑sufficiency. However, this is extremely dif‑ ficult for a small city like Hong Kong with a very limited buffer. CWM sharing has been actively explored. In fact, since 2006 Hong Kong has been sending its CWM to Jiangmen through an official channel for land reclamation (Lu et al., 2020).

Figure 4.2  The Greater Bay Area (GBA) in China.

74  Weisheng Lu In Shenzhen, the rapid economic development has demanded enormous con‑ struction activities to supply housing and infrastructure. A large proportion of C&D waste, particularly from its underground projects, has failed in the past to be properly processed, causing negative environmental impacts and even secu‑ rity risks (Bao and Lu, 2023). In an extreme case, a construction waste landslide in 2015 in Shenzhen resulted in 73 deaths and ruined over 30 buildings (Liu et  al., 2018). As a response, Shenzhen closed all landfills so that contractors would be forced to reduce, reuse, and recycle construction waste (Bao and Lu, 2023). A building permit is granted only when a ‘zero waste’ target is dem‑ onstrated in a waste management plan. Even though, Shenzhen has to export CWM to completely digest the waste materials generated from its massive con‑ struction plans. Waste sharing has been actively explored in the GBA. Nevertheless, such ef‑ forts are still too piecemeal and discrete. There is an urgent need to look more widely into the GBA cities to develop a sharing economy of CWM. There is great potential given the imbalanced development among GBA regions. It also provides a much larger buffer than a single economy. However, concerns about whether this will lead to a predatory economy are heard every now and then. It is also unclear whether a sharing economy could emerge given the uniqueness of CWM and the present non‑existence of such a market. A mixed‑method approach

Focusing on the GBA, we collected valuable secondary data from various public domains such as statistics yearbooks, government websites, reports, and other chan‑ nels. We also collected first‑hand data through field studies in the GBA including site visits, case studies, and focus group meetings, accompanied by semi‑­structured interviews and non‑participant observations. We conducted around 50 site visits, 20 workshops, and 120 interviews with stakeholders including government offi‑ cials, construction professionals, recyclers, environmentalists, policymakers, and scholars. A cross‑sectoral learning methodology was adopted to enable us to learn from sharing economy successes in similar scenarios. For example, we learned from the theories and real‑life practices of smart grids and carbon trading and applied them to the CWM sharing economy using design thinking and economic analyses. We also conducted research about stakeholders’ Extended Producer Responsibility for construction waste management. The research team also conducted in‑depth analyses using methodologies such as systems thinking, two‑sided market analyses, cross‑sectoral learning, qualita‑ tive data analyses, triangulation, simulation, and so on. In particular, we adopted a Design Science Research (DSR) method, which involves five stages: empathy, definition, ideation, prototyping, and testing. Woven into the DSR were the analytic framework as shown in Figure 4.1 and cross‑sectoral learning. The whole process is highly iterative rather than linear, allowing data to be sufficiently triangulated to draw a conclusion.

Boosting construction waste material circularity  75 Data analyses, results, and findings The great potential of a sharing economy

Waste is often stigmatised as a cause of pollution and illness. This negative im‑ pression is exacerbated by news headlines reporting on waste being sent to less‑­ developed regions with loose environmental regulations. This is often characterised as predator trade by rich regions creating a waste haven effect. However, while this impression may be accurate for some waste, it is less so for CWM sharing. Over 90% of CWM is inert, meaning it has limited impacts on the natural environment and is largely reusable or recyclable in other construction activities such as land reclamation, foundation backfilling, and road bases. This CWM sharing reduces the consumption of virgin construction materials, creating a perfect example of the circular economy in the construction sector. Recent studies (Zhang et  al., 2020) on upgrading CWM rather than just downcycling them provide feasible manage‑ rial and technological approaches to do so. Another concern is the higher cost and carbon emission to transport the low‑value CWM across borders. This needs to be carefully planned in the context of transportation innovations (e.g., using barges via the sea, higher cost tolerance owing to the higher carbon neutrality goal). No matter how hard one city tries to develop self‑sufficiency, it may not be able to digest its CWM. In the GBA, massive construction activities generate mountains of construction waste. However, economic development is not evenly distributed over time and space in the GBA, and CWM generation at a certain time might exceed reuse or recycling capability. To address this mismatch between CWM gen‑ eration and consumption capability, cross‑border CWM sharing is becoming an ideal option. A region with surplus recycling capacity can receive CWM from an‑ other in exchange for suitable compensation. Or, instead of purchasing virgin infill material for site formation or land reclamation, a region with a short CWM supply could import CWM from another region. The GBA provides a bigger buffer for CWM management than those provided by individual cities. In a city like Shenzhen, where land is extremely precious, there is little buffer for CWM disposal. However, an important characteristic of economies in the GBA is their variety in institutional background and socio‑­ demographic situation, such as economic aggregate, population, and land area. The different endowments of GBA economies allow them to compensate for each other’s disadvantages and offer more flexibility in CWM management, achieving a win‑win situation. Anecdotal evidence shows big gaps in the demand and sup‑ ply of construction materials such as river sands, aggregates, road bases, and fill materials for ambitious land reclamation projects (Hiete et al., 2011). Meanwhile, research reveals that the GBA can produce 364 million m3 of construction waste in a typical year (Lu et al., 2021), over 50% of which is concentrated in the three core GBA cities Shenzhen, Guangzhou, and Hong Kong. Landfilling such a huge amount of solid waste materials would lead to a loss of 92.26 million tonnes of embodied carbon emissions (Peng et al., 2021), hindering the achievement of the national carbon neutrality goal. Instead, there is strong potential to foster a CWM sharing economy within the GBA.

76  Weisheng Lu Learning across other sectors

In fostering a CWM sharing economy, we do not have to start from scratch. Rather, we can learn from successful parallels and their commodity sharing, platform technologies, institutional setting‑up, and other supporting strategies. We focus on three successful cases: (1) smart grids, (2) carbon trading, and (3) Uber and Airbnb. In the energy sector, the term ‘Energy Internet’ refers to the well‑developed and innovative smart grid (Irfan et al., 2017). This can provide a learning refer‑ ence for the CWM sharing economy. Comparing commonalities between electricity and CWM in production, market, transmission, distribution, and consumption, we formulated three overall strategies for forming a bilateral CWM sharing economy in the GBA. First, CWM needs to be standardised (Lu et al., 2020). For example, accountable bodies can certify CWM based on standards for type, properties, prov‑ enance, suggested uses, circularity, and other information items (e.g., batch number, men‑in‑charge, time, and dates) in a ‘CWM passport’ (Wu et al., 2023). Second, a digital platform, like the smart grid itself, needs to be developed to realise the flow of CWM information between the supply and demand sides and to improve CWM in‑ formation transparency and transaction efficiency (Wu et al., 2023). Third, a series of institutional arrangements must be formulated (Lu et al., 2020). These arrangements should be conducive to the materialisation of a CWM sharing economy market as well as the establishment of an administrative agency for negotiation, enforcement, supervision, and dispute resolution in different jurisdictions (Lu et al., 2020). Carbon trading also provides a reference for the CWM sharing economy. Suc‑ cessful carbon trading programs reflect how carbon markets contribute to envi‑ ronmental sociology theories (Vatn, 2015) and to the core concepts of designing effective schemes and establishing operational markets (Calel and Dechezleprêtre, 2016). Inspired by the carbon cap‑and‑trade scheme, we developed a construction waste trading scheme (CWTS) with preparation, implementation, evolution, and review (PIER) roadmap (Peng et al., 2022). In the preparatory phase, in order to set waste caps, environmental authorities should investigate the environmental impact and economic performance of the local or regional construction industry (Peng et al., 2022). Next, during the implementation phase, environmental authorities should use a benchmarking approach to assign permits to participants in the CWTS (Peng et al., 2022). The allocation of these permits is determined through transactions between CWTS participants in an open competitive market. Finally, in the evolution and review phase, the authorities must monitor and review market conditions to adjust waste caps to further improve market structure and combat abuse or unintended consequences (Peng et al., 2022). In other words, a CWTS needs strong laws and government regulations to ensure market efficiency and fitness for purpose. Uber and Airbnb also provide references for developing the CWM sharing economy missing market. These services took the idea of ratings and ran with it, creating a two‑way feedback and reputation system that benefits both drivers/ landlords and customers (Tadelis, 2016). On the one hand, the system allows the company to quickly and expediently identify problem drivers or landlords based on collected customer feedback (Tadelis, 2016). Thus, if a driver or landlord’s rat‑ ing slips below a certain average, they are required to improve their service. On

Boosting construction waste material circularity  77 the other hand, this system protects Uber drivers/Airbnb landlords from problem customers (Tseng et al., 2019). If a customer is abusive or aggressive, for example, the driver/landlord can rate them poorly. CWM trading can also adopt this two‑way feedback and reputation system to improve the quality of transaction services and prevent opportunistic behaviour. Certifying the sharable commodity

CWM must be properly categorised and certified before it can be shared like a regular commodity. Unlike electricity distributed in a smart grid, carbon emission permits traded in a market, car rides shared via Uber, or idle living space trading via Airbnb, CWM is not homogeneous. It comprises materials of different quality that can be used for different purposes, such as reclamation and earthworks, road base and road sub‑base of pavements, and recycled aggregates. These materials involve different waste processing costs and technologies, so their prices should be different. Ideally, regulations would be set to stipulate the quality standards of different CWM and for different beneficial uses. These sharing/trading CWM regulations should apply to Hong Kong and other GBA cities. In our research, we identified regulations across Hong Kong, Guangzhou, Shenzhen, and national specifications in Mainland China. Based on this work, we drafted a ‘Review and recommendations of specifications on the reuse of construc‑ tion waste material in the GBA’. Learning from Airbnb and Uber, we propose a ‘green labels’ system (see Figure  4.3) to regulate different types of CWM to be

Figure 4.3  Green labels certifying sharable CWM.

78  Weisheng Lu shared for different purposes. In operation, a third party can certificate a bulk of CWM as suitable for ‘public fills’, ‘land reclamation’, ‘site formation’, or ‘recy‑ cling’. These green labels can thus help alleviate information asymmetry, foster trust between demand and supplier sides, and lower transaction costs. We also noticed that individual cities, particularly Hong Kong, have specifications/codes/ technical notes for CWM for certain uses. It is recommended a set of such speci‑ fications/codes/technical notes should be developed across the GBA cities as the standards to certificate CWMs. Innovative technical‑institutional systems to boost the sharing economy

A CWM sharing economy is not possible without various innovative technical‑­ institutional arrangements. In particular, digital platforms need to be developed to match idle resource demand and supply, creating a P2P economy that is facilitated by digital intermediaries. Learning from the idea of the material passport (MP), we also propose a waste MP, which is further supported by advancements in block‑ chain technology. In developing the sharing economy market, it is also important to foster, enforce, and continuously improve these technical‑institutional arrange‑ ments that will sustain it. Bridging the demand and supply sides

Learning from successful sharing economy examples (e.g., Uber, Airbnb, and Didi), a platform to bridge demand and supply sides is indispensable for P2P sharing. As we have indicated above, a sharing economy is also called a platform economy or P2P economy in which ‘transaction platforms’ or ‘digital matchmakers’ serve as a virtual marketplace for parties (Fitzgibbons, 2019). In many cases (e.g., Uber, BlablaCar), demand and supply information is matched while sharing (e.g., cars or rides) is also involved. These platforms provide a model for the type of platform the CWM sharing economy needs. Some platforms for the CWM sharing economy already exist. For example, a ‘Construction Debris Bank’ has been established to store, distribute, and share construction debris among eighty construction projects in Shenzhen. Construc‑ tion clients in Hong Kong also periodically broadcast CWM supply information to the market. Hohoskips is a Hong Kong‑developed app platform for booking CWM hauling from small‑scale building renovation activities. Underpinning these measures are attempts to balance generated and consumed CWM within a region. Active governmental intervention is needed to establish an intercity collaboration platform for real‑time information disclosure. The above cases mainly involve direct P2P sharing, ideal as it can reduce han‑ dling costs, and if the distance is reasonable, transport costs. There are initiatives to develop this P2P sharing into Peer‑to‑Business‑to‑Peer (P2B2P) sharing where to enhance opportunities to match demand and supply sides, a business can step in to receive any qualifying CWM. This may require storage of bulky CWM while the business explores its sale to end users (peers) if direct P2P sharing is difficult.

Boosting construction waste material circularity  79 This is like a practice adopted in Hong Kong, where the Environmental Protection Department and Civil Engineering and Development Department run fill banks to temporarily store CWM for future use. Certainly, the extra loading, uploading, storing, and maintaining costs must be considered to make the sharing economy business case. Waste material passport

An innovative idea is the MP first introduced in the EU’s ‘Buildings as Material Banks’ (BAMB) initiative as a digital credential to store the characteristics of ma‑ terials embedded in building stocks (EU Horizon, 2020). The MP allows stakehold‑ ers from different sectors to record and share material information to maximise material circularity. It is intended to enable swift and convenient communications so that stakeholders can understand the values of circularity and make informed decisions (Damen, 2012; Jensen et al., 2023). In a sense, CWM cross‑border sharing is a type of international travel for goods, which pass through borders for reuse or recycling. The issues of information iden‑ tification and fraud prevention are vital for establishing a stable sharing link. In‑ spired by travel passports and the huge success of the MP in recent years, we have developed a CWM passport system that can facilitate the CWM sharing economy (Lu et  al., 2023). A CWM passport endows with two identities: information re‑ corder and market medium. The former builds a database of a material’s character‑ istics that make it suitable for direct reuse or recycling. To enhance the credibility of the CWM passport system, the data is cross validated by suppliers of virgin and waste materials as well as the buyers. The market medium identity requires a CWM passport to present price information and trading records, which allow potential buyers to compare and make an optimal decision. The CWM passport system can serve as a mutually trusted credential. It can record and exhibit to stakeholders complete and transparent information, lowering the information asymmetry barrier and boosting CWM trading across economies. Ensuring the authenticity, immutability, and traceability of information in this pass‑ port is of paramount importance. However, a major concern is that CWM pass‑ ports are not issued by authorities that can guarantee information authentication. To achieve this, therefore, we explore advancements in blockchain technology and non‑fungible tokens (NFTs) in particular. Blockchain non‑fungible token

Blockchain technology was primarily proposed to support cryptocurrencies (e.g., Bitcoin). It has three main components supporting its functionality: a distributed database, a consensus mechanism, and cryptography (Risus and Spohrer, 2017). First, the blockchain is a trustless transaction database maintained by a group of peer nodes (Perera et al., 2020). It holds all transactions packed chronologically into groups (i.e., blocks) (Lu et al., 2021; Penzes et al., 2018). Second, block‑ chain protocol incorporates a consensus mechanism to verify the sequence and

80  Weisheng Lu correctness of blocks (Perera et al., 2020). Only when the blockchain network participants reach an agreement, transactions can be included in the blockchain as a new block. Third, blockchain uses a cryptographic algorithm to ensure the immutability of recorded transactions by converting transactions into hash values (Hasselgren et al., 2020). An NFT is a unique digital certificate that cannot be copied, substituted, or sub‑ divided, and that is used to certify authenticity, uniqueness, and ownership of a digital object, such as a song or a video (Wang et al., 2021). An NFT has three main characteristics. First, NFTs can digitalise both intangible and tangible items into tokens in a user‑friendly manner providing clear information (Chandra, 2022). Second, each NFT has a unique digital identifier, so there are no identical copies of the same NFT in circulation (Sestino et al., 2022). Third, NFT has verifiabil‑ ity (Dowling, 2022). Owners of NFTs can easily prove their ownership because creations and transfers of ownership are recorded on the blockchain together with digital signatures. These characteristics of blockchain and NFTs offer great potential for imple‑ menting passports in CWM cross‑border trading. A blockchain NFT‑enabled CWM passport can (1) allow stakeholders to digitise CWM into an NFT‑enabled passport via tokenisation; (2) prevent issuing of a duplicate CWM passport due to its unique NFT identifiers; (3) enhance CWM trading information sharing and transparency via blockchain distributed ledgers; (4) improve cross‑border CWM trading effi‑ ciency via its decentralised consensus; and (5) secure transaction records via its cryptographic algorithms (Wu et al., 2023). Developing an evaluation system

As learned from Airbnb, TripAdvisor, Uber, Yelp, and other platform economy cases, online feedback mechanisms or reputation systems are critical for the sus‑ tainable growth of a sharing economy. Botsman and Rogers (2010) list critical mass and trust as two important principles in a sharing economy. That is, online feedback mechanisms or reputation systems stimulate large word‑of‑mouth net‑ works to nurture confidence between individuals who do not know each other in person and impact the critical mass of a sharing economy (Dellarocas, 2003; Mellet et al., 2014). It is suggested that such an evaluation mechanism should be developed in line with the trust‑building technologies described in the previous section related to innovative technical‑institutional systems. That is considered an effective way to downgrade or even disqualify the demanders or suppliers who have not performed in a desirable way (e.g., not providing qualified CWM, or not providing/receiving it on time). Developing a Waste Trade Organisation in the GBA

Cross‑border CWM sharing will not happen without strong government leader‑ ship. GBA governments must develop novel policy frameworks to foster a CWM

Boosting construction waste material circularity  81 sharing economy. We suggest developing a Waste Trade Organisation (WTO) to boost CWM sharing in the GBA. The WTO can have four main functions: (1) to certify CWM and guarantee it as sharable/tradable recycling material; (2) to provide a GBA‑level information sharing platform; (3) to devise taxation, pricing, subsidy, and non‑tariff measures; and (4) to resolve disputes via its multilateral systems, procedures, and boards. First, the WTO needs to boost confidence in the CWM sharing economy. Stake‑ holders fear that what they purchased is not what it claims to be. The public fears a predatory economy. The WTO can serve as a certifying organisation of CWM qual‑ ity and categories, ensuring authenticity, credibility, immutability, and traceability, and enforcing CWM sharing economy initiatives in the GBA. Second, the WTO needs to establish a GBA‑level information‑sharing platform. While the CWM passport can alleviate the information asymmetry issue of CWM as a commodity, it is not until the information is fluid enough that a market can fully operate. Third, the WTO needs to develop various innovative technical‑institutional systems to boost the sharing economy. Initiatives to ensure information authenticity or an in‑ formation platform need to be developed and enforced by the WTO. The WTO can target to devise taxation, pricing, subsidy, and non‑tariff measures that allow the market to allocate CWM resources that have residual value. The last and probably most important function of the proposed WTO is to resolute disputes via its multi‑ lateral systems, procedures, and boards. Conflicts exist in nearly every commercial activity. Consequently, a specific framework and WTO body are recommended to encourage stakeholders to play by the rules and to punish misconduct in the shar‑ ing economy. Challenges, opportunities, and future research There are also challenges and opportunities ahead to be tackled via further re‑ search and development. First, it is the high transportation cost vs. the relatively low value of the goods to be shared. Cross‑border CWM sharing opens a win‑ dow of opportunity to match the demand and supply sides in a wider temporal and spatial buffer. However, such sharing cannot go too far in terms of physical distance. CWM, as mentioned in the second subsection of the literature review section, is not a high‑value good; transporting it too far will incur a cost that can easily offset the value of its sharing. There are several opportunities to tackle this challenge. For example, climate change has triggered global efforts to cut carbon emissions from our human activities. China has pledged to guide carbon‑­ intensive industries to reach peak emissions by 2030, so policies will be skewed to the industries, e.g., C&D waste recycling, which has significant implications for these carbon reduction ambitions. Environmental, social, and corporate gov‑ ernance (ESG) finance will be increasingly available for costs that were previ‑ ously unaffordable. Another challenge is the high cost of guaranteeing on‑quality and on‑time deliv‑ ery of CWM. Although using blockchain NFT and CWM passports can guarantee some of the authenticity, immutability, and traceability of the information, it is not

82  Weisheng Lu easy to guarantee what is happening in the off‑chain world. We have heard griev‑ ances receipt of inferior materials (e.g., for backfilling, aggregates) from construc‑ tion project managers. It is often too late to discover the inferior supply when it arrives onsite. Nevertheless, we can exploit surveillance or Internet of Things (IoT) technologies to ensure on‑quality and on‑time delivery in real life. The evaluation system needs to be carefully developed to foster the healthy development of a shar‑ ing economy. Given the enormous potential of the CWM sharing economy, more studies are desired to gain a deeper understanding of the initiative. There are many interesting and highly pertinent aspects to study. For example, the green label system as elabo‑ rated in this chapter can be further developed. Also, while the platform to match demand and supply information is key to the success of a CWM sharing economy (see subsection ‘innovative technical‑institutional systems’), little is known about what the matching algorithms would look like though it would be both a time‑ and location‑based approach. There are researchers trying to enrich this part by devel‑ oping auction theories. Certainly, policymakers would not dive into this market directly. Ideally, simulation platforms need to be built up and perform sufficient simulations to gain a confident understanding of the CWM sharing economy. Conclusion The surplus materials generated from C&D activities are not entirely waste and can be shared for different beneficial uses. Amid the global trend of advocating the circular economy, there is a compelling case for sharing these CWMs for better cir‑ cularity. This research helps people to understand how to achieve CWM circularity from a sharing economy perspective. This study discovers the enormous potential of a CWM sharing economy to reduce consumption of virgin materials and high carbon emissions associated with waste disposal (e.g., transporting, landfilling). Successful stories from other sectors, such as smart grids, carbon permit trading, and Uber and Airbnb, all provide useful experiences for developing this CWM sharing economy. A basket of innovative technical‑institutional arrangements must be made to es‑ tablish the CWM sharing economy market and boost its sustainable development. CWM must be properly certified before it can be shared like a regular commodity. We, therefore, propose a green label system to certify CWM to different standards for different uses. To enhance the authenticity, immutability, and traceability of CWM information, we suggest developing a CWM passport based on the Euro‑ pean MP idea, which can be further enhanced with trust‑building technologies such as blockchain NFTs. One of the most important technological arrangements is to match the demand and supply sides to allow for a sharing economy transaction. To facilitate a CWM sharing economy, such platforms must be built, and feedback mechanisms developed for platform accountability. All these arrangements, if per‑ ceived from an economic perspective, are related to reducing information asym‑ metry and lowering the transaction cost when a CWM sharing market is missing or still weak.

Boosting construction waste material circularity  83 Even with these innovative technical‑institutional arrangements, CWM sharing, particularly when it straddles different jurisdictions, will not happen without strong governmental support. Related governments need to consider the costs and benefits (e.g., compensating economy, better circularity, and carbon neutrality promises) of involvement in this sharing economy, and on the other hand, must carefully avoid ‘zero‑sum game’ thinking and accusations of predatory trading. In the GBA, we suggest establishing a Waste Trading Organisation to initiate, negotiate, imple‑ ment, and improve the innovative technical‑institutional arrangements across its 11 cities in order to boost the CWM sharing economy in this economically vibrant region. References Abdelshafy, A., & Walther, G. (2023). Using dynamic‑locational material flow analysis to model the development of urban stock. Building Research & Information, 51(1), 5–20. Bao, Z., & Lu, W. (2020). Developing efficient circularity for construction and demoli‑ tion waste management in fast emerging economies: Lessons learned from Shenz‑ hen, China. Science of the Total Environment, 724, 138264. https://doi.org/10.1016/ j.scitotenv.2020.138264. Borbon‑Galvez, Y., Curi, S., Dallari, F., & Ghiringhelli, G. (2021). International indus‑ trial symbiosis: Cross‑border management of aggregates and construction and demoli‑ tion waste between Italy and Switzerland. Sustainable Production and Consumption, 25, 312–324. https://doi.org/10.1016/j.spc.2020.09.004. Botsman, R., & Rogers, R. (2010). What’s mine is yours. The rise of collaborative con‑ sumption, 1. https://tantor‑marketing‑assets.s3.amazonaws.com/sellsheets/1920_MineIs Yours.pdf. Cadman, E. (2014). UK sharing economy companies told of 9bn potential. Financial Times, 15. https://www.ft.com/content/5e0348ac‑23c3‑11e4‑8e29‑00144feabdc0. Calel, R., & Dechezleprêtre, A. (2016). Environmental policy and directed technological change: Evidence from the European carbon market. Review of Economics and Statistics, 98(1), 173–191. https://doi.org/10.1162/REST_a_00470. Chandra, Y. (2022). Non‑fungible token‑enabled entrepreneurship: A conceptual frame‑ work. Journal of Business Venturing Insights, 18, e00323. https://doi.org/10.1016/ j.jbvi.2022.e00323. Charef, R., & Emmitt, S. (2021). Uses of building information modelling for overcoming barriers to a circular economy. Journal of Cleaner Production, 285, 124854, Charef, R., Lu, W., & Hall, D. (2022). The transition to the circular economy of the construc‑ tion industry: Insights into sustainable approaches to improve the understanding. Journal of Cleaner Production. https://doi.org/10.1016/j.jclepro.2022.132421. Cheung, E. (2019). Greater Bay Area: 10 facts to put it in perspective. South China Morning Post, 1 April 2019, https://www.scmp.com/native/economy/china‑economy/topics/ great‑powerhouse/article/3002844/greater‑bay‑area‑10‑facts‑put Cohen, B., & Muñoz, P. (2016). The emergence of the urban entrepreneur: How the growth of cities and the sharing economy are driving a new breed of innovators (Vol. 3). ABC‑CLIO. California, USA. Damen, M. A. (2012). A resources passport for a circular economy. [Master’s thesis, Utre‑ cht University]. https://studenttheses.uu.nl/bitstream/handle/20.500.12932/12157/A%20 resources%20passport%20for%20a%20circular%20economy.pdf?sequence=1.

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5

The role of standardisation in circular economy for the construction sector Michael Neaves

Introduction The term ‘standard’ means different things to different people. In lay terms, a standard is the norm or the usual, and in many cases refers to a level of quality that is normal or acceptable. This acceptability makes a standard a valuable tool for policymakers and industry because it can determine and consolidate state‑of‑the‑art knowledge and in‑ formation through mutually accepted criteria and quality, which a market operator can then use in practice. In this context, the EU standardisation regulation (1025/212) de‑ fined a standard as a ‘technical specification, adopted by a recognised standardisation body, for repeated or continuous application, with which compliance is not compul‑ sory’. Given the characteristics of a standard, policymakers use them to help regulate and control the market to meet socio‑political objectives where relevant and viable. The construction sector is arguably the most reliant and regulated by such standards, with a long‑held emphasis on their use in relation to structural integrity, safety, and, increasingly, sustainability, but in all cases, they fundamentally play both a mediator and facilitator role (e.g., Bouchlaghem et al., 2004; Buyle et al., 2013) meaning there is great potential to use of standards to help meet policy ob‑ jectives. In recognition, policymakers are beginning to use policies underpinned by standards to nudge the sector towards sustainability, partly to be achieved by transitioning the sector to a circular economy. In response to policy actions, the market is now increasingly demanding that standards be developed to support the transition. Based on demand from the market, standards have a role and challenge to support a transition to circularity for the construction sector. While combining bottom‑up market‑driven standards designed for the sector, with standards developed to support regulation can be an effective way to ensure market actors support progress towards policy objectives, the composition of a combined system of policies and standards does not guarantee that necessary pro‑ gress will be made. Therefore, using standards for reducing climate and environ‑ mental impacts has an element of risk that policymakers need to mitigate. In this context, the role and value of standards to address critical challenges in the tran‑ sition to a circular built environment should be interrogated to develop the most effective approach possible to guarantee success in meeting EU and global climate and environment objectives. DOI: 10.1201/9781003450023-7

The role of standardisation in circular economy   89 Notably, standards that mainstream knowledge and practices in the construction sector in the pursuit of sustainability and circularity should be evaluated regard‑ ing practical implementation and their implications for the sector’s sustainability. Fundamentally, there is no single and well‑defined role for standards suitable in all cases and contexts, making it crucial to define where and how standards should be deployed as the transition to a circular construction sector accelerates. Conse‑ quently, ensuring policies fill regulatory gaps and that standards gaps for circularity are effectively filled by forthcoming standards in a relatively short time horizon is a joint effort for industry, policymakers, and civil society to agree on the most ef‑ fective process and composition of the combined policy and standards framework. The author hopes this chapter can progress towards this goal by building con‑ sensus in defining the role of standardisation for the circular economy in the con‑ struction sector. This chapter will also offer policy recommendations to clarify the role of policymakers to standards in addressing these challenges, and therefore what level of policy intervention and types of actions are needed by policymakers in conjunction with standards, as well as how best to use standards in the context of sound, anticipatory policymaking to accelerate the transition to a circular economy in the construction sector. Circular construction – progress and challenges so far Standards for circular construction

Already over fifteen years ago, Andersen (2006) highlighted that as environmen‑ tal policies become increasingly aligned with the potential benefits of a circular economy, the theory and tools for circularity are being integrated into relevant legal frameworks by policymakers seeking to ensure reuse and recycling are im‑ plemented efficiently and in a socially desirable way. Yet in practice insufficient progress has been made before and since the policies mentioned above were intro‑ duced, with circularity stagnating at a level of low adoption and impact. Standards as a tool for harmonising and mainstreaming practices is one of several solutions already being used at a local level but with limited impact on the sector as a whole in Europe and globally. To remedy this, the newly formed CEN sub‑committee on Circular Economy in the Construction Sector (CEN/TC 350/SC 1) has the main task of developing stand‑ ards that define circular principles and guidelines and requirements to facilitate the transition to a more sustainable circular economy including tools and processes to achieve this; covering design to deconstruction and end‑of‑life scenarios in all stages of current and subsequent life cycles (CEN, 2022). Forthcoming standards will build on the existing research, pilots, and projects channeled into the stand‑ ards via representatives of National Standardisation Bodies (NSB) and stakeholder organisations such as the Environmental Coalition on Standards (ECOS), which represents the environmental voice in the standardisation system. Therefore, the development of European standards in circular construction will attempt to deliver a common understanding and practices of the new normal in a circular construction

90  Michael Neaves sector, which will ideally aspire to the highest levels of environmental ambition by codifying the mechanics of circular economy, resource‑efficient thinking with cli‑ mate and environment benefits of the highest magnitudes in support of EU climate and environment objectives. To achieve this, inscribing conscious environmental and economic paradigms into sectoral practices will be critical to realising the potential benefits of circularity for climate and the environment (Andersen, 2006; Flynn and Hacking, 2019). How‑ ever, going from theory and a relatively small number of existing circular practices to a fully circular and sustainable construction sector equates to transforming a typ‑ ically conservative and low‑innovation sector (Kanters, 2020), making it a defining challenge for the future of the sector. Achieving this is paramount if the construc‑ tion sector wants to become sustainable and a climate asset rather than a climate liability. Consequently, it will need to develop standards that effectively respond to the climate crisis in record time and policymakers need to ensure this happens. Circularity standards as a response to the climate crisis?

To expedite an effective standardisation process, policymakers and stakeholders must quickly formulate a strategy, plan, and framework for standardising the circu‑ lar economy in the construction sector. Through recent non‑legislative initiatives, the European Commission has acknowledged the need for such strategic actions as part of the development of the recently released Construction Ecosystem Transi‑ tion Pathway (European Commission, 2023a), in which it sets out several policy actions for a more resilient, green, and digital ecosystem. Additionally, the Eu‑ ropean Commission recently carried out research on the application of circular approaches in the construction industry ecosystem (Deloitte, 2023) to better un‑ derstand what market actors are already doing in terms of circularity. Within these documents, there is evidence that EU policymakers are aiming to rapidly address what many authors highlighted as one of the most common barriers for the adop‑ tion of Circular Economy concepts  –  a lack of standard practices for the reuse of materials, and the assessment of existing practices can help decide what the necessary policy interventions are to ensure the sector responds to the climate and environmental crises (Adams et al., 2017; Huang et al., 2018; Van Bueren et al., 2019 in Benachio et al., 2020). However, one failing so far from policymakers is that there has been a lack of action beyond recycling and waste characterisation which aligns to the priorities of energy‑intensive industries producing the most resource‑intensive construction products in the market today. This should be corrected through greater recognition for the potential of high‑level circularity and the role of standards in facilitating actions such as building retrofit and product reuse, which represents a departure from conventional linear waste and recycling practices. The need for action on high‑level circularity points to a need for build policymaker and industry capacity to develop standardised practices for the reuse of buildings, building elements, and construction products that can be proven and commonly adopted by the industry to transform the practices of traditional construction, but this cannot be done alone

The role of standardisation in circular economy   91 and will require changes at the policy level to drive adoption (Esa et al., 2017). On top of this, the sector remains fragmented, largely uncoordinated, and slow to change proactively or radically with only some frontrunners have been able to be‑ gin addressing these challenges and fill the standards and policy gaps through close partnerships with authorities or clients, but this is not possible for many of the mi‑ cro, small, and medium enterprises that the sector is almost exclusively comprised of.1 In future, a broad transition to a circular economy will require standards ac‑ cepted by a broad range of market actors in the construction ecosystem and beyond (e.g., financial institutions) to help create a critical mass of circular products and services to steadily scale‑up circular economy in the construction sector. Progress so far and these dynamics demonstrate that while industries involved in the development of standards so far are conscious of the potential of circularity, stronger governance, and regulatory impetus will be needed to have a comprehen‑ sive and ambitious vision of a policy framework fit for circularity that can increase the adoption of high‑level circular practices in parallel throughout the value chain, using standards to facilitate adoption to the greatest extent possible. Effective policy interventions for a circular construction sector

In the past, national‑level policies for buildings, and European Harmonised Stand‑ ards (a European standard developed by a recognised European Standards Organi‑ sation: CEN, CENELEC, or ETSI) have led the way when it comes to governance of the construction sector. While the sector is valuable in terms of GDP and jobs, the sector is responsible for a disproportionately high share of EU carbon emissions (40%), resource consumption (50%), and waste (33%) with these impacts point‑ ing to the imperfections and lack of sustainability requirements within national building codes combined with little urgency from European or National industry standards. These statistics could in time become a threat to the industry itself, but change is underway to adapt to a new circular and sustainable sector, compatible with a climate‑neutral economy of the future. However, Flynn and Hacking (2019) suggest that standards cannot simply ac‑ company neoliberal, market‑based policymaking but that policymakers should de‑ ploy legal instruments that confront the existing, unsustainable system to change market relations to reverse the trend of ever‑increasing resource consumption. Sys‑ temic changes like this will require deploying policies promoting new economic models, and not just new approaches that are incompatible with the current take, make, waste economics. Still, within the current economic system, circularity can help to decouple growth from resource consumption and use all existing tools to enable the sector to transition the construction ecosystem by providing precise and environmentally ambitious circularity standards that enable market actors, from concept and design to maintenance, renovation, and possibly deconstruction, to make the most sustainable decisions at each project phase. Consequently, a tran‑ sitional and transformative approach to policies and standards is needed in which requirements and practices make circularity competitive now and future‑proofed for climate‑neutral policies.

92  Michael Neaves Regarding standards already used under policies for the built environment and construction sector, European and International energy performance and LCA standards will continue to be used in implementing the Energy Performance of Buildings Directive (EPBD) at the national level. These standards have to provide numerous options for implementation due to the differences in building policies defined at the national or even regional level rather than at the EU level, reducing the harmonisation of relevant practices on the ground. At the product level, standards for construction products have been used as pseudo‑regulatory measures whereby compliance with standards permits access to the EU Single Market. Both systems have pros but many shortcomings when setting a clear and straightforward regulatory basis for standards for circularity at different levels (building, product, material) to be accepted and implemented. Policymakers, therefore, need to ensure current and future policy cycles align and improve upon the current policy landscape that has made it challenging to mainstream circularity and will present challenges in the standardisation process. Under the current EU political term, the role of EU and National policies and standards has come under greater attention than ever with the simultaneous revision of the primary EU building and construction product policies, various upstream industrial policies, and other non‑legislative policy initiatives. While they have triggered voluntary standardisation activities, revision proposals for the EPBD and the Construction Products Regulation (CPR) have included at least the possibility of setting common functional, environmental, and circularity information and per‑ formance requirements at the EU level. Elsewhere, end‑of‑life requirements under the Waste Framework Directive (WFD) and incentives for investment in sustain‑ able construction under the EU Sustainable Finance taxonomy. However, these policies fall short of performance requirements partly due to the lack of standards that enable full‑scale implementation of sustainable practices such as circularity. The current policy landscape illustrates how policy interventions have fallen short in harmonising the policy environment and the ambition of policies and therefore failed to direct standardisers towards the next milestone on the way to sustainabil‑ ity. The policy context is complex, and knowing how and where standards should underpin policy requirements is a significant challenge. A paradigm shifts to cor‑ rect these failings is needed to change how buildings and the construction sector are regulated and governed. This could spark a circularity rush based on a stable and clear policy context in which standards are developed and implemented by firms. In the current climate, environment, and policy context, a strong case can be made for a more prominent role of EU policies in future so that both policies and standards are implemented across Europe in harmonised and effective manner. Such a change could require major policy reforms, including a sharing or division of competencies on building and construction policy competencies between the EU and Member States. However, the following analysis will therefore focus on the current policy framework and outline what standards should currently do to respond to the crisis

The role of standardisation in circular economy   93 and where policymaker interventions are more appropriate in relation to the key challenges that represent the journey from ideas for circularity‑driven sustainabil‑ ity to achieve it, namely: 1 Delivering a common understanding of the new normal in the circular construc‑ tion sector. 2 Bridging the gap between theory and practice to scale up circularity. 3 Integrating the circular economy hierarchy to maximise resource efficiency and environmental benefits. 4 Measuring resources and impacts for decision‑making in a circular construction sector. Standards for delivering a common understanding of the ‘new circular normal’ in the construction sector Establishing a common vision and framework for circularity in the construction sector

There are diverging views and perspectives on what circularity and circular economy are and are not. The Ellen Macarthur Foundation (EMF) asserts that ‘the circular economy is a systems solution framework that tackles global chal‑ lenges like climate change, biodiversity loss, waste, and pollution’ (EMF, 2022). Beyond the environmental NGO community, Geissdoerfer et al. (2017) similarly defined circularity in the built environment as a ‘regenerative system in which resource input and waste, emission, and energy leakage are minimised by slow‑ ing, closing, and narrowing material and energy loops’ (p.7). Like many of the 114 definitions analysed by Kirchherr et al. (2017), both refer to its substantial systemic potential to address various ongoing ecological crises by continuously replenishing and supplying the resources that society demands (Geissdoerfer et al., 2017). Elsewhere, researchers and practitioners with an economic and industrial ecology perspective have primarily focused on the resource efficiency potential of circularity, in isolation to environmental sustainability (Benachio et al., 2020), which can also be observed in industry and the sector itself. For example, Lacy and Rutqvist (2015) highlighted the role of circularity in keep‑ ing resources in productive use in the economy for as long as possible, but this aspirational approach doesn’t provide us with a clear end‑goal for resources in the economy in relation to environmental sustainability. Fundamentally, in comparison to a linear economy, circularity represents a new way of operat‑ ing in the construction sector. Andersen (2006) states that circularity acknowl‑ edges the environment’s role in fulfilling essential functions that support our socio‑economic welfare, something linearity does not (Andersen, 2006). This means that resource‑use minimisation and reduced use of virgin raw materi‑ als can unlock environmental and societal benefits that have not yet been fully understood or realised by the sector. These differing perspectives with equally positive views illustrate that circularity is seen to have panacea‑like potential

94  Michael Neaves from both the sustainability and resource or economic perspectives, which is reflected by the popularity of the concept among researchers and industry alike (Benachio et al., 2020). In practice, an agreed vision of circular construction will be codified as a frame‑ work standard, as is typical for standards for the construction sector. The existing framework standard for the sustainability of construction works (EN 15643) es‑ sentially contains common definitions for all relevant standards, normative ref‑ erences, and principles, complemented by informative guidance. The framework for circularity standards for the construction sector is already under development and will be built upon the ISO framework standard (ISO/DIS 59004), which will be elaborated upon to be relevant and operationalised by the construction sector. Doing so will be a challenge, one that will be exacerbated by the need for the framework to be comprehensive and holistic by covering a range of geographical and temporal scales while also being practically useful. In this sense, the frame‑ work standards will also need to act as an appropriate standardisation basis for applying methods and processes throughout any project cycle, in which all scales from material up to system are inherently involved. In other words, the framework standard is the circuit board on which all other standards can plug into and connect the market. To deliver a robust framework standard suitable for all potential contexts in which circular construction will be deployed in the sector, stakeholders involved in standardisation will have to consolidate experience and agree on a common under‑ standing of resource flows, links between market actors, connotations for environ‑ mental sustainability, and sector policies relevant to the implementation of circular construction. Terms, definitions, and principles can then be defined and tested on this basis to ensure they meet the needs of stakeholders and are legally and envi‑ ronmentally robust. This process will involve the identification of knowledge and experience gaps that require further consideration if standardisation is necessary and possible, as well as if new circular practices and business models are or will become economically viable. New business models for a circular construction sector

As alluded to, the new normal in a circular construction sector requires market actors to adopt a new and initially challenging way of doing things to be more sustainable. While standards can demonstrate how market actors can operate dif‑ ferently, creating a robust legal structure for market actors will provide the re‑ quired certainty and clarity to assist firms in pursuing sustainability, in part by developing and implementing circular business models. Here standards (along‑ side existing competencies and the availability of information) are crucial for developing a greater understanding of certain operating practices according to which a company can offer a clear circular value proposition and the resulting economic benefits (de Arroyabe et al., 2021). In this function, standards are espe‑ cially important to guide market actors, something which policymakers will not intervene on in detail.

The role of standardisation in circular economy   95 For firms to implement circularity, the business case and operational model must be clear to justify firm decision‑making in favour of circularity, and policymakers cannot rely upon firms to independently change the way they operate in all cases, despite some positive examples. Moreover, a clear business case is often a positive enabler of progressive policymaking by strengthening the economic case at the macro level (e.g., as part of the European Commission’s Better Regulation Impact Assessment). However, Flynn and Hacking (2019) suggest that alongside existing neoliberal, market‑based policymaking, policymakers, and industry cannot deploy standards that guide actors in implementing circularity practices and expect de‑ sired sustainability improvements without a change in the economics that business models are based. Policymakers will therefore have to deploy policy instruments that confront the existing, unsustainable system to change market relations and reverse the trend towards ever‑increasing resource consumption and carbon emis‑ sions (UNEP, 2022), with relevant standards in support. In short, policymakers need to be more decisive and radical in charting a course and creating an environ‑ ment favouring circular business models over linear ones. In practice, policymakers should take encouragement from current trends and act to catalyse those trends to circularity and sustainability already in the market to the mainstream. For example, as illustrated by the literature reviewed by Bena‑ chio et al. (2020), the interest of market actors in the reuse of materials is already evident in the sector due to the clear link between economic cost and resource use (Benachio et al., 2020). Still, while this has fostered some adoption, existing research shows that a lack of adequate policies combined with incorrect or lack‑ ing standards acted as a barrier to large‑scale adoption, pointing to the need for large‑scale harmonisation at the European level (Charef et al., 2021). Therefore, European standards should consolidate economic and environmental decision‑making criteria that effectively integrate climate and environment con‑ siderations, and by highlighting mutual costs and benefits associated with resource use and the potential value that firms can unlock by deploying circular strategies. In this case, standards can help consolidate, structure, and formalise processes that enable market actors to properly consider the environmental economic case, and highlight other social benefits of reduced resource use where relevant, equating to a new economic normal fostered by circular processes that firms can implement if the market environment allows. As illustrated, reconciling the differing perspectives on overlapping topics will be crucial to delivering a common understanding of the circular economy in the construction sector that will deliver necessary improvements to sustainability through a transformation of firm behaviour and operating practices. While stand‑ ardisation is a useful process through which to achieve this, policymakers should be more directly involved in ensuring that the fundamental understanding, vision, and framework for standardisation matches the climate, environmental, and cir‑ cularity ambitions of the EU for the construction sector and the built environment more broadly. Better coordination and cooperation by policymakers will be needed moving forward for a holistic and climate‑aligned approach to circularity in the construction sector. The next step will be turn to words into action.

96  Michael Neaves Bridging the gap between theory and practice to scale up circularity Circularity is already a practice for some, but for most of the sector, it remains a by‑product of existing actions or simply a theory yet to be integrated into a firm’s business model meaningfully. As with traditional structural or product standards, circularity standards can act as an integral legal and technical reference point throughout various stages of project development, planning, and implementation. As sustainability requirements increase, firms will need to use circularity standards to operate and to demonstrate in compliance with relevant regulatory instruments such as permitting or planning conditions, procurement criteria, and product regu‑ lations; as well as private sector contractual obligations upon which a market actor or group of market actors must deliver. Still, technical and practical challenges remain in operationalising circularity, and these challenges act as barriers to the real‑world adoption of circular strategies (Benachio et al., 2020), which in turn slows down sustainability policymaking based on the viability of compliance by market actors and a desire not to paralyse an entire sector. In addressing these practical barriers to circularity, standards cannot lay down highly complex rules and instructions for implementing circularity across a large and fragmented sector and expect results. The right standards will instead codify and simplify in a way that can be used to inscribe this knowledge into actionable strategies and practical tools for deploying circularity throughout the entire sector to ensure a fully circular value chain is viable. Moreover, even internally within a firm’s own operations, the right standards will be needed to connect different parts of their own business to see how they can internally direct resources of value to their own benefit. Alongside policies as the core legal framework, circularity standards can be‑ come the practical part of the operational skeleton which connects all market actors, as well as with legal requirements and policymakers, to realise more signifi‑ cant environmental, economic, and societal benefits for people and, ultimately, the planet. Nevertheless, there will be more context‑dependent aspects that standards will not be able to address relating to the specific business model or project in which circularity is being implemented. If well developed, standards can help overcome practical challenges by playing a crucial facilitator role, providing the knowledge and tools to implement circular‑ ity practically and at scale based on standardised practices (Adams et al., 2017). In practice, based on the actions of existing practices and the actions of frontrunners, summarising and describing the significant strategies for implementing circularity and codifying best practices for implementing circularity within a standard(s) can enable all relevant market actors to scale up circularity. For example, there is a need to include standardised processes that enable all market actors to engage and interact appropriately with the resources around them. For example, a standard for resource mapping combined with tools for evaluating the circularity of a build‑ ing, product, or materials can inform local authorities, developers, architects, and asset managers alike in the development of a concept and project, leading to the reuse of existing buildings, products, and materials. In this hypothetical example,

The role of standardisation in circular economy   97 not only will such standards have to be designed to act as tools for disseminating knowledge and building capacity, but they will facilitate cooperation regarding the use of resources with greater technical certainty, which can be linked to legal and economic policies. For example, Charef (2022) proposed a BIM‑based trans‑scalar theoretical framework to support practitioners in their understanding and implementing the circular economy approach. The holistic organisation of the framework in two scales, the asset lifecycle phases and the material flow, whether new or recovered, will support practitioners in their shift towards circular thinking. The trans‑scalar theoretical framework was established based on an extensive literature review. The sustainable end‑of‑life was incorporated as a phase in the circular economy and UK contexts. The trans‑scalar theoretical framework aims to clarify and illustrate the main asset lifecycle phases (including the end‑of‑life), their related stakehold‑ ers, and the connections between them (Charef, 2022a). If such a framework were standardised, it would undoubtedly support coordination and cooperation through‑ out the value chain. However, the nature of construction value chains exacerbates the challenges of implementing standards effectively, a challenge that will act as a significant bar‑ rier to developing suitable standards and implementing circular economy practices. The array of regulatory and sectoral requirements shared and distributed among many different market actors involved in building construction makes the precise allocation of responsibility regarding compliance extremely important. Examples can be found of authorities taking leadership in ensuring that structural standards are implemented effectively (see Rutesic et al., 2015). These examples largely ap‑ ply to joint projects for the delivery of a common goal (i.e., delivery of a building) in compliance with legal requirements, as opposed to the actions of actors distrib‑ uted across the value chain and the lifecycle of a building, often taking place at different moments in time and by different market actors. Therefore, delivering a circular construction sector will require substantial coordination among industry stakeholders, policymakers, and civil society to overcome the challenges that such a fragmented context presents. Standards will only be a partial solution. Policies will be needed to bring greater clarity and cohesion, and harmonisation among market actors concerning the mode of operation and obligations they are assigned, as this is not something that standards can accomplish alone. In view of trying to transition the entire European construction sector to circularity, there is a strong case for EU‑level policies to take the lead in doing so far beyond what has already been enacted under the European Green Deal in 2020.
Integrating the circular economy hierarchy to maximise resource efficiency and environmental benefits Moving from linear to circular economy

The EU Waste Framework Directive (WFD) enshrines the waste hierarchy into EU and National waste policies, but it is not yet effectively integrated into policies and standards that cover other building lifecycle stages. The hierarchy establishes a five‑step hierarchy that prioritises the most effective means to prevent waste from

98  Michael Neaves top to bottom. This hierarchy has been translated into circular actions that deliver the corresponding waste hierarchy actions. The higher up this hierarchy that an ac‑ tion climbs, the more circular and beneficial the action becomes. Structuring and prioritising standards from the highest down to the lowest levels of circularity is therefore crucial. Moreover, it is essential to relegate or even exclude actions that are not truly circular, including most, if not all, actions labelled as recycling, as illustrated below. Both policies and standards need to be organised by policymakers in such a way as to pull the sector as high up the waste and circular economy hierarchies in terms of strategy and prioritisation of actions to maximise resource efficiency as well as environmental and climate impact mitigation. The urgent need to facilitate high (positive) impact circularity is driven by the short time frame in which the impacts of sectors such as construction need to be reduced and eventually eliminated, com‑ bined with the lengthy lifecycles and investment cycles in the construction sector, as well as the limited number of policy and standards cycles. With products lasting 15–25 years, and structures lasting 50–100 years, time is not on our side, and there is no room for error in fostering highly sustainable circularity as there may only be one or two lifecycles in which to guarantee that beyond 2050 very few resources are needed for a product or firm’s operations. Ensuring standards are immediately holistic will be the most direct way to provide a standardised basis to transition to circularity by providing clear technical guidance to implement high‑impact circu‑ lar strategies effectively. Standards must contain knowledge and guidance on key considerations and pro‑ cesses at all scales that establish the necessary homogeneity, trust, and legal basis for circularity to flourish in a way that maximises the environmental benefits. By providing the standards basis for practices at the highest levels of the waste hier‑ archy, EU policymakers can more confidently promote, incentivise, and require highly circular, resource‑efficient business models and practices. These dynamics illustrate how policy and standards give and take progress from one another to in‑ crease the maturity and scale of circular construction, but progress must accelerate in parallel. Consequently, more direct support and non‑linear economy expertise are needed to channel expertise and capacity into developing standards to ensure the prioritisation of the highest levels of circularity. The following sections will therefore focus on what is needed to rapidly pro‑ mote sufficiency to refusing or reducing demand for resources, reuse as a means to increasing the number of lifecycles a building element or product can endure, meaning that new primary products will not be needed in a given context. The waste hierarchy: various levels with different impacts Implementing sufficiency

Sufficiency enables consideration of existing resources to meet a given societal need. In other words, it is a concept that considers and validates if existing re‑ sources are sufficient to meet the needs of people, such as a community or client.

The role of standardisation in circular economy   99 Sufficiency is the implementation of measures and daily practices to avoid the de‑ mand for energy, materials, land, water, and other natural resources (EEB, 2023). Therefore, when referring to sufficiency in the built environment, it can relate to the sufficiency of almost any resource. In existing policy debates, mainly in France but elsewhere, sufficiency or sobriety has primarily focused on energy which in‑ creased in the context of the recent energy crisis fueled by a lack of gas and energy for much of Europe. The REPowerEU was innovative in bringing forward meas‑ ures to save energy by using less. Still, it should be the first of many EU policy ini‑ tiatives to promote sufficiency across a broader range of resources intensely used in the built environment. Fundamentally, the forecasts for continued increases in resource use by the sector are driven by the continued increase in floor space through construction (see UNEP, 2022). The Renovation Wave and revision of the EPBD are already indirectly pro‑ moting sufficiency by making the existing buildings fit for the future (see European Commission, 2020). Still, it will not directly target measures that will limit construc‑ tion or change the way that space is used to make better use of existing assets and material resources, which also have positive impacts on the level of energy, water, and other resources which increase as the space used per person increases. Extrapo‑ lated to a neighbourhood, town, city, or even regional scale, evaluation of used and available spaces for different building typologies and purposes can shift the view of planning authorities to ensuring that buildings meet the needs of a population or com‑ munity. For example, the London Plan 2021, also known as the New London Plan, surveyed available space for different types of buildings across various city boroughs to provide a basis for policy recommendations to inform decisions on planning appli‑ cations (GLA, 2023). As with this example, the focus is on available square metres, but the type of building and the adaptability also help define if sufficient buildings exist, so greater development of quantitative and qualitative sufficiency indicators on which to build policies and for standardised methods to underpin. Currently, as with the definition of even the most basic terms in the syntax of circularity, agreeing on what sufficiency is and will be a challenge in the context of sustainable vs beyond growth policy debate regarding what climate policies should ultimately pursue and, therefore the relevant means to the defined end in terms of a truly sustainable economic model. Nevertheless, this focus on preventing resource use to minimise resource flows to unite sufficiency and circularity as one, which should be the starting point and remain a common thread for defining necessary policies and standards for sufficiency. The IPCC AR6 report chapter (Intergovernmental Panel on Climate Change) on buildings points to the dire need to promote sufficiency in Europe and world‑ wide, where populations are growing faster, by highlighting that efficiency gains to date have been almost entirely offset by rapid growth in floor space, enabled by the lack of sufficiency policies targeting this vector of sustainability. Therefore, cir‑ cularity policies and standards must align and combine to mainstream a sufficiency approach to the built environment as a starting point for deploying high‑level circu‑ larity. However, in a sector responsible for half of all resource use and one‑third of all waste, implementing this at the scale required to EU climate and environmental

100  Michael Neaves goals requires standards that will enable all market actors to view existing structures and resources through the lens of sufficiency and as a viable strategy from a tech‑ nological standpoint, and importantly for firms, and viable business model, but this will also rely on getting the economic rights. Currently, real‑estate market trends and demolish‑rebuild economics are all working against sufficiency. The client is still king, and while a linear resource and wealth extraction model is viable, it will continue to be the norm by continuing to be a highly profitable business model. Moving to repurposing, adaptation, retrofit, refurbishment, and renovation, which are not new practices, will require reinvention by policymakers and reintegration into standardised practices for the industry in a way that will be viewed as circular and more sustainable by bringing down the resource use and environmental impacts of the sector. In practice, standards for sufficiency and circularity should help piece together existing standards that assess the structural integrity, modularity, adaptability, and energy performance of a building and the overall lifecycle impacts of building service‑life extension and retrofit in comparison to fully demonstrate the superior sustainability of sufficiency over traditional demolish, waste, and rebuild models. Moreover, using existing ISO standards for the circular design of buildings, Eu‑ ropean standards should elaborate on design strategies for adaptability and disas‑ sembly of buildings to guide the sector in combining and implementing design principles into project concepts and building design. These standards must be as‑ sembled correctly to guide the sector to carry out such processes. This requires fur‑ ther elaboration and technical work to create a circularity schematic of existing and missing standards needed in a typical project and should be developed by the Eu‑ ropean Commission in the form of circular building scenarios. The need for policy interventions in the case of sufficiency is heightened by the fact that most expertise in the standardisation community are from industries that are not operating in this way, and largely see sufficiency policies and standards as an anti‑growth approach that could harm their business and the economy. Policymakers need to make the case and support the development of such standards by reframing sufficiency as a viable circularity strategy that firms need to mutually consider. To support, resources such as the recently published a Circular Built Environ‑ ment Playbook which could act as a basis for theorising project scenarios and iden‑ tifying where and how standards have a role to play in delivering sufficiency at the building or construction works level (WGBC, 2023). The same issues in terms of where and how circularity can be implemented are true for reuse and recycling. Still, while the sufficiency of an existing asset is geographically a static action, the reuse of products and materials is more dynamic, crossing many system boundaries with many different routes to return to use in a different asset which will now be analysed. Reuse

As alluded to, regulators and market actors are often viewed in isolation due to their separation from a structure and therefore attain an independent profile on the

The role of standardisation in circular economy   101 market. Currently, policymakers are attempting to reconcile the opposing nature of reuse products that are climate‑friendly and heterogenous with a conservative, risk‑averse sector with substantial environmental impacts that have long since re‑ lied on industrial‑produced, homogenous inputs. In truth, the existing linear system has not been without its failures in delivering high‑quality products and materials. This decision led to an ECJ (European Court of Justice) that standards were part of EU law rather than outside.2 Consequently, with reuse in the construction sector so reliant on a firm legal basis, it is down to both policymakers and standardisers to legitimise secondary used construction products and, in doing so, bust the myths that secondary isn’t safe. Like sufficiency for buildings, reducing the resources used for various parts of a building through reuse requires evaluation and validation of existing resources in all forms (Benachio et al., 2020), and standards for reuse, using existing standards for functionality and safety can help build trust in the use of secondary components or products by providing precise instructions and methods to verify product con‑ ditions and performance for use in a second lifecycle for the same or even a new purpose. For example, the reuse of bricks can be both in a structural function and aesthetically in the form of a façade which can offer industrial and historic aesthet‑ ics to a modern structure such as in the case of the historic Carlsberg brewery in Copenhagen (Adept, 2020). Therefore, standards for reuse need to consider a broad range of characteristics and potential reuse case studies when delivering guidance on evaluating and preparing deconstructed building elements and products for their primary use‑case and first lifecycle. That being said, in the absence of standards, different forms of circular reuse at the product level have been implemented in the construction sector and ana‑ lysed by researchers, which demonstrate the ability of local projects to access the untapped potential of various components to be reused with great benefits for sustainability, especially for the reuse of structural components as a significant embodied carbon hotspot for new constructions, typically through the use of con‑ crete and steel (Nijgh and Veljkovic, 2019). In their analysis, Nijgh and Veljkovic highlighted the high potential for component reuse and reduced environmental impact when reused in the case of concrete composite floor systems. Steel struc‑ ture reuse systems have also been well‑documented by Fujita (2012), among oth‑ ers, which demonstrates how steel, among other metals, can be manufactured, designed, and assembled in a way that can facilitate product reuse both in terms of expected end‑of‑life conditions of components and the required refabrication or lack thereof. Based on the collective experience of the sector to date, standards can consider the full range of case studies and applications for reuse that future standards need to help accommodate and consequently provide all market actors with the tools to implement similar strategies where the conditions of products allow. Importantly, it’s essential to learn from existing cases of reuse exactly how the functionality is guaranteed and that environmental benefits are maximised. For example, Bertin et al. (2022) highlight the need to minimise functional downgrad‑ ing and material losses during the use and end‑of‑life stages to deliver high envi‑ ronmental performance throughout a forthcoming lifecycle in which a structure or

102  Michael Neaves structural components are being reused. In this regard, standards will be needed to both asses and measure material characteristics when products are being placed on the market, when in use, and when at the end of life to verify performance on the most relevant functional indicators crucial to validating reuse potential such as durability and strength for structural products. Other functional groups of products will require other forms of performance validation. For example, glass or insula‑ tion products will be more concerned with verifying the u‑value to check that there are no unnecessary thermal bridges that will reduce the energy‑efficiency of a building. Product legislation can help point to the relevant range of functional characteristics that need to be considered in developing horizontal standards but will have to be elaborated on by industry experts to ensure guidance is suitable and sufficient. In terms of actions to enable reuse in the future, design is a critical driver across many sectors, embodied in the form of the EU’s Ecodesign Directive, which fo‑ cuses on product design actions to enable greater sustainability and circularity. In the case of a building, design has always been considered a key enabler of archi‑ tectural quality and performance, and now for circularity. Design for Disassembly and adaptability has already been standardised at the international level in the form of ISO 20887(2020), but policies and standards for the reuse of these disassem‑ bled components across Europe are still missing and will act as a bottleneck for large‑scale reuse until they are delivered. The reason that this gap acts as such a barrier is that the potential routes and scope for product reuse will otherwise be constrained to a relatively small number of frontrunner projects willing to set their project‑specific standards and contend with the risks of an uncertain legal environ‑ ment, rather than an entire market of projects with an appetite for reuse to reduce their environmental impacts. Ideally, there will be equal or even surplus demand for reuse components and pipeline of projects ready and willing to provide and use secondary building components or products, either within or between property portfolios. Standards containing the technical expertise to realise the vision of policymak‑ ers will connect the dots, giving the industry the impetus to invest in the market for reused construction products, a legitimate means to reduce the sector’s im‑ pact. In this regard, the standardisation community is awaiting the outcome of the EPBD and CPR revisions which will trigger revisions to building codes and product standards used across Europe to integrate embodied carbon and circularity as a mitigation measure illustrating how important EU policy leadership is. As a consequence of current policymaking, the revised regulatory framework needs to chart a clear course for reuse to become mainstream in the construction sector in a way that reflects the diverse contexts and ways in which reuse can and should be implemented for a wide range of product types and materials. Such policies would provide numerous routes to reuse and avoid being overly conservative by always providing sufficient legal certainty regardless of the route. To support reuse holistically, EU and National policymakers should increase and accelerate their efforts to evaluate and support the reuse of products, which are so far living in the shadow of recycling materials into new products to mitigate

The role of standardisation in circular economy   103 rather than eliminate impacts of the energy‑intensive industries that take, make, and help waste resources. Resource efficiency and recycling

Circularity is fundamentally about making the best use of available resources to minimise their use. At the material level, resources used in each product’s lifecycle should be minimised. At the design and product stage, standards have already been developed in the case of energy‑related products through the EN 4555X standards series on material efficiency to extend product lifetime (related to sufficiency and reuse) but also for the systematic integration of recycled content into the supply chain of firms supplying products to the construction sector. Unlike other sectors, many products used in the construction sector, especially those consuming the most significant amount of resources, have significantly more extended service life periods, often between 15–25 years. However, the scale of resources used by the sector makes it critical to ensure design minimises the use of material and maxim‑ ises the use of secondary inputs at every opportunity, but not in place of measures that facilitate multiple, numerous lifecycles and warrant attention in the context of this chapter. Despite recycling not being part of a truly circular and sustainable economy, recycling remains the most mainstream waste prevention measure according to the EU Waste Hierarchy and therefore warrants attention within this chapter. In short, resource‑efficient recycling of C&D waste streams and other industrial or household waste streams is not yet the norm, with the term recycle too ambigu‑ ous to ensure resources are used correctly. In the case of the construction sector, downcycling and backfilling are still prevalent, with minimal in the way of upcy‑ cling of materials, meaning recycling is essentially a mitigation measure. Research on applying the concepts of upcycling and downcycling in the built environment has increased in recent years (see Akhimien et al., 2021; Monsù Scolaro and De Medici, 2021; Rose, 2019) but EU and national policies remain essentially un‑ changed. This body of literature shows that the most common form of recycling in the sector still equates to downcycling. For example, backfilling concrete structures for inferior purposes, such as using ground concrete on roads, or even incinerat‑ ing high‑performing composite materials with residues used in separate production processes (e.g., wind turbines, plastics, or biomass). Policymakers and the sector will need standards to understand materials and how to maximise resource effi‑ ciency and, ultimately, value retention. Common standards for characterising and evaluating waste streams and their suitability for construction will be crucial for recycling to increase in scale and to become more resource‑efficient by retaining the value of materials through their use in a similar or improved application. This type of standard will help tackle the recycling greenwash tendency and regulate the circular economy principles to make them adequately assessed and addressed. The cement sector is a prime example of where standards are already being developed that foster the acceptance of materials using secondary materials from various waste streams, complemented by methodologies for indoor and outdoor

104  Michael Neaves environmental compatibility of secondary materials to ensure that secondary mate‑ rials are safe and sustainable to use. While energy‑intensive sectors such as cement and steel are moving forward to create a European market for primary products with increasing recycled content, a broader range of stakeholders need to under‑ stand standard processes to facilitate recycling at each project phase and lifecycle stage of a building. Despite what policymakers consider progress on recycling, the recycling of nu‑ merous industrial and municipal waste streams is mainly being used to mitigate the impacts of energy‑intensive industries in a non‑discriminatory manner. Such mitigation measures are very temporary mitigation measure, and for the construc‑ tion sector to become genuinely sustainable, downscaling of primary resource and product demand needs to be accompanied by the most efficient forms of recycling, which focus on closed-loops that maintain and improve material characteristics in a way that maximises sustainability of the entire economy. For example, complex composite materials used to make wind turbines need to be effectively redesigned, reused, or recycled in a way that maintains their value as essential components of a renewable energy system rather than be incinerated for the energy‑intensive, fossil‑fuel‑powered production of cement to generate heat and ash, and with very little in the way of material recovery (WindEurope, 2021). Measuring resources and impacts for decisions making in a circular construction sector Standards are known for providing clear methodological guidance to practitioners in the built environment, but this has typically been in a static, linear context. Now in the transition to circularity, practitioners need clear guidance on how to treat numerous primary and secondary resources of different forms, across different geographical and temporal streams, involving a variety of different use cases. The common aim that policymakers and standardisers therefore have is to deliver a sys‑ tem of data and information on buildings, products, and materials that work across all contexts and for all project types. Such a ubiquitous and highly harmonised system will be a challenge to deliver, as has been proven by the existing Environ‑ mental Product Declaration (EPD) system which is still lacking in harmonisation (BPIE, 2021). Policymakers will therefore need to lay down a common system for measuring and reporting circularity data and information that is interoperable with existing systems for building and product information under the EPBD, national building codes, and the CPR. In practice, the interface between the linear and cir‑ cular economies must be bridged robustly through decisive policymaking and ef‑ fective standards in support. The benefit of data being standardised is that this can be more easily understood in isolation and across a property portfolio. In this regard, data standardisation enables interaction with other market actors that facilitate and implement circular‑ ity on their behalf, such as structural engineers and other contractors involved. Projects such as BAMB2020 developed numerous resources that illustrate the ben‑ efits of data standardisation to overcome challenges of a common understanding in

The role of standardisation in circular economy   105 multi‑stakeholder circularity processes. Moreover, in the context of digitalisation, the use of BIM throughout the asset lifecycle will generate a lot of data, including different BIM models that will be created and fueled at different time of the asset lifecycle. Charef (2022) identified three types of BIM Models and explained them. The PIM (Project Information Model) and the AIM (Asset Information Model) have been detailed in ISO 19650. However, the author suggested the DIM (De‑ construction Information Model) based on around twenty interviews with BIM ex‑ perts (Charef, 2022b). Data standardisation also helps link circularity in practice with policy initiatives and requirements as described. These threads turn a circular economy into a proverbial spider web of links between actors at different levels and scales of operation. A reliable system of data and information based on common standards will help the sector optimise circularity at all levels by informing decision‑making about the best use of an asset, product, or material based on functional and environmen‑ tal considerations. Regarding data standardisation specifically, Villaizan (2022) raised the key role of data standardisation to ensure the integration, at the national and international levels, of the new solutions into an existing structure (Villaizan, 2022). Getting circularity‑related data to firms is essential for them to understand the performance and value of their resource to consider and decide on how they can implement circularity and the financial implications. Doing so will be essential to effectively operationalise circularity, optimise resource use, and uphold the eco‑ nomic case as part of a firm’s business model, which will be challenging to estab‑ lish, as already referred to in this chapter. For example, an asset manager aiming to operationalise their assets’ circularity through extending the asset’s service life or reutilising existing building elements or construction products in a renovation or construction will need the data and information on the structural integrity and con‑ dition of building components to inform their decisions. Without this information, as is the norm today, linearity is an easy decision and usually leads to a demolish and rebuild approach as we so often see today. Building Information Modelling (BIM) is one existing and transferrable tool for the circular economy to harness at scale. Indeed, Charef (2022a) identified the vari‑ ous scenarios for using BIM throughout the asset lifecycle. The data collection pro‑ cess is different for each scenario, ranging from the asset designed, constructed, or/ and managed in BIM (Charef, 2022b). Such a dynamic tool will require standards to deliver reliable data and information, with policies (sometimes supported by standards such as Eurocode structural standards) setting legal boundaries regarding what is possible. However, the greater the scale at which circularity is measured, the more comprehensive and more complex the measurement of circularity and its benefits for sustainability becomes. So far, the development of circularity stand‑ ards at the ISO level has followed a more pragmatic approach to set manageable boundaries at which firms can measure and assess their performance in a circular economy. However, sector standards for circular construction should build upon the general international standards being developed by designating the key metrics and stages at which circularity can be measured, which can then be appropriately integrated into BIM systems.

106  Michael Neaves Standards will also need to guide the measurement of data, information, and evaluation of circularity and environmental performance information across multiple lifecycles and across system boundaries of various kinds (e.g., waste to production, old project to new project). Standards should demonstrate how practitioners should consider resources and environmental impacts across mul‑ tiple lifecycles of a single asset and between assets to help elucidate the broader environmental benefits of projects. For example, a city or a prominent asset owner or manager, adopting and implementing circularity across a large geographical and temporal scale, understanding where and how environmental benefits can be unlocked across a portfolio of real‑estate assets by identifying critical linkages within and between projects traditionally viewed as standalone from a resource‑­ use perspective. As a result, standards to be developed have an essential role in mainstreaming systems‑level resource and environmental impact considerations across multiple scales and lifecycles, which can be achieved by adopting the com‑ mon view and approach of circularity advocates into a European standard that the sector can then adopt with confidence and move forward in elaborating the different elements of the circularity framework to the level of detail required for full implementation. Measuring and assessing circularity in the context of scaling up circularity in the sector stems from the intrinsic relationship between circularity and environmental sustainability, which is under increased scrutiny from regulators in recent years. In this context, standards should enable a robust assessment and clear understanding of the environmental benefits of circularity by tracing the resources with intrinsic environmental impacts. Gaining a robust assessment and clear understanding will be particularly challenging in which linear‑economy‑style environmental sustain‑ ability assessments are only just becoming mainstream at the product level (i.e., EPDs), with building‑level LCA reaching the same scale and maturity only by 2030 at the earliest. Sector standards should demonstrate how to evaluate the climate and environ‑ ment benefits of implementing circularity from different levels, whether for a prod‑ uct, a project, or a firm and up to the overall systems level of a city, region, or country. This will become increasingly relevant as policies for Whole Life Carbon and other resource‑use‑related impacts are rolled out across Europe. While relevant standards should be used to help mainstream multi‑lifecycle, trans‑scalar thinking for considering the environmental benefits of circular buildings or materials, it is not their role to change the boundaries and rules that govern the implementation of environmentally robust LCA. Using EU and national policies, policymakers should act as the gatekeepers of climate progress by ensuring the measurement and reporting of carbon emissions and progress on decarbonisation is as robust as pos‑ sible. Otherwise, the construction and economy will be walking with a blindfold when it comes to arriving at climate neutrality in time, with dire consequences for the entire planet. While scholars have theorised the application of different approaches to the al‑ location of multiple lifecycles (Malabi Eberhardt et al., 2020), the current method known as the ‘cut‑off’ method of allocation still best reflects the upfront immediate

The role of standardisation in circular economy   107 impacts construction products, with circularity then benefitting future projects through the impacts that a project has not made. This does not disqualify the consideration of different concepts, design, and use of circularity (among other decarbonisation strategies) that are possible to model and more quickly adopt the most sustainable option. However, this forces practi‑ tioners to find and deploy any viable solution to leverage circularity and reduce impacts to the greatest extent possible upfront by building upon the experience and content of standardisation activities for product specification and lifecycle as‑ sessment. This also requires practitioners to consider how to achieve the highest possible environmental ambition from implementing circularity, which in turn can support more harmonised and effective implementation. One significant challenge standardisers face is the complexity of material flows at different scales and over different lifecycles makes measuring and assessing circularity. Once complete, rel‑ evant standards will become significant determinants of how effectively practition‑ ers implement circularity in the construction sector. In the absence of robust circularity standards, EU policymakers should establish a common Whole Life Carbon framework to measure buildings’ carbon emissions to clarify how embodied and operational emissions based on resource use are to be measured and reported across Europe. This will provide a basis for overlaying product and material flows in the built environment as per the common approach of evaluating environmental impacts. The ongoing revision of EN 15978, combined with the relevant LEVEL(s) indicator guidance for lifecycle carbon emissions and circularity, can support EU policymakers and national experts to agree on a joint approach to ensure the environmental benefits of circularity are appropriately evaluated. A common framework will then provide a clear basis for deploying all forms of decarbonisation solutions with clear and reliable data on their benefits for stakeholders to understand at all scales. Moreover, this can provide the basis for environmental performance requirements to be introduced that will help make cir‑ cularity the norm as a major decarbonisation, and not just in theory, by increasing the overall capacity and acceptability of circularity by the sector. This will grow the capacity of market actors and public and private demand‑side actors to integrate circularity criteria into policies with greater confidence that criteria can be adhered to. Standards can therefore help act as a basis for public and private actors while helping to initiate a positive feedback loop between sector capacity and policy with increasing environmental benefits. Standards can, therefore, help avoid bot‑ tlenecks in setting legal or project requirements for the assessment of circularity and environmental sustainability or even achieving a desired level of performance (Adams et al., 2017). One clear case is the integration of regulatory requirements for project accept‑ ance and implementation based on robust qualitative and quantitative circularity criteria that can be measured, assessed, and evaluated using common European standards. Specifically, policymakers should use product legislation (Ecodesign for Sustainable Product Regulation (ESPR) and the Construction Product Regu‑ lation (CPR)) to require lower carbon footprint to enter the EU Single Market in

108  Michael Neaves conjunction with enabling reuse and requiring higher levels of recycled content. Beyond the production stage, ecodesign requirements can introduce use‑phase measures to support the maintenance and repair of relevant building elements, maintain product functionality and material characteristics, and address end‑of‑life considerations in tandem with EU and national construction and demolition re‑ quirements. Moreover, at the local level, climate, environment, and circularity cri‑ teria can be integrated as part of essential planning criteria that a project proposal must fulfil, or in the context of procurement, mandatory award criteria as part of a project tender specification will represent a substantial incentive. Policy recommendations and concluding remarks This chapter has explored and analysed the interface between standards and poli‑ cies to help clarify the role of standards in the development of the circular economy in the construction sector. Here below in list form are the recommendations for policymakers and standardisers to best contribute to a circular sector that maxim‑ ises benefits for climate and environment as soon as possible. Based on common EU and National climate and environment ambitions, policymakers should: • In the development of standards, policymakers should support and orchestrate the development of essential standards for circularity in the construction sector, with priorities defined based on climate and environment benefits, and an open and transparent consultation process for the allocation of public funding for circular standards development. • Policymakers should also act as a supervisor and gatekeeper to ensure that the standardisation community define standards that reinforce rather than under‑ mine the robustness of climate and environment impact measurement standards and to ensure that standards do not foster ineffective circularity solutions that promote downcycling and resource‑inefficient practices. • Strengthen policy interventions to prioritise and adopt a policy‑first approach to promote and incentivise the highest levels of circularity in the built environ‑ ment, including through standardisation requests to provide resources that en‑ sure technical expertise and consensus is gathered to deliver the required suite of standards needed for the variety of use‑cases, for sufficiency and reuse in particular, with emphasis on the involvement of a broad range of expertise from stakeholders throughout the value chain and from civil society. • Use climate, environment, finance, and economic policy measures as part of the real estate market, building, product, material, and waste policies linked to the built environment to promote ambitious decarbonisation, levels of environmen‑ tal performance, and circularity as mutually inclusive criteria for incentives and legal requirements at both EU and Member States level. Standards for circular economy in the construction sector can play a vital mediator and facilitator role within the sector and support policymaking to help ensure more circular and sustainable construction is the norm. Standards have great potential to

The role of standardisation in circular economy   109 codify a common understanding of circularity as the new normal economically and practically for the construction sector to foster resource use reduction and environ‑ mental impacts. In short, standards are not a silver bullet for a circular construction sector but are crucial to bringing about a transition to circularity within the sector by guiding stakeholders and practitioners to understand how reductions in resource use and environmental impacts at the project or organisational level can be achieved and how actions at all levels can contribute to reductions at a macro or systems level. In this regard, it is paramount that policymakers and industry accelerate the development of ambitious policies and the development of the essential standards referred to in this chapter with a new sense of urgency for the sector to mainstream the implementation of circularity as soon as possible to contribute achieving cli‑ mate targets as soon as possible, and to mitigate non‑carbon environmental impacts that are largely neglected by EU and national policies to date. Notes 1 https://www.ebc‑construction.eu/about‑us/facts‑figures/. 2 ECF James Elliot case ruling (ECLI:EU:C:2016:821).

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Part 2

Practical strategies for circular construction Building and material levels

6

How can we view buildings as material banks? Learning from the pre‑redevelopment process Katherine Tebbatt Adams and Gilli Hobbs

Introduction In times of rising inflation, price volatility and issues with the availability of con‑ struction products and materials, the incentives to use what is already “banked” in the built environment grows ever stronger. According to government figures, build‑ ing materials prices in the UK were 25% higher in 2022 than they were in 2021. The latest Building Materials and Components Statistics (GOV.UK, 2023), released in January 2023, also show that the average annual building materials prices for 2022 were over 50% higher than in 2015. This trend also constitutes a significant “infla‑ tion risk” for projects that may not break ground for a year or more. Additionally, there has been general price volatility for all materials over the last decades. The UNEP Report on Global Resources Outlook (UNEP, 2019) stated that since 1970 global population has doubled, whereas the extraction of materials has tripled. This has a big impact on the environment since the ex‑ traction and processing of natural resources account for more than 90% of our biodiversity loss and water stress and approximately 50% of GHG emissions (UNEP, 2019). The UK is highly dependent on importing their construction products and materials, resulting in a trade deficit of £11,592 million (GOV.UK, 2023). This dependence on imports also has impacts in relation to availability and lead in times to get some products. In 2021, there were many shortages and prices increased by over 60% over 12 months, some of which were linked to delays at ports. According to the Brick Development Association, lead‑in times for bricks were also an issue over the last few years, with imports used to meet the shortfall until new streams of bricks are produced in 2023 and 2024 (Con‑ struction News, 2021). Latterly, rising energy prices have created uncertainty around inflation and the pricing of products, such as steel, cement, bricks, blocks, glass and ceramic tiles (CLC, 2021). Moreover, when looking at the other end of the pipe, there are similarly press‑ ing reasons to avoid waste and maximise the value of materials arising from dem‑ olition and other construction activities. Around 62% of all waste generated in England in 2018 (GOV.UK, 2022). Was from the construction, demolition and

DOI: 10.1201/9781003450023-9

116  Katherine Tebbatt Adams and Gilli Hobbs Table 6.1 Summary of CD&E waste characteristics and opportunities to reduce arisings (Green Construction Board, 2020). Waste arisings

Considerations

Waste from manufacturing activities

Process dependant, it will often be reused back into the manufacturing process. This includes waste generated from offsite manufacture. Largely soils, coming from the groundworks of construction projects or from infrastructure projects such as roads and railways Opportunities to reduce from cut and fill. Generated from new build activities and use of temporary systems. Wastage may occur for a variety of reasons such as over‑ordering, poor storage, design changes and workmanship. Packaging waste is also produced. Includes elements that are defined as construction products such as plasterboard, doors and joinery. It also includes elements subject to different definition that are not construction products per se such as. Light fittings, HVAC and so on. This can encompass waste from the products being taken out and from the installation of new products including packaging. A lot of this will be inert waste from the demolition of existing buildings and structures. Some of this cannot be avoided – certain hazardous waste, for example asbestos or legacy wastes. Demolition waste is avoidable if the building lifetime is extended, or elements of the buildings are reused. Be designed to be flexible, adaptable and long lasting. At the end of their life, demolition waste may be avoided through designing for deconstruction and subsequent reuse.

Excavation waste

Construction waste on construction sites

Fit‑out waste and refurbishment waste

Demolition waste

Existing buildings New buildings

excavation (CD&E) waste at around 120 million tonnes (and this doesn’t include waste from materials extraction or manufacturing of products). There are no single causes or solutions to addressing this enormous waste of resources, as shown in Table 6.1. When these materials and waste issues are combined with the opportunities to reduce the embodied carbon of developments through displacing new products with reused and remanufactured ones, the case for retention and reuse becomes very compelling. As Figure 6.1 shows, a report from the Green Alliance (2019), the potential embodied carbon reductions from reusing construction products and materials are highly significant. Although there are established standards and protocols to measure embodied car‑ bon (and other impacts) through life cycle assessment, they do not really take into account the full opportunities that circularity approaches can offer.

How can we view buildings as material banks?  117

Figure 6.1 Carbon reduction opportunities for increasing resource efficiency in construc‑ tion (based on Green Alliance (2019).

Three lifecycle approach The concept of a three‑life cycle approach was first developed during the Buildings as Material Banks (BAMB) project (see Figure 6.2). As the infographic suggests, the three life cycles that can be impacted by circularity approaches are: – Existing assets whereby the already built environment can be retained and refur‑ bished (in preference to demolition). If this is not possible, the products, materi‑ als and elements should be harvested at the highest material value to offset the impacts of new developments. – New/current assets whereby the material impact is minimised through using ex‑ isting products/materials and the lifespan of the asset is optimised. For example, designing and constructing with flexibility and durability to reduce the risk of functional or technical obsolescence. In the case of renovation or refurbishment, every new material used needs to be circular by having the potential to be reused or recycled without generating waste. – Future assets whereby resource impacts of the future built environment are taken into account. For example, designing for disassembly and reuse and the mate‑ rials prescribed in new buildings should be recovered materials to minimise raw material extraction. However, if new materials are needed, they should be circular, having the potential to be reused or recycled without generating waste.

118  Katherine Tebbatt Adams and Gilli Hobbs

Figure 6.2  Three life cycle approaches to circular building (BAMB, 2020).

In addition, circular business models which enable the take‑back at the end of use, should be employed. This involves generating, maintaining and transfer‑ ring relevant data (such as product passports) throughout the “new” asset life cycle. Many of these opportunities lie in the existing built environment, particularly to fo‑ cus on the immediate challenges to reduce carbon emissions and the other impacts associated with the extraction of new resources. Therefore, in the UK and beyond, clients, policymakers and planning authorities have been instrumental in requiring the development of pre‑demolition inventories and setting targets for asset reten‑ tion, reuse and higher‑value recycling. Even before this stage (of pre‑demolition), there is growing recognition that many assets should be evaluated for retention and refurbishment, rather than demolition and rebuild. As part of the planning permitting process, there have been big changes in this respect for many development projects in London due to the circular economy statement requirements issued in 2022. As a principle, for existing assets, much more consideration is placed upon retaining as a first principle; before deciding to demolish and replace with new. Pre‑redevelopment and pre‑demolition audits Applying for planning permission for referable developments, where existing assets are involved (nearly always the case in London) now requires certain au‑ dits and templates to be completed. These include pre‑redevelopment audits and pre‑demolition audits. The pre‑redevelopment audit is described as follows: A pre‑redevelopment audit is a tool for understanding whether existing build‑ ings, structures and materials can be retained, refurbished, or incorporated into the new development. The audit should be carried out early on (at the pre‑application stage) and should inform the design.

How can we view buildings as material banks?  119 They should also “fully explore options for retaining existing structures, materials and the fabric of existing buildings into the new development; and the potential to refurbish buildings before considering substantial demolition” (GLA, 2022). Where the decision to demolish needs to be justified, including an assessment of whole‑life carbon impacts considering how the loss of embodied carbon in existing buildings would be mitigated and offset; for example, through integrating into the new development. The pre‑demolition audit is described as “a detailed inventory of the materials in the building that will need to be managed upon demolition”. The report should also include aspects, such as key components and materials present in the existing buildings, with an estimate of the quantities and associated embodied carbon and whether they are suitable for reclamation; opportunities for reuse and recycling either within the proposed development or off‑site nearby/locally or further afield; and target reuse and reclamation rates (GLA, 2022). GLA further advises that the audits should be undertaken by a third‑party in‑ dependent specialist with expertise in the reclamation of components and mate‑ rials and experience in preparing these types of reports. There is also a detailed template for completion to be attached to the circular economy statement (GLA). The template and the statement are required at different stages of planning. The template requires actions to be filled out in relation to circular economy principles for any existing and new buildings, a Bill of Quantities, recycled content values and end‑of‑life scenarios for projects, as well as the targets that will be met for the project. The statement and template are completed by the project team (usually a sustainability/circular economy consultant) through workshops and project infor‑ mation. The GLA will comment on the template and Statement to ensure compli‑ ance with the guidance. It is mandatory for projects that are referred to the GLA, which are usually larger developments. Reusefully has been engaged to carry out multiple pre‑redevelopment evalua‑ tions on varying projects, providing insight into the decision‑making processes, en‑ vironmental, economic and technical aspects of implementing a circular economy through optimising the assets already in place. Many of these are linked to the GLA Circular Economy Statement requirements and/or the waste credits embed‑ ded within BREEAM. The latter sustainability standard is currently considering ways to embed Circular Economy further (BREEAM, 2023) with three principles, referencing resource optimisation of existing buildings. The first principle is “opti‑ mising resource use” which requires design teams to challenge design briefs from the beginning and deliver strategies on how to build less and more efficiently from a resource perspective. The second principle is “designing and enabling circular buildings” which is about embedding circularity in a project from a whole‑life cycle perspective, from strategic planning to enabling the next use for materials, through careful design decisions and material specification. The third principle is “circular resource management” which is to facilitate material flow management from ideation to construction, demolition/demounting and operation with the inten‑ tion of enabling the highest value re‑use of materials to avoid lower value cascad‑ ing and eliminate all waste. This requires design teams to challenge design briefs

120  Katherine Tebbatt Adams and Gilli Hobbs from the beginning and deliver strategies on how to build less and more efficiently from a resource perspective. The methods used by Reusefully Ltd have evolved over the last two years. This is because the original emphasis on producing an inventory of the demolition prod‑ ucts and materials (with best practice guidance on reuse and recycling) is starting to shift to a more involved consideration of retaining value and reducing impacts in the new development. However, the information available on existing build‑ ings and assets is often quite scarce, so it can be time‑consuming and challenging to carry out the initial quantification. Using assumptions and building upon data acquired from previous audits are helping reduce this load. The PreaDem project

Also, further Research and Development (R&D) is being undertaken through an Innovate UK‑funded project called PreaDeM (Pre‑demolition environmental as‑ sessment and decision‑making) (Reusefully, 2022). The project is supported by Innovate UK under the NICER programme (National Interdisciplinary Circular Economy Research). PreaDeM aims to help the social housing sector realise better circularity outcomes when considering whether to demolish or refurbish homes. A key objective of PreaDeM is to develop a smarter way to quantify what is there (for example using more state‑of‑the‑art technology such as point cloud, photogrammetry and walk‑through scanning) combined with detailed specification information and assumptions to determine what can be extracted for further reuse, closed‑loop recycling and other resource management options. From this recent work and in the many years previously at BRE (Building Re‑ search Establishment), where the driver for pre‑redevelopment audits was embed‑ ded into BREEAM requirements, it is clear that the quality and level of detail for pre‑redevelopment audits can be highly variable. It was for this reason that the Code of Practice (CoP) for pre‑redevelopment audits was developed with industry stakeholders and published in 2017 (CIWM, 2017). This provides recommenda‑ tions for the steps when undertaking a pre‑redevelopment audit (Figure 6.3). This CoP needs to be updated as the requirements to carry out these audits become prevalent and challenging. It is no longer the case that a simple Bill of Quantities arising from demolition and refurbishment and some reuse/recycling recommendations will align with increasingly ambitious targets and the informa‑ tion required by the design team.

Figure 6.3  Code of Practice (CoP) for pre‑redevelopment audits overview.

How can we view buildings as material banks?  121 Value retention approach Materials hierarchy

DONOR (DEMOLITION) Material value retention target g

RECIPIENT (CONSTRUCTION) Material efficiency y indicator Value retention target

0.8 8

0.6

0.5 5

0.4

REUSE on site REUSE off site RECYCLE on site

RECYCLE off site

Low value recycling on site

0.1

Material efficiency weighting %

Weighted %

0.9 9

RETA T INED RETAINED

0.2

0.35

0.5

0.7

0.9 0.3 .3

REUSED on site

0.9

REUSED off site

Value retention weighting %

R TAIN if RET RETAIN po possible

Undertake preaisal redevelopment appraisal

0.8

RENEWABLE

RECYCLED from on site RECYCLED from off site

Virgin & locally sourced

(n/a)

0.5 0.4

(n/a) ( /a (n

Low value recycling off site

1.0 Notre librairie : Presses des Ponts, Presse de l’école nationale des ponts et chaussées. ed, AFGC, COFREND. Paris. Brière, R., 2016. Etude ACV des chantiers de démolition en vue de la préservation des res‑ sources: focus sur les procédés de transport et de décharge. PhD thesis. Paris Est. Charef, R., 2022. Is Circular Economy for the Built Environment a Myth or a Real Opportu‑ nity? Sustainability 14, (24), 16690. https://doi.org/10.3390/su142416690 Charef, R., Lu, W., Hall, D., 2022, The Transition to the Circular Economy of the Construc‑ tion Industry: Insights into Sustainable Approaches to Improve the Understanding. Jour‑ nal of Cleaner Production 364, 132421, https://doi.org/10.1016/j.jclepro.2022.132421

152  Ambroise Lachat et al. de Larrard, F., Colina, H., 2018. Le béton recyclé, Ifsttar. ed. Marne la Vallée. Deweerdt, M., Mertens, M., 2020. Un guide pour l’identification du potentiel de réemploi des produits de construction (version préliminaire). Interreg North‑West Europe. EUROCODE 2, 2005. Calcul des structures en béton Partie 1‑1 : Règles générales et règles pour les bâtiments. (NF EN 1992‑1‑1). AFNOR. Fischedick, M., Roy, J., Abdel‑Aziz, A., Acquaye, A., Allwood, J., Ceron, J.‑P., Geng, Y., Kheshgi, H., Lanza, A., Perczyk, D., Price, L., Santalla, E., Sheinbaum, C., Tanaka, K., 2014. Industry, in: Climate Change 2014: Mitigation of Climate Change. Contribution of Work‑ ing Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change ‑ [Edenhofer, O., R. Pichs‑Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (Eds.), IPCC. Cambridge and New York. Fleury, F., Mouterde, R., 2019. Comprendre simplement‑ la résistance des matériaux, 3 ème édition. ed. Editions Le Moniteur. Glias, A., 2013. The Donor Skelet: Designing with reused structural concrete elements (masters). TU Delft. Küpfer, C., Fivet, C., 2021. Déconstruction sélective ‑ Construction Réversible: recueil pour diminuer les déchets et favoriser le réemploi dans la construction, EPFL. ed. Zenodo. https://doi.org/10.5281/zenodo.4314325 Lachat, A., 2022. Le réemploi appliqué au domaine de la construction: principe, impact environnemental et mesure dans le cadre d’une économie circulaire. PhD thesis. Ecole des Ponts ParisTech Lachat, A., Mantalovas, K., Desbois, T., Yazoghli‑Marzouk, O., Colas, A.‑S., Di Mino, G., Feraille, A., 2021. From Buildings’ End of Life to Aggregate Recycling under a Circular Economic Perspective: A Comparative Life Cycle Assessment Case Study. Sustainability 13, 9625. https://doi.org/10.3390/su13179625 Mai‑Nhu, J., 2015. Corrosion des armatures: intérêt des inhibiteurs de corrosion et mé‑ thodologies pour le suivi durant la vie de l’ouvrage (Rapport d’étude et de recherche No. 276.E), Developpement durable, Durabilité. Cerib. Mosley, W.H., Hulse, R., Bungey, J.H., 1996. Reinforced concrete design to EuroCode 2 (EC2), Basingstoke: Macmillan. ed. Nguyen, M., Wardeh, G., Ghorbel, E., 2015. Etude de l’endommagement des bétons à gran‑ ulats recyclés, in Rencontres Universitaires de Génie Civil (pp. 1–10). Bayonne, France. Nguyen, N.T., 2014. Évaluation non destructive des structures en béton armé: étude de la variabilité spatiale et de la combinaison des techniques (These de doctorat). Bordeaux. Omary, S., Wardeh, G., Ghorbel, E., Gomart, H., 2014. Comportement à la flexion des pou‑ tres en béton armé à base de graviers recyclés. Proceedings of the 32èmes Rencontres de l’AUGC, Orléans, France, 4–6. Rakhshan, K., Daneshkhah, A., Morel, J‑C., 2023. Stakeholders’ Impact on the Reuse Po‑ tential of Structural Elements at the End‑of‑life of a Building: A Machine Learning Ap‑ proach. Journal of Building Engineering 70, 2023. Rakhshan, K., Morel, J.C., Alaka, H., Charef, R. 2020. Components Reuse in the Building Sector–A Systematic Review. Waste Management & Research 38(4), 347–370. Rakhshan, K., Morel, J.C., Daneshkhah, A. (2021). Predicting the Technical Reusability of Load‑bearing Building Components: A Probabilistic Approach towards Developing a Circular Economy Framework. Journal of Building Engineering 42, 102791. te Dorsthorst, B.J.H., Kowalczyk, T., 2005. State of Deconstruction in the Netherlands (No. 5). TU Delft, Rotterdam (Netherlands). Torrenti, J.M., Barre, F., 2016. Fissuration et durabilité des structures en béton armé. Techniques de l’Ingénieur C6 152, 13. (http://observatoire.batiment‑energiecarbone.fr/ statistiques/experimentation‑en‑chiffres/consulted on January 19, 2022).

8

Building together with the site materials A practitioner’s perspective Louis‑Antoine Grégo

Introduction Studio Mediterranée was established by the author in Nice in 2016. It is a structure that hosts both an architecture and a carpentry studio and follows the following principles:   i The systematic use of local, bio‑sourced, and natural materials; ii The use of natural resources and energies; iii Preference for careful renovation and deconstruction, with the reuse of materi‑ als for new buildings. iv On‑site, participatory, and experimental architecture. In every project, the hope is to develop a long‑term reasonable and responsible scheme, in which wisdom and tradition, harmoniously combined with progress and modernity, would bond architecture and landscape in a single entity by the collaborative act of making. We employ a systematic method that is consistently applied to each project we undertake. Our pre‑project studies are structured into six comprehensive steps: 1 Topographical and Geological Analysis: We commence with an in‑depth exami‑ nation of the site’s topography and, notably, its geological composition. This study delves into the earth’s constituents on the site, helping us understand its nature, distribution, history, and genesis. 2 Heritage Evaluation: If a built heritage exists on the site, we conduct a thorough examination to appreciate its significance and potential impact on our design. 3 Climate Assessment: We meticulously study the local climate, taking into account factors such as precipitation, humidity, prevailing winds, sunshine, temperatures, and historical trends, aiding us in making climate‑responsive design decisions. 4 Resource Investigation: Our team investigates local resources and identifies key points for their extraction, resale, transformation, or storage, ensuring sustain‑ able and resource‑conscious project planning. 5 Reuse Strategies: We assess the availability of local reuse channels, which may include platforms, storage facilities, old material resellers, and ongoing decon‑ struction sites. This commitment to reuse minimizes waste and promotes sus‑ tainable practices. DOI: 10.1201/9781003450023-11

154  Louis‑Antoine Grégo 6 Indigenous Knowledge Catalogue: We compile an inventory of indigenous know‑how, emphasizing the study of local, ancestral, and contemporary con‑ struction methods and their evolution. This enables us to integrate time‑tested techniques into our designs. Depending on the unique characteristics of each project, these steps are adapted and developed to varying degrees, aligning with their relevance and significance. For instance, in the case of the Beaucastel Project, which we will explore further in the following chapter, Steps 1, 2, 3, and 4 have proven to be particularly pertinent and insightful. The context of the Beaucastel project

In this chapter, we delve into a project, focusing on the restoration and expansion of the iconic winery, “Domaine de Beaucastel,” under the esteemed ownership and direction of the Perrin Family. This project warrants a contextual understanding of the site and its unique needs. Château de Beaucastel, nestled in Châteauneuf‑du‑Pape and the Côtes du Rhône (France), has been under the careful stewardship of the Perrin family since 1909 (Truc, 2022). A trailblazer in sustainable viticulture, the Perrin family initiated organic farming in 1950, followed by biodynamic farming in 1974. The wines produced by this esteemed Domaine are today celebrated by experts as some of the finest in France, cherished by connoisseurs in over sixty countries. Since its inception by Pierre de Beaucastel in the 17th century, the Domaine has steadily evolved. Multiple expansions, driven by the shifting needs of its custodians, have shaped the Château into its current form. However, the architectural quality of the existing structures does not always match the excellence of the wines they house. Driven by this recognition and a need for space in alignment with their grow‑ ing activities, the Perrin Family sought to embark on a transformative renovation ­project – e­ nvisioning Beaucastel in the 2100s and beyond. For the ambitious renovation of this historic estate, an architectural competition was launched, drawing an astounding 1200 entries from 32 different countries. This process exemplified the global interest and importance of the project. After an extensive selection journey, the Perrin family identified a project that resonated with their aspirations. Studio Mumbai, an acclaimed architectural firm based in India, and our own office, Studio Méditerranée, rooted in the South of France with expertise in renovation and eco‑responsible construction, had the honour of joining forces to realize this remarkable vision. While the Domaine currently spans approximately 4000 square metres and manages nearly 130 hectares of vineyards, the primary objectives of this renova‑ tion were threefold (Figure 8.1): 1 Expansion of vinification and storage: Expanding the vinification and storage capacities to meet increasing demand while upholding the highest standards of wine production.

Building together with the site materials  155

Figure 8.1  Situation of the Beaucastel project.

2 Sustainability: Implementing eco‑friendly measures to reduce energy and water consumption, with a specific emphasis on cooling the expansive spaces to the ideal temperature of 14 degrees Celsius. 3 Elevating the Image: Enhancing the aesthetics and visual identity of Beaucastel to reflect the exceptional quality of the wines it produces, positioning it as an emblem of excellence in the wine world. This collaborative effort represents a bold step towards the future while honour‑ ing the heritage and traditions that have made Domaine de Beaucastel a global wine icon. Building together with the site materials

A seemingly subtle shift in terminology can reveal a profound shift in philosophy and approach. Thus, we would deliberately employ the phrase “Building Together with the Site Materials” rather than simply “Building with the Site Material.” This linguistic distinction underscores a fundamental ethos that underpins our architec‑ tural practice – one rooted in collaboration, reverence, and a deep understanding of the materials that shape our built environment. The term “Building with” often conjures an image of the practitioner wielding materials at their disposal, shaping them according to their will, regardless of the intrinsic properties and character of those materials. It aligns with the hylomorphic model, which emphasizes the idea of practitioners imposing preconceived forms

156  Louis‑Antoine Grégo from the recesses of the mind onto inert material. However, our approach diverges from this notion. As we embark on the journey of creating spaces and structures, we view materials not as passive entities but as active collaborators. In the words of Tim Ingold, eloquently articulated in his masterpiece “Making,” materials become our partners in a creative dialogue. They are not mere resources for manipulation but vital actors in the narrative of construction. “These materials are what we have to work with, and in the process of making, we ‘join forces’ with them, bringing them together or splitting them apart, synthe‑ sizing and distilling, in anticipation of what might emerge,” as Ingold beautifully elucidates (Ingold, 2013). This perspective humbles our ambitions as architects. We do not stand as omnipotent creators, imposing designs on a world waiting to re‑ ceive them. Instead, we intervene in the ongoing worldly processes, complement‑ ing, and enhancing the forces and energies already at play. “Building Together with the Site Materials” encapsulates our fundamental ethos. It signifies a state of mind – a mindset that embraces the presence and uniqueness of each material in its context. It embodies a curiosity to explore the material’s spe‑ cificities and its untapped potential. It goes beyond the mere use of site materials; it signifies an active partnership with them. To illustrate this specific state of mind, let us delve into an example – a construc‑ tion method that we extensively considered for the Beaucastel Project, although it was ultimately not chosen. This method exemplifies our commitment to building in harmony with materials. The top‑down construction method

After a comprehensive analysis of program demands and environmental condi‑ tions, we recognized the need for most of our structures to be buried underground to minimize energy loss and consumption. The conventional construction approach would have involved excavating a hole and then building the structure from the ground up. However, our commitment to using minimal reinforcement presented challenges, particularly when constructing large‑scale vaulted ceilings of such scale, which would require complex formwork installations. This led us to explore the top‑down construction method. In this innovative approach, vertical supports are initially constructed within the soil before excavation (Figure 8.2). The soil itself becomes the formwork for the structure that is placed on top. Subsequently, the soil is removed, and the process is repeated for each floor. The relatively slower excavation process suited our needs, allowing us to carefully separate and sort the soil with care. In this method, we collaborated with the soil itself, leveraging its unique prop‑ erties. We aimed to make it sturdy enough to mix directly with lime or cement for peripheral walls while ensuring it was pliable enough for excavation using aspira‑ tion. While this approach was not ultimately chosen for the Beaucastel Project, it exemplifies our philosophy of “Building Together with the Site Materials.” Despite the innovative potential of the top‑down construction method for a non‑urban scale project, and its alignment with our philosophy of “Building To‑ gether with the Site Materials,” it was ultimately decided not to implement it for the

Building together with the site materials  157

Figure 8.2  Top‑down construction method.

158  Louis‑Antoine Grégo Beaucastel Project. It is important to acknowledge that the client’s unfamiliarity with this technique with the client was a significant factor in this decision. Under‑ standably, a construction approach that deviated from conventional norms raised concerns and uncertainties. The client was already taking a significant leap of faith by entrusting us with this prestigious project. The inherent risks associated with pioneering a relatively unknown technique for that scale of project added another layer of complexity to their decision‑making process. In such circumstances, it was a pragmatic choice to opt for more conventional construction methods which provided a greater sense of certainty and security. However, it is essential to emphasize that the essence of the top‑down construc‑ tion method and our philosophy of “Building Together with the Site Materials” continues to resonate with every member of the project team. Even though this specific technique has not been used, the mindset it embodies remains an integral part of our collective consciousness. Our commitment to working inclusively and thoughtfully with the materials of the site, collaborating with them rather than sim‑ ply imposing our will on them, remains a guiding philosophy. It informs our ap‑ proach to every project, reminding us that each material has its voice, its potential, and its unique contribution to the architectural narrative of architecture. Considering that it is not simply a matter of using the materials from the site; it is about building collaboratively, learning from the material, and allowing it to reveal its capabilities. The artisan’s desire to witness what the material can do, rather than the scientist’s quest to understand what it is, allows us to discern a life within the material. In the words of political theorist Jane Bennett, this allows us to “collaborate more productively” with the material (Bennett, 2010). In the world of manufacturing, every material follows a trajectory, a path through a maze of possibilities. “Building Together with the Site Materials” embraces this notion of correspondence – paraphrasing Tim Ingold. It is not a question of the imposition of preconceived forms on raw material, but the unveiling and nurturing of poten‑ tials inherent in a world in perpetual evolution. In this chapter, we invite you to explore how this philosophy shapes our architectural practice, guiding us to create spaces that harmonize with nature, context, and the very essence of the materials themselves. Site materials: elaboration of the available material corpus Understanding differentiation of site material

We have come to recognize the existence of two distinct categories of site materi‑ als, each with its unique characteristics and origin: Type A – “Natural” Site Material: Type A site material encompasses elements in‑ trinsic to the site, recalling the timeless presence of nature. These materials include earth, stone, and other substances deposited or formed by the forces of Mother Earth over millennia. Their origin dates back to the geological and environmental history of the site, reflecting its geological composition, history, and genesis.

Building together with the site materials  159 Type B  –  Human‑Introduced Site Material: In contrast, Type B site material includes substances that have been transported to the site by human intervention. This category mainly includes pre‑existing structures, buildings, or even entire cit‑ ies. These materials bear the marks of human ingenuity and know‑how, represent‑ ing architectural and cultural histories. Type B materials have often been shaped, transformed, and adapted to meet ever‑changing human needs. It should be noted that in a world where every building is constructed primarily with construction site materials, the distinction between Type A and Type B would become insignificant. Take the example of a sandcastle built on a beach, where the construction materials and the site materials are indistinguishable, forming a har‑ monious whole. This harmonious fusion characterizes often vernacular architecture, where structures emerge from the landscape, embracing readily available natural materials. Vernacular architecture illustrates the intimate relationship between hu‑ manity and its surroundings. In less abstract terms, when a convent or any structure is erected on the remains of ancient buildings in an old city, it often reuses the founda‑ tions and stones of those pre‑existing structures. This practice illustrates how archi‑ tectural heritage evolves, building upon the materials and history of its predecessors. Our mission is to recognize, respect, and work collaboratively with these diverse materials, each with its own story and essence. With this understanding, we strive to create spaces that not only reflect cultural and environmental context but also honour the timeless interplay between human ingenuity and Earth’s raw materials. Type A, the “natural” site material and Type B, representing the “built environ‑ ment,” will be discussed in detail in the two next subsections. “Natural” site material: history of its formation

The Domaine de Beaucastel is located in the heart of the Quaternary terrace in the Rhône valley known as Châteauneuf du Pape, composed of entirely siliceous cover‑ ing stones, beneath which a true wealth of materials is revealed, relatively easy to use for construction without significant transformation. As is the case in vernacular ar‑ chitecture, local geology is the source of construction materials (Johnson, 2014). For thousands of centuries, the valley was filled with alluvium from the Alps, or the sea, depending on the climate, the emergence of the Alps, and the formation of the Medi‑ terranean Sea. This explains the variety of the soil layers (Figures 8.3a and 8.3b). Let’s take a look at the geological history that created this wealth. At the end of the Cretaceous period, around 125 million years ago, the South‑East of France, af‑ ter having been little submerged since the Triassic period – which brought salt and gypsum, gradually emerged, particularly during the Barremian period following the Durancian Uplift, leading to a significant erosion of the landscape. Around 45 million years ago, during the Eocene period, the collision of the Iberian Peninsula formed the Pyrenees and, more locally, the Lampourdier Mas‑ sif, lifting the limestone sediments of the Urgonian Formation onto the Triassic gypsum and salt. Then, around 35 million years ago, at the end of the Eocene, the creation of the Pyreneo‑Provençal chain further caused the rotation of Corsica and

160  Louis‑Antoine Grégo Without scale ALPES

-250 Ma Submerged land -125 Ma Alpine sea Beaucastel

Mediterranean sea Mountain Lampourdier massif

Rhone

Nîmes Fault

PYRENEES

At the end of the Cretaceous period

Around -125 million years ago, the Sousubmerged since the Triassic period which brought salt and gypsum - gradually emerged, especially during the Barremian period following the Durancape erosion.

Around -45 million years ago, during the Eocene period, the collision of the Iberian Peninsula formed the Pyrenees and, more locally, the Lampourdier Massif, Urgonian Formation over the Triassic gypsum and salt.

Emerged land

Emerged land

Mediterranean sea

Mediterranean sea

Emerged land

Falling sea levels

Mediterranean sea

-400

Sea level rise

the end of the Eocene, the creation of the Pyreneo-Provençal chain further caused the rotation of Corsica and Sardinia, creating the Nîmes Fault that tore through the landscape of Châteauneuf, simultaneously mixing the terroirs of old.

-25

Beaucastel

-800

Beaucastel 0

Beaucastel

During the Miocene Approximately -10 million years ago, the Alpine thrust accompanied a lowering of the Châteauneuf du Pape region’s elevation,

cant sandy deposits.

-

Around -6 million years ago, at the end of the Miocene, due to the narrowing of the Strait of Gibraltar, the Mediterranean Sea’s water level dropped by 1500 meters, leading to the deepening of the Rhône Valley by over 800 meters.

Figure 8.3a  Understanding the geological history of the soil.

Around -5 million years ago, the Strait of Gibraltar reopened, causing a rise in water levels along the true canyons of the Rhône Valley, creating thick layers of sands that

Building together with the site materials  161 Without scale e Isèr

Terrace

Miocene marly sands

Colluvium drapery

Coarse sandstone

Rhone

Very old terrace 120-130 m

High terrace 70 m Beaucastel Beaucastel Low terrace 30 m

Colluvial sheet Recent and modern alluvial deposits

Quaternary terraces Mountain Mediterranean sea Rivers Envelope of the large Villafranchian terrace at the time of its formation. Envelope of the large Villafranchian terrace at the time of its formation.

periods, formed large Quaternary terraces, with the older and higher ones being gradually eroded by the next.

Miocene

Quaternary

Colluvial sheet composed of a layer of debris and sediments that accumulates at the base of slopes, typically as a result of erosion and gravity.

Around -2.5 million years ago, the beginning of the Quaternary period was characterized by a succession of shorter glacial and interglacial periods. During interglacial periods, moraines gave way to large rivers, particularly the Isère Ririous types of stones that it deposited along the entire Rhô-

Stage 1

Stage 2

Native quartzite pebbles coexist with limestone, eruption-formed rocks (granite), and metamorphic rocks (gneiss and micaschist); all encased in a matrix composed of more or less clayey sand.

Chemical alteration has occurred: the limestones have almost completely disappeared, and the other rocks have under-

Figure 8.3b  Understanding the geological history of the soil.

Stage 3 weathering reacted to form red clays in the marily composed of quartzite pebbles combined with a clay-sandy matrix intensely colored by iron oxides.

162  Louis‑Antoine Grégo Sardinia, creating the Nîmes Fault which tore apart the landscape of Châteauneuf, simultaneously mixing the old terroirs. It is in this context that, in the Miocene, approximately 10 million years ago, the Alpine overlap was accompanied by a lowering of the altitude of the Châteauneuf du Pape region, allowing the Mediterranean Sea to flow there. Sea level will then fluctuate significantly for several million years, sculpting the existing relief and creating significant sandy deposits. Around 6 million years ago, at the end of the Miocene, the Messinian Salinity Crisis (MSC) occurred: due to the narrowing of the Strait of Gibraltar, the water level of the Mediterranean Sea fell by 1,500 metres, leading to a deepening of the Rhône Valley over more than 800 metres – with the Lampourdier Massif largely protecting the territory of Beaucastel. In the Pliocene, around 5 million years ago, the Strait of Gibraltar reopened, causing water to rise along the true canyons of the Rhône Valley, creating thick layers of sand that filled these canyons. Around 2.5 million years ago, the beginning of the Quaternary period was char‑ acterized by a succession of shorter glacial and interglacial periods. During in‑ terglacial periods, moraines gave way to large rivers, particularly the Isère River, which flowed through the heart of the Alps, carrying various kinds of stones which it deposited along the entire Rhône Valley. These waves of deposits, alternating with glacial periods, formed large Quaternary terraces, the oldest and highest being gradually eroded by the following ones. Finally, on the one hand, the dissolution of the limestone elements in these de‑ posits, and on the other hand, the hydrolysis of gneisses, granites, and mica schists into a layer of clay approximately 1 metre thick, gave birth to an exclusive land‑ scape of rolled quartzite pebbles, siliceous conglomerates, and quartz grains from the Triassic, originating mainly from the Var region of Tarentaise in the case of Beaucastel. From top to bottom, the soil layers of the site, illustrated in Figure 8.4, are: • Earth with red clay coloured by iron oxides made up of the alteration of the Quaternary Terrace, composed of mixed plastic clay, sands, and pebbles. These clays are up to 0.60/0.80 m depth and are very suitable for the rammed earth technique, which can be used for the construction of load‑bearing walls and superstructures. • +/− clayey sands with pebbles and limestone rolled gravels, results of the final erosion of the Miocene marine molasse, present up to 8.00/12.00 m deep. By combining it with a hydraulic binder (cement or lime), this carefully stored, sieved, and screened material is a mixture of very high‑quality aggregates to produce “a site‑rammed concrete” with very good mechanical and physical properties. It is reserved for the creation of all the load‑bearing vaults of the infrastructure, and the creation of all the two‑storey up walls. • Beyond 8.00/12.00 m depth, safre yellow molasse (soft sandy rock) is rela‑ tively easy to overcome and can be used in the construction of stone masonry – ­provided it is protected from erosion.

Building together with the site materials  163

Figure 8.4  Theoretical and geological soil section.

Built environment Comprehensive diagnostics for built heritage analysis

When embarking on the study of built heritage, a structured approach is essential to gain a holistic understanding of the condition and potential of the structure. To achieve this, we organize our analysis through six key diagnostics, each serving a unique purpose: 1 Technical Diagnostic: The Technical Diagnostic delves into the structural and infrastructural aspects of the building. This includes a thorough review of the stability of the building, as well as the condition of its networks and systems. It raises questions such as: Is the entire building stable, or do specific areas need special attention? Can some parts be reused, making them suitable for alterna‑ tive uses? 2 Health Diagnostic: The Health Diagnostic is essential to ensure the health and safety of occupants. It addresses concerns related to hazardous materials such as lead, asbestos, termites, and more. This diagnostic aims to determine if the building is safe for physical contact, breathing, and overall well‑being.

164  Louis‑Antoine Grégo 3 Architectural Diagnostic: The Architectural Diagnostic aligns with the effort of the design team, assessing how well the building meets essential aspects of the design. It considers factors such as orientation, ventilation, natural light, and acoustic and thermal insulation requirements. This diagnostic checks whether the building is correctly oriented, sufficiently lit by natural light, sufficiently ventilated, and has effective acoustic and thermal insulation. 4 Landscape Diagnostic: The Landscape Diagnostic places the building in its sur‑ rounding context. It explores how the building integrates into its environment and assesses the quality of the surrounding surfaces. This diagnostic also ex‑ amines the choices made regarding vegetation and landscaping, ensuring they harmonize with the region and endemic plant life. 5 Materiality Diagnostic: The Materiality Diagnosis focuses on the different com‑ ponents and materials incorporated into the building. It assesses the condition of these materials and identifies whether they have deteriorated over time. Ad‑ ditionally, it considers the ease with which these materials can be reused or detached from each other. 6 Historical Diagnostic: The Historical Diagnostic provides valuable insights by taking us on a journey through the construction period. This approach involves meticulous research, often involving family photographs combined with histori‑ cal maps and aerial images. It allows a precise analysis of the history and evolu‑ tion of the building. Using these six diagnostics, we build a comprehensive framework for assessing and understanding existing constructions. This approach ensures that no crucial aspect is overlooked, and it allows us to make informed decisions regarding pres‑ ervation, renovation, and adaptive reuse. In general, the date of construction is a robust indicator of the material potentially used for the building. Of course, after World War II, the variety of industrial materials increased and made this indicator less robust. The existing buildings: three main construction periods, decisions, and actions taken accordingly

Our exploration of the built heritage reveals three main construction periods that shaped the architectural narrative of the site. These periods include: Period 1: XVII Century – WWI: During the first period, which spanned from the XVII century, the construction featured pebble‑thick walls built using lime mortar, wooden frameworks for first‑floor structures with flat terracotta tiles and plaster flooring, support for roofing via wooden structures, stone ground floors, and occasional reinforcements with select reinforced concrete and metal beams. It is noted that these buildings predominantly used local or site materials, such as stone sourced from a 40‑kilometre radius, terracotta, plaster, and locally harvested timber. The lack of insulation is also a characteristic of this period. In our Beauca‑ stel case study, most structures have been preserved and have undergone necessary

Building together with the site materials  165 repairs, driven by considerations of durability and sustainability rather than nos‑ talgia. Usually, roofs were replaced with new ones. The vertical structures such as walls, while adding partial insulation, were preserved. Stone floors were largely retained, and up‑floors were repaired. Period 2: WWI to 70s: During Period 2, which spanned from the 240s to the 70s, construction involved the use of non‑industrial poured concrete mixed with site aggregates and pebbles. The roof structures were characterized by metallic trusses and non‑insulated, non‑industrial tile roofing. In our case, around 40% of the structures from this period were deconstructed and reused, except for the old winery that was kept intact. Salvaged tiles were carefully stored for future reuse, metallic trusses were subjected to standard recycling processes, and old site con‑ crete was preserved for potential future applications. Period 3: 80s to 2010s: In Period 3, which extended from the 80s to the 2010s, construction featured a combination of industrial reinforced concrete and metal structures. Infill construction utilized partially insulated red bricks, and roofing was comprised of metal corrugated sandwich panels with limited insulation. Plaster‑ board subdivisions were integrated into the structures. For the project, during this period approximately 70% of the structures were deconstructed, while the rest had to be discarded. Notably, newly industrialized tiles were set aside for crushing,

Figure 8.5  History and construction period.

166  Louis‑Antoine Grégo

Figure 8.6  Materiality across periods.

suitable for gardening or mortar colouring. Concrete walls were retained without separating the steel components, and metal structures and roofing were dismantled for external gifting and reuse. Plasterboard and multi‑components were designated for disposal. Throughout these different eras, two major observations emerge. First, the buildings were constantly oriented away from the cold and formidable Northwest‑ ern Mistral winds (Figures 8.5 and 8.6). Second, a natural hierarchy of domesticity was evident, with orchards, water tanks, and vegetable gardens succeeding one an‑ other. The first “circle” of domesticity life always encompassed a square 100 me‑ tres by 100 metres. It’s important to note that newer buildings have proven less amenable to reuse due to two main factors. They are mainly made of composite materials that are difficult to separate and reuse. They also incorporate plastics derived from environ‑ mentally unfriendly petroleum sources. Practical organization of the corpus Logistics and storage

Efficient organization and logistics play a central role when handling construction materials that require significant space, time, and cost, especially when they need to be relocated multiple times. The project team’s objective was to establish a dedicated quarry or material bank, complete with a specialized organization and logistics.

Building together with the site materials  167

Figure 8.7  Site resource organization and logistics.

In terms of storage, a careful strategy in three steps, three‑sites was developed: on‑site (1), the “Oliviers” ground (2), and the “Martini” ground (3), Figure 8.7. Method

Unfortunately, the site’s circumstances necessitated simultaneous handling of sev‑ eral aspects: (A) Identifying the appropriate rammed concrete formula for the site. (B) Coordinating the excavation of various types of earth. (C) Managing materials salvaged from the existing structures (Figure 8.8). Looking for the right site rammed concrete formula

This phase began before excavation, relying on drilling data, and continued throughout the excavation process. This involved extensive testing, mock‑ups, and laboratory verifications to determine the aggregate size, binder type, layer thick‑ ness, and material proportions required for the project. This process is typical of cooperation between professionals who usually do not cooperate, such as masons, structural engineers, researchers with laboratory tests, and architects. The chal‑ lenge was to find the lowest binder content (here white cement) to reduce the cost and environmental impacts. This is only possible through a performance approach, that is to say by testing samples to get their compressive strength. The challenges are therefore to ensure that the samples to be tested in the lab are the same as the material implemented to build the real structure. This challenge can be overcome by the strong cooperation of the previously cited stakeholders.

Figure 8.8 Phasing.

Building together with the site materials  169

Figure 8.9  Photographs of the different phases.

170  Louis‑Antoine Grégo Organizing the excavation of different soils – “natural” materials

The excavation process involved several distinct stages. (1) Initially, we removed the upper layer of organic soil and pebbles, which extended to a depth of approxi‑ mately 40 cm. During this phase, pebbles and organic soil were separated, with the organic soil earmarked for future landscaping purposes. Additionally, pebbles were partially crushed into aggregates ranging from 30 to 50 mm, with some left in their natural state. (2) Following this, we embarked on the delicate removal of the red clay layer, which extended to a depth of roughly 80 cm. This clay was specifically designated for use in the rammed earth construction process, with allowances made for clay containing pebbles within certain limits. (3) The excavation process also involved addressing the “mixed” zone, consisting of Myocène sand and clay, at an approximate depth of 10 cm. Sand with an excessive clay content was deemed un‑ suitable for on‑site concrete, and similarly, clay with a sand mixture was not usable for our purposes. Therefore, the material from this “mixed” zone was set aside for potential future backfill projects. (4) Subsequently, we excavated Myocène sand and gravel. During this phase, any clay moan (silt) encountered had to be sepa‑ rated. Unfortunately, this clay moan did not serve a practical purpose in the build‑ ing process, except possibly for ceramics. Excessively sandy Myocène, resembling beach sand, was separated and could be utilized without further processing. (5) The materials obtained from each of these excavation stages were categorized and stored on the Martini ground, as illustrated in the attached graphic. (6) To ensure compliance with the established formula for correct aggregate sizes, each type of material was screened based on size. (7) Finally, we completed the process by tak‑ ing inventory of the different materials and crushing the largest gravel elements to align with the formula’s required proportions. Organizing material from former buildings – “heritage building” material

The primary materials salvaged from the former building encompassed a range of components, each strategically chosen to align with the principles of sustain‑ ability in a circular economy context. These materials included old site concrete, which was diligently recycled, and new reinforced concrete, which was similarly repurposed for recycling, contributing to resource conservation and reduced envi‑ ronmental impact. In addition, a selection of old tiles was carefully reclaimed for direct reuse, highlighting the preference for this eco‑friendly strategy in the circular economy model. Simultaneously, new tiles were incorporated into the project’s sustainability efforts, finding a new purpose and extending their lifecycle, thus re‑ ducing waste and promoting responsible resource utilization. Implementation

The recovered material, as depicted in Figure 8.9, takes on an earth‑like appearance and is intentionally maintained in a dry state. This dry condition is of paramount importance to avert any undesired chemical reactions when mixed with cement.

Building together with the site materials  171 These site materials may contain trace amounts of clay or other particles that, if allowed to retain moisture, could potentially result in cracks or structural damage. In the case of site‑rammed concrete, the final step involves precise mixing with the appropriate quantity of water and white cement to sustain a “dry” consistency that facilitates optimal compaction. Consequently, this material is applied in suc‑ cessive layers, each compacted meticulously, mirroring the technique employed in traditional rammed earth construction. This approach ensures both structural integ‑ rity and durability while embracing sustainable practices, as it harnesses reclaimed materials to create a resilient building material that aligns with the principles of circular construction. Tables 8.1 and 8.2 provide a comprehensive Correspondence Summary Table for each site material. This table offers a consolidated overview of the vari‑ ous site materials, their corresponding characteristics, and their respective ap‑ plications within the construction project. It serves as a valuable reference for understanding how each material contributes to the project’s sustainability and circular construction objectives. The (*) indicates where improvement could take place.

Table 8.1  Correspondence summary table for each “natural” site material “NATURAL” SITE MATERIAL Quantity 25,000 m3 Type 500 m

3

500 m3 1,000 m3

9,000 m3 8,000 m3

6,000 m3

Rolled pebbles.

How

– Crushed for the site concrete formula (70%) – As it is for drainage purposes (30%) Topsoil – Landscaping (80%) – Mortar finishing coat. (10%) Clay – Used « pure » without any addition, for classical rammed earth Myocène sand with – Part of the Site gravel concrete formula Myocène sand without – Part of the site gravel concrete, mixed with crushed pebbles (60%) – Part for embankment (20%) Clay loams (silt) – Partly for ceramic (5%)

Note 100% used

100% used 100% used

100% used 80% used The rest of the 20% spread out on “Martini” ground 5% used 30% spread out on “Martini’s” ground. 65% cleared out*

172  Louis‑Antoine Grégo Table 8.2  Correspondence summary table for each “building heritage” site material “BUILDING HERITAGE” SITE MATERIAL Quantity

Type

NA.

Old site concrete

NA.

How

Note

– Crushed for the site concrete formula (80%) – As embankment material Industrial reinforced – Separated from its metal concrete – Crushed for the site concrete formula Old tiles – Set apart for the Olive tree cloister Industrial tiles – Crushed for landscaping (50%) – Cleared out (50%) “Pont du Gard” stone – Set apart for later use (possible extension etc.) Old Wooden beam – To build part of the furniture of the structure project. (30%) – to build part of the doors and windows of the project (70%)

100% used 100% used 100% used 50% used 100% used 100% used

Stay flexible Actual excavation vs. bore‑based forecast

When utilizing on‑site materials for construction purposes, the design team, client, and builder must remain adaptable. In our specific case, an underground map had been theoretically charted, and the approximate quantities of each material were forecasted through various surveys, whether borehole‑based or derived from exca‑ vation data. However, the reality of our excavation revealed a significant discrep‑ ancy from these predictions, as illustrated in Table 8.3. We found ourselves with Table 8.3 Summary of drill holes and table summarizing expected quantities by type of material Forecast quantity per type of material versus quantity actually found Type

Forecast quantities. Quantity found (24,000 m3)

Clay

3,000 m3

1,500 m3

Myocène sand with small pebbles

18,000 m3

9,000 m3

Myocène sand without pebbles Clay loams

0 m3

8,000 m3

– 1,500 m3 – 50% of the quantity for the rammed earth missing. – 9,000 m3 – 50% of the quantity for the rammed concrete is missing. + 8,000 m3

3,000 m3

6,000 m3

+ 3,000 m3

Building together with the site materials  173 a notable shortage of essential earth (the clayey soil) and sand containing small pebbles, respectively used for rammed earth and site concrete development. The subsequent paragraphs delve into the solutions we devised to address this unforeseen challenge. Scope of options and solutions regarding the lack of clay used for the rammed earth

After analysing the soil composition, it became evident that the scarcity of clay would hamper the use of the rammed earth technique. As a result, we explored three potential solutions to address the discrepancy between our predictions and the actual amount of clay available: (a) Search for clay nearby, vicinity, within a reason‑ able radius (around 20 km), (b) Modify or adapt the design of the project, and (c) Adjust the formula for rammed earth. The following details each of these solutions. Locating additional clay

Through extensive research of the land surrounding the project site and consulting local sources, we managed to obtain a small portion of the required clay (approxi‑ mately 150 m³). Fortunately, we acquired it at a minimal cost, mainly covering trans‑ port costs, as it was considered “excavation waste” from another construction site. Adapting the project design

The project initially included a balance of site concrete and rammed earth, with site concrete making up approximately 75% and rammed earth 25%. However, in earlier phases of the project, our proportions were more evenly distributed (around 50–50%) based on initial drilling forecasts. To optimize costs, as rammed earth proved more expensive than site concrete, we decided to adapt the proportions of the project. We were convinced that the strength of the project lay in its ability to adapt to real field conditions rather than sticking strictly to preconceived designs. At this stage, we are considering further modifications, which may shift the propor‑ tions to 85% site concrete and 15% rammed earth. Such a change would not only solve the rammed earth dilemma but also provide financial benefits. However, we were aware of the historical importance of clay in the Beaucastel region and will only implement this option if absolutely necessary. Adjusting the rammed earth formula

The third solution appeared to be the most effective, responding simultaneously to two challenges. While it was initially thought that only “pure” clayey soil could be used for rammed earth, closer examination of the remaining piles of earth led the researcher expert in earth material involved in the project, to speculate that some of the earth could be combined with “pure” clayey soil to create a viable rammed earth mixture. Simple laboratory tests on different remaining piles of earth

174  Louis‑Antoine Grégo confirmed this possibility. As a result, we developed a mixture of rammed earth composed of 60% “site” clayey soil, 10% earth sourced from a nearby location, and 30% “site” silt. Our solution essentially involved a combination of these three approaches: we collected additional clay from the neighbourhood, but not in sufficient quantity, reduced the proportion of rammed earth, and optimized the clay mixture by cost‑ef‑ fectively incorporating different types of materials. This adaptive approach allowed us to effectively address the challenges posed by the unique site conditions. Scope of options and solutions regarding the lack of pebbles in the Myocène for site concrete

In addressing the challenge posed by the scarcity of Myocène stony sand, of which nearly half was unavailable, we embarked on a comprehensive exploration of po‑ tential solutions, mirroring the approach taken with the rammed earth. These solu‑ tions included the following: a Procurement of Materials: While it may have been expedient, this option con‑ flicted with the project’s guiding principles of utilizing site‑derived materials whenever possible. b Additional Excavation: The prospect of excavating more in search of suitable quality materials was considered but ultimately deemed cost‑prohibitive, mak‑ ing it a less favoured choice. c Local Material Scouring: In a bid to source materials of similar type from the vicinity, we embarked on a mission to investigate nearby construction sites for viable resources. d Project Adaptation: Similar to the approach taken with rammed earth, project adaptation or modification was contemplated to accommodate the limitations of available materials. e Adjustment of Site Concrete Formula: This option, as with rammed earth, emerged as a particularly influential solution, especially where economic and ecological considerations converged. As expected, our project team opted for a blend of these solutions. The pur‑ chase of materials (solution (a) was held in reserve as a final contingency, while option (b), although attractive, was considered unprofitable due to budgetary constraints. Options (c), (d), and (e) were ultimately merged to formulate a holistic project approach. Option (c) consisted of sourcing materials locally by recovering a pile of earth from the Perrins’s land, known as the Oliviers, located 500 m to the west. Al‑ though the earth was considered a “secondary” quality for our purposes, 50% of it was recovered by screening. This operation also made it possible to create a natural barrier on the plot using the remaining earth, thus benefiting both the project and the Perrins. This approach enabled us to recover a significant quantity of material.

Building together with the site materials  175 Alongside this local solution, another pile was sourced a few kilometres from the site, contributing to another project to remove excess excavation materials, a fortuitous link between the backfilling and the excavation sites. Option (d) was carried out selectively, mainly in complex implementation areas where site concrete was replaced by “classic” concrete or concrete blocks, driven by logis‑ tical and planning requirements. However, option (e) was the one that had the most significant impact, particularly where economic and ecological considera‑ tions converged. According to our initial projections, the most deficient materials were those with a stony composition, particularly lacking in Myocène sand with pebbles. The old concrete from the structures described above, having undergone rein‑ forcement removal and consisting of site‑derived pebbles, was crushed to achieve the desired values, resulting in excess stock. Combined with the abundant sand available, and after numerous tests and iterations of the formula, we opted for a composition: a mixture of 60% site‑derived materials and 40% crushed concrete from the former building. This formula not only aligned with the project’s philoso‑ phy of using all materials from the site but also allowed us to reuse the remains of the former buildings, improving both the economy and ecology of the project. Conclusion During the journey of our project, after having used all “pre‑human geological materials” a crucial question arose once we had harnessed the full potential of the materials on‑site: what materials should we use to complete the construction, especially for the roof structure, roofing tiles, and floor tiling? The design of the project, characterized by a minimum of non‑load‑bearing secondary walls, intensi‑ fied the significance of this choice. Crucially, our commitment to energy conserva‑ tion and efficiency highlighted the need for “non‑transformed” materials. These materials, such as stone and wood, do not require any additional energy to convert into building materials. In contrast, materials such as cement, lime, and tiles re‑ quire considerable energy to manufacture (embodied energy). In this context, after having exhaustively exploited the materials from the site, we opted for mainly non‑transformed materials, whether old or new. We discerned two categories of “off‑site” materials: (1) locally acquired used materials, and (2) locally sourced new materials, often from nearby quarries and sawmills. In terms of energy, certain old materials, transformed and in use for centuries, such as tiles, could be consid‑ ered energy neutral in our project, testifying to their lasting usefulness. This ration‑ ale led us to integrate, transformed materials such as local “parefeuille” terracotta and tiles into our project. Returning to our material inventory, it was abundantly clear that our material bank thrived through a harmonious blend of natural site materials and the methodi‑ cal deconstruction of unsuitable and poorly constructed site buildings. The meticulous organization of deconstructed products and materials followed a systematic process that allowed the contractor to understand its specificity through

176  Louis‑Antoine Grégo detailed specifications during the tender phase. This process marked a collective learning experience for all parties involved: 1 We meticulously categorized each element, including photographs, dimensions, description, condition, and our subjective assessment of their potential for fu‑ ture use. 2 The storage process involved a straightforward categorization: • • • •

Items intended to be reused in Beaucastel were stored indoors. Items intended to be reused in Beaucastel were stored outdoors. Items to be donated/sold, are stored indoors. Items to be given/sold, stored outdoors.

3 We proactively contacted the local municipality to explore potential donation opportunities. 4 We shared the comprehensive list with various REUSE platforms and networks to maximize the materials’ potential for reintegration into other projects. 5 To engage with the community and facilitate the reuse of specific objects to‑ wards the end of the list, we organized flea markets, fostering sustainable prac‑ tices and community involvement. This endeavour also yielded valuable insights and observations: • Our society has seemingly overlooked the intrinsic practice of reuse, which was an integral component of the construction process. • Challenging prevailing norms requires additional and intricate efforts, fre‑ quently resulting in increased costs for clients. • Interestingly, individual workers readily embraced the concept of “preserving” materials, whereas the company as a whole did not endorse it. • Collaboration with a specialized material reuse company did not yield substan‑ tial advantages in the context of this distinctive project. A particularly noteworthy example of on‑site upcycling revolved around the use of severely deteriorated structural timber. Initially employed as struts during con‑ struction in a rather conventional manner, these timbers had been allowed to dry over three centuries. In our approach, we opted to repurpose these aged timbers for the creation of doors, windows, furniture, and parquet flooring within the two newly constructed houses and the historically renovated house (See Figure 8.10). This transformative process entailed: 1 Developing an exhaustive inventory system, categorizing wood according to its type and dimensions. 2 Conducting meticulous examinations of all timber to preempt unforeseen issues. 3 Precision‑cutting the timber into transportable segments of suitable dimensions for our intended purposes. 4 Conveying the timber to a nearby sawmill for the fabrication of boards with the specified thickness.

Building together with the site materials  177 The duration invested in this meticulous process, in contrast to the acquisition of new wood, ultimately struck a remarkable equilibrium – an unequivocal testament to the immeasurable value of timber that had grown three centuries before the Industrial Revolution. This value proposition clearly outshone the expenses associ‑ ated with waste disposal and the procurement of new materials.

Figure 8.10  Reuse existing beams.

178  Louis‑Antoine Grégo The discovery of a cooperative sawmill willing to process well‑scanned, re‑ claimed exterior wood—where proximity to return transport was negligible, raised awareness that a competent architect needed to embody the role of both builder and local craftsman, equipped with the capacity to cut beams indoors. In summary, there is no distinction between an “ecological architect” and any other architect, nor between an interior designer and an architect. All architects share the same fundamental responsibilities. It is essential to recognize that 80% of waste in Europe comes from the construction sector. We find ourselves at a critical moment, marked by the dissolution of the out‑ sourcing of tasks inherent to architecture to the detriment of its intrinsic purpose. It is time to move from a system of disempowerment to a system of shared responsibil‑ ity, a transformation that can be nurtured through academia, schools, and knowledge transfer. This perspective is not a specialized approach; rather, it is an attitude, a philosophy that architects must embrace. I remember the initial survey of our re‑ source‑rich “mine” in 2018, where I envisioned a meticulous 1:100 hand‑drawn map of the entire garden. This effort demonstrates a comprehensive understanding that can only be achieved through such painstaking efforts, cherishing every corner and detail, a philosophy close to that of our agrarian ancestors. However, the investment of substantial time should not be limited to a single project. It must be shared and proliferated. This led us to document and share our daily experiences, making our journey an integral part of the project itself, serving as a reference point for others. By incorporating responsibility for material reuse into architectural practice, alongside physical design aspects, architects counteract the depersonalization often associated with compartmentalization of architectural roles. Through the sorting, cutting, and reusing of the beams, architects reaffirm the noble essence of their profession. The essence of architecture lies not in remotely drawn sketches or 3D images but in hands‑on engagement. We aspire for the lessons we have learned, enriched by the documentation, pub‑ lications, and thesis contributed by students and trainees who participated in this project, will serve as a beacon for future endeavours. Ideally, we will facilitate the sharing of descriptive, quantitative, and qualitative data stemming from processes, both small and large scale. Challenging tasks are not insurmountable. It is a testa‑ ment to the transformative power of perseverance and dedication, even in the face of seemingly daunting challenges. References Bennett, Jane. Vibrant matter: A political ecology of things. Duke University Press Books, Durham, 2010. Ingold, Tim. Making: Anthropology, archaeology, art and architecture. New York, USA, 2013, Johnson, Matthew H. English houses 1300–1800: vernacular architecture, social life. Rout‑ ledge, New York, USA, 2014. Truc, Georges. Châteauneuf‑du‑Pape. Syndicat des vignerons de l’appellation d’Origine Châteauneuf‑du‑Pape, 2022, https://www.vinadea.com/accueil/438‑georges‑ truc‑chateauneuf‑du‑pape‑histoire‑geologique‑et‑naissance‑.html, Accessed 15.01.24.

9

Towards a situated understanding of challenges in the design and construction of circular earth buildings The case study of an office building in France Antoine Pelé‑Peltier and Jean Goizauskas

Introduction In Europe, half of the waste comes from the construction industry, and excavated soils represent 75% of those waste (Rouvreau et al., 2010, p. 42). As material se‑ lection or substitution strategies are among the most cited ways to implement a circular economy (CE) approach in the construction industry (Eberhardt et al., 2020), earth‑building techniques have great potential (Morel et al., 2021). How‑ ever, attempts to develop earth construction and material substitution more broadly in building projects are encountering many practical challenges (Pelé‑Peltier et al., 2022b). After recalling the challenges that have been highlighted so far in research on the CE and earthen construction, we propose to analyse them through the case study of a building project in France. Approach: a case study to understand practical challenges towards more circular building projects in earth Defining circular economy

The concept of CE has been increasingly used in the last decade. However, some authors have highlighted the lack of a consensual and clear definition of CE (Kirch‑ herr et al., 2017) and stressed the need to systematically spell out the definition of CE in each scientific communication. The most prominent definition of CE has been provided by Ellen MacArthur Foundation (Ellen Macarthur Foundation, 2015, p. 7) which reads: [CE] is an industrial system that is restorative or regenerative by intention and design. It replaces the ‘end‑of‑life’ concept with restoration, shifts to‑ wards the use of renewable energy, eliminates the use of toxic chemicals, which impair reuse, and aims for the elimination of waste through the su‑ perior design of materials, products, systems, and, within this, business models. DOI: 10.1201/9781003450023-12

180  Antoine Pelé‑Peltier and Jean Goizauskas In this sense, the core principles of CE lie in a different perspective on the manage‑ ment of resources in order to keep them in a closed-loop, reducing waste genera‑ tion and resource extraction. However, as shown by Kirchherr et al. (2017), such a definition does not insist enough on the degrees of circularity that were declined for instance by Potting et al. (2017) in their “9R framework” – from the worst to the best: Recover, Recycle, Repurpose, Remanufacture, Refurbish, Repair, Reuse, Reduce, Rethink, Refuse (Kircherr et al., 2017; Potting et al., 2017). Furthermore, the Ellen MacArthur Foundation’s definition of CE tends to hide the potential im‑ perfection in the application of CE while “the laws of thermodynamics and the inevitability of human error mean that ‘perfect’ resource circularity is unlikely to emerge” (Figge et al., 2023). Besides, while the definition of Kirchherr et al. (2017) adds the dimension of “social equity”, Figge et al. (2023) argue that integrating “social equity” provides a too narrow definition. Figge et al. (2023) thus insist on the need for different concepts to achieve sustainable use of resources. For this chapter, it will therefore be preferred the recent definition of Figge et al. (2023): The circular economy is a multi‑level resource use system that stipulates the complete closure of all resource loops. Recycling and other means that optimise the scale and direction of resource flows contribute to the circu‑ lar economy as supporting practices and activities. In its conceptual perfect form, all resource loops will be fully closed. In its realistic imperfect form, some use of virgin resources is inevitable. Moreover, we will consider that this definition should be in strong relation to that of sustainability, including three criteria as defined by Ruggerio (2021): a) account for the complexity of SESs [Socio‑Ecological Systems] by en‑ compassing economic, ecological, social and political factors; b) account for intergenerational and intragenerational equity; and c) address the hierarchi‑ cal organisation of nature, that is, acknowledge the feedback between the SESs and their surroundings. Contrasting circularities when building with earth: a qualitative life cycle analysis

In recent years, more and more building projects, whether public or private, have sought to integrate earthen materials into their design. Building with earth can cover a variety of techniques – from rendering to load‑bearing walls – with more or less outsourced and mechanised processes, with various raw resources, whether earth or potential additives such as plant fibres, biopolymers, or hydraulic binders. There are thus different versions of earthen construction, some of them being more environmentally and socially virtuous than others (Morel et  al., 2021; Ventura et al., 2022). As pointed out in the definition chosen for the CE, there exist differ‑ ent levels of circularity, highlighted by the different “Rs”. With its great variety of methods and techniques, earthen construction does not escape to this hierarchy of

The case study of an office building in France  181 circularity and does not provide intrinsically a circular material. This makes it es‑ sential, in every research, to systematically situate and specify the kind of earthen construction to discern how much it falls, or not, within the scope of “greenwash‑ ing/brownwashing” (Willis et al., 2023). Such a call is in line with recommenda‑ tions made in some research in CE to couple each case study with assessment tools (Kircher et al., 2017; Lovrenčić Butković et al., 2021). From there, several analytical and assessment approaches, based on the study of its environmental, economic, social, and/or territorial consequences/effects, make it possible to contrast these versions of earth construction. The most prominent one is lifecycle assessment (LCA). Although there is a growing body of research in the field of LCA for earthen construction (Ventura et al., 2022), their numerical results are not so easily transposable as the conditions can drastically change from one project to another (origin of raw material, transport, production method). Further‑ more, for the building project studied in this chapter and as is often the case due to lack of existing data, the actors did not have a dedicated LCA at the time of design. Such a study was not carried out afterwards. Nevertheless, a qualitative analysis framework is proposed in order to benefit from known trends and to contrast the constructive choices that can be made. The qualitative framework, represented in Figure 9.1, is based on the different stages of LCA, namely, product manufacture, construction, in‑use, and end‑of‑life. In the case of earth construction, “manufacturing” will be preferred to “product manufacture” as earth material cannot always be defined as a product when, for example, the transformation of the resource is directly made on‑site leading to the construction, which is quite common in France. Besides, we added a stage called “resource”, related to the origin of the soil. If considering earth products (such as boards or blocks), this stage might not be relevant for designers while the resource will be directly collected by the manufacturer, and designers will then select prod‑ ucts through a catalogue. The resource can come either from excavation work, landfill, quarry (Van der Linden et al., 2019), or short‑term storage (after deconstruction with the purpose of reusing). Extraction from quarries appears to be the worst solution in the CE con‑ text due to the use of primary resources (Kirchherr et al., 2017), although it has the advantages of a short‑term continuous availability and controlled quality (Van der Linden et al., 2019). On the contrary, earth as a secondary material can come from quarry waste, demolition, excavation, or deconstruction (Hall and Swaney, 2012). Upcycling earth from excavation work, or using it from landfills, is a valuable optimisation of waste into construction materials, which represents an enormous amount of available resources for the building sector. For instance, in Brittany, 2.8 million tons of earth were landfilled in 2012, where at least 23% could have been used for earth construction to build about half of the single‑family dwellings required in the region that year (Hamard et al., 2018). Direct on‑site extraction should however be prioritised because it is harder to use earth that has been dis‑ posed of in landfills and potentially mixed with other earth (Morel et al., 2021). In addition to the origin of earth material, there are different possibilities for manufacturing and construction. Some contractors have developed off‑site

182  Antoine Pelé‑Peltier and Jean Goizauskas

Figure 9.1 Schematic representation of a circular framework, with various versions of earth construction. A differentiation has been made to highlight the use of hydraulic binder as an adjuvant (text and arrows in red) as it adds a resource extraction and a recycling or disposal step. (Author: Antoine Pelé‑Peltier).

construction by prefabrication in factories, delivering products on construction sites (“Cycle Terre”, 2021). Although prefabrication has different advantages, in‑ cluding better quality control, better repeatability of the manufacturing process (Giuffrida et al., 2019), and cost efficiency, off‑site manufacturing tends to increase transportation, and thus the environmental impact (Ventura et al., 2022). Transpor‑ tation, at any stage, needs to be minimised. Therefore, in a CE approach, workmen manufacturing on‑site with local resources tend to optimise the circularisation of the building process. In this sense, traditional on‑site construction with local earth and workmanship seems to be the most circular approach. A case of compromise between artisanal and industrial production is the flying factory (Meunier, 1981; MacDougall, 2008), i.e., pre‑manufacturing on‑site (or close to the site) with small transportable machine units. Besides, from a design perspective, manufacturing and construction choices have to be related to the composition of the entire wall. As reported by some authors, earthen structural walls do not necessarily need finishing works, the latter being not reusable and hardly recyclable due to the paint or paper wall put on them (Charef et al., 2021a).

The case study of an office building in France  183 The use of earth as a construction material has also potential benefits in the in‑use phase. For instance, thick rammed earth walls can ensure the hygrothermal stability of the indoor air, especially during hot and dry periods (Mellado Masca‑ raque et al., 2020). In addition, most end‑users recognise that the atmosphere inside earth buildings is different and pleasant (Charef et al., 2021a). The maintenance of earth buildings follows similar principles as the manufacturing and construction described previously. Moreover, some experts argue that well‑designed earthen walls will require less maintenance compared to conventional walls (Charef, 2019, p. 162). For the end of life, deconstruction should be preferred to demolition. Indeed, deconstruction is “the process of dismantling a building in order to salvage its ma‑ terials for recycle or reuse” (Rios et al., 2015). Regarding the earth material, any mixing with other materials (such as finishes) complexifies the reuse or recycling of the wall. A deconstruction would thus help to separate properly the different ma‑ terials. Adjuvantation with hydraulic binders is unsuitable for a circular approach as resource extraction or production (cement, lime, …) is added and once adju‑ vanted, the material is way more difficult to reuse or recycle (Morel et al., 2021).1 The process of adjuvantation is mainly seen as the water sensibility of the earth without mentioning the drawback of hampering its reusability (see e.g., Muguda et al., 2021). In scientific literature, the word “stabilisation” is generally used to refer to ce‑ ment or lime adjuvantation. However, the authors consider that it creates confusion by distinguishing a “stabilised” and “unstabilised” form of earth material. In this chapter, the authors will prefer the word “adjuvantation” referring to the addition of an external material (commonly cement or lime) not being naturally present into the earth. The schematic framework proposed in this chapter (Figure 9.1) enables a quali‑ tative approximation of the degree of circularity in each case study. As all these considerations should be integrated into the design phase, they could also be mo‑ bilised as a tool for decision, or at least a means of understanding and discussion. The many challenges towards the construction of circular earth buildings

The massive production of waste in the building industry is relatively recent if one looks at the long history of construction: it has particularly intensified with the development of industrial and non‑recyclable building materials over the last three centuries (Guillerme, 1995). Writing about the CE is thus an attempt to respond to the dramatic consequences of deleterious modes of production that invite us to revisit ancestral building techniques rather than disruptive technological innova‑ tions. However, it appears that the professional institutions inherited from these last three centuries do not cope well with both circularisation and vernacular building practice. Various literature reviews have been performed recently on the implementation of CE in the built environment (Benachio et al., 2020), including literature reviews on barriers towards its implementation (Charef et al., 2021b), on challenges and

184  Antoine Pelé‑Peltier and Jean Goizauskas trends (Hossain et al., 2020) or the different assessment tools (Lovrenčić Butković et al., 2021). Similarly, some studies have revealed some barriers to the use of earth material in construction (See Pelé‑Peltier et al., 2022 for a review). Some authors, based on a meta‑synthesis of the literature, provide clarification on forty‑two sus‑ tainable approaches to improve the understanding of the CE context (Charef et al., 2022). Although those studies provide interesting insights, they remain quite gen‑ eral in recommendations for practitioners, in particular towards the design phase and the use of earth as a construction material. To identify more precisely some of the challenges, and thus better anticipate them, some authors recommend investigating building designs that adopt circular materials (Hossain et al., 2020; Osobajo et al., 2020). Integrative design has al‑ ready been highlighted as a driver of both CE (Charef and Lu, 2021) and earthen construction (Morel et al., 2021). However, case study analysis is quite rare and generally focused on end‑of‑life and waste management (Hossain et al., 2020). In contrast, this chapter proposes to rely on a thorough investigation of a building case study in the design and construction phases. Case study as a methodology

Describing how building projects are carried out makes it possible to embody the practical challenges mentioned above in professional realities more precisely than interviews detached from a situated project. Opting for such an approach implies opening up to social science methods of investigation and analysis. Our chapter is humbly inspired by research in science and technology studies that focuses on the description of building projects as they are built (Yaneva, 2009), or as they fail to be built (Latour, 1996) rather than on their last version. In other words, this approach involves tracing the history of a project without completely presuming the outcome in advance, as the design and building actors themselves during the building process. Such a detailed approach to a case study has several epistemological implica‑ tions. First, from a methodological point of view, it implies access to detailed and plural sources of data (Bryman, 2016, p. 556) in order to describe the case study as finely as possible. Our study includes a documentary analysis based on many reports and emails between the different actors, a series of 15 interviews with key stakeholders and ethnographic observations of the building site. Second, the focus on a single case study necessarily limits the general scope of the results. Such an approach, therefore, requires the case study to be situated as clearly as possible, on different levels, so as not to state generalities that would not make sense in another context. We state that this contextualisation effort should in‑ clude at least the following elements: a programmatic typology of the project (type of building and dimensions) and of the building systems (construction techniques and architectural typology), the ecosystem of actors involved and local norma‑ tive context. From the perspective of a CE analysis, the description of the build‑ ing system should allow to situate the degree of circularisation implemented for the project by specifying the origin of the resources and the production mode of

The case study of an office building in France  185 the building systems. Such a description can be achieved through the qualitative framework presented above and schematised in Figure 9.1. The “Projet de l’Orangerie”, a case study in the French context This part provides a quick description of the building, its implementation from a CE perspective, and the French normative construction context. Orangerie’s building description

The object of this case study is a two‑storey office building, called Orangerie, of about 1000 sqm, part of a larger project composed of five buildings in total and located in an urban area in Lyon (France). The four other buildings were seven to eight storeys. Orangerie’s building was thus part of a bigger project. The design team won the latter after a private competition, at the end of 2015, and the construc‑ tion occurred between 2018 and 2020. The building is made of load‑bearing rammed earth facades forming arches (see Figure 9.2b), with a substructure of limestone blocks. The inner structure (floors, pillars, and central core) is built with timber. Only the foundations are made with concrete integrating underground parking.

Figure 9.2 (a) Picture of the building under construction (source: Antoine Pelé‑Peltier), (b) recent picture of the building (source: Antoine Pelé‑Peltier).

186  Antoine Pelé‑Peltier and Jean Goizauskas The rammed earth facades were assembled from earth blocks (see Figure 9.2a) pre‑manufactured on‑site by using a specific machinery developed by the masons that followed the principle of a flying factory (Meunier, 1981). The rammed earth blocks were assembled with an earth mortar using the fine part of the earth. Orangerie’s earthen structure in the circular approach

As explained before, the use of earth material enables the achievement of different levels of circularity. In order to assess more thoroughly the level of circularity of this building, a LCA analysis would be useful and studies on the in‑use phase, re‑ lated to maintenance and energy consumption, could be performed. In the absence of such data, we suggest analysing this project’s circularity through the qualitative framework presented in Figure 9.1. It should first be noted that no specific level of circularity was targeted by the clients and no CE principles were purposefully followed by the design team. However, the project had high environmental objectives, including targeted la‑ bels such as the BREAAM label which involved, for instance, selecting a part of the resource within 30 km of the construction site. Earth was considered as a reused waste, making it possible to carry out an upcycling approach. The manu‑ facturing occurred on‑site, where the soil was stored, thus reducing transport which is known as one of the major energy demand criteria for earth (Ventura et al., 2022). The choice of a building technique with no adjuvant – such as ­cement – and no other material on the wall also improves the circularity of the building as it makes the wall easily recyclable, with no loss at the end of the life of the building. The selected process of earth construction for this building thus led to great achievements in terms of circularity. This level of optimisation did not occur with‑ out some challenges that will be described in the next sections. Some of those challenges were related to the French insurance context, presented to some extent in the next section. French construction insurance context

The French insurance system for construction is an “all‑insurance” system, which distinguishes it from its European neighbours (GT biosourcés action 18c, 2012). The system is structured by the “Spinetta” law of the 4th of January 1978 (note 1). The law defines four guarantees for clients, two of which are mandatory and im‑ portant for understanding the issues of the case study: – Ten‑year insurance for builders (Architects; Engineers; Construction company) to cover potential damage to the building. – A “Dommage‑Ouvrage” (D.O.) insurance for the clients that aims to cover the need for funding in case of building damages to accelerate the repair. (GT bio‑ sourcés action 18c, 2012).

The case study of an office building in France  187 The “Spinetta” law introduced a new actor in the building process, the control of‑ ficer, whose role can be decisive in the design and construction process. The control officer is only mandatory for some types of buildings or situations defined by the law. The client can entrust him with different missions. In the case of compulsory technical control, the minimum missions include an assessment of the robustness of the building and the safety of people. Although clients and insurance companies are not required to follow the technical advice produced by the control office, they strongly facilitate the insurability of construction projects and the limitation of ad‑ ditional insurance costs. To provide its opinion, the technical controller will carry out a risk assessment based on a comparison between the design proposed by the designers and the norms (or standards) and regulations (or codes). Norms and regulations should be distin‑ guished to avoid any confusion. Following the definition of Foliente (2000), on the one hand, regulations (or codes) are legal documents that set minimum require‑ ments, dependent on the context, that should be followed. On the other hand, stand‑ ards are technical documents representing guidance to attain these requirements. In France, norms are classified for insurance companies in two categories: tech‑ niques with standards approved by the Agency for the Quality of Construction (AQC) and other techniques, the insurability for the former being easier than for the latter. Currently, there are no standards approved by the AQC for load‑bearing earth‑building techniques in France. However, a good practices guide has been written by French professional organisations for those wishing to use rammed earth (Confédération de la construction en terre crue, 2018). This description of the French insurance context highlights the major role of the control officer and standards in obtaining insurance for the client. Challenges encountered associated with the use of a circular earth building This section will describe challenges related to the use of earth material that were encountered during the project. It will first introduce some elements of context for the design and the path towards the design of the building facade. Then, it will highlight how this choice of element challenged the design of the building through life cycle categories: resource, manufacturing, construction, and in‑use phase. The end of life will only be considered in the first part because no element related to it has been identified, which can be explained by the absence of a CE approach in the design of this building. Some elements of context for the design Stakeholders

In addition to the common stakeholders usually involved in this scale of build‑ ing (clients, architects, two structural engineer offices, thermal and environmen‑ tal engineers, and control officers), other ones were engaged in the design phase

188  Antoine Pelé‑Peltier and Jean Goizauskas (masons, researchers). Many stakeholders of the project, including control officers, architects, and structural engineers, had no or little knowledge of earth construc‑ tion and especially rammed earth, and earth construction more broadly. In order to compensate for the lack of knowledge about rammed earth within the design team, researchers specialising in earth construction and masons were involved to provide their expertise and know‑how. The early involvement of all these stakeholders in the design phase was con‑ sidered a key to the success of the project, in line with recommendations of the literature on the implementation of CE or sustainable buildings (Giesekam et al., 2016). It required significant coordination and collaboration work (Charef and Lu, 2021) and led to some tensions between stakeholders that will be described below. Standards and regulations

As already highlighted by many authors in other contexts, the lack of standards and regulations is seen as a barrier to the use of earth in construction (Ben‑Alon et al., 2020; Dorado et al., 2022; Kulshreshtha et al., 2020). To compensate for this lack of standards in this project, the control officer had to take or share responsi‑ bilities, including asking for a certified semi‑public centre of research to provide expert advice, through a specific procedure called ATEx (Appréciation Technique d’Expérimentation). The latter, being time‑consuming, and having no guarantee of success is considered as a risk by the clients. A path towards the design of a wall

The walls of the building as they currently are, made up of assembled rammed earth blocks, do not correspond to what had been specified by the team for the architectural competition. Several changes from the initial design have been made. Especially, the competition documents reveal various definitions of the element of wall, with different levels of precision, including “massive mineral elements with

Figure 9.3 Schematic representation of the different elements of wall considered during the design and construction of the building. (Author: Antoine Pelé‑Peltier).

The case study of an office building in France  189 load‑bearing timber pillars” or “load‑bearing lime‑adjuvanted rammed earth”. The insulation was considered because it appeared on the drawings and plans. Then, choices were made leading to the final element of the wall, which affected the level of circularity of the building (Figure 9.3). The circularity of the building is closely linked to the specification of the right materials, having the potential to be indefi‑ nitely reinjected in the loop without a loss (Antwi‑Afari et al., 2022). Adjuvantation (note 2)

While adjuvantation was considered by the structural designers before winning the competition, the idea was quickly abandoned for various reasons. The mason was reluctant to the adjuvantation of the earth, highlighting the risk that lime adjuvanta‑ tion could represent in the event of frost. Besides, most of the stakeholders agreed to say that the purpose of using adjuvantation was for reassuring others, thus rais‑ ing educational and cultural issues. The design team thus decided no adjuvantation in the material early in the design phase. However, during the construction phase, the control officer asked for justification for the absence of adjuvantation. The matter of adjuvantation might have created confusion and tension. Besides lime adjuvantation, structural designers also proposed a fibre admixture to potentially increase the tensile strength of rammed earth, to avoid any tensile in the arches that could lead to collapse. This proposition was also denied by the mason, highlighting the difficulty of execution for rammed earth, while the use of fibre is more common for the earth with high levels of clay and silt such as for cob (Morel et al., 2021). By choosing un‑adjuvanted rammed earth, designers increased the level of circularity in terms of material recyclability. Insulation

At first, insulation for the wall was planned. During the early design, one of the researchers suggested that using an insulation material was not necessary. This brought a debate until insulation was removed during the construction phase. Three main reasons explained the choice of avoiding insulation: (i) the risk of wa‑ ter accumulation in the wall due to the water sensitivity of the rammed earth com‑ pressive strength, (ii) the risk of slowing down the drying process of the walls, or (iii) also because adding insulation to the wall was complexifying the justification of the design towards the control officers. Insulation was restrained by targeted labels and specifications required by the planners, for which a derogation was required. Load‑bearing capacity of rammed earth

The load‑bearing capacity of rammed earth was discussed from the early design phase to the delivery of the building, taking different forms, explained in the fol‑ lowing subsection. Although it was probably the most important debate during the design phase, this chapter will not dwell on it in depth.

190  Antoine Pelé‑Peltier and Jean Goizauskas During the first design phase, two constructive solutions were suggested, cre‑ ating tension between the stakeholders, particularly between the two structural design offices and with the involvement of various expertise in earth construction, that the clients had to arbitrate. Finally, after long discussions, while a timber structure (see Figure 9.3) had been designed to sustain the façades for the compe‑ tition version of the building, it was decided to remove this structure before con‑ struction. Then, the load‑bearing capacity of rammed earth has been constantly reconsidered by the control officers until the delivery, through adding timber posts. Finally, after long negotiations, timber posts were manufactured but not implemented. Resource related challenges

Earth is a natural heterogeneous material challenging a construction industry that is more familiar with industrial standardised products (Harries et al., 2020), and, as written above, only a few guidelines exist in France when choosing this resource. Some specific steps were thus required during design for the sourcing of the ma‑ terial and for its characterisation, requiring good coordination and collaboration between stakeholders that were not used to working together. Materials sourcing

For this project, the excavated soil on the building site – situated in a former in‑ dustrial area – was too polluted for a construction use, making it necessary to find another material for the project. During the design phase, the task of material sourcing was delegated to the mason, who thus had to locate another construction site with an excavated soil suitable for the project. This material sourcing was subjected to different constraints related to logistic and earth validation. Logistic constraints include the need for a storage of the soil on‑site that would be avail‑ able during mason’s sourcing research, as diggers have short deadlines themselves. Good coordination and collaboration with diggers are thus required. Deadlines are also variable during the step of sourcing, as finding an appropriate earth depends on opportunities, as well as the deadlines to validate the selected earth are variable. Those delays need thus to be anticipated in the design phase. Earth validation methodology and selection criteria can be of various types according to the stakeholders. The mason who selected the earth had his own characterisation criteria. But for this project, the laboratory measures of the com‑ pressive strength of the rammed earth were major selection factors for engineers and control officers. Indeed, the amount of load, related in particular to the archi‑ tectural form, implied choosing an earth with a specific minimum compressive strength. As mentioned above, a maximum distance of 30 km from the exca‑ vation site to the construction site was required to obtain the BREEAM label for this building that was specifically difficult to achieve in an urban area with many polluted soils. Aesthetics was another selection criteria, in particular for the architects.

The case study of an office building in France  191 Characterisation

Once earth was previously selected by the masons and validated by the architects, various laboratory tests have been achieved for the project, including compressive strength assessment and hygrothermal testing of the earth. Different aims were related to this laboratory characterisation. The first was to structurally design the building. The compressive strength testing was useful for earth selection as explained above. Hence, two earths were tested in the laboratory and the one showing the highest compressive strength was selected. Then, con‑ sidering the water sensitivity of compressive strength (Bui et al., 2014; Champiré et al., 2016), it was measured at different water content. In addition to the hygro‑ thermal characterisation, these measures made it possible to follow the evolution of compressive strength during construction and use‑in phase and to assess the drying time of walls. Such monitoring was justified by the optimisation of the structure’s dimensioning in terms of loads. However, different problems were related to the laboratory characterisation and particularly to the representativity of lab testing compared with site construction. Indeed, there was a lack of procedure and data for scaling up lab results which led to multiple testing on big samples (element of a wall of 200 kg), which are costly and longer to perform due to drying time. Since, authors have established similitude relations to obtain representative results (Pelé‑Peltier et al., 2022). As the masons manufactured most of the laboratory samples during the project, this process also raised some challenges, including the necessity of good coordination and collaboration between masons and laboratories in terms of logistics but also in terms of data. Both the manufacturing water content of samples and the reference manufacturing water content on‑site were required to analyse laboratory testing. The definition of the latter was problematic due to the lack of suitable protocol for earth containing an important amount of large grains. Second, according to some stakeholders of the project, the characterisation helped to reassure the client and mostly the control officer. However, these lab test‑ ing did not meet all their needs for justification. Indeed, some lab procedures were lacking, for example, the assessment of rammed earth shrinkage. Another example is the justification of fire resistance, as no official report existed on fire resistance. Even though the design team believed fire resistance was not an issue for rammed earth, certified laboratory testing would have been required, which is costly and was not anticipated and thus off‑budget. To decrease fire resistance requirements, the design team and clients decided to change the programmatic typology of the building by restricting the access to the flat roof. Finally, the necessity for certain laboratory testing procedures was subject to debate between control officers and the design team (including researchers), such as the procedure to assess the joint between rammed earth blocks. While control officers requested the characterisa‑ tion, the design team considered it unnecessary, given the size of the blocks. These examples show the need for a clear agreement on the protocol to charac‑ terise rammed earth, according to the type of buildings, stated early in the design phase to avoid any unanticipated over‑cost.

192  Antoine Pelé‑Peltier and Jean Goizauskas Manufacturing/construction‑related challenges

As manufacturing, construction, and assembly happened on‑site for this project, these phases are analysed together in this case. Some issues related to the con‑ tractor’s capacity, implementation, and quality control will be described in this subsection. Contractor’s capacity

The lack of skilled professionals is usually cited in the literature as a barrier to a broader implementation of earth‑building materials and methods (Ben‑Alon et al., 2020). In this region of France and for this type of building, there was a lack of skilled professionals able to build this earth structure at the time of construction. Only two contractors responded to the tender, one of which was more expensive than the contractor involved early in the design phase. The latter was considered by many stakeholders as being the most qualified and capable of building this project. However, having only one contractor capable of pursuing the project represented a risk for the client. In this case, the contractor is a craft company that had low financial resilience given the building budget and that was not used to dealing with such large projects, which made it difficult to quantify the costs. On the other hand, the clients, unaccustomed to working with craft companies, did not first reconsider the terms of payment to factor in the financial risk for the contractor and his need to be paid in advance. One solution adopted to reassure the client about the financial resilience of the contractor was to bring together the various companies involved in the project (timber, foundation, and rammed earth companies). Those issues did not block the project but generated tensions between stake‑ holders that could have been avoided by a proper contractualisation between cli‑ ents and contractors, considering the problems of each. Implementation

Although the mode of implementation chosen for this project, i.e., on‑site pre‑­ manufacturing and assembly, has many advantages, including a good level of cir‑ cularity, easing quality control, and reducing costs, it was subjected to specific constraints. First, the period of feasibility of the construction excluded the period of freezing. The implementation had thus to occur between May and November. Second, as previously highlighted, two kinds of storage spaces were required, which raised difficulties in an urban area: a space for the storage of earth, about 300 m3, protected from impairments and bad weather to avoid soaking the earth, and another space for manufactured blocks. Agreements from the planner of the area made this storage possible. Finally, as mentioned above, the material’s drying process put a strain on the construction. It has been decided to allow for the deliv‑ ery of the building, only when the blocks achieved a sufficiently low water con‑ tent to ensure their compressive strength requirements. A collaborative monitoring

The case study of an office building in France  193 of the drying process between masons and structural engineering was thus put in place to allow the successive advancement and loading of rammed earth blocks (addition of the top row of blocks and addition of floors). Control of quality

In order to assess the drying process and the load capacity of rammed earth, a spe‑ cific quality control protocol has been created for this project. On‑site, the manu‑ facturing water content was measured for each block. The latter were then weighed to obtain the dry density and to verify if it was above the reference dry density. Some blocks were kept aside and successively weighed to follow their drying pro‑ cess by successive weighing. Besides those objectifying procedures, the masons performed self‑monitoring all along the manufacturing process. The aim of the quality control was diverse. First, it was recommended by the Eurocode 6 of masonry structure to justify the choice of safety factor applied on the compressive strength of rammed earth. Second, it was a way to reduce the risk for the control officer as no standards and norms exist for rammed earth to inform his risk analysis. Those procedures created tensions between masons and control officers of the project. While the control officer asked for objectification through engineering data analysis of the manufacturing process, the masons were concerned by a potential appropriation of their knowledge by engineers. Besides, the control officer did not trust the mason while the latter felt pressured by this permanent control. In‑use related challenges

Different challenges occurred during the design phase, related to the in‑use of the building, regarding erosion were raised in particular. Indeed, the surface appear‑ ance of rammed earth changes over time (Bui et al., 2009). This seemed to worry the client frightened by the possibility of falling pieces of earth at the foot of the vaults which would require cleaning and could affect the reputation of the build‑ ing. One solution adopted to decrease the risk of earth deposits was to brush the rammed earth walls, removing the first layer of fine earth which should have been removed by the weather. Another issue related to erosion was the treatment of the angle of the building at risk of breaking over time. To avoid this problem, the de‑ sign team decided to chamfer all the angles of the building. Moreover, in order to maintain the building, storage of earth on‑site for a time of ten years and contractu‑ ally agreed with the clients and buyers has been planned. Related to the quality control of this building, a contract for an inspection mis‑ sion has been signed with the contractor of the building. Besides, a contract for monitoring the residual water content of the rammed earth walls was also es‑ tablished, at the request of the control officer, with the thermal engineers of the project. Finally, end users must be warned of the specificities of the material and its water sensitivity in particular.

194  Antoine Pelé‑Peltier and Jean Goizauskas Conclusion As several studies have shown, designing and constructing with earth is a complex affair, posing challenges, and involving political changes. While some of these studies shed light on some of these challenges, we have sought to show that a case study offers a more detailed analysis, embodied in professional situations. Al‑ though this is a very specific case, we hypothesise that a detailed and circumstantial examination of the difficulties encountered in a construction project, in practice, can make it possible to anticipate the challenges encountered in future projects. The main limitation of a case study is the scope of its results. The study pre‑ sented in this chapter, thus insisted on the importance of situating the case study to circumvent these results. From the perspective of an analysis oriented towards a CE, this effort to situate consists in qualifying what type of circularity is at stake, in explaining why more virtuous options have been abandoned and how less virtuous options have been avoided. A qualitative framework is proposed in this chapter to identify the degrees of circularity, in the case of earth construction. The case study carried out in this chapter concerns an on‑site production method (and therefore not a standardised product in a factory), using material excavated a few kilometres from the construction site. This approach allows a high level of circularity but poses several constraints that were analysed. Due to its particular ar‑ chitectural typology (arches), its dimensions (three floors), and French insurability requirements, this project was also subject to significant socio‑technical justifica‑ tion constraints. Based on this context, several elements of the analysis may be of general inter‑ est for construction projects and make it possible to anticipate the particular con‑ straints linked to the use of a variable resource, echoing recommendations already made elsewhere in the CE studies. It seems crucial to maximise the presence of actors aware of the specificities of these materials from the first phases of the project (programming, first sketches) to make choices that anticipate the other phases. In this process of anticipation, the masonry company appears to be in the best position to anticipate the phases of searching for resources, manufacturing, and construction. In the French case, par‑ ticular attention must be paid to the choice of the control office. But more broadly, as the case study shows, it only takes one reluctant actor for the project to run into serious difficulties. However, trust between the actors in such building projects is rarely self‑­evident, especially in the absence of normative texts and standardised test protocols. It is therefore important that the various project stakeholders establish a clear protocol for resource validation, built element validation, and quality control as early as possible in the design phase. Finally, the case study shows the fundamental place of temporalities: soil search time temporal constraints for the storage of materials, stages of validation for the performances of construction systems (mechanical resistance, fire resistance, insu‑ lation), seasonality of the construction, the prefabrication and drying times of the materials.

The case study of an office building in France  195 In summary, a key to the success of such a project lies in the quality of the re‑ lationships between the project stakeholders, their collaboration, and coordination throughout the project, as is often the case in the building sector. In the last sec‑ tion, we have distinguished the challenges encountered throughout the project by “life cycle phase”. This analytical choice should not, however, lead one to believe that these phases are considered to be distinct, or that they should be treated in one order rather than another. On the contrary, it is precisely because they are so closely linked when working with local unprocessed material that the coordination constraints between actors are so acute. A number of the challenges encountered in this case also relate to difficulties that go beyond the project scale and concern the territorial scale (availability and competence of local companies) or the national scale (recognition of techniques standards by control and insurance companies, circulation of normative texts, etc.). Nevertheless, institutional actions at other scales must be based on these field realities. Note 1 In scientific literature, the word “stabilisation” is generally used to refer to cement or lime adjuvantation. However, the authors consider that it creates confusion by distin‑ guishing a “stabilised” and “unstabilized” form of earth material. In this chapter, the authors will prefer the word “adjuvantation” referring to the addition of an external material (commonly cement or lime) not being naturally present into the earth.

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Part 3

Fostering circular construction through digital transformation

10 Digitalising the deconstruction process Towards a circular economy for the construction industry Annie Guerriero, Elma Durmisevic, Calin Boje and Nico Mack Introduction The overall activity of the construction industry is responsible for a large amount of waste in European Union (EU). In 2020, Construction and Demolition Waste (CDW) accounted for 37% of the total waste generation in EU, meaning around 800 million tons of waste (Eurostat, 2020a). With the aim of reducing the environ‑ mental impact of the construction industry, the European Commission has identified CDW as a priority waste stream. The EU Waste Framework Directive (European Commission, 2008) aimed to reach a minimum of 70% by weight of CDW recycled by 2020. This objective has been reached in most of the EU countries, but in prac‑ tice, most of the CDW is unfortunately used for backfilling operations (especially for roads and motorways) and not for reuse, which remains below 1% (Bougrain & Doutreleau, 2022). This is of course not aligned with circularity principles, and the construction industry will have to profoundly change in the next years. Moreover, the greenhouse gas (GHG) emissions resulting from the activity of the construction industry are estimated at 5–12% of total national GHG emissions (European Commission, 2023). Optimal construction material usage could save 80% of those emissions (Hertwich et al., 2020). Thus, promoting circularity prin‑ ciples throughout the building life cycle across construction stakeholders is in line with reducing climate impacts. These development paths are envisaged to support a strategy towards a sustainable built environment and to reduce the use of resources in the future. The scarcity of resources has been at the origin of a new consideration of the materials in the construction industry reconnecting with the practices of the past, when materials from demolition were still used to construct new buildings (Ghyoot et al., 2018). The paradigm shift from demolition to deconstruction (i.e., careful dismantlement) begun some time ago but putting it into practice still faces many challenges (Allam & Nik‑Bakht, 2023). Throughout this chapter, we will highlight the difficulties and opportunities in terms of digitalising the deconstruction pro‑ cess, by looking at available technologies and how they represent a key component in helping the construction industry to adopt a circular supply chain of materials and building components. Finally, an innovative digital decision support system DOI: 10.1201/9781003450023-14

202  Annie Guerriero et al. for reuse strategy developed in the framework of the Interreg NWE Digital Decon‑ struction (Digital Deconstruction, 2023) as well as the result of its deployment on a pilot case in Luxembourg will be presented. Towards a circular economy As defined by Ellen MacArthur Foundation, “The essence of the circular economy lies in designing goods to facilitate disassembly and re‑use, and structuring busi‑ ness models so manufacturers can reap reward from collecting, refurbishing, re‑ manufacturing, or redistributing products they make” (cited in (Cheshire, 2021)). Concretely, circular economy (CE) implies to transform our “take‑make‑­ dispose” economy which leads to significant waste of resources, by changing the way we consider materials and resources in use and by thinking about how to retain their value as long as possible. The implementation of CE principles will lead to profound changes at multiple levels in the society, and for the construction indus‑ try, it means that there is an opportunity to reinvent itself. Within this section, we will develop why circularity is important within our mod‑ ern society and especially for the construction industry, with a focus on shifting from material consumerism to reuse and from demolition to deconstruction. We will also look at how available tools and frameworks will help us to make this transition. From demolition to deconstruction

Reusing materials and components was always common in the past, but our mod‑ ern society is now driven by convenient manufacturing of advanced composite materials at low prices, an increased level of living, new construction techniques, mechanised demolition, and strict building regulations. Consequently, it progres‑ sively became too expensive to maintain an activity of materials preservation and the construction industry started to generate a large source of waste and pollu‑ tion. During the last century, this has shifted our mindset, leading to unsustain‑ able practices in developed countries. Recent climate change events and scarcity of resources demand more responsibility and novel ways to assess existing building material stocks and reuse them accordingly. We can already notice a shift from demolition to deconstruction practices that will support the careful dismantlement of materials to avoid waste and encourage reuse (Bertino et al., 2021; Ellen Mac‑ Arthur Foundation, 2020). In practice, there are numerous reasons why the demoli‑ tion of buildings is sometimes necessary. Belli‑Riz et al. (2022) have identified the most important ones: – Technical reasons: Buildings must be demolished due to the risk of structural collapse. In many cases, some buildings have to be demolished as they no longer meet the current construction technical regulations (e.g., fire resistance, seismic resistance, etc.). – Economic reasons: The difference in costs (or investment) between reno‑ vation and new construction is a primary driver in the choice of demolition.

Digitalising the deconstruction process  203 When looking to achieve high energy performance and net‑zero designs, the costs involved can be considerable for renovation when compared to a new con‑ struction. The incentive to demolish therefore increases, at the risk of leaving behind significant demolition waste. – Functional reasons: The older buildings cannot always be adapted to new functions or usage, due to difficulties in reorganising interior spaces, and their connections. – Urban and land reasons: Increased urban density and land use push investors to maximise space and increase their profits. This leads to large old urban areas being demolished and replaced with new developments. – Symbolic reasons: Two opposite points of view are often debated: the pres‑ ervation of patrimony (1) and the modern developments (2). This is mostly due to the intrinsic architectural value of certain buildings, which is difficult to quantify. The reasons listed above highlight the complexity developers have to face when demolishing existing buildings. Because the buildings in the linear economy have not been designed for disassembly, the decision of demolition is really a point of no return. One cannot ignore anymore that the construction industry is a considerable source of waste and that a transition to a CE is more than urgent. At the end‑of‑life (EoL) of a building, any decision conducting to the demolition of a building should be motivated not only by economic but also environmental criteria, as demolition waste has a considerable impact on the environment. Circular economy in the construction industry

Within the EU, we can argue that the economy is principally linear when it comes to construction products, and a shift from a linear to a CE is a real challenge (Hei‑ sel & Rau‑Oberhuber, 2020). In the construction industry, the concept of CE relies on the use of resources, products, and materials as long as possible (Romnée & Vrijders, 2018). CE encourages the maintenance, repair, and reconditioning of ex‑ isting products and ultimately recycling of embedded materials, with a preference for upcycling. The construction industry is constantly developing new tools and processes to support predictive maintenance of buildings, which has extended the lifespan of products and equipment. One example is the pre‑demolition audit, which is re‑ quired to quantify generated waste and to support the first steps towards recycling processes. Figure 10.1 illustrates the transition from linear to CE and from demoli‑ tion to deconstruction. CDW generates multiple types of waste: mineral fractions (e.g., concrete, gyp‑ sum, bricks), wood, metal, and plastics but also hazardous materials like asbestos or lead. Most of the waste is landfilled, metal is the only exception as it has a posi‑ tive market value. In order to reach the objectives of the European Green Deal by 2050 and limit the impact of the construction industry on climate change, rethink‑ ing the construction industry with the CE principles is really urgent.

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Figure 10.1  From linear to circular economy in the construction industry.

For several years, researchers have been actively working on the reduction of CDW and the reuse potential of materials (e.g., (Durmisevic, 2019; Arora et al., 2020)). Progressively, the research community has started to think of a building as a material bank (e.g., (Rose & Stegemann, 2019)), and the city as a place for urban mining promoting resource conservation through reuse, recycling, and recovery of secondary resources from waste (e.g., (Arora et al., 2017)). When a building comes to the end of its service life, its constituent materials can be reused and regenerated into new products. The long‑term vision is to progress towards an urban landscape that will be modified and developed using a closed stock of materials. This implies profound societal and economic changes, but also a transformation of the design and architectural practices. Naturally, this will also require resilient cities. To speed up the transition from linear to circular, governments are addressing it in policy documents. The strategy defined by the Dutch government, for example, is sketched in Figure 10.2. This figure summarises the paradigm shift in valorising existing materials and building components and the three types of economy. In Charef et al. (2021), the authors distinguished these three types of economy and their underlying concepts in the construction domain: – Linear economy implies a design for construction excluding the consideration of the end of life during the design phase, meaning that the demolition of build‑ ings is at the origin of a lot of waste.

Digitalising the deconstruction process  205

Figure 10.2 Dutch strategy: From Linear to circular economy (Figure elaborated based on (Government of the Netherlands, 2015)).

– Reuse economy implies a Design for Disassembly, transformable structures, etc. that will support the reuse of non‑recyclable products, remanufacturing, and recycling process, and contribute to reducing waste during the deconstruction stage. – Circular economy relies on a closed‑loop reuse and recycling, a design out of waste or with reclaimed materials, etc. in which there is no raw material de‑ pletion for new construction and no waste anymore at the end‑of‑life of the building. In the Dutch strategy, the government’s national goal is to develop a CE in the Netherlands by 2050 and to achieve a 50% reduction in the use of primary raw materials by 2030. This should be achieved by designing products and buildings in such a way that they can be reused with a minimum loss of value and without harmful emissions to the environment (Government of the Netherlands, 2015). To keep with the European agreements, the Dutch government set up the following ambition: By 2050, the construction industry will be organized in such a way, with re‑ spect to the design, development, operation, management, and disassembly of buildings, as to ensure the sustainable construction, use, reuse, mainte‑ nance, and dismantling of these objects. Sustainable materials will be used in the construction process, and designs will be geared to the dynamic wishes of the users. (Government of the Netherlands, 2015)

206  Annie Guerriero et al. To implement such kind of mid/long‑term vision, extensive efforts will be re‑ quired. Supporting CE strategies with a focus on reuse and high‑quality recycling (also called upcycling) of building elements and materials will rely on three major axes of effort to be promoted along the value chain (European Commission, 2020): – Axis 1: Durability. This axis encourages a long‑term focus on the design life of major building elements. – Axis 2: Adaptability. This axis focuses on the extension of the service life of the building as a whole. – Axis 3: Reduce waste and facilitate high‑quality waste management. This axis considers the reduction of waste and the valorisation of building elements fol‑ lowing deconstruction through reuse, or high‑quality recycling. Factors limiting reuse

In general, even if construction stakeholders are volunteers and active in developing CE principles in their architectural projects, they are facing several dilemmas: “structural resistance versus easy to disassemble, longevity versus flexibility, simple versus com‑ posite products, renovations versus new build, etc.” (European Commission, 2020). At the building EoL, there are multiple factors influencing the material recovery during the deconstruction process which we summarise below (European Commis‑ sion, 2012), (Durmisevic et al., 2021), (Heinrich & Lang, 2019), (Cheshire, 2021), (Belli‑Riz et al., 2022): – Safety: Deconstruction of the building may pose a safety risk for workers and generate a need for specific insurance. The cost of these insurances may moreo‑ ver contribute to an increase in the deconstruction costs. – Time: The time required for the deconstruction of a building is more manual and can consequently be considerably longer than for a traditional demolition, this implies adapting the schedule considering this constraint. – Economic feasibility: As the time needed to carefully deconstruct building com‑ ponents is much longer than in a traditional demolition, this implies stretching schedules and supporting higher costs. To be a viable option, these extra costs of deconstruction should be compensated by the gain regarding the sale of materi‑ als, and in ideal conditions, it should generate profit. Moreover, some materials like metals have fluctuating prices. This complexifies the analysis of scenarios for deconstruction. – Market acceptance: Currently, the reuse of materials is not a common practice in the EU, and a change of mind in society needs to take place in order to increase the use of reclaimed products in new design projects. – Space: Materials collected during the deconstruction of the building have to be separated and sorted on site. When there is limited space available for sorting on site, it requires particularly precise planning. – Location: The presence of recycling facilities, the logistic platform for reus‑ ing materials, and well reconditioning of materials in the surroundings of the

Digitalising the deconstruction process  207

– –

– –

deconstruction site is key to support the recovery of materials, as well as to limit transportation that could have a considerable environmental impact. Weather conditions: Some techniques may require specific weather conditions which are not compatible with the schedule. Lack of technical knowledge. Deconstruction projects are facing appropriate technical knowledge and information on the feasibility and actual implementa‑ tion procedure of the deconstruction process. This requires the designers to be more flexible. Lack of information about the material composition of existing buildings: This lack of information about materials composing a building and their value limits the analysis of the deconstruction scenarios and their actual reuse opportunities. Mismatch between supply and demand: There is a mismatch between supply and demand in terms of quantity and quality of recovered materials. Moreover, there is a risk that the elements coming from deconstruction need to be stored for a long period of time before they are reused in a new architectural project. Conse‑ quently, the organisation of the market is crucial to support the practice of reuse.

Moreover, when considering the reuse of building elements in a new architectural pro‑ ject, the design team faces other major barriers. In addition to economic constraints which are quite common, other types of barriers appear during the design process ((Addis, 2006), (Charef et al., 2021), (Gorgolewski, 2008), (Adabre et al., 2022)): – Commitment of stakeholders: The client and the whole project team have to be convinced by the approach and really involved in the (decision) process regard‑ ing reuse, reclaim, and recycling. – Design and procurement process. The process for reusing building materials/ components is different from “normal” practice. – Lack of understanding of the global approach. One can see a lack of aware‑ ness of reuse and recycling potentials in the sustainable and deconstruction approaches. – Lack of trust: There is a lack of trust in the reclaimed products, notably due to the fact that the construction industry relies on the idea that materials coming from a plant are reliable and that there is no real other alternative. The creation of certifications could contribute to reinforcing trust in these types of product. – Bad perception of reclaimed products: The use of reclaimed products in archi‑ tectural projects suffers from a bad image as, in general, people think that using reclaimed products impact negatively the aesthetics of the building. – Institutional and regulatory barriers: There is a lack of circular requirements in public procurement and in general, a lack of regulations on CE. The literature has highlighted that the construction industry is facing a lot of barri‑ ers, but we can also observe that national strategies are progressively implemented to reduce CDW. In addition, more and more research works are developed on the topics of CE for the construction industry meaning that the process of transforma‑ tion towards a circular design has already started. This transformation will imply a

208  Annie Guerriero et al. systemic approach relying on technological interventions but also on institutional, organisational, social and behavioural changes for sustainable development (Ada‑ bre et al., 2022). Available tools and frameworks for circularity

When looking at the available tools for building design, the focus has already started to shift from a linear process to a more circular one, with the mandatory inclusion of various sustainability frameworks for new and renovated buildings. Frameworks such as LEED, BREAM, and more recently LEVEL(s) in the EU context, are usually part of the design process. This requires specialised expertise and includes the aggregation of multiple aspects, covering calculation methods on the use of materials, water and energy, the impacts on human wellbeing, as well as reuse. LEED, LEVEL(s), and BREEAM include life cycle assessment (LCA) as part of the process, while BIM tools and platforms already facilitate some degree of integration with LCA tools. Several standards exist on LCA, starting from the ISO 14040 series on the ge‑ neric process, and the more recent ISO 21931 on buildings and construction works, or the EN 15804 on environmental product declarations for construction products. Their application in practice has led to several tools and technical integrations with BIM. However, the estimation of environmental effects using LCA methods is al‑ ways uncertain (often complemented by uncertainty analysis), due to many fac‑ tors which are hard to determine during the deconstruction phase. Additionally, although the recent ISO 21931 includes guidance on deconstruction and demolition impacts calculation, the effects of waste processing and disposal are considered out of scope. Thus, deconstruction practitioners cannot rely on LCA alone to make a decision as it has been developed in a linear economy and needs to be adjusted according to the CE principles. They need additional tools to estimate more real‑ istically if components can be reused, and if not, what are the disposal methods. The management of data and properties associated with materials and building components is essential when thinking about reuse and integration of the com‑ ponent in a new architectural project, especially because buildings must conform to a lot of regulations and standards. Today, BIM models contain a large amount of information about components and materials (e.g., size and performance), but old buildings without BIM lack this level of information and are usually limited to drawings. The process of collecting information is consequently fastidious and practitioners lack tools for reuse strategy analysis. Therefore, we consider that the development of dedicated digital solutions is a key component for the success of the deployment of CE strategies. Method We have highlighted that one of the limits of the CE in the construction industry is the lack of information regarding the materials and components composing the buildings that have to be demolished. A substantial effort is required to collect

Digitalising the deconstruction process  209

Figure 10.3  Research method.

these data and to define the reuse strategy. We formulate the hypothesis that digital technologies could support this process of data collection and analysis and make it more efficient. With detailed information, better decisions regarding reuse could be made, and this finally should help to reduce the volume of demolition waste. As described in Figure 10.3, first, we have conducted a literature review and an inventory of the existing solutions for the CE in the construction industry. Then, we have defined a collaboration process for the definition of reuse strategies. This process has been implemented in a platform called the Digital Deconstruction inte‑ grated platform. During the design process, both the process and the platform have been regularly presented to end‑users (i.e., researchers and professionals) during workshops in order to collect their feedback and refine it accordingly. After its development, the platform has been experimented on several pilot cases. In this book chapter, we will present the results of the deployment of the platform on the deconstruction of the Ettelbruck train station in Luxembourg. This experimentation has allowed us to validate the approach and assess the impact of the deconstruction process. Emerging technologies for deconstruction Over the course of the past two decades, the construction industry has gone through a major digital transformation, mostly driven by the adoption of Building Infor‑ mation Modelling (BIM). Knowing that data about the building materials and components can be leveraged to support the decision about reuse strategy and to contribute to CE principles, the paradigm of buildings as banks of materials (De‑ backer & Manshoven, 2016) can be implemented in a digitalised way. In this sec‑ tion, we will address the inventory of the type of digital solutions which currently exist to gather and transform data, and which can be used to support the process of deconstruction as a whole. We define the deconstruction process in several steps in Figure 10.4. Collect‑ ing data (1) about the building to be deconstructed is the first step. Plans, draw‑ ings, and technical documentation are needed to identify the building composition. The creation of an inventory of the building components (2) is the second step of the deconstruction process. This is currently subject to manual processes by

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Figure 10.4 Steps required for the implementation of a reuse strategy on a building to be deconstructed.

experts, based on a visual inspection and manual data entry, which is costly and time‑consuming. If toxic substances are identified, hazard assessments may also be required, prolonging the process. The collected data needs to be considered for an adequate reuse strategy (3) of components and materials with high reuse po‑ tential. Then the professionals plan the deconstruction stage (4) with this in mind, dismantling high‑value components first, ensuring that they suffer the least dam‑ age possible. The usual deconstruction or demolition of low‑potential components resumes (5). Recovered components from the site, are potentially stored (6b) and/ or reconditioned (6c) in a logistics platform until they are resold to a third party (6a) and ultimately reused (7) in new buildings or infrastructures. In the current professional practice, this process is mostly manual and largely paper-based. The digitalisation of the deconstruction process is quite new, but we can see that more and more research works and commercial solutions address this question. The emerging technologies for deconstruction can be divided into four distinct categories: • • • •

Reality capture technologies, Materials inventory creation technologies, Deconstruction and waste sorting technologies, Marketplace technologies.

The following sections will go into further details for each of these categories. Reality data capture technologies

Collecting data about the building is the first step of the Digital Deconstruction process. Document management systems are widely adopted in the AEC sector and used to centralise and share data about the deconstruction process. This process is

Digitalising the deconstruction process  211 complemented by other technologies which automate data collection. 3D scanning and photogrammetry are widely used on construction sites today and are emerging for deconstruction sites as well. A 3D scanner is a non‑contact, non‑destructive digital device that uses a light line/laser to accurately capture the shape of a physical object into Computer‑­ Aided Design (CAD) data. It generates a point cloud or a set of data points in a coordinate system that accurately depicts a physical object’s size and shape. (Haleem et al., 2022) This is a relatively fast process, and convenient in capturing detailed photographs and the geometry of the building shell, as well as interior spaces. The main limita‑ tion is that the laser cannot penetrate surfaces, thus the interior of components can‑ not be captured. Nonetheless, it is a convenient way to scan and create the points of interest around a deconstruction site and use them to create an inventory from a point cloud directly. An inventory of construction components and materials requires a certain level of information, with a predefined structure (e.g., pictures, location data, and prop‑ erties of the objects). The resulting 3D point cloud lacks providing such semantic information for all the scanned building components. This means that the inter‑ pretation is required either by a human observer or by modern image processing AI (artificial intelligence) techniques such as computer vision, to identify shapes and discern specific objects. When employing 3D point clouds, deconstruction engineers have access to a very detailed view of the building in which they can navigate, take measurements of elements, observe the real context, annotate, and share information. These simple features are an essential step to begin digitalising the deconstruction site and are very close to a BIM approach where solutions of scan‑to‑BIM can fill the gap (Adán et al., 2018). Once building objects are identi‑ fied, these can be adapted to be BIM‑compatible. Coupling this with BIM is termed a Scan‑to‑BIM process (Volk et al., 2014), whereby scan data is converted to se‑ mantically rich BIM objects. If 3D point clouds and photogrammetry are more and more commonly used in the design, construction, operation, and maintenance phases (Wong et al., 2018), the use of the 3D scan in the context of deconstructing a building is still relatively new. Nevertheless, this has been gaining interest from deconstruction experts who need more reliable 3D site information to support the decision process regarding reuse strategies. Materials inventory creation technologies

Several commercial web‑based platforms are available today, which support data consolidation and centralisation about a materials and deconstruction project. The inventory creation process involves creating lists of items (components or materi‑ als), which compose the building. The presence of platforms such as Cirdax (2023) or Madaster (2023) signals that the deconstruction actors are already engaged

212  Annie Guerriero et al. in procuring digitalised ways of working. Such platforms also provide so‑called material passports on deconstructed components further encouraging the reuse of materials. This benefits the end‑user by providing more transparent product infor‑ mation but is also envisaged as a technical link with the design of new buildings and material marketplaces. In general, materials passports are a digital dataset of a specific building, providing a detailed inventory of all the materials, components and products used in a building, as well as detailed information about quantities, qualities, dimensions, and locations of all materials. (Heisel & Rau‑Oberhuber, 2020) In some applications (e.g., Cirdax, 2023), materials passport creation is coupled with blockchain technology in order to record ownership, enhance information transparency, and reinforce trust, which are key when considering the reuse of ma‑ terials/building components (Namburu, 2021; Wu et al., 2023). As a step further in developments, some applications of inventory include func‑ tionalities for automatically populating an inventory from BIM datasets, with the addition of user‑friendly dashboards including various kinds of indicators (e.g., CO2 impacts, material value, etc.). Other applications (such as (Cycle Up, 2023)) ensure the users add data on the digital marketplaces. They can describe the building components for sale and add related data on the platform using a mobile application. The connection between offer and supply is supported by the digital platform itself, and the process of popu‑ lating the database is done collectively by different kinds of resellers (i.e., both in‑ dividuals and professional resellers), which contributes to enlarging the offer while reducing the effort of data collection. The inventory creation process of the above‑mentioned tools is still highly man‑ ual, with different views on what types of data should be gathered by deconstruc‑ tion experts. Research projects such as the Interreg NWE FCRBE (FCRBE, 2021) have investigated this workflow and started to propose a common data collection method and data structure (i.e., xls form) for site capture data in a harmonised way. This represents the first step in achieving some interoperability between commer‑ cial tools and the needs of deconstruction supply chain actors. More disruptive research works consider the potential of AI‑supported materi‑ als inventory creation. Vrijders et al. (2022) have tested computer vision using AI‑based object detection system for automatic material inventory generation. This technology seems very promising and should facilitate and accelerate the mate‑ rial data collection process, which is crucial to maximise the reclaimed materials ratio. Other research works have focused on the use of AI to develop a deep learn‑ ing model for predicting the amount of salvaged waste resulting from demolitions (Akanbi et al., 2020). These are some examples of automatic data collection and tracking of actual reused materials, but recent research has addressed topics such as Design for Disassembly that consists of pre‑emptive measures to avoid waste creation in the first place (Oluleye et al., 2023).

Digitalising the deconstruction process  213 Furthermore, we can see a lot of research works addressing BIM as support for constituting the materials inventory, and more generally supporting the whole process of deconstruction. BIM has progressively been adopted by the sector and its use covers the whole lifecycle of the building and, more recently, the EoL stage. The model proposed by Charef et al. (2019) introduced a BIM‑based theoretical framework that includes the PIM (Project Information Model), the AIM (Asset Information Model), and the DIM (Deconstruction/Dismantling/Decommission‑ ing Information Model). Extending on this research work, the author proposes to add an 8th dimension of BIM where “the 8D enables the design team to simulate the deconstruction and its related costs, provides support for decision‑making for component selection, assess the sustainability and even the circularity of the asset during the design process” (Charef, 2022). This emphasises the role and potential of BIM‑based tools for deconstruction in the near future. Three major roles of BIM when supporting EoL practices were identified by (van den Berg et al., 2021): 1 Supporting the analysis of existing conditions, 2 Labelling of reusable elements, 3 Supporting deconstruction planning (i.e., 4D BIM). Another example of BIM‑supported deconstruction is the work done by (Durmise‑ vic, 2006) where BIM is used as an input to assess the feasibility of deconstruct‑ ing buildings. The method has been tested and verified during the H2020 BAMB research project. The process was next adapted into a tool and the concept of “Re‑ versible BIM (RBIM)” has been tested on pilot buildings. The tool is based on Au‑ todesk Revit and Dynamo, and it enables a digital assessment of the reuse potential and reuse options of building materials. This is achieved by assessing technical and physical dependencies between building products and their constituent materials. This gives an indication of the difficulty of dismantling building components. Deconstruction and waste sorting technologies

Several technologies are dedicated to support the deconstruction stage. This sec‑ tion first introduces the solution for deconstruction based on 4D BIM and then, elaborates on robotics‑based solutions. Solution for deconstruction scheduling/4D BIM

We have seen in the previous section the potential of BIM for supporting the stage of materials inventory. As an extension of BIM for scheduling use, 4D BIM “brings in a virtual representation of another dimension (time), which means that all as‑ pects of the BIM process (graphical models, management, costs, resources, safety issues, etc.) can now be represented, viewed and analysed from a temporal perspec‑ tive” (Boje et al., 2020). 4D BIM can of course be used to support the scheduling of the deconstruction process (van den Berg et al., 2021), or for the deconstruction process simulation and visualisation of several scenarios (Marzouk et al., 2019) but

214  Annie Guerriero et al. some research works go further and propose algorithms to streamline estimation and visual planning of construction waste for on‑site reuse, and off‑site recycling (Guerra et al., 2020). In such a context, 4D BIM use allows considering on‑site waste reuse opportunities in advance and improving resource recovery while mini‑ mising waste disposal in landfills. Robotics

Although the construction industry relies on manual operation, there are many developments towards more automatic machinery and robotics, with some appli‑ cations in the deconstruction use case (Detert et al., 2017). The benefits of using robots in the construction sector from a CE perspective have been highlighted by (Setaki & van Timmeren, 2022). Use cases usually involve the use of robots for supporting tasks with high risk for workers such as asbestos removal (Detert et al., 2017), intervention on contaminated sites, or involvement in direct reno‑ vation (Cruz‑Ramírez et al., 2010) and dismantlement of buildings (Lublasser et al., 2017). In this last case, the intention is to support automated deconstruc‑ tion strategies that will guarantee a high degree of material integrity for effec‑ tive material recycling. Supporting the sorting of waste on‑site and recycling is another topic addressed in the scientific literature (Wang et  al., 2020; Chen et al., 2022). In the near future, robotics could be a new option to disassemble and prepare materials and components for reuse, tackling some of the limitations of deconstruction regarding the costs of dismantlement. However, currently, em‑ ploying robots for deconstruction remains still little tested and reserved for ex‑ perimental activities. Marketplaces technologies

Most of the digital marketplaces dedicated to reclaimed materials draw their inspi‑ ration from widely popular online platforms which permit the exchange of goods (e.g., Ebay), but most of them are associated with dedicated physical marketplaces where all the materials and products are stored. As predicted in (Addis, 2006), the number of marketplaces has considerably increased these last years (see Opalis, 2023) to access to a list of resellers of reclaimed materials. The materials we find on these marketplaces depend on several factors (Addis, 2006; Bougrain & Doutre‑ leau, 2022): (1) construction practices and assemblies used in the past, (2) durabil‑ ity of the buildings and components, (3) current methods for deconstruction, (4) current demand for reclaimed building materials, (5) national specificities in terms of construction techniques (e.g., use of bricks in Belgium and stones in France). We can imagine that the offer of materials will be richer and more diverse in the next years if we consider that practices will change towards sustainable and circular design. Buildings that are designed to facilitate the dismantlement are extremely rare at the moment, but we can consider that innovative Design for Disassembly practices and new standards (e.g., ISO 20887:2020) will contribute to support and dynamise the market of reuse and recycling (Addis, 2006).

Digitalising the deconstruction process  215 The last decade brought several digital platforms for marketing materials and components coming from deconstruction sites, some of them supported by AEC actors motivated by the idea of reducing the volume of waste in the industry (e.g., RotorDC, 2023). Some are dedicated to a specific type of product such as antiques and reclaimed building materials (e.g., Salvo Ltd., 2023), while others are dedicated to new materials from sites or manufacturing surpluses (e.g., Stock Pro, 2023). Some of them associate circular, social, and solidarity economies, hiring people involved in a project of socio‑professional reintegration (e.g., Cor‑ nermat, 2023). The existing digital marketplaces offer convenient functionalities to their users, such as (1) filtered product searches, (2) detailed product descriptions (including photos, locations, availabilities, etc.), (3) purchase baskets, (4) order tracking and history, etc. Most of the marketplaces dedicated to the reuse of construction mate‑ rials only allow people to access data from their catalogue, but some of them also allow the users to add materials to their marketplace by using a mobile application allowing them to describe a building product (e.g., Cycle Up, 2023) and offering the possibility to resell some building materials/components they own. Some platforms (e.g., Cycle Up, 2023) have also addressed the question of lack of trust in the reclaimed product and propose insurance to cover the warranty of the products and/or the damages that could occur due to the defect of the product. That is something that will clearly contribute to a larger adoption of reclaimed products in the construction industry. Finally, some other platforms have contributed to federating other marketplaces offering centralised access to thousands of products present on the partner mar‑ ketplaces and contributing to linking offer and supply (e.g., Upcyclea/Noah, (Up Cyclea, 2023). As a summary, Table 10.1 below presents the technologies, their use, the step of the process their cover, and their expected use by the end‑users. We can see that if the technologies are initially dedicated to one step towards the reuse strategy (see Figure 10.4), some of them have started to extend their core business (e.g., materi‑ als inventory applications have started to propose a dashboard to support the reuse strategy or generates material passports to support the resale stage). Additionally, BIM (and derived Reversible BIM (RBIM) and 4D BIM) appears as a central tech‑ nology covering a lot of steps of the process. According to the deconstruction project and its complexity, the roles of the actors can vary. Nevertheless, the table presents an overview of the common situations. Depending on the context, owners, architects, engineers, deconstruction experts, contractors, and reclamation dealers are key actors in the creation of the materials inventory. Most of the existing applications for materials inventory do not require a high level of expertise/technological maturity to be used. But other technologies (e.g., 3D Scan, RBIM, robotics) require involving experts with specific skills. The different technologies described in the above sections are the sources of informa‑ tion allowing us to better assess the reuse potential of building components and to reduce waste on the deconstruction site. These technologies will generate useful in‑ puts for reuse scenario analysis. The potential buyers would be able to access a lot

Table 10.1  Summary of the existing digital solutions for supporting the deconstruction process

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Digitalising the deconstruction process  217 of data about building components including 3D Scan, BIM model, and material passport that will contribute to reinforcing trust in the materials to be reused. This should encourage the expansion of circular practices in the construction sector.

Results: proposal of collaborative process and an integrated platform The study about existing solutions for supporting CE and reuse in construction has highlighted the diversity of existing solutions for supporting CE in the construc‑ tion industry, but also the need for integrating these technologies in order to cover the whole process for decision‑making regarding the reuse strategy. The Interreg NWE Digital Deconstruction (DDC) project aims at developing an innovative digi‑ tal decision support system that integrates the following technologies: 3D scan‑ ning, BIM, a digital materials and buildings database, and blockchain technology in order to help to define the most sustainable and economical deconstruction and reuse strategy for buildings. These technologies and the integrated platform have been tested on pilot projects. This section will describe the collaborative process supported by the application, as well as its functional scope. Collaborative process supported by the DDC integrated platform

As seen previously, regarding the reuse strategy, several actors are involved in the data collection and the decision‑making process. Figure 10.5 illustrates the collabora‑ tive process that is supported by the DDC integrated platform. First, the owner must upload existing documentation on the platform. Then, the scan expert makes a 3D scan of the building and shares it on the platform. Later, this 3D scan is used by BIM experts to create the BIM of the building, and finally to provide RBIM and related calculations. All data created is also shared on the platform. In parallel, the inventory expert can collect material data and generate material passports by using its dedicated blockchain‑based service. All data is shared on the platform so that the owner can consult the data as well as consolidate indicators inside a dashboard, and work on the best reuse scenario. At the end of the process, the owner can consult the final figures. During the deconstruction of the buildings, workers can access information on‑site, such as dismantlement advice that will allow them to prevent building components with high reuse potential from being damaged during the deconstruction stage. Buy‑ ers can then search for materials to be reused in another architectural project. Concept of the DDC integrated platform

As seen earlier, a lot of digital tools can currently support the definition of a reuse strategy. Nevertheless, these tools are very segmented, and they do not cover by themselves all the pieces of information required for studying the different options for reuse, that is the reason why we have developed an integrated platform combin‑ ing 3D scan, Reversible BIM, material database, and Blockchain technology.

218  Annie Guerriero et al.

Figure 10.5  Collaborative process supported by the DDC integrated platform.

Digitalising the deconstruction process  219

Figure 10.6  Concept of the DDC Platform.

The Digital Deconstruction (DDC) integrated platform is an innovative digital deci‑ sion support system aiming at defining the most sustainable and economical decon‑ struction and reuse strategy for buildings that will be deconstructed. The platform is based on a conceptual architecture that is modular and comprises various inde‑ pendent technical modules (TM1‑4) into an interoperable system (see Figure 10.6): 1 Scan‑to‑BIM: This process includes building a 3D scan technique (TM1) which provides 3D point clouds and photo recordings (using photogrammetry). AI al‑ gorithms are also deployed to automatically detect some of the building materi‑ als and components. Points of Interest (POI) extended with materials properties are provided to the platform. The post‑processed scans are used as input for the creation of an as‑built BIM. 2 Reversible BIM: This process is initiated by a scan‑to‑BIM phase. Then, the geometric assets are used for a Digital Reversibility Assessment (DRA) sup‑ ported by TM2. This step provides the platform with an IFC model, materials inventory, and indication of the reuse potential of the materials/components. 3 Asset catalogue creation: This process delivers the list of digital assets describ‑ ing all the components to be deconstructed and reused by using the 3D scan’s POI and BIM/RBIM inputs. This process is supported by TM3. 4 Environmental and economic assessment: This process enriches the data for material/components that have high reuse potential. The digital assets are en‑ riched with material/components‑related data (e.g., technical information, com‑ position, trademark, etc.), and environmental and economic data are provided to support the decision‑making process. Products with a high reuse potential are intended to be advertised for sale on external digital marketplaces for construc‑ tion materials. This connection with marketplaces is out of the scope of the DDC project but has been considered since the beginning of the design of the

220  Annie Guerriero et al. DDC integrated platform and is key to supporting the economic viability of the reuse strategy. 5 Blockchain‑based ownership tracking: TM4 is all about reinforcing transpar‑ ency regarding ownership of the digital assets and accountability regarding the quality and accuracy of the attached material passport. The process relies on smart contracts to achieve this. When using the DDC platform, after logging into the Web frontend of the platform, the user has access to the various aspects of the deconstruction project of interest (Figure 10.7): – Details: The Details tab gathers all administrative data pertaining to the de‑ construction project, like name, description, street address, deconstruction start date, and contact person. – Participants: If the user has Project Manager credentials, the Participants tab allows him to invite other platform users to either passively consult (Guest) or actively contribute (Contributor) to the managed construction project. – Locations: The spatial structure of the deconstruction project can be captured in the Locations tab. GPS coordinates can be attached if desired and visualised on a map. – Documentation: Documents and files (e.g., plans, technical reports) can be at‑ tached to the deconstruction project in the Documentation tab. If the building(s) taxonomy was previously captured in the Locations tab, documents, and files can be attached to the respective level (site, building, floor, and space) of the projects’ building(s). – 3D Scan: In case a 3D Scan of the building(s) to be deconstructed is available, the 3D Scan tab gives the connected user the possibility to explore the 3D Scan

Figure 10.7 Filtering of timber wood load‑bearing elements with a high Reuse Potential (in green) in the Digital Deconstruction Platform.

Digitalising the deconstruction process  221 and the potential points of interest identified during the scanning process. Geo‑ metric data extracted from the 3D scan (point clouds and panoramic pictures) is used to initialise the inventory of the building. Computer vision automati‑ cally identifies and geolocates assets of interest (e.g., doors, windows, light fixtures, etc.) thus enriching the inventory and the Reverse BIM model of the building. – Reversible BIM: An IFC file of the building to be deconstructed can be up‑ loaded and visualised in the Reversible BIM tab. The full potential of this tab stems from its close integration with data from the Digital Reversibility Assess‑ ment (DRA) tool, an external expert system. The DRA is a digital application for the assessment of reversibility and disassembly of buildings and building products resulting from calculations of the reuse potential of building products and materials. At the same time, RBIM stores and manages data about build‑ ing materials, life cycle, functions, dimensions, volume, embodied carbon, and reuse potential in a BIM environment. This enables micro and macro analyses of the circular capacity of the building and its material and supports the analysis of reuse scenarios. An Inventory File of all the analysed components (IFC Ele‑ ments) with their respective metadata from the DRA can then be uploaded to the platform in the Inventory tab. – Inventory: The Inventory tab allows users to browse the previously imported inventory. Multi‑criteria filters allow narrowing down the list of inventory ele‑ ments shown. Selecting elements of interest will highlight and colourise the respective elements in the BIM model shown in the Reversible BIM tab based on their respective reuse potential. Shuttling between both tabs enables the user to quickly identify and locate elements and components with a high reuse potential. – Dashboard: A dashboard tab allows the user to access indicators about environ‑ mental and economic criteria to support the collective decision‑making process regarding the reuse strategy. Initial validation

In order to validate the general concept of the process and the platform, several meetings at regional and international levels have been organised in the frame‑ work of the Digital Deconstruction project. These meetings have allowed us to present both the process and the concept of the platform before the develop‑ ment phase of the prototype to a panel composed of professionals and research‑ ers mainly coming from France, Belgium, the Netherlands, and Luxembourg. Mock‑ups of the platform and its functionalities have also been designed and pre‑ sented to this panel and have served as a basis for discussion to refine the scope of the Digital Deconstruction integrated platform, and to collaboratively sketch the major functionalities required for supporting the analysis of reuse strategies. After these initial validation steps, a prototype has been developed and experi‑ mented on several pilot cases. The following section elaborates on a case study in Luxembourg.

222  Annie Guerriero et al. A case study: the deconstruction of a train station in Ettelbruck Presentation of the building

CE is a huge concern in Luxembourg, especially since the last decade. The law of 21 March 2012 (Legilux, 2012), and its recent modification in 2022 (Stradalex, 2022) define the obligations for waste management with the aim to limit waste when demolishing buildings. The law states that an inventory must be done to identify the various materials composing the building and to support the sorting and recycling of waste. Materials containing hazardous substances must be treated separately in order to avoid the contamination of the non‑contaminated waste. Re‑ use and preparation to reuse are encouraged. In our pilot case, the strategy was to maximise the reuse of materials coming from the deconstruction of a building in Luxembourg: Ettelbruck’s train station (see Figures 10.8 and 10.9). It was an old building constructed in 1862, which was

Figure 10.8  View of the platform.

Figure 10.9  Facade of the Ettelbruck’s train station (LU).

Digitalising the deconstruction process  223 the property of the Luxembourg National Railway Company. The building was de‑ constructed in 2022, making room for a new building supporting the strategy of the multimodal exchange hub of the Ettelbruck’s station in order to reinforce mobility and development in the north of the country. Reuse scenario analysis

In order to support the data collection about the composition of the building, the building was scanned. Then, a Reversible BIM was made, and it enabled the au‑ tomated digital assessment of the reuse potential of building elements/products based on the methodology developed by Durmisevic (2006). This was done by analysing for example the type of connections, number of relations between build‑ ing elements/products, disassembly sequences, remaining life cycle, etc. The more effort is needed to recover an element/product, the lower the reuse potential score will be. This effort reflects the time needed for the recovery process, but also the complexity of the process. This is represented in RBIM by the Reuse potential score which is a value from 0.1 to 0.9, and which is visualised with a colour code from red to green. Reuse potential score is associated with a reuse option for an element/product as listed here: 0.9: Direct reuse, 0.7‑0.9: Reuse by minor repair, 0.5‑0.6: Reuse by major repair, 0.4: Remanufacture, 0.3: Mono‑material Recycle, 0.2: Downcycle, 0.1: Waste. This RBIM methodology has been used on Ettelbruck’s project to identify the reuse potential of elements and associated information that reflects the ease of element recovery and the potential environmental impact of its reuse con‑ sidering the embodied CO2. Figures 10.10 and 10.11 present a visualisation of some RBIM indicators including information about volume per, embodied CO2, number of connections, type of connection, remaining life cycle, and reuse po‑ tential score. According to the RBIM assessment, the building has 3149.9 tons of material and embodies in total 695.5 tons of CO2. Both 3D scans and RBIM datasets have been centralised in the DDC integrated platform to allow centralised access to these visualisations but also to the materials inventory, material passports, and dashboard. Based on data provided by the demolition company at the end of the deconstruc‑ tion stage, we can see that the time needed for deconstructing the building was considerably increased: the deconstruction took three months instead of 1 week in general for a similar building. Of course, this had also significantly impacted the costs. Wooden framework as well as stone from the facade and framing are expected to be reused for the renovation of a mill and for future projects of re‑ construction in Luxembourg. It represents approximately 370 tons for the stone window frame and the stone of the facade. Based on data coming from the engineering company in charge of the pre‑­ demolition audit, we have compared the classical deconstruction process in Lux‑ embourg and our pilot case encouraging materials reuse (see Figure 10.12). We can estimate that a “classical demolition” of this building in Luxembourg would have

224  Annie Guerriero et al.

Figure 10.10  Reversible BIM of the Ettelbruck’s train station.

Figure 10.11 Reversible BIM of the Ettelbruck’s train station. The charts at the bottom of the figure result from the RBIM methodology and represent a theoretical over‑ view of the proportions of embodied material and CO2 (based on data from the ICE database) in the building for each of the four reuse options.

reached around 87% of recycling, 2% of energetic valorisation and 11% of waste. Most of the recycling part is used for backfilling under the roads and wood waste is energetically valorised. In the context of the Ettelbruck’s train station, we reached 17% of reuse, 71% of recycling (i.e., backfilling and crushing), 1% of energetic

Digitalising the deconstruction process  225

Figure 10.12 Comparison of reuse and recycling rate in classical demolition site and in the deconstruction of the Ettelbruck’s train station.

valorisation, and 11% of waste. RBIM values are a bit more optimistic indicating that 34% of material has potential for reuse, 51% of material ends up in recycling and 15% as waste. Difference between RBIM assessment and realisation is related to the actual situation on the market and logistics which is not fully built for circu‑ larity of materials yet. That is why the ratio between reused and recycling content is slightly different when comparing realisation with Reversible BIM ­assessment. Nevertheless, these values are quite promising, and the project has already inspired other building ­owners in Luxembourg who would like to promote a strategy of CE for the deconstruction of their buildings. Discussion

In this deconstruction, the context was really good for multiple reasons, and this considerably contributed to reaching a relatively high percentage of reuse. This building was small and constructed with high‑value materials which were easy to dismantle. The building has been well maintained during its exploitation stage. The materials were consequently in good condition and considering the patrimonial value and the high scarcity of this kind of stone, the owner, as a public institution, agreed to bear the additional costs regarding the deconstruction and the dismantle‑ ment of the materials/components. These costs will be compensated in the future when constructing/renovating another building and integrating these stones. More‑ over, one of the most important challenges for the professionals involved in such kind of pilot project is to adopt new practices, regarding both the deconstruction process (i.e., impact in terms of time, effort, and equipment required), and the use of new digital tools. In this experiment, all the stakeholders were very motivated and inclined to adapt their activity to new requirements. In the end, they were very satisfied to have contributed to reclaiming materials and avoiding waste on site. Of course, there is still room for improvement, especially regarding the reuse of tech‑ nical and sanitary equipment, for example, which were not considered of interest in this pilot case. Additionally, at this stage of our research, we cannot assure that this percentage of reuse can be reached in any situation. The parameters of success have to be consolidated notably based on the replication of the DDC process on other types of buildings.

226  Annie Guerriero et al. Conclusion and future works In conclusion, this book chapter has addressed the question of CE in the construc‑ tion industry and the barriers the industry is currently facing. The digitalisation has appeared as a key element to support the transformation of the sector by facing the challenge of breaking with the “take‑make‑dispose” economy and by thinking about how to retain the value of materials and resources for as long as possible. A state‑of‑the‑art of existing technologies for supporting the process regarding the definition of reuse strategies has been presented. The current individual solutions have a limited focus, and there is definitely a need for centralising data coming from these individual technologies and supporting the study of reuse strategies. That is the reason why the Digital Deconstruction integrated platform has been developed by combining 3D scan, Reversible BIM, material database, and Block‑ chain technology. The deployment of the platform on a pilot case has demonstrated that the percentage of reuse could be increased, and the percentage of waste could be significantly reduced. But at this stage of this research, we cannot validate that our proposal is ef‑ ficient in any case of deconstruction. We can imagine that several parameters such as the year of construction, the quality of the buildings’ materials, the construction techniques, etc. have an impact on the percentage of reuse when deconstructing old buildings. Consequently, we need to further investigate the factors of success for the deployment of such a platform and process. Moreover, the decision‑making process required access to specific data/indicators. In order to be more complete, the dashboard developed in the DDC integrated platform should extend its set of environmental and economic indicators and create a connection with LCA tools. Finally, the scale‑up of the application from the building to the urban environment is an ambitious prospect for the DDC platform. This should contribute to supporting the concept of urban mining and more efficiently articulating supply and demand. Acknowledgements The authors acknowledge financial support from Interreg NWE to the Digital Deconstruction project, grant reference: NWE 975. They also acknowledge all the partners of the project for their active collaboration, and especially BIM‑Y, Schroeder & Associés and Greenflex for their contribution on the Luxembourg pilot case and the data collection. Finally, the authors would like to thank the So‑ ciété Nationale des Chemins de Fer Luxembourgeois and Baatz Constructions Ex‑ ploitation Sàrl for allowing the authors to collect data on the deconstruction of the Ettelbruck train station. References Adabre, M. A. Chan, A. P. C. Chan, Darko, A., & Hosseini, M. R., 2022. “Facilitating a transition to a circular economy in construction projects: Intermediate theoretical mod‑ els based on the theory of planned behaviour.” Building Research & Information 51(1): 85–104, https://doi.org/10.1080/09613218.2022.2067111

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11 Accelerating material reuse in construction Two case studies: One life, multiple cycles, a longer life Ana Rute Costa, Rachel Hoolahan, and Melanie Martin Introduction This chapter presents two case studies, the refurbishment of two existing office buildings located in London (UK). The client is The Crown Estate, and the design team is led by Orms Architects (Orms). The first case study is 10 Spring Gardens, a building located in the St James’s area of Central London. The second case study is 20 Air Street, a building that sits exactly on the footprint of the former Regents Palace Hotel in London. The relationship developed between both stakeholders, the client and the architects, shows the importance of stakeholders to collaborate, share sustainable values, and develop a circular economy approach to achieve a commercially viable project. Orms architects

Orms is an award‑winning London practice established in 1984 and currently employs 70 architectural staff. Orms seeks to elevate the human experience through insight, collaboration, design integrity, and a strong focus on sustainable approaches. The practices are signatories to Architects Declare, the RIBA 2030 Climate Challenge, and Race to Zero, with an emission reduction target  aligned to the SBTi 1.5‑degree pathway. In 2020/21, Orms participated in a joint research piece between several organisations, supporting Grosvenor Britain and Ireland in an Innovation project to accelerate material reuse. Through this work, Orms developed an approach for delivering material passports (MPs) for existing buildings and has now established an MP working group in the UK construction industry. For the last few years, Orms has increased its focus on sustainable design approaches, performing whole life cycle carbon assessments for their designs, delivering enhanced circular economy strategies, and now offering a sustainability consultancy service. The practice is regular contributors to numerous industry research groups and guidance pieces. The Crown Estate

The Crown Estate is one of the UK’s largest landowners and an independent commercial business that has committed to becoming net zero by 2030 and climate positive thereafter. To deliver these commitments on their real estate portfolio, DOI: 10.1201/9781003450023-15

232  Ana Rute Costa et al. The Crown Estate Development Sustainability Principles (DSPs) (The Crown Estate, 2019) provide a framework and targets for the Proposed Development, which have been embedded since the early design stages to drive best practices. The Crown Estate has been continuously reviewing its policies and sustainability targets and applying the lessons learned across different projects. The commercial relationship between Orms and The Crown Estate started back in 2019, when the client was reviewing their targets, developing their DSPs and the design team was utilising the project as a test bed for these sustainable ambi‑ tions. The enhanced sustainability brief presented across these two projects reflects complementary sustainable aspirations brought from both sides, the client, and the design team. The collective motivation and enthusiasm were driving forces to learn by doing, maximising material reuse, minimising waste, and promoting a circular economy. The first section of this chapter will present the current context of material reuse in construction and how MP can be used to facilitate a circular economy. After, the refurbishment process of the two existing office buildings in the centre of London will be presented. While describing the refurbishment process, the chapter high‑ lights the measures that can take place to accelerate material reuse in construction. The chapter will end with reflections on the two case studies and present final remarks and guidance for the future. Current context: material reuse in construction and circular economy New buildings can represent more than 50% of their total life cycle emissions (Lützkendorf & Balouktsi, 2022). According to the operational and embodied carbon trajectories proposed by London Energy Transformation Initiative (LETI, 2020), when meeting the current building regulations in the UK, embodied carbon in the construction phase of a building’s life typically equates to 30/35% of its total life cycle emissions. However, if we design ultra‑low energy buildings with heat pump, the embodied carbon can equate to more than 80% of the whole life carbon. Therefore, the focus on embodied carbon is a fundamental step towards meeting the Net Zero targets defined by the UK government. Since 80% of buildings that will exist in 2050 have been already built, it is imperative that we make the most of the materials already in existence, this is a real‑life challenge. Figure 11.1 presents an embodied carbon analysis of eight projects designed by Orms, three new build projects and five retrofit projects. It demonstrates the carbon impact of the structure and the substructure in a new build and clearly illustrates why we should be adopting a retrofit approach whenever possible. Reuse of construction materials is the most energy‑efficient solution for a cir‑ cular economy, ensuring material value is preserved as long as possible (Wang, Regel, Debacker, Michiels, & Vanderheyden, 2018). The use of reused materials in construction has the potential to significantly reduce the embodied carbon of construction, in addition to minimising the extraction and production of virgin ma‑ terials, as well as reduce construction waste.

(Author: Orms).

Accelerating material reuse in construction  233

Figure 11.1  Embodied Carbon Analysis of eight projects designed by Orms.

234  Ana Rute Costa et al. There has been a great deal of academic research on this topic. MPs was a concept developed by BAMB (Building Materials as Material Banks) European research project. An MP acts as a one‑stop shop for material information that could support circular decision‑making. Furthermore, MPs can help to overcome sev‑ eral economic, political, sociological, technical, environmental, and organisational barriers identified by Charef & Emmitt (2021). The Material Passport Framework (BAMB, 2017) has inspired and guided the development of different product data initiatives (Honic, Kovacic, & Rechberger, 2019). The Madaster ICT Platform and myUpcyclea are examples of commercial tools developed to document and store material‑related information on products. Complementarily to these recording tools, Orms has developed the Orms Material Database (OMD) an opensource and freely available design approach for MP (Orms, 2023). Their approach proposes the development of a Material Database for existing buildings, with MP acting as a user interface to filter relevant information for the reader. The OMD offers an op‑ portunity to gather and organise data about materials contained within a building and support material reuse in construction. To minimise waste in Architecture, Engineering and Construction (AEC) in‑ dustry, materials/components/products should be kept in use as long as possible to enable a fully circular economy. To enable a circular economy, the concept of 3R’s (Reduce, Reuse and Recycle) suggested by the European Union (EU) and United Nations (UN) has been widely adopted in many waste regulations across the world (Cavallo & Cencioni, 2017). Later, the 3R’s concept has been reframed and reorganised into a 10R hierarchy (from R0‑R9) (Vermeulen, Reike, & Witjes, 2019) and then revised to the 9Rs (Khaw‑ngern, Peuchthonglang, Klomkul, & Khaw‑ngern, 2021). To implement a circular economy in the AEC industry, we need to go beyond the 9R’s and map all the possibilities within the lifecycle of a material. In the table below, we present the circular economy strategies proposed by Khaw‑ngern, Peuchthonglang, Klomkul, & Khaw‑ngern (2021), expanded to include a third and fourth column (highlighted in grey) which describes how these relate with the AEC industry and AEC stakeholders, respectively. These two addi‑ tional columns were informed by Orms’ practical experience, by the UNEP circu‑ lar economy approach using the 9R’s concept (UNEP, 2023), and by (Vermeulen, Reike, & Witjes, 2019) (Table 11.1). To extend the life cycle of materials from an existing building without losing material properties, we prioritise three main options: reuse, remanufacture, and repurpose. These three options can be unfolded into six if we reuse/remanufacture/ repurpose materials offsite or on‑site. When using materials on‑site, we need to understand if they need to be disassembled and where they can be stored during the refurbishment phase to be later reassembled. When reusing materials offsite, these can be bought/collected by a reseller company to be later commercialised or directly bought/donated to another building under construction. The option of reusing materials on‑site is the most carbon‑efficient solution because we can minimise the carbon costs of transportation. Repurposing materials for another use is also a viable option, which can mitigate some of the risks associated with reuse. For example, a fire‑rated door may be repurposed as a tabletop or decorative

Accelerating material reuse in construction  235 Table 11.1 Circular economy strategies (Khaw‑ngern, Peuchthonglang, Klomkul, and Khaw‑ngern, 2021) and their connection with AEC industry and Stakeholders R

Strategy

R1

Refuse

R2

R3

R4

R5

R6

R7

R8

R9

Description (reduced)

AEC industry connection Stakeholders

Refuse the need for Make a product redundant a completely new by abandoning its function building/product and or by offering the same extend lifecycle of the function by a radically existing ones. In AEC, different (e.g., digital) Retrofit can be seen as product or service an answer to Refuse. Rethink Make product use more Perform a series of intensive feasibility studies that analyse and compare the different options. Reduce Increase efficiency in product Increase efficiency of manufacture or use by the design to reduce consuming less natural embodied carbon and resources and materials. material expenditure. Reuse a product/ Reuse Reuse of a product that is material/building still in good condition and element on site or fulfils its original function offsite. Carefully (and is not waste) for the consider the same purpose for which it disassembly process to was conceived ensure the integrity of the product/material/ building element. Repair Repair and maintenance of Repair a product/ defective product so it can material/building be used with its original element on site or function offsite. Refurbish Restore an old product and Prioritise the bring it up to date refurbishment and of buildings and products and avoid demolition. Remanufacture products Remanufacture Use parts of a discarded when they can no product in a new product longer be reused with the same function or repaired. These (and as‑new‑condition) remanufactured products can then be used on site/offsite. Repurpose a material/ Repurpose Use a redundant product or its parts in a new product product/component to be used on site/offsite. with different function

Recycle

Recover materials from waste Prioritise materials recycled materials to be reprocessed into in detriment of raw new products, material, or materials. substances whether for the original or other purposes.

Client/Developer/ Owner (C/D/O) and Design Team

(C/D/O) and Design team Design Team

Consultancy Services (Pre demolition Audits), design team, Contractor, and (C/D/O), Stockholders Manufacturer (C/D/O), Demolition Contractor, Manufacturers, Stockholders (C/D/O) and Design team Contractors, Stockholders, manufacturers

Used on site: (C/D/O), Design team, deconstruction contractor Used offsite: stockholder and repurposing manufacturers. Contractor and recycling Manufacturers

236  Ana Rute Costa et al. finish. While it is beneficial that the material is kept in use, it must be recognised that this is a lower value use and therefore reuse should always be prioritised over repurposing. Despite recent advancements in material reuse strategies, there is still only a small reuse market in the construction industry which primarily focuses on architectural reclamation and salvage. Even today, many materials that are not reused on site are sent for recycling or to landfill. The concept of demolition is particularly damaging, as it is inherently destructive. Orms advocate for the adoption of ‘deconstruction’ rather than ‘demolition’ strategies, as it intrinsically shifts the conversation in initial design stages. The reused materials market is changing, but it needs to grow quickly and evolve to become a facilitator at dif‑ ferent stages of construction. For example, it is usually understood at an early stage that a building is going to be partially/totally disassembled. At this early point, stockholder companies could be invited to bid and collect materials during the deconstruction process. Ideally, MPs would be created for these materials, so that an overview of typical material availability could be shared with design‑ ers. During the design stage, this material availability data enables designers to create a loose fit design and specification, broadly aligned to the known and anticipated materials. During construction, this aligned and loose‑fit approach enables a smoother procurement of reused materials, which could be procured by the contractors directly from the supply chain as normal. The scale of the re‑ used materials market needs to increase significantly to support the agile process of construction. Pre‑redevelopment and pre‑demolition audits (PRDA) are now being used by clients and designers to define a more sustainable brief. These PRDA reports have an increasing level of detail that gives decision‑makers enough information to characterise existing materials and inform material reuse approaches. Based on these PRDA reports, the design team can identify the existing materials that are not going to be used on the refurbishment project but have an offsite reuse value. During the design phase, architects, engineers, and the wider design team write specifications to define, curate, and ultimately control the end product. To acceler‑ ate material reuse in construction and minimise embodied carbon expenditure, a fundamental shift in the way design teams specify materials is crucial to change the current trajectory of waste and material consumption that is contributing to the climate crisis. In the two case studies presented here, Orms has explored the key circular economy principles of reuse through a ‘loose‑fit’ approach to specification for the procurement and use of reclaimed materials on a live project (Adams et al., 2020). Figure 11.2 presents the ideal cycle to accelerate material reuse in construction and avoid material waste. The buildings already in existence are our starting point. When redeveloping these, we need to avoid demolition and minimise the quantity of materials going to recycling or landfill. By prioritising Retrofit/Repurpose or Disassembly/Reuse, we can extend the lifecycle of the materials and stimulate the reused materials market.

(Illustration by Ana Rute Costa).

Accelerating material reuse in construction  237

Figure 11.2  Material Reuse in Construction: the ideal cycle.

238  Ana Rute Costa et al. Case study one: 10 Spring Gardens, London 10 Spring Gardens is located in the St James’s area of Central London, to the south‑ west of Trafalgar Square and to the northeast of St James’s Park. 10 Spring Gardens sits within the City of Westminster and the St. James’s Conservation Area. The building was designed by Howard V Lobb & Partners and completed in 1975, in collaboration with Sir Frederick Gibberd, to provide a modern office for The Brit‑ ish Council for Offices (BCO) while respecting the height and scale of the adjacent Nash terraces. The client approached Orms in 2019 with a brief to reposition the existing building, making it attractive to future tenants, as it was due to be vacated by the BCO. The project presented a wonderful opportunity to build upon the rich character of the site and make significant improvements to the existing built fabric. The development proposal retains the office use on the upper floors and provides an improved reception on the ground floor, introducing a new cafe use. The team focused on sustainable practices during design, strip‑out and construction to reduce the associated environmental impacts of the project. The project began design in 2019 and is due to be completed in 2024 (Figure 11.3). Before defining the brief for 10 Spring Gardens, the client had requested a Building Condition Inspection (BCI) (TFT Consultants, 2017) followed by a Reuse Viability Assessment Report (RVAR) (McGee, 2020). The BCI concluded that the building was at a stage in its lifecycle where above‑average levels of maintenance expenditure would be expected. The renewal of roof coverings and overhaul or replacement of all the windows (deduced to be original) would be required, to en‑ sure the building remains weathertight for the foreseeable future and presented an

Figure 11.3  Visualisation of 10 Spring Gardens after the refurbishment process. (Author Orms).

Accelerating material reuse in construction  239 opportunity to improve the building’s thermal performance. The building services (ventilation, heating, and cooling systems) would also require significant expendi‑ ture or replacement to ensure continued service for the next 10 years. This report was essential to confirm the refurbishment potential of the building. Complementary to this document, the RVAR report was produced by a demoli‑ tion contractor to understand the extent of non‑hazardous materials that can be re‑ used on‑site or elsewhere, upcycled, recycled, and sent to a landfill. This audit was used by the design team to assess the quantity and value of the materials on‑site and to interrogate the end‑of‑life strategy for these materials. The report also eval‑ uated the opportunities for waste minimisation during the refurbishment and to identify any opportunities to improve the recycling and reuse of materials whilst implementing the waste hierarchy. This document enabled the client to realise the value of the existing materials, analyse the reuse potential of different elements and inform the refurbishment brief. Furthermore, this document had also identified several factors to consider that would impact the potential reuse of items, such as space available for storing items on site and also the impact on the programme for time taken to segregate the waste streams. These two documents (BCI and RVAR) were essential in establishing the refur‑ bishment framework, informing the brief, and identifying the value of existing ma‑ terials. These reports would now be described as enhanced pre‑redevelopment and pre‑demolition audits, which are described in the Greater London Authority (GLA) 2022 Circular Economy Statement Guidance (GLA, 2022). Around the time that the reports were being completed, Orms released their MP research and was keen to test it on a live project. This culminated in a clear brief being defined by the client, which prioritised the reuse of existing materials, a requirement to improve the building’s performance, and a willingness to contribute to the development of research initiatives. In implementing the brief, the design team decided to focus on maximising the retention of existing materials onsite and limiting the procurement of new materials by sourcing reused materials wherever possible. At the time, it was not common to trade unwanted materials with reuse potential. As a result, materials that were not required for this project were removed as part of the strip‑out and sent for recy‑ cling by the demolition contractor. For new materials with future reuse potential, MPs have been prepared as a way of giving those materials an identity. The Crown Estate was aware of the value of existing materials previously identified by the BCI and RVAR and was keen to ensure that the value of these materials would be maintained for future reuse. One of the first design interventions made was the introduction of a raised ac‑ cess floor (RAF) to facilitate the distribution of IT and electrical services. Through Orms research on earlier project, the embodied carbon impact of a RAF tile was well understood. A reuse alternative was sought and specified, which was very unu‑ sual at the time, as the expectation for ‘shiny’ floors was a default position within the industry. The brief also required a complete replacement of all the mechanical services because the existing equipment was already beyond its serviceable life. The

240  Ana Rute Costa et al. building had very tight floor to ceiling height and therefore the mechanical ventila‑ tion options were limited. The typical solution of having ceiling‑mounted units to heat and cool the air with ceiling‑mounted ducts to distribute the fresh air was not viable, because it would compromise the floor to ceiling heights. The design team considered the alternatives and proposed the solution of having wall‑mounted units with fresh air distribution under the newly introduced RAF. However, by pushing air through the floor, there was now a need for a com‑ pletely sealed surface so the air could travel through the plenum and be distributed evenly across the space. The default detail for this would be a RAF tile installed with perimeter gasket to prevent air leakage. At the time, the RAF supplier did not have the capability to supply a reused tile with a gasket on it. Prior to the tender period, the team were asked to investigate reverting the specification from a reused floor tile to a new tile which could be specified with a gasket tape. The team were able to demonstrate that this change would represent a significant increase in em‑ bodied carbon. At that point, the client decided that they would relax the air leakage requirements and proceed with a reused RAF tile, as ultimately a floor finish would be installed on top of the RAF which would effectively seal the floor. The project is now under construction and using reused tiles. In this project, Orms identified several elements that could potentially come from reclaimed sources – brick flooring, raised access flooring, sanitaryware, fea‑ ture lighting, and furniture. Items that could be defined in the tender documentation through a performance type specification would set out the technical requirements alongside a wider ‘band’ of perhaps aesthetic considerations, e.g., reclaimed engi‑ neered bricks. Two items (windows and clay pavers) have been selected from the project to illustrate two different realities of what is possible in today’s market. Windows

The design process is not always linear, in some cases there is a need for spe‑ cific analysis and considerations to inform the design decisions. While looking at the whole lifecycle carbon assessment, designers need to ensure they balance the operational and embodied carbon. For example, while considering the right approach to upgrade the window’s performance, there were four different options available. First, the team examined keeping the existing window and installing new secondary glazing, second investigating the retention of the frame and replacing the glass with a double or triple‑glazed unit, and lastly, replacing the window al‑ together. The team used embodied carbon and thermal modelling studies to help determine what were the optimal specifications and the carbon payback period for these options. After careful analysis, the designers were able to justify their design decisions. The final solution is a new double‑glazed unit with a timber frame and aluminium facing (to the external face of window frames). This final product has a higher carbon than a timber‑only product; however, it would not have been feasible to maintain external timber frames on a building of this scale. This was a rigorous process that was supported by the window manufacturers to help the clients and designers to make an informed sustainable design decision (Figure 11.4).

Accelerating material reuse in construction  241

Figure 11.4  10 Spring Gardens, reception entrance. (Author: Orms).

Clay pavers

A red brick had been selected for the reception entrance, in reference to old Eng‑ lish garden paths and as a nod to the history of the site. Spring Gardens is the site of several pleasure gardens with records as early as the 1590s. The proposal was to use reclaimed bricks, a practice that is relatively common in small domestic projects. This approach was immediately challenged in the commercial setting, as there is a higher expectation to meet various technical requirements, introduces liability issues, and affects timings for procurement (Penman, 2021). This includes pedestrian and vehicular loading, slip resistance as covered in BS EN 1344:2013 (British Standards, 2015) and a construction programme that requires products to be agreed upon roughly a year before installation. While the technical requirements can be set out in a performance‑type specification, an allowance for a degree of variation in colour will need to be accepted by the client as stock at the time of purchase cannot be guaranteed without early purchase. Currently, salvage yards are not yet capable of confirming the provenance or technical properties of stock, and therefore despite large quantities of bricks being available, there is this impediment to data and testing. This is further complicated by the small module of the brick, as pallets of reclaimed bricks can often include bricks from different sources, so even if testing could be undertaken on a small sample from a ‘batch’, it could not be deemed as completely reliable. To minimise risks, a new product was speci‑ fied, and the installation has been considered to enable disassembly for reuse in the future. This will be enabled by specifying an appropriate bedding material and populating the BIM model with classification system ‘Uniclass’ and NBS data to

242  Ana Rute Costa et al. enable easy identification and location of specification information. The team have also been engaging with new brick suppliers to discuss the possibility of future take‑back schemes. There are numerous advantages to the supplier controlling re‑ use and retesting of their own products. But ultimately the feasibility of material reuse relies heavily on accurate records of technical properties, provenance, and certification in addition to reaching a critical mass of stock availability. Case study two: 20 Air Street, London 20 Air Street sits exactly on the footprint of the former Regents Palace Hotel, constructed in c.1915–1917 and added to c.1933–1935. It was later redeveloped in 2011 by Dixon Jones architects into a mixture of uses, with much of the area allocated to high‑quality office spaces. The building is currently owned by The Crown Estate. The project design started in 2021 and was delivered in 2023 (Figure 11.5). Works were being undertaken as a tenant had vacated two of the floors. The brief was to carry out an internal refurbishment of the reception, lobbies, and two office floors. The client and the design team have taken into consideration the les‑ sons learned from 10 Spring Gardens.

Figure 11.5  Visualisation of the building 20 Air Street after the refurbishment process. (Author: Orms).

Accelerating material reuse in construction  243 The Orms proposal again embraces a design approach that prioritises retention and refurbishment over strip‑out and replacement. This time, the team added the offsite reuse of existing elements to the brief. Spaces are designed so that they can be adapted, reconstructed, and deconstructed to extend their life and that al‑ low components and materials to be salvaged for reuse or recycling. Two design philosophies underpin this concept. The first considers the life expectancy of the different building elements, allowing different layers of the building to be refur‑ bished as necessary. The second utilises the waste hierarchy. Refurbishment of the existing building and re‑use of high carbon elements such as the RAF tiles, metal ceiling tiles, Fan Coil Units (FCUs), and the stone floor tiles will contribute to large carbon savings. For this project, the team located the Operation and Maintenance manuals that had been produced for the previous tenants. These manuals contained information about the material specifications, technical performance, and installation details for the existing fitout. With this enhanced level of detail, there was a bigger potential to reuse these materials both onsite and offsite. Air Street was partially occupied throughout design and construction and the brief requested to enhance the existing building, principally the main reception area and two of the office floors. Orms studied the existing materials in these spaces and presented a detailed feasibility study to complement the design proposals. This included mapping all the reuse possibilities and considering how much material would need to be taken away (send for offsite reuse or landfill) and how much can be put back and reused/repurpose materials already on site. In this case study, natural stone, RAF tiles, metal ceiling tiles, and most of the services were kept. However, there was also a significant quantity of materials with a potential reuse offsite, e.g., Carpet tiles, built‑in kitchens, joinery units, and internal glass parti‑ tions (Figure 11.6).

Figure 11.6  Building 20 Air Street, proposed reception. (Author: Orms).

244  Ana Rute Costa et al. The final solution for the reception is a hybrid solution. In the reception, the original stone floors and column cladding were kept. A new ceiling, lighting, and joinery elements were added. As part of this design approach, some of the stone cladding is being removed. The specification required this material to be carefully removed. It was feared that this would be broken in the removal process, but in fact, the panels have been removed without damage. The client and the design team have been involved in this process and are keen to reuse or repurpose this highly limited natural resources in a future project. On the office floors, the RAF tiles were one of the materials successfully kept onsite and reused. RAF tiles are high embodied carbon elements found in almost all commercial office developments and are fundamental to a good quality office space. The creation of a floor void enables easy distribution of services such as IT and electrical cabling, and the utilisation of lightweight RAF tiles allows for these underfloor services to be easily accessed and adjusted to suit the changing needs of the office space. Historically, there has been an expectation that a shiny new RAF was needed to help ‘sell’ a space, but as tenant expectations for a sustainable product have become more prominent, the aesthetic consideration of something that is ultimately going to be covered up has become less critical. Typically, the architect would specify a manufacturer and product, but in this case, the retention of the existing RAF was specified instead. Where there was a need for additional tiles, due to the removal of screeds or damaged tiles, the client was able to reuse existing RAF tiles from another of their buildings and supply it to 20 Air Street (Figure 11.7). The metal ceiling tiles were also retained in the 20 Air Street building. The manufacturer was asked to refinish/recoat the existing ceiling tiles. However, at that stage, they were not ready to offer that service. As an alternative, the existing

Figure 11.7  Metal Ceiling Tiles – reuse process. (Author: Orms).

Accelerating material reuse in construction  245 metal ceiling tiles were disassembled and stored on‑site to allow for reconfigura‑ tion of the mechanical and electrical services above. They were later reinstalled, and spray painted in situ by the contractor. Considering the reuse potential of internal glass partitions, which are designed as demountable systems, Orms approached a partition manufacturer, with a view to disassembly and reuse off‑site. A survey was arranged with the manufacturer team, and a deconstruction approach was developed to support the detailing of the strip‑out specification and method statement. Later, despite best efforts, the deconstruction contractor was unable to keep all frames intact so only the glass was salvaged, and the aluminium frames were recycled. It is key to understand any potential risks arising from reuse at an early stage, so it had been previously agreed that any reclaimed glass would have to be de‑rated in terms of fire and acoustics regulations. It was discovered during the survey that the partition system was produced by a different manufacturer and the specifica‑ tion was toughened glass that was not heat soaked. This presented a challenge for the manufacturer, as the glass did not meet their minimum specifications – it is normally laminated. Toughened glass that has not been heat soaked is now not typically used as it presents a risk of nickel sulphide expansion and spontaneous breakage. However, when not used in an atrium or in a context with small chil‑ dren, it was determined that there was no major health and safety risk. After some consideration, the manufacturer accepted the glass for future reuse in a different project, where the design team had ambitious sustainability goals and were willing to specify in a flexible way to facilitate reuse. Working through this process, another useful reflection was discovered. Internal glazed partitions are designed to be demountable systems, meaning they can be removed without damaging the surrounding elements (walls, floors, and ceilings). This does not necessarily mean that the partitions can be uninstalled without being damaged themselves. In particular, the aluminium frames are vulnerable to bend‑ ing, which prevents future reuse. Therefore, demountable glazed partitions are not inherently suitable for material reuse, and an opportunity exists to address this in the design of future systems which would extend the material lifecycle beyond the length of a typical installation. It also takes significantly longer to deconstruct the elements carefully, which adds expensive labour costs to the project. This too could be addressed in the design of future systems. In this case study, the salvage of the glass from the glazed partitions was only possible through a strong involvement of the design team, deconstruction contrac‑ tor, and manufacturer. In the future, we need an efficient reuse material supply chain that we can feed materials stock to and buy materials stock from. Discussion Orms recognises the value of MPs as an enabler for both existing and new ma‑ terials, and the importance of tagging materials for future reuse and mainte‑ nance. However, in most cases, there is a disconnect between expectations and reality. Reusing materials takes time, which often leads to longer construction

246  Ana Rute Costa et al. programmes and additional costs. Unfortunately, there are still many stakeholders that need to be convinced of the reused material value and treat every material as a treasure. The location of a building and the level of finish quality expected for a specific area also have an impact on the reuse potential of materials. For example, the Air Street Case Study is a Grade A building with top‑quality materials and finishes, designed to attract a tenant typically looking to occupy the area. However, the aesthetic expectations are often different for buildings located in other areas of London. Therefore, the retrofit strategy of minimal intervention and maximum material reuse should be aligned to suit the brief and anticipated tenant aesthetic expectations. But information is regularly being collected and collated by many teams, which could be considered as MPs. Currently, the main contractor is often committed to physically tagging Mechanical and Electrical (M&E) equipment as part of the cli‑ ent’s maintenance and replacement strategy for the building. Although full tagging of architectural elements does not occur on the presented projects, on BIM projects the main contractor is ordinarily committed to producing an accurate as‑built digital model of the building which can act as a future material database. The 10 Spring Gardens project has MP data incorporated as a requirement within the final BIM model. Research (Atta, Bakhoum, & Marzouk, 2021) shows that this is an essential approach to extending the lifecycle of the material and to quan‑ tify building material and component stock flows (Arora, Raspall, Cheah, & Silva, 2019). The existence of MPs at the end‑of‑life stage of a building can be seen as an outstanding advantage for reuse and recycling (Honic, Kovacic, & Rechberger, 2019; Honic, Kovacic, Aschenbrenner, & Ragossnig, 2021). Furthermore, MPs can be used to measure the circularity of materials (Moraga, Huysveld, Meester, & Dewulf, 2021). The MPs information gathered on the BIM model can be used to physically tag the materials in the future and enable reuse. Alongside this digital approach, The Crown Estate and Orms have identified some architectural elements to be physically tagged (e.g., windows) and are seeking to evaluate the viability of this approach at scale. This is an evolving process, where the lessons learned by The Crown Estate and Orms in these case studies will inform future approaches and will shape fu‑ ture briefs and design decisions. Different stakeholders are at different stages of their journeys. However, having a client and a design team that are committed to sustainable and ethical solutions is an advantage to identify and deliver these ambi‑ tious approaches. Conclusion To accelerate material reuse in construction, clients and design teams need to ex‑ plore and accept a degree of flexibility in both the aesthetic potential and perfor‑ mance of materials. The industry is like a tanker ship, slowly moving towards this potential, but it needs to happen much faster if the AEC industry is to achieve its

Accelerating material reuse in construction  247 Net Zero commitments. Government incentives should be considered to encour‑ age the establishment of reclamation yards to undertake testing and certification of key building materials. Schemes with reputable organisations such as the British Board of Agrément (BBA) can enable specification in larger commercial projects by undertaking independent testing, assessments, and certification of products. An agreement certificate for a product for a particular application is based on a perfor‑ mance about safety, habitability, installation, practicability, durability, and main‑ tenance. Perhaps a more direct route, which could also benefit from government incentivisation, is to encourage manufacturers to offer take‑back schemes. As an industry, we should be lobbying the government to support this necessary shift in practice. Existing products and materials are a precious resource, and their reuse is a fundamental action we need to embed in the construction industry to create a more sustainable and circular way of building. The market is changing, and the case studies presented here are an example of wider practices across the AEC Industries. The aesthetics of reuse and design for loose‑fit are becoming more popular. Sustainable‑driven approaches diversify what is visually accepted and set up an important ethical approach. However, a shiny and brand‑new building is still a request in many contexts. It requires a social and cultural shift where new materials are no longer the sign of a healthy and ethical built environment but a consequence of unsustainable decisions. We need to embrace this paradigm shift and promote the aesthetics of reused materials aligned with carefully considered design approaches, a unique way to reduce embodied carbon and implement a successful circular economy in construction. Initiatives like the FCRBE project funded by Interreg North‑West Europe pre‑ sent a roadmap to foster reuse practices in the construction sector (Gobbo, Ghyoot, Bernair, & Paduart, 2021) and offer a collection of inspiring actions for public au‑ thorities alongside with a series of material sheets that provide further details and guidance. These are useful tools to shape the future of reuse in construction and support different stakeholders involved in the process. When we cannot reuse the full building, a detailed PRDA should be carried out. Through this process, we can create basic passports for the materials that have a reuse potential, identify possible stakeholders interested in trading/buying them and minimise waste in construction. Every stakeholder across the AEC industry needs to get involved and be in‑ spired by an ethical conscience that preserves material resources. Governments need to be the first ones leading by example and providing policy and guidance that promotes a second‑hand market and enables a circular economy. We need poli‑ cies and practices that encourage reuse, remanufacture, and repurpose practices across the construction industry. MPs can accelerate material reuse in construction, provide accurate records of technical properties, provenance, and traceability, and facilitate re‑certification of materials. New buildings and refurbishment projects need to be fully passported, designed for deconstruction and disassembly, and al‑ low building layers to be replaced according to their life expectancy. Every AEC industry stakeholder has a key role to play on this circular construction process.

248  Ana Rute Costa et al. References Adams, K., Fishwick, R., MacNamara, E., James, N., Edwards, M., Charlson, A., Kelly, P., Grafakou, G., Law, C., Rose, C., Epstein, D., Claussner, R., 2020. Circular Economy How‑to guide: Reusing Products and Materials in Built Assets. London: UKGBC. Arora, M., Raspall, F., Cheah, L., & Silva, A., 2019. Residential building material stocks and component‑level circularity: The case of Singapore. Journal of Cleaner Production, 216, 239–248. doi:10.1016/j.jclepro.2019.01.199 Atta, I., Bakhoum, E. S., & Marzouk, M. M., 2021. Digitizing material passport for sus‑ tainable construction projects using BIM. Journal of Building Engineering, 43, 103233, doi:10.1016/j.jobe.2021.103233 BAMB. 2017. Framework for Material Passports. Retrieved from https://www.bamb2020. eu/wp‑content/uploads/2018/01/Framework‑for‑Materials‑Passports‑for‑the‑webb.pdf, Accessed 15.01.24 British Standards., 2015. BS EN 1344:2013 Clay pavers, Requirements and test models. ISBN: 978 0 580 90218 5 Cavallo, M., and Cencioni, D., 2017. Circular Economy, Benefits and Good Practices. Milano: Edizioni Ambiente, Milano, Italy, https://www.cittametropolitana.bo.it/pro‑ getti_europei/Engine/RAServeFile.php/f/Pubblicazioni/ebook_Circular_Economy.pdf, Accessed 15.01.24. Charef, R., and Emmitt, S., 2021. Uses of building information modelling for overcoming barriers to a circular economy. Journal of Cleaner Production, 285, 124854, doi:10.1016/ j.jclepro.2020.124854 GLA. (2022, 03). London plan guide ‑ circular economy statements. London. Retrieved from https://www.london.gov.uk/sites/default/files/circular_economy_statements_ lpg_0.pdf Gobbo, E., Ghyoot, M., Bernair, C., & Paduart, A., 2021. A Roadmap to Foster Reuse Prac‑ tices in the Construction Sector. Interreg North‑West Europe FCRBE, Brussels, Belgium, https://opalis.eu/sites/default/files/2022‑02/FCRBE‑en‑roadmap_for_public_policies. pdf, Accessed 15.01.24. HM Government. (2021). Net Zero Strategy: Build back Greener. London. Retrieved from www.gov.uk/official‑documents Honic, M., Kovacic, I., & Rechberger, H., 2019. Improving the recycling potential of build‑ ings through Material Passports (MP): An Austrian case study. Journal of Cleaner Pro‑ duction, 217, 787–797. doi:10.1016/j.jclepro.2019.01.212 Honic, M., Kovacic, I., Aschenbrenner, P., & Ragossnig, A., 2021. Material Passports for the end‑of‑life stage of buildings: Challenges and potentials. Journal of Cleaner Production, 319, 128702, doi:10.1016/j.jclepro.2021.128702 Khaw‑ngern, K., Peuchthonglang, P., Klomkul, L., & Khaw‑ngern, C., 2021. The 9Rs strat‑ egies for the circular economy 3.0. Psycology and Education, 58(1), 1440–1446, DOI: https://doi.org/10.17762/pae.v58i1.926. LETI. (2020). LETI Embodied Carbon Primer: Supplementary guidance to the Climate Emergency Design Guide. London: LETI, https://www.leti.uk/_files/ugd/252d09_8ceffc bcafdb43cf8a19ab9af5073b92.pdf, Accessed 15.01.24. Lützkendorf, T., & Balouktsi, M., 2022. Embodied carbon emissions in buildings: Ex‑ planations, interpretations, recommendations. Buildings and Cities, 3(1), 964–973. doi:10.5334/bc.257 McGee., 2020. Reuse Viability Assessment Report, 10 Spring Gardens, London. London.

Accelerating material reuse in construction  249 Moraga, G., Huysveld, S., Meester, S. D., & Dewulf, J., 2021. Development of circular‑ ity indicators based on the in‑use occupation of materials, 279, 123889, doi:10.1016/ j.jclepro.2020.123889 Orms , Architects and Designers ltd. Retrieved from Orms.co.uk: https://orms.co.uk/ insights/materialpassports/#dearflip‑df_5690/3/, Accessed 26.04.23 Penman, B., 2021, May 13). What’s at Risk with Reuse. Retrieved April 24, 2023, from UKGBC: https://ukgbc.org/news/whats‑at‑risk‑with‑reuse/ TFT Consultants, 2017. Building Condition Report, 10 Spring Gardens, London SW1A 2BN. The Crown Estate, 2019. Development Sustainability Principles, version 3. (D. a. Man‑ agement, Ed.) Retrieved 20.04.23, from The Crown Estate: https://www.thecrownestate. co.uk/media/3003/development_sustainability_principles_2019.pdf UNEP, (2023, Building Circularity. Retrieved from United Nations Environment Programme Circularity Platform: https://buildingcircularity.org/wp‑content/uploads/ 2019/11/Circularity_Diagram_UNEP.pdf Vermeulen, W. J., Reike, D., & Witjes, S., 2019. Circular Economy 3.0: Solving Confusion around New Conceptions of Circularity by Synthesising and Re‑organising the 3R’s Con‑ cept into a 10R Hierarchy. Renewable Matter. Wang, K., Regel, S. d., Debacker, W., Michiels, J., & Vanderheyden, J., 2018. Why invest in a reversible building design? IOP Conference Series: Earth and Environmental Science, 1, 225, doi:10.1088/1755‑1315/225/1/012005

12 Additive manufacturing and circular economies Jennifer Johns, Daniel Eyers, Rick Lupton, Aris Syntetos, and Jessica Robins

Introduction In the context of climate change and resource pressures, circular economies in the built environment are receiving increasing attention from academics, industry, and policymakers, due to the concentration of the human population in urban areas. Both circular economies and digitalisation have been highlighted as potential new models and tools to enact positive change. The circular economy (CE) has emerged as a new economic model that seeks to decouple economic development from the consumption of finite resources, gaining academic, government, and organisational recognition (Munaro et  al., 2020). Similarly, digital technologies as part of the “Fourth Industrial Revolution” promise to launch us into a new era of globalisation and drive a shift in where and how goods are produced, distributed, and consumed (Johns, 2019). The role of digitalisation in supporting and creating new opportuni‑ ties to make environmental cost savings across a range of sectors is a key topic of debate and research (Andrews, 2015; Rajput & Singh, 2020; Okorie et al., 2021). The digitalisation of the construction sector also has the potential to facilitate the management of the end‑of‑life of buildings sustainably and to ease the transition towards the CE (Charef and Emmitt, 2021); (Van Den Berg et al., 2021). Although the benefits of digitalisation are highlighted by several authors, others have called for limitations or negative consequences to be considered and have suggested the benefits of a low‑tech approach (Bihouix & McMahon, 2020; Charef, 2022). Despite the prominence of both drivers of future change, there is a relative pau‑ city of discussions around how digitalisation and circularity intersect. The points of intersection become clearer when a systemic thinking is used to understand the entire life cycle of a product (or building) and the value chains of industries, involving greater communication between stakeholders. CE aims to improve re‑ source efficiency, taking us from linear models of extraction, production, and con‑ sumption to a model in which resources flow in a circular manner. Many digital technologies can play pivotal roles in enabling the circular flow of resources, both through providing the digital tools to track and trace materials within and across closed‑loop systems and through the use of specific use of digital tools in each stage of CE. Depending on their maturity level, digital technologies play a vital role in transitioning towards CE (Bicket et al., 2014; Nascimento et al., 2019; DOI: 10.1201/9781003450023-16

Additive manufacturing and circular economies  251 Shahbazi et al., 2016). There are overlaps between the objectives of the CE ap‑ proach and digital technologies (in the context of developing more sustainable ap‑ proaches to production). However, digital technologies include robotics, artificial intelligence, big data and digital modelling, and advance manufacturing technolo‑ gies, and each has specific capabilities and limitations with regard to contributing to more circular approaches. This chapter focuses specifically on additive manu‑ facturing (AM; also known as 3D printing) which is defined as “the process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies, such as traditional machin‑ ing” (ASTM, 2012). This chapter examines the current and potential use of AM in the construction industry to create more sustainable built environments. The construction industry is one of the largest industries in the world, with annual revenues of nearly 10 trillion USD or about 6% of global GDP (Gerbert et al., 2016). However, it is the largest consumer of natural resources, accounting for 50% of global steel pro‑ duction and consuming more than 3bn tonnes of raw materials (Zimmann et al., 2016). It is responsible for approximately 38% of greenhouse gas release, 40% of solid waste, and 12% of portable water use (Khan et al., 2021). In order to meet the built environment’s social and economic needs, more efficient, innovative, and sustainable strategies and technologies must be developed and adopted by the con‑ struction industry (Gengagel et al., 2020). The construction sector is characterised by low material efficiency, low productivity, and comparatively high volumes of non‑renewable materials (Kromoser et al., 2022). It is facing significant challenges characterised by the adoption of digital technologies, sensor systems, intelligent machines, and smart materials (Craveiro et al., 2019). Drawing an analogy with manufacturing’s “Industry 4.0”, this transformation has been termed “Construction 4.0” (Berger, 2016; ECIF, 2017). Despite this, relatively few studies have inves‑ tigated which digital technologies could enable the CE in the built environment (Çetin et al., 2021; Chauhan et al., 2022). For discussion of building information management (BIM), see Charef and Emmitt (2021) and Van Den Berg et al. (2021). Literature review In response to growing need, the exploration of the concept of CE to manage re‑ sources better and more efficiently while eliminating waste has become a key focus for many academic disciplines. One of the strategies to implement CE in the built environment is to select the appropriate building materials and components from the early stages to carry out the concept’s principles along the value chain and create a closed‑loop system (Rahla et al., 2021). While the built environment – particularly the construction industry – is in need of more efficient, innovative and sustainable strategies, technologies, and instruments (Khan et al., 2021) and repre‑ sents a significant opportunity to embrace the CE, the literature regarding the topic is still emerging and is mainly theoretical (Pomponi & Moncaser, 2017). Ghisellini et al. (2016) suggest the industry has been following the same linear economic model with little consideration of the end‑of‑life state of consumed materials.

252  Jennifer Johns et al. Concurrently, there are ample examples of practitioners implementing AM to achieve the circularity of supply chains (Hettiarachchi et al., 2022). For example, airlines including Singapore Airlines and KLM are 3D printing tools and compo‑ nents from recycled materials, using 3D printing to reduce inventory and redesign parts as part of broader “lightweighting” strategies to reduce fuel consumption and extend aircraft life (see also Diaz et al., 2022). Hettiarachchi et al. (2022) cite Signify, a leading Dutch light company that manufacturers light shades using AM and fittings from 100% polycarbonate material recycled at the end‑of‑life, thereby reducing their carbon footprint, using fewer parts and avoiding glue for assembly (Signify, 2019). Despite this, relatively few academic studies focus on AM and CE. Those that do highlight the technical characteristics of AM technology that are beneficial to CE strategies (Colorado et al., 2020; Hettiarachchi et al., 2022; Kreiger et al., 2014; Santander et al., 2020) while Ferreira et al. (2021) discuss AM and CE with a focus on waste and input materials and Ponis et  al. (2021) explore AM methods, materials and applications in recycling, reuse, remanufac‑ turing and repair. AM differs from other conventional manufacturing techniques that are subtractive (milling for example) or use moulds (injection moulding for example). A Computer-Aided Design model can be directly transformed into a 3D object that is built layer by layer from a range of different materials. This avoids the time‑consuming and costly tooling of conventional methods. Other advantages over conventional production methods include the ability to design and produce more complex shapes at low cost (these complex “geometries” offer new possibili‑ ties with shape and form, can have significant weight savings, maximise material properties and reduce the number of components needed – see the airline use case example above), greater speed of innovation, customisable production and fea‑ sibility in small production runs, reductions in production waste and energy use, reduced warehousing and the production of legacy and spare parts (Johns, 2022). Finally, another way in which AM can disrupt existing production and sup‑ ply chains is through the reduction in the physical distance between producers and consumers. This localisation effect is not a universal outcome of the adoption of AM  –  in many applications, it does not necessitate the shortening of supply chains – but in the context of supply chain disruption it is an additional attraction of using AM in many sectors. This resonates with the spatial consequences of sustain‑ ability and CE, as drives to reduce carbon emissions, particularly in the transporta‑ tion and logistics of materials, can lead to localisation. We can therefore establish that AM is a digital technology that is being increas‑ ingly adopted across many sectors, particularly high‑value manufacturing, and of‑ fers many advantages as a production method, several of which help to support sustainability in general, and CE in particular. Yet, the built environment – in par‑ ticular the construction industry – is in urgent need of more sustainable strategies to mitigate its high environmental cost. AM in construction is increasing worldwide with CyBe, Apis Cor, and Winsun already undertaking 3D printing projects for con‑ struction throughout Asia and Europe (Alhumayani et al., 2020). Well‑publicised examples of additively manufactured building projects include a bridge in Am‑ sterdam, a four bedroom in‑situ house in France and an office in Dubai (Gerrard,

Additive manufacturing and circular economies  253 2018). However, the environmental impact and life cycle assessment of 3D print‑ ing technology for construction is primarily unexplored in almost every phase, including design, process technology, and materials (Dixit, 2019). Construction companies face numerous and substantial challenges regarding the costs of production and sometimes the drive to save costs can overlap with sustain‑ ability goals. For example, the over‑ordering of concrete and tied‑up formwork are the main contributors to extra CO2 emissions of in‑situ concrete casting and a huge waste of materials (Tam et al., 2006). In construction virtually every wall, floor, panel, partition, structure, and façade are unique in dimension, which means either standard‑sized materials are cut down to fit or bespoke moulds are created to form each component (Lim et al., 2012). There is a cost‑based opportunity to save time and materials by reducing waste. If formwork and mould making is removed waste decreases – construction formwork typically accounts for 40% of the total budget for concrete work (Tay et al., 2017). AM can also help to reduce the quantity of materials by optimising form and allowing customisation. “Design of structures will not be limited to a collection of monotonous prefabricated elements” (Tay et al., 2017: 262). Khan et al. (2021) suggest that AM has unlimited potential in terms of ma‑ terial flexibility, savings, labour costs, design flexibility, and operation agility in construction. They also highlight that it allows the introduction of unconventional materials and locally available materials to increase sustainability. It is possible to print building parts using aggregate‑based materials, metals, or polymers, using a range of different processes and structures to do so. As building components are often large and made outside of a controlled environment, AM systems have been adapted to respond to this shift in scale. This has led to a range of different solu‑ tions (Labonnote, 2016). Often the printing head is moved by a large gantry robot with three degrees of freedom (Paolini et al., 2019). Advantages of this solution are that the gantry can support heavy weights and are easily controlled; however, they have limited mobility. For greater range of movement, arm‑based systems can be used (Keating et al., 2017), but these are less stable and harder to control. The integration of robotics with AM is a leading area of innovation in the sector to pro‑ vide different systems including collaborating robots (on the ground and in the air). While increasing attention is being paid to the use of alternative materials that can be 3D printed, such as sand, clay, adobe, and cob (Alqenaee & Memari, 2022; Gomaa et al., 2021a, 2021b, 2022; Rückrich et al., 2023), most research has con‑ centrated on concrete printing (Paolini et al., 2019). The extrusion printing, powder bed and 3D printed permeable technique methods are three leading 3D printing techniques used for concrete structures (Khan et al., 2021). There are a number of practical applications of concrete printing in the built environment, as high‑ lighted by Lim et al. (2012). First, in construction and architecture for acoustic panels, cladding panels, free‑form components, and functional walls. Second, pub‑ lic spaces, printing street furniture, fountains, and partitions. Third, for arts and de‑ sign applications such as furniture and sculpture (interior and exterior) (Lim et al., 2012). A leading area of research focus is on solutions for integrating reinforce‑ ment in printed concrete structures. Paolini et al. (2019) state that various projects

254  Jennifer Johns et al. have been implemented based on this research, for example, a bicycle bridge in the Netherlands (Salet et al., 2018). Lim et al. (2012) review three large‑scale AM pro‑ cesses used in construction – contour crafting, D‑shape, and concrete ­printing – and find that each has strengths and weaknesses. As construction components of any significant size are heavy, they suggest that in‑situ deposition approaches whereby parts are printed on site followed by assembly or ultimately printing large parts of a building in‑situ are preferred. Onsite production can increase quality, speed of production, and health and safety (Lim et al., 2012). At present, the bulk of the academic literature on AM in the built environment focuses on construction and does so from an engineering perspective in which dif‑ ferent technologies and processes are developed, tested, and evaluated. When the concept of CE is introduced, the range of literature narrows and still tends to take a technical focus (Colorado et al., 2020; Ferreira et al., 2021; Hettiarachchi et al., 2022; Kreiger et al., 2014; Ponis et al., 2021; Santander et al., 2020). This leaves great scope for further research and conceptualisation of the use of AM in sup‑ porting, or even creating circular economies in the built environment. As such, we will discuss the contemporary and potential application of AM in the construction industry by examining the different stages of the construction industry life‑cycle, from design through to demolition and the different destinations of materials. Additive manufacturing and the construction circular economy To understand the circularity of construction using AM, we focus on each of stage in turn, discussing design, manufacturing materials, construction, and post‑ construction. Design

Although AM can be relevant to design in multiple ways (e.g., as a prototyping tool for producing scale models during the design process), a central issue is how components and buildings can be designed to achieve the benefits of circularity using AM. From a design perspective, AM can currently be used in six ways. First, to optimise existing components (Çetin et al., 2021; Buchanan & Gardner, 2019) (primarily concrete, but also potentially polymer and metal components), allowing the quantity of material to be reduced. Optimisation most commonly focuses on optimising the geometry of the component, to place the material exactly where it is required, but there is also potential for customised material properties (Ngo et al., 2018). Second, to make use of recycled materials (Çetin et al., 2021), potentially local waste materials that can be recycled directly through a 3D printing process, thereby minimising transport distances (Pavlo et al., 2018) and avoiding the need for new material extraction. Third, to make use of bio‑based materials through 3D printing (Çetin et al., 2021). Fourth, to improve energy performance (Çetin et al., 2021), although Agustí‑Juan and Habert (2017) found that the energy performance benefits were outweighed by greater material production impacts. Some studies focus on the potential benefits without considering these trade‑offs, e.g., He et al.

Additive manufacturing and circular economies  255 (2020) discussed benefits of a green wall enabled by 3D printing geometry, but it is not clear whether the benefits outweigh the extra concrete that may be required. Fifth, to improve the potential for reuse (Çetin et al., 2021), through the opportu‑ nity to produced tailored connector pieces to enable reuse of existing components which are not perfectly sized for new uses. The possibly modular nature of 3D printed components may also enable reuse of parts, although this conflicts with in‑situ approaches to AM in construction (see discussion below). Sixth, to contrib‑ ute to producing buildings and built environments that are functional and attractive, helping to keep materials in productive use for longer (De Los Rios & Charnley, 2017) – recognising that frequently the reasons for obsolescence are non‑technical (den Hollander et al., 2017). As well as new opportunities, as a technology AM does have technical limita‑ tions which designers need to be aware of. The range of geometries that can be achieved through 3D printing of concrete is limited by the need for the concrete structure to remain stable before it can set, which limits overhangs and construc‑ tion height. If there is a need for structural reinforcement, this must be somehow either embedded with the printed concrete, or hollow voids must be included into which post‑tensioned steel reinforcement can be added later (Tay et al., 2017). There are always conflicting goals and trade‑offs in the design process that must be considered. The need to think about CE strategies in design comes on top of many existing “Design for X” issues, such as Design for Manufacturing or Design for Assembly. One way of looking at it is to introduce some variant of “Design for Circularity” as another item in the list. Many such “X”s have been proposed with greater or narrower breadth, such as Design for Adaptability (Geldermans, 2016), Design for Multiple Lifecycles (Go et al., 2015), and Design for Product Integ‑ rity (den Hollander et al., 2017). Material efficiency is an overlapping perspective (Allwood et al., 2011). However, Holt and Barnes (2009) caution how this can result in looking at everything in isolation, and an integrated top‑down approach is needed to balance conflicting priorities and Charef et al. (2022) highlight the limitations of design‑only approaches (like prefabrication where deconstruction is not prepared). Even within the “Design for Circularity” scope, there are conflicting goals to balance. The potential for customisation and optimisation of components is in conflict with reusability and flexibility, which benefit from standardisation and modularisation. Beyond this, even though there may in principle be benefits to being able to produce high‑performance complex optimised geometries, there can be a “complexity penalty”, where the opportunity to produce complex designs, perhaps for aesthetic reasons, leads to less efficient designs in the end (Dunant et al., 2021). Although multi‑functionality is proposed as a benefit of AM (He et al., 2020; Agustí‑Juan & Habert, 2017), it can also increase the chances of early ob‑ solescence (den Hollander et al., 2017). The ability to tune material properties to optimise performance can potentially reduce the quantity of material needed (Ngo et al., 2018) but can make recycling more difficult than for simple pure material components. Clearly, material selection is an important design consideration, and thus, we now turn to examine manufacturing and material.

256  Jennifer Johns et al. Manufacturing and materials

Material selection in AM is always a compromise between the material charac‑ teristics desired and the capabilities of the process type selected. This extends to applications in the construction sector, for which material availability is currently relatively limited in both variety of options and performance capabilities. From a CE perspective, the choice of materials used has a significant environment impact; both in terms of their initial application, and subsequently in reuse, recycling, and in eventual disposal. In the construction sector overall, concrete is the most abundantly used ma‑ terial for projects worldwide, with attributes such as cost, strength, availability, and formability making it suitable for a wide range of applications. Production of Portland cement produces between 600 and 800kgs of CO2 per tonne of ce‑ ment (Nature Editors, 2021) as a result of its heating to high temperatures, and the breakdown of calcium carbonate into calcium oxide and CO2. Furthermore, concrete places demand on the world’s energy resources: overall, cement produc‑ tion represents 7% of global industrial energy use (International Energy Agency, 2018). Notably, many other construction materials have worse environmental cre‑ dentials in production; steel for example produces 1–3 tonnes of CO2 per tonne of steel (Somers, 2022). Currently, a selection of materials compatible with AM offers some potential opportunities for printing in the construction sector. Polymer materials are rela‑ tively low cost and have low density but have limited strength and need fibrous reinforcement (e.g., glass fibre and carbon fibre) that constrains their suitability for larger applications (Ghaffar et al., 2018). Wood composites comprising starch, wood particles, and lignosulfonate have been demonstrated in the production of fully recyclable walls (Kromoser et al., 2022). Earth materials such as cob offer significant advantages over construction methods such as concrete; a recent syn‑ thesis (Gomaa et al., 2021b) highlighted that cob has lower CO2 emissions, lower embodied energies, creates less waste material, whilst also being complaint with building regulations. Similarly, efforts have been extended in utilising heated sand with suitable binders, which is particularly of interest in environments that have an abundance of sand. Clay also provides opportunities in construction (Konto‑ vourkis & Tryfonos, 2020). These options noted that it is concrete that is most used in AM for construction purposes. Many of the commercial deployments of AM in the construction sector have drawn on opportunities to use concrete. However, concrete presents significant challenges in adoption for AM, through material failure (where yield, flow, or frac‑ ture occurs once material strength is exceeded), or through stability failure (lead‑ ing to uncontrolled deformations or displacements) (Mechtcherine et  al., 2020). Getting the right mix is also problematic; there needs to be sufficient extrudability in order to flow from the additive process, maintaining buildability characteristics when laid down, and having a workability time that is adequate for deposition, but setting quickly enough to support subsequent layers (Le et al., 2012). AM offers some potential opportunities for reducing the environmental impact of concrete. Changing the blend of materials by partially substituting Portland

Additive manufacturing and circular economies  257 cement can significantly alter the CO2 emissions (Lothenbach et al., 2011), us‑ ing materials including granulated blast‑furnace slag, fly ash, silica fume, marble sludge, and quarry dust (Khan et al., 2021). Introducing these materials affects the material characteristics of the cement produced, and therefore careful considera‑ tion of the implications for the final structure is needed; however, such substitu‑ tions do offer considerable environmental benefits. Such material exchange takes the waste from one industrial process as the raw materials for another; this indus‑ trial symbiosis represents an important contribution to the CE. Utilising waste in this manner not only lessens the CO2 impact arising from the concrete, but it also negates the need to manage the waste disposal from other processes through land‑ fill (or similar), benefiting the environment. Where this waste can be sourced local to the construction site, Khan et al. (2021) identify that CO2 can be reduced further by lessening transportation requirements for raw materials. One of the other key advantages identified in AM for construction is the op‑ portunity to lessen material content in the structures that it produces. Traditional constraints associated with conventional approaches to construction in concrete present significant limitations on the geometries that can be achieved. In applica‑ tions of concrete using AM, the ability to produce complex geometric structures enables designers to propose shapes that offer optimal performance with much less material (Lim et al., 2012; Gosselin et al., 2016; Ooms et al., 2021). As a result, there is a lessened need for cement materials in construction, and at end‑of‑life for the structure, there will be less waste to manage. How materials are selected, manu‑ factured, and integrated into the built environment is fundamental to construction, to which we now turn. Construction

When considering the use of AM in the construction process consideration needs to be made regarding how (process selection) and where (location) printing takes place. Some forms of AM processes (of which there are seven – material extru‑ sion, sheet lamination, binder jetting, material jetting, directed energy deposition, powder bed fusion, and vat photopolymerisation) are relatively infeasible and have therefore received limited research or commercial attention. Material extrusion is the dominant approach to AM in construction. Compared to other process types, it is relatively scalable to accommodate production of structures of sizes seen in construction projects. Du Plessis et al. (2021) provide examples including houses, shelters, bridges, and other large‑scale structures for construction projects, and note some of the challenges presented by the technique. Material extrusion also enjoys relatively good alignment with preferable material choices used in the construction industry such as concrete. In operation, cementitious materials are transferred from a reservoir or store by pumping and/or gravitational flow to the extruder. Processes such as Contour Crafting use an extrusion nozzle (typically affixed to a crane) to successively lay layers of materials on top of each other, building large‑scale struc‑ tures from a 3D CAD model. Whilst there are currently many constraints around the mechanical characteristics of this approach (Arunothayan et al., 2023) and a

258  Jennifer Johns et al. reliance on specialist quick‑setting concrete materials (Gosselin et al., 2016), the speed and scalability of such extrusion‑based approaches have led to much enthu‑ siasm for their application in construction projects. Locational choices may have a significant impact on the environmental impact of construction. Typically, construction projects deliver their outcomes at a specific location (e.g. a building site); however, the fabrication process may take place in a multitude of locations by a wide range of organisations. Whilst on‑site construc‑ tion negates the need to transport finished components to their required designation (often physically impractical due to size and weight constraints), it introduces ad‑ ditional challenges around the physical environment and availability of specialist resources to be collated at a single site (Waris et al., 2014). Off‑site construction is a nuanced concept with many synonyms, but broadly concerns prefabrication, where manufacturing takes place at a specialised facility to form components of the final installation and pre‑assembly, where various materials and prefabricated com‑ ponents are joined together for subsequent installation as a sub‑unit (Tatum, 1987). Whilst much research in AM has explored the general benefits around localisa‑ tion of production in terms of responsiveness (Demir et al., 2021), effective inven‑ tory management (Bonnín Roca et al., 2019), and other opportunities for supply chain improvements (Ryan et al., 2017; Khajavi et al., 2020), as yet there is little detailed research that extends these principles in the construction sector. Examples such as Bazli et al. (2023) demonstrate that AM may be employed within construc‑ tion in direct fabrication on‑site. Likewise, examples such as Anton et al. (2021) highlight off‑site construction in line with activities undertaken within the termi‑ nology of prefabrication. While there is little emphasis on implications arising for the CE of this model in literature, several potential benefits are apparent. In terms of transportation emis‑ sions, by producing local to demand, transportation of finished structures is elimi‑ nated (Bazli et al., 2023). Similarly, by recycling materials on‑site, benefits may be observed in the extent of recycling, and the environmental implication of doing so. Furthermore, on‑site production may extend to in‑situ repair (Delgado‑Camacho et al., 2018), allowing structures to be fixed rather than replaced. This is both ben‑ eficial from a circularity perspective, but also can positively affect time and cost measures for the construction project too. On‑site construction using AM offers the potential to produce housing in remote locations, providing better housing that has improved environmental credentials than is possible using traditionally available resources (Bazli et al., 2023). Concentrating production in off‑site facilities typically offers productivity ben‑ efits arising from specialism and the achievement of economies of scale, though recent studies suggest AM may overcome such traditional constraints (Helkiö & Tenhiälä, 2013; Eyers et al., 2022). In prefabrication with AM, Anton et al. (2021) identify benefits in terms of better machine calibration capabilities, ability to pro‑ duce in different orientations than final application, and better controlled environ‑ mental conditions for the construction materials. All these characteristics imply less likelihood of waste generation in the fabrication process compared to site‑based production. By extension, prefabrication lessens the need for site‑based workers

Additive manufacturing and circular economies  259 (reducing transport), enhances safety through controlled conditions, improves ef‑ ficiency of resource usage, and offers the potential for more effective waste recy‑ cling through well‑defined recycling processes (Chang et al., 2018). Post‑construction

While we can observe increasing research and academic literature around circu‑ lar economies and design, materials, and construction, the application of AM in the construction sector post‑construction is rather more limited. When considering the 9Rs of CE strategies, Yang et al. (2022) note that the construction industry concentrates on recycling and reuse, in contrast to manufacturing, for example, which tends to achieve higher levels of circularity due to broader implementation of remanufacturing and industrial symbiosis. There is certainly greater scope for AM to enable circularity in construction – and the loop cannot be closed without consideration of this stage – but focus is currently placed on design and construc‑ tion. This section will outline some of the tentative steps that are being taken within this stage of the built environment lifecycle. As suggested in the construction section above, researchers have been working to develop environmentally friendly construction materials to reduce energy and resource consumption, designed to be partial or complete substitutes for Portland cement (Sahin et al., 2021). Consideration also needs to be made regarding the huge amounts of construction and demolition waste (CDW) generated at the end of the life of a building. As more advanced materials are being developed, such as ge‑ opolymers, work is progressing to recycle demolition materials into new material for AM (Panda et al., 2018). Mir et al. (2022) have developed a method that utilises CDW, creating a geopolymer from hollow brick, red clay brick, roof tile, and glass to form a sustainable resource. As CDW requires crushing, milling/griding, and mixing to produce the geopolymer binders, it can involve intensive consumption of electricity. Life cycle assessments indicate that renewable sources of electricity should be used (Mir et al., 2022). AM can also be used within the wood construction industry, manufacturing structures made of a composite of renewable secondary resources. Kromoser et  al. (2022) introduce a new strategy for AM called 3DP Biowall, which uses only renewables coming from waste/side streams, i.e., from the sawing and paper industries and is fully recyclable. The use of AM as a method to use bio‑based waste (such as particleboards, panels, laminated floors, furniture, and construction formworks) in construction would be a significant contribution to CE strategies in construction. Caldas et al. (2021) report that more than 10 million tons of wood waste are generated annually in Brazil, 63% of which is burned, often without energy recovery. The scope of existing literature on AM and the 9Rs of CE strategies highlights the emphasis placed on the adoption of AM technologies unevenly across the con‑ struction lifecycle. This is driven by the emphasis placed on AM to reduce waste and material usage, placing necessary emphasis on design stages. Consideration of the use of AM post‑construction has yet to seriously explore the potential role

260  Jennifer Johns et al. of AM in reuse, remanufacture, recycling and repair. This section has highlighted some contemporary innovations, focused on recycling waste materials, but there is much potential for research on how AM could be utilised to repair (the use of AM in spare parts, to reduce logistics and warehousing, printing on demand and at the site of use), and to remanufacture (particularly in metals, see Sato et al., 2022 although not applied in construction). In contrast, the use of AM in construction could hinder reuse, particularly where the technology has been used to manufacture highly customised construction items. Conclusion This chapter has discussed the use of AM towards circular economies in construc‑ tion, covering design, materials, construction processes, and post‑construction. El‑Sayegh et al. (2020: 21) suggest that “3D printing has the potential to revolu‑ tionise the construction industry. Along with advances in Industry 4.0, it has a high potential to lead to a more efficient and sustainable construction”. While there is much positive rhetoric about 3D printing in construction, application is still limited in scope. Although there are many opportunities for AM to aid circular economies, there are still several barriers related first to the technologies themselves, and sec‑ ond to the ways in which the technology is understood and applied in practice. AM can be an environmentally friendly technique with minimal waste but can be energy intensive so sourcing renewable energy sources is important. Much con‑ temporary technological development in AM is focused on developing printers that can use multiple materials (e.g., printing circuit boards within a plastic or metal object). However, as Lederer et al. (2017) highlight, the risk of introducing heavy metals into any material loop can hinder future recyclability. As our above discus‑ sion of materials and construction demonstrates, this is also a concern in construc‑ tion. Other limitations relate to the methods by which materials are extruded. Here, technological development and innovation focus on how other digital technologies such as robotics can expand and stabilise construction printing. We conclude this chapter with reflection on where the greatest effort could be concentrated within the CE for the construction sector to best make use of AM to increase the sustainability. We argue that designing for circularity (and designing for AM) demands designers or design teams have broader skill sets. These need to cover not only the technical design requirements but also designers’ broader role in educating and influencing consumer perspectives (De Los Rios and Charnley, 2017). In reference to CE in general, Andrews (2015) argues that designers can‑ not wait for circular business models and the infrastructure to support them before starting to design for a CE. They must lead the paradigm shift and are best placed to close the loops by influencing business and consumer behaviour through “ex‑ tending actual product life and increasing perceived value of products” (Andrews, 2015: 312). In the construction industry, architects and other designers are key to the drive towards circularity, but they need to develop the core competencies to understand, assess, and design for circularity (Sumter et al., 2018). As in many

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13 Conclusion Rabia Charef

This chapter serves as a brief conclusion to the book, summarizing the key ele‑ ments discussed in earlier chapters. It provides summaries of each section, raising questions and dilemmas for further consideration and avenues for future research. The construction industry’s transition to a true circular economy is essential for sustainable development, resource conservation, climate change mitigation, and long‑term economic viability. By embracing circular principles, the sector can play a vital role in building a more resilient and environmentally friendly future. This book has helped to clarify what the circular economy applied to the built environ‑ ment truly is, by curating some of the world’s leading research. In particular, it is crucial to implement rigorously the circularity principles in their complexity and paradigm‑shifting dimensions. This needs to be done in a society that has been driven by greenwashing for decades, and the environmental and societal challenges remain and continue to worsen. An additional distinctive feature of the book is its collaboration among academia, industry, and practitioners to address global challenges, showcasing cutting‑edge practices, research findings, and innovative initiatives. Embracing an inevitable paradigm shift: a multi‑level re‑organization Numerous authors concur that a profound paradigm shift is essential to embrace a circular approach. Other approaches, such as the low‑tech approach, could fit seamlessly with the circular economy and become part of the circular economy principles. These concepts may share common objectives and strategies, such as improving resource efficiency, and diminishing environmental footprints. By as‑ similating circular economy principles into the low‑tech approach, the construction industry could elevate its commitment to sustainability and environmental stew‑ ardship while bolstering economic viability and societal well‑being. This harmo‑ nious synergy fosters a more resilient and resource‑conscious built environment. The multi‑level organization paradigm shift also refers to a fundamental trans‑ formation across various levels of, technicity, society, and industry. The first re‑­ organizational level of high‑tech/low‑tech likely involves categorizing or choosing between these two broad approaches when designing, constructing, and managing DOI: 10.1201/9781003450023-17

Conclusion  269 buildings and infrastructure. It is about deciding whether to embrace advanced technology and digitalization (high‑tech) or to opt for simpler, resource‑efficient methods (low‑tech) to achieve circular and sustainable goals. This choice can have significant implications for how projects are executed and how resources are man‑ aged within the built environment. This shift involves reorganizing and rethinking how we approach construction, design, resource management, and waste reduction at multiple levels, including social, economic, political, organizational, and tech‑ nical aspects. It entails moving away from traditional linear models of resource consumption and waste generation toward circular models that prioritize sustain‑ ability, resource efficiency, and reduced environmental impact. This paradigm shift acknowledges the interconnectedness of these levels and aims to align them in a way that promotes a more circular and sustainable built environment. As for technology, its role can be dual‑edged: it can either facilitate or pose a potential risk to the transition toward a circular economy. The outcome largely hinges on how technology is conceptualized, applied, and integrated into circular economy strategies and the low‑tech approach. The industry must understand that it is not anymore possible to continue Business As Usual using greenwashing. Urgent action is needed by all construction stakeholders to address the climate emergency. Is technology an enabler or a danger for the transition to the circular economy? Technology plays a significant role in several key aspects. Technology enables im‑ proved tracking and monitoring of resources throughout their lifecycle, helping to enhance resource efficiency, reduce waste, and optimize material flows. Advanced technologies like robotics and AI improve recycling processes, making it more efficient to recover valuable materials from waste streams. Innovations in mate‑ rial science also contribute to easier recycling and upcycling. Digital technologies and platforms support the development of circular business models, encouraging practices like product‑as‑a‑service and sharing economy platforms. These mod‑ els promote product longevity, repairability, and resource sharing, aligning with circular economy principles. Moreover, technology can connect stakeholders, businesses, and consumers within circular economy networks, fostering collabo‑ ration, knowledge sharing, and the exchange of materials, products, and services. Blockchain technology can enhance transparency and security in circular supply chains, improving trust and traceability. As a result, these technological advance‑ ments collectively contribute to the transition toward a circular built environment by promoting resource efficiency, reducing waste, and encouraging sustainable practices. However, there is also a potential danger associated with the use of technology in the construction sector. The digitalization of processes can lead to resource‑­ intensive technologies, electronic waste generation, dependency on finite resources, data privacy concerns, complexity and overengineering, exclusionary practices, rebound effects, and compatibility issues. Indeed, the rebound effect, where

270  Rabia Charef increased efficiency and convenience in resource use may encourage more con‑ sumption and construction, thereby offsetting the environmental gains. Addition‑ ally, there are concerns about the environmental impact of producing and disposing of electronic devices and the energy consumption associated with digitalization. These challenges need to be carefully addressed to ensure that the benefits of tech‑ nology enablement in the circular economy outweigh the drawbacks. Therefore, the key lies in responsible and strategic use of technology, ensur‑ ing that it promotes not only efficiency but also sobriety and sufficiency. These challenges need to be carefully addressed to ensure that the benefits of technology enablement in the circular economy outweigh the drawbacks, ultimately promoting sustainability, resource efficiency, and reduced environmental impact in the built environment. Future research requirements Pursuing research in the area of the circular economy for the built environment is crucial to address the complex challenges and uncertainties that lie ahead. Re‑ searchers should focus on several key areas to ensure the responsible and effective use of technology: • Rebound Effect Mitigation: Investigating strategies to mitigate the rebound effect associated with technology adoption is essential. Understanding how to balance increased efficiency with responsible consumption will be a critical area of research. • Life Cycle Assessment (LCA): Advancements in LCA methodologies tailored to the circular economy are needed. Researchers should develop comprehensive tools and models for assessing the environmental impact of circular construc‑ tion practices, including the life cycle analysis of digital technologies. • Digital Innovation: Researching emerging digital innovations and their poten‑ tial to disrupt and enhance circular practices is valuable only if conducted with an assessment of their benefits beyond private advantages for the industry. This includes investigating the applications of blockchain, artificial intelligence, and the Internet of Things (IoT) in material tracking, supply chain management, and circular design, while considering their broader implications, especially in terms of environmental impact. • Policy and Regulation: It is crucial to explore the development of policies and regulations that support discernment in the use of new technologies in the circular economy. Researchers should help create frameworks that encourage sustainable practices and discourage environmentally harmful technological applications. • Education and Awareness: Future research should also focus on educating stakeholders, including industry professionals, policymakers, and the public, about the responsible use of technology in the circular economy. Raising aware‑ ness about both the benefits and potential risks of technology is vital for in‑ formed decision‑making.

Conclusion  271 Policy and practical recommendations Policy recommendations aimed at advancing the principles of a circular economy within the construction sector hold significance in addressing critical challenges such as waste reduction, environmental impact mitigation, and the promotion of sustainable practices. To strengthen the construction industry’s commitment to sustainability and circularity, a set of policy suggestions and practical recom‑ mendations for construction companies, architects, builders, and other stakehold‑ ers are suggested. The recommendations are classified into four categories as follows: Education and awareness • Develop training programs for construction professionals, including architects, engineers, and builders, to promote awareness and knowledge of circular econ‑ omy principles and practices, including the benefits of using bio‑based and natu‑ ral materials such as earth from excavation. • Launch public awareness campaigns to educate consumers and homeowners about the benefits of choosing circular and sustainable construction options. • Collaborate and partner with suppliers, reusers, recyclers, and other stakehold‑ ers to create closed‑loop material supply chains. • Invest in research and development programs focused on circular construction technologies, materials, and methods through industry‑academia collaboration. • Encourage design innovation by providing grants, subsidies, or tax incentives to construction firms and architects adopting circular design principles, such as modular construction and sustainable architecture. Circularity design and material strategies • Design for Disassembly and Reuse by incorporating modular and standardized building components, easily disassembled components with reversible connec‑ tions to facilitate deconstruction. • Opt for a strategic material selection to prioritize sustainable and low‑carbon recycled materials, and also opt for bio‑based and locally sourced materials to reduce transportation‑related emissions (e.g. earth from excavation, stone). • Prefer adaptive reuse strategies by exploring opportunities to repurpose existing structures instead of demolishing them. Retrofit and renovate buildings to meet modern standards and sustainability goals. Circularity assessment and incentives • Use Life Cycle Assessments (LCA) to evaluate the environmental impact of construction projects and identify areas for improvement. • Establish a circular economy certification system for construction projects and companies embracing circular economy principles to incentivize their participation.

272  Rabia Charef • To ensure accountability and transparency, establish a robust system for track‑ ing and reporting the progress made in circular economy initiatives within the construction sector. • Revise building codes and standards to include requirements favoring the reuse and recycling of recovered materials, while striving to maintain their highest possible value. • Develop certification programs and labeling schemes for bio‑based and natural materials (e.g., stone and earth) to help clients and architects to choose these sustainable options. Waste management and responsible procurement recommendations involve various initiatives • Enforce regulations requiring building deconstruction and salvage to recover valuable resources and reduce landfill waste. • Invest in efficient infrastructure for waste management, prioritizing reuse, re‑ conditioning, and upcycling. • Introduce taxes on the extraction of virgin resources and landfills while incentiv‑ izing the reuse of products, components, or materials and strategies to maintain them at their highest value. Also, encourage the production and use of bio‑based and natural materials in construction making them more cost‑competitive with traditional materials. • Implement the “polluter‑pays” tax to align economic incentives with environ‑ mental responsibility. It aims to encourage businesses to minimize waste, re‑ duce pollution, and adopt practices that contribute to a more sustainable and circular approach to resource management. Material responsibility and traceability recommendations could be: • Create and maintain “material passports” for construction materials to facilitate tracking and reuse. They should contain their origin, composition, and reuse/ recycling potentials, as a minimum. • Implement material tracking systems and maintain detailed documentation. • Encourage Green Procurement Policies (GPP) for sustainable construction ma‑ terials (including bio‑based materials, stone, and earth from excavation waste) to prioritize products with preferably high reuse and recycled content and low environmental impact. This creates a market for sustainable construction materials. • Explore circular business models and remanufacturing opportunities. • Introduce Extended Producer Responsibility (EPR) programs that make manu‑ facturers and suppliers responsible for the end‑of‑life disposal and recycling of their construction products. This will encourage Design for Disassembly, reuse, and recyclability.

Conclusion  273 In light of these extensive recommendations, it is crucial to approach digitalization and high‑tech advancements in construction cautiously. While these innovations offer circular economy potential, we must be wary of rebound effects. Achieving waste reduction and sustainability requires a shift in our relationship with nature; a shift in our thinking and a re‑orientation of our values. Implementing circular‑ ity principles calls for a holistic approach, encompassing education, collaboration, innovation, and responsible procurement. Sustainability is not just a goal; it is a mindset committed to resource preservation. By following these recommendations and respecting nature, we can create a more sustainable, circular future.

Index

adaptability 15, 99, 100, 102, 206, 255 adaptive reuse 24, 164, 271 additive manufacturing–AM 3, 250–61 adjuvantation 183, 189, 195 aesthetic 15, 55, 146, 155, 207, 240–55 aggregate 46, 75, 124, 129, 170 Airbnb 72, 76–78, 80, 82 architectural system 130 artificial intelligence 12, 19, 55–56, 251, 270 asbestos 116, 163, 203, 214 as‑built digital model 246 assessment 3, 14, 106–07, 119–20, 135–38, 144, 176, 181, 187, 191, 208, 213, 219, 221, 225, 270–71 asset catalogue 219; asset lifecycle 41, 97, 105; asset manager 105; asset retention 118 ATEx (Appréciation Technique d’Expérimentation) 188 audit 41, 118–20, 126, 203–04, 236, 239 authenticity 79–82 availability 39, 54–55, 62–64, 115, 125, 236, 256 awareness 8, 18, 58, 133, 149, 178, 207, 270–71 backfilling–backfill 27, 103, 201, 224 barriers 14, 18, 47, 96, 126–27, 135, 183–84, 207; hurdle 35–36 behaviour 137, 140, 143, 145 big data 62, 251 Bill of Quantities (BoQ) 119–20 BIM model 41, 105, 208, 217, 221, 241, 246 Building Information Modelling (BIM) 1, 41, 51, 54, 56, 58–60, 105, 208–09, 211, 213–15, 217, 219, 221, 224, 246 buildings as material banks (BAMB) 55– 56, 62, 79, 115–27; building attributes

56, 59; building codes 91, 102, 104, 272; building component reuse 24–25; building element reuse 24; building footprint 51, 53, 58; building inventory 52, 57; building level 71; building services 239; building specifications 50; building stock 1, 13–14, 47, 50–52, 54, 57–58, 79; building surveying 56; building system 9, 184–85; building technique 179, 183, 186–87 bio‑based 254, 259, 271–72 biodiversity 93, 115 bio‑sourced 13 blockchain 2, 19, 78–82, 212, 217, 270 bottom‑up 48, 50–54, 59, 61, 88 BREEAM 33, 40, 119–20, 190, 208 brick 24–26, 29–30, 115, 124, 241 brownwashing 181 Business As Usual (BAU) 122, 127, 269 business models 72, 94–96, 98, 100, 118, 125–27, 202, 260, 269, 272 by‑product 96 cadastral 48, 51 carbon‑efficient 234; carbon emissions 51, 75, 91, 95, 106–07, 118, 252; carbon expenditure 236; carbon footprint 15, 107, 252; carbon‑intensive 46–47, 51, 81; carbon payback period 240; carbon trading 74, 76 carpet 125 CE marking 36, 40 cement 103–04, 183, 186, 256–57; cement‑based 27, 30 certification 19, 47, 59, 63, 207, 242, 247, 271–72 characterisation 90, 136, 190–91 circular approach 90, 125, 182–83, 186, 251, 268, 272; circular construction 1–5, 24, 70, 89–94, 97–98, 104–05, 171,

276  Index 270–71; circular buildings 13, 25, 100, 106, 118–19, 179; circular resource 119; circular thinking 97 circular economy principles 70, 103, 119, 150, 236, 268–71 classification 50, 52–53, 57, 61, 241 cleaning 24, 28, 31, 130, 132, 193 climate change 11, 16, 129, 150–51, 202–03, 268; climate crisis 37, 90, 236; climate impact 98, 201 closed‑loop 70, 120, 205, 250–51, 271; closed stock 204 cloud 57, 120, 211, 219, 221 codes 49, 78, 91, 102, 104, 187, 272; national building codes 91, 104 CO2 emissions 256 collaboration 58, 63, 151, 188–91, 268–73 comfort 10–11, 13–14, 17–18 commitment 18, 20, 151, 153, 156–58, 175, 207, 268, 271 common goal 20, 97; common system 104 complexity 9–10, 14, 107, 151, 158, 180, 203, 215, 223, 255, 268, 269 compliance 88, 92, 96–97, 119, 122, 170 component intensity 53; component‑level 53–54 Computer‑Aided Design (CAD) 211, 252 conservative 90, 101–02 constraints 18, 31, 63, 135, 145, 148, 150, 174, 190, 192, 194–95, 207, 257 construction and demolition waste (CDW) 46, 259, 201–04, 207, 259; construction waste material (CWM) 2, 70–83 construction circularity 70, 73; construction costs 15 Construction Products Regulation (CPR) 92, 102, 104, 107 consultation process 108 consumerism 202 consumer society 34 consumption patterns 7, 11, 13 contaminated sites 214; contamination 61, 63, 222 contractor 26, 32, 73–74, 121–22, 133, 175, 192–93, 235–36, 239, 245–46 control officer 187–89, 191, 193 costs 9–10, 15, 26–27, 30–31, 36–38, 69– 70, 75, 78, 81–83, 121–27, 166–67, 192, 206, 213–14, 223, 225, 252–53, 256 Cradle‑to‑Cradle 125 damage 7, 149, 171, 186, 210, 244 database 40, 48, 79, 212, 217, 224, 234; data centres 9–10, 19; datasets 50–55, 57, 62, 212, 223; data storage 62

data capture 57–60, 62, 210 data management 57 data standardisation 104–05 decarbonisation 106–08 decision‑makers 236; decision making 93, 95, 105, 119, 158, 213, 217, 219, 221, 226 deconstruction 2, 19, 121–22, 129–30, 132–50, 153, 181–83, 201–26, 235–36, 245, 271–72 degrowth 7 Delft Ladder 24, 27; Ladder of Lansink 24 demand 7, 78–82, 125, 207 demolition 26–30, 36, 54, 69, 115–26, 201–06, 208–10, 223, 233–37, 239, 259; demolition waste 46, 116 demountable 245 depletion 25, 27, 31, 40, 205 design phase 149, 187–94, 236; design flexibility 20, 253; Design for Adaptability 255; Design for Assembly 255; Design for Circularity 255, 260; Design for Deconstruction 12; Design for Disassembly 12, 102, 205, 212–14, 271–72; Design for Manufacturing 255; Design for Multiple Lifecycles 255; Design for Product Integrity 255; Design for X 255; Design Science Research (DSR) 74; design stages 232, 236, 259; design team 119–20, 185–86, 188–89, 191, 232, 235–36, 239, 244–46 digital data 126; digital dataset 212; Digital Deconstruction (DDC) 209–10, 219–21, 226; digital infrastructure 9, 58; digitalization 1–3, 7–8, 269; digital matchmakers 78; digital model 246; digital passports 126; digital product 235; Digital Reversibility Assessment (DRA) 219, 221; digital system 9; digital technology 55–56, 252; digital tools 2, 217, 225, 250; Digital Twin 32, 58 discernment 1, 270 dismantling 24–26, 29–31, 36–38, 132, 213; dismantlement 214 dispute 76, 81 distrust 34 donor and recipient 121 door 55 downcycling 9, 75, 103, 108 durability 135, 138, 145–46, 206 earth blocks 186–88, 191, 193; earthen materials 180 ecodesign 102, 107, 108; ecosystem 90–91

Index 277 Ecodesign Directive 102 economic system 12, 72, 91; economic viability 20, 27, 220, 268 education 19, 270–71 efficiency 10–11, 20, 31, 76, 93, 103, 235, 269–70 Ellen Macarthur Foundation (EMF) 93, 179–80, 202 embodied carbon 40, 46, 51, 116, 119, 232– 33, 235, 240; embodied energy 51, 175 EN 15804 40, 208; EN 4555X standards series 103; EN 15978 107 end‑of‑life (EoL) 32, 41, 101 end‑of‑pipe 11–12 end‑users 78, 122, 183, 193, 209, 212 energy consumption 8, 15–17, 186, 270; energy intensive 33, 260; energy leakage 93; energy loops 93; Energy Performance of Buildings Directive (EPBD) 92, 99, 102, 104; energy system 104; energy transition 9, 16; energy use 69, 252, 256 environmental authorities 76; environmental benefits (gains) 9, 93, 106–07, 151; Environmental Product Declaration (EPD) 40, 104, 106; environmental performance 40 erosion 159–62, 193 Eurocode 6 193 European Commission 1, 16, 36, 90, 99–100, 201, 206; European Court of Justice (ECJ) 101; European Green Deal 1, 16, 90, 95, 99–100, 201, 206; European level 36, 95; EU Single Market 92, 107 evaluation system 80, 82 excavated soil 179, 190 exchange platforms 124–25 existing buildings 13–14, 16, 116–20, 164; existing assets 117–18 Extended Producer Responsibility 74, 272 extend product lifetime 103 fabrication 125, 176, 258 façade 39, 53, 56–57, 59, 101, 132, 185–87, 222–23, 253 feedstock 125–26 financial risk 192 finite resources 250, 269 fire resistance 191, 194, 202 fiscality 26, 37 flooring 28, 125–26, 132, 164, 176, 240 flying factory 182, 186 fossil fuel 9, 37 Fourth Industrial Revolution 250

fragmented 91, 96–97 framework 1–2, 13–14, 31, 61–62, 70–74, 80–81, 89–97, 102, 106–07, 164, 182– 83, 202, 208, 213, 234; (9R) framework 180; policy framework 80, 91–92; qualitative framework 181, 185–86, 194 frontrunners 91, 96 Geographical Information System (GPS) 50, 57, 220 glass partition 125, 243–45 global scale 9 government 7, 11, 18, 74, 80, 83, 204–05, 247 green building 40, 42, 46, 71; green jobs 16; green label 77–78, 82; greenwashing 8, 129, 181, 268–69 growth 7, 70, 73, 80, 99; economic growth 11, 16; green growth 7; post‑growth 12; anti‑growth 100 guidance 98, 104, 247 health 163; health and safety 122, 163, 245, 254 hierarchy 24, 69, 97–98, 121, 166; 10 R hierarchy 234; economy hierarchy 93, 97; waste hierarchy 98, 103, 239, 243; value retention hierarchy 121 high‑value 52, 81, 210, 225, 252; high‑level circular(ity) 90–91, 99; high‑tech 1, 7–10, 14–15, 18, 20 holistic 11, 14, 18, 94–95, 163, 273 horizontal standard 102 housing crisis 11 human activities 81; human behaviour 11; human labour 12, 15, 19, 34, 37 implementation 18–20, 47, 106–07, 136, 170, 183, 192, 210 incentives 19, 121, 271–72 indicator 129, 145, 150, 164; circularity indicator 150–51; economic indicators 226; functional indicator 102; efficiency indicator 121; LEVEL(s) indicator 107; RBIM indicators 223; reuse potential indicator 148–49; value retention indicator 121 industrial ecology 47, 55, 93; industrialisation 26–27, 31; industrial system 9, 41, 179 inert material 69; inert waste 69, 116, 121–24 information‑sharing 81 infrastructure 20, 26, 46–47, 57–58, 210, 260; recycling infrastructure 121

278  Index initial cost 10 innovation 19, 30–31, 270–73; digital innovation 2, 270 in‑situ repair 258 insulation 164–65, 189 insurance–insurability 186–87, 206 integrated platform 209, 217–23, 226 integrative design 184 Internet of Things (IoT) 82, 270 in‑use energy 14, 16; in‑use phase 183, 186–87 inventory 41, 48, 50–53, 56–57, 59, 61, 63, 120, 170, 176, 215, 220–23; material inventory 175, 210–13, 215, 219 ISO 14040 40, 208; ISO 20887 102, 214; ISO 21931 208 Jevons paradox 10 job‑driven activity 19 labelling schemes 33, 40 labour 34, 37, 54; labour cost 15, 19, 37–38, 245, 253 lack of information 53, 207–08 landfill 181, 272; landfill tax 121 laser 57, 211; LiDAR 48–49, 57, 59 layers 25, 137, 159, 162, 171, 243, 247, 256 legislation 36; product legislation 36, 40, 102, 107 level of detail (LoD) 57–59, 61, 64, 106, 120, 136, 143; level of certainty 61; level of circularity 186, 186, 189, 192, 194; levels of maintenance 238 lifecycle (life cycle) 97–98, 101, 103, 105– 07, 117–18, 235, 269; life cycle analysis 149–51, 180; life cycle assessment (LCA) 116, 129, 270–71; lifecycle thinking 34; material lifecycle 245–46 life expectancy 243, 247; lifetime 51–52, 54, 62; extend product lifetime 103 lighting 125 lime‑based mortar 30 limitations 61, 174, 250–51, 255, 257 linear economy 1, 7–9, 34–35, 37–38, 70, 203–04, 208; linear paradigm 31; linear protocols 31; linear system 101 load‑bearing 162, 180, 185, 187, 189–90, 220; local authority (ies) 18, 96, 123; local community (ies) 15, 125; local material 15, 174; local reuse 36, 153 location 56, 206, 212, 220, 257–58; location‑based 71, 82

logistics 35, 166–67, 191 loss of value 205; low productivity 251; lower value 119, 236 low‑tech 1, 10, 12–15, 17–20, 250, 268–69 machine learning 56, 59, 61–62 maintainability 10 maintenance 183, 203, 235, 243, 245–47 manufacturers 26, 43, 125–26, 235, 247, 272 market actors 88, 90–91, 94–97, 100–01, 104, 107; market economy 30–31; marketplaces 212, 214–15, 219 material database 217, 226, 234, 246; material mines 2, 46–64; material flows 97, 107, 119, 269; material takeoffs 50, 56, 59; resource flows 94, 99, 180 material passports (MPs) 55, 59, 78–79, 212, 215, 217, 219–20, 223, 231–47, 272; product passports 118 material stocks 46, 202; material availability 54, 236, 256; material composition 50, 54–56, 63, 207; material efficiency 103, 121, 251, 255; material extrusion 257; material flexibility 253; material integrity 214; material intensity (in mass) 50; material properties 63, 135, 234, 252, 254–55; material selection 179, 255–56, 271 mechanical and electrical (M&E) 245–46 metal 9, 141, 146–47, 164–65, 203, 243– 45, 260 metrics 56, 105 mineral wool insulation 126 modular (modularisation) 11, 29, 149, 255, 271; modularity 100 multi‑disciplinary 62, 64 multi‑functionality 255 municipal solid waste (MSW) 70 narrowing 93, 162, 221 natural resources 153, 235; natural materials 153, 159, 170–72; natural ventilation 13, 15 needs 8, 11, 154, 212, 256; comfort needs 11; economy needs 78; industry needs 247; housing needs 7; human needs 159; information needs 50, 54–55, 58, 61, 63; market needs 236; material needs 12; mobility needs 12; occupation needs 11; practitioners (stakeholders) needs 94 networks 9–10, 12, 16, 26, 58, 80, 163, 176; circular economy networks 269

Index 279 net zero 126, 231–32, 247 new buildings 56, 116–19, 121, 153, 201, 210, 212, 223, 232, 235, 247 new products 42, 47, 63, 102, 116, 235 9R (Nine R) framework 180, 259; 10R (ten R) 234 non‑fossil fuel 9; non‑hazardous 19, 239; non‑inert waste 69; non‑recyclable 183, 205; non‑renewable 251 obsolescence 10, 27, 117, 255 ocean acidification 40 off‑chain 82 off‑site 119, 245, 255; off‑site construction 181, 258; off‑site facilities 258; off‑site manufacturing 182; off‑site materials 175; off‑site recycling 214; off‑site reuse 24 online feedback mechanisms 80 Open Street Map 48, 57 optimisation 31, 35, 37–38, 119, 181, 186, 191, 254–55 out‑of‑the‑box thinking 64 owner 16, 34, 54–55, 125, 215, 217, 225, 233, 235; building (asset) owner 63, 106, 225, 271; ownership 24, 80, 122, 154, 212, 220, 271; landowners 231 packaging 24, 116 paradigm 31, 56, 90, 209; circular paradigm 52; linear paradigm 31; paradigm shift 1, 8, 11, 63–64, 92, 201, 204, 247, 260, 268–69 partition system 245 passive design 15 passport system 79 Peer‑to‑Business‑to‑Peer (P2B2P) 78; Peer‑to‑Peer University 72 photogrammetry 120, 211, 219 planning 20, 52, 63, 96, 99, 108, 119, 153, 175, 206, 214; planning authorities 99, 118; planning collaboration 151; deconstruction planning 213; planning permissions 118; regional and city planning 12 plasterboard 116, 126, 147, 165–66 plastic 46, 69, 141, 143, 145, 166, 203, 260 platform 72, 78, 82, 153, 206, 208–12, 215, 234, 269; digital platform 71, 76, 78, 215; integrated platform 217–21, 226; material exchange platform 124–25; platform economy 78, 80; sharing platform 81; REUSE platforms 176

point cloud 57, 120, 211, 219, 221 points of interest (POI) 211, 219, 221 policy instruments 95; policymakers 36, 74, 82, 88–92, 95, 118, 250, 270 polluter‑pays 272 practitioner 97, 104, 106–07, 153–55, 208, 268 predatory economy 74, 81 pre‑demolition 63, 118–26, 203, 223, 236–37 prediction 39, 172–73 prefabrication 182, 194, 255, 258 pre‑redevelopment audit 2, 115, 118–20, 125, 235–36, 239 principles 9–11, 20, 80, 94; circular principles 70, 89, 103, 119, 150, 202– 09, 236, 268–73; circularity principles 201, 268–73 probability distributions 52 processing 25, 59, 62, 69, 122, 170; extraction and processing 115; image processing 211; processing and reconditioning 32; transportation and processing costs 70; waste processing 77, 208 procurement 174, 177, 207, 236, 272–73 property management 62 protocol 40, 42, 134, 136, 149, 191; blockchain protocol 79; control protocol 193; linear protocols 31; Quality Protocol 122, 124; standards and protocols 116; test protocol 140, 194 public funding 38, 108 quality control 38, 182, 192–94 quantity of material 174, 236, 241, 243, 253–55 quarry 166, 174, 181, 257 radar satellite data 56 rammed earth 162, 170–74, 183, 185–93 raw materials 1, 20, 25, 34, 205, 235, 251, 257 real estate 26–28, 59, 108, 231 reality capture technology 210 rebound effect 8, 10, 14, 16, 18, 266–70, 273 recirculation 72 recommendations 41–42, 108, 120, 271–73 reconditioning 18, 25, 32, 37, 150, 203, 206, 272 recovery facilities 32, 35; recovery market 40; reclamation market 32

280  Index recycling 7–9, 27, 33–34, 36, 69–70, 75, 78–79, 102–04, 118–27, 129, 203–07, 214, 222–25, 255–60, 269, 272; recycling rate 7, 9, 11, 34, 225 redesign 10, 104, 252 refurbishment 13, 40–43, 116–20, 130, 231, 233–40; refurbishing 25, 33, 46; rehabilitation 13, 130 refuse 180, 235 regenerative 179; regenerative system 93 regulations 18–20, 75–77, 187–88, 202, 245, 256, 270 regulatory standards 47 reinforced concrete 129–35, 145–46, 148–51, 164–65, 170 remanufacture 10, 125, 202, 234–35, 259–60 remote sensing 54, 57, 62 renewable economy 9; renewable energy 8, 104, 179, 260 renovation 10, 13–14, 16–17, 24, 130, 132, 153–54; renovation wave 16, 99 repair 10–12, 18–19, 164, 222–23, 233, 257, 260; repairability 269 replacement 7, 37, 130, 239, 243, 246 REPowerEU 99 repurpose 69, 125, 180, 234, 243–44, 247, 271 requirements 1, 15, 62, 89, 91–92, 96–97, 105, 107–08, 118–22, 148, 163, 174, 187, 191–92, 194, 207, 225, 239–41, 246, 254, 257, 260, 270; legal requirements 96–97, 108 research and development (R&D) 19, 81, 120, 271 resellers 27–29, 37, 40, 153, 212, 214 resilience 11, 64, 192; resilient 10–12, 15, 18, 20, 90, 171, 204, 268 resource cadaster 2, 46–47, 50–64 resource circularity 47, 180 resource consumption 7, 10, 91, 95, 259 resource depletion 27, 40 resource‑efficient (‑cy) 20, 47, 90, 98, 103, 269 resource extraction 31, 46, 125, 180, 182–83 resource‑intensive 90, 269 resource management 119–20, 269, 272 resource use 95, 99–100, 105, 107, 109, 119, 180, 270 resource use system 180 responsibility 11, 20, 74, 97, 125–26, 178, 202, 272 restorative 179 retaining 103, 119–20

rethink (‑ing) 10, 180, 203, 235, 269 retrofit 71, 90, 100, 232, 235–36, 246, 268, 271 reusability 125, 135, 148, 183, 255 reused component 25, 40, 47 reuse economy 36, 205; reuse offsite 243; reuse potential score 223 risk assessment 187 robotics (robots) 12, 214–15, 253; robotic‑based solutions 213 safety factor 136, 193 salvageability 31; salvaged material 26, 28, 36, 46, 63 scan‑to‑BIM process 211, 219; scanning 54, 57, 120, 144, 211, 217 scarcity 1, 70, 72, 173–74, 201–02, 225 secondary cadasters 54; secondary resources 46–47, 50, 54, 64, 104, 204, 259; secondary material 52, 103–04, 181; secondary component 101 second‑hand 19, 27–30, 35, 39, 41, 63, 124, 247 security 10, 30, 74, 158, 269 self‑monitoring 193; self sufficiency 71 sensor 58, 141–42, 251 serviceable 34, 239 service life 10, 54, 103, 105, 140, 204, 206 sharing economy 2, 69–83, 269 shortage 2, 115, 173 situated project 184 skepticism 10, 47 skills 10, 15, 25, 70, 72, 215 smart city 9, 14, 58; smart grid 74, 76–77, 82; smart material 251 sobriety 7, 9, 11, 13, 16, 99, 270 social equity 180; social housing 120; social impact 25 societal acceptance 35; societal structure 7; societal values 7 solid waste 69–70, 73, 75, 251 sorting 24, 178, 206, 210, 213–14, 222 sourcing 174, 190, 239, 260 specification 18, 50, 77–78, 119–24, 189, 236, 240–47 spectral imaging 57 stakeholders 54–55, 61–64, 74, 79–81, 94, 97, 187–95, 230, 233–34 standard 1, 36, 88–109, 187–88, 195; standardisation 36, 88–89, 94–95, 105 stock availability 239; stock flows 243; stock of materials 204 stockholder 233–36 storage 150, 153–54, 166–67, 176, 192–94

Index 281 structural material 54, 101; structural elements 63, 129–30, 133–37, 140, 145–47, 149–51; structural integrity 100, 105; structural system 25 sufficiency 98–101, 103, 108, 270 supply and demand 43, 63, 76, 121, 207, 226; supply chain 27, 31, 103, 125, 236, 245, 252 support system 201, 217, 219 sustainability 14–15, 18–20, 88–89, 91–96, 169–70, 230–31, 249–50; sustainability goals 15, 245, 253, 271 sustainable development 1, 82, 208, 268; sustainable economy 7, 99, 103; sustainable material 12, 205; sustainable practices 15, 92, 151, 153, 171, 176, 238, 269–71; sustainable approaches 184, 231, 251; sustainable strategies 251–52 system boundaries 100, 106 tagging 245–46 take‑back 118, 125, 242 tax incentive 271; tax system 19 taxonomy 92, 220 technical documentation 39, 209; technical guidance 98; technical knowledge 13, 207; technological advancement 7, 269 tender 32, 39, 41, 108, 122, 124, 176, 192, 240 test protocol 140, 194 timber 7, 13, 126, 164, 176–77, 185, 189– 90, 192, 220, 240 time‑consuming 19, 58, 120, 252 thermal comfort 11, 13, 17–18; thermal performance 239; thermal renovation 10, 14, 16–17 third parties 28, 78, 121–22, 124–25, 210 three D (3D) picture 54 three D (3D) printing 3, 20, 251–55, 260 three Rs (3Rs) 69–71, 234 tools 208, 212–13, 247 total mass of construction material 53 toxic waste–toxic chemical 71, 179, 210 traceability 79, 81–82, 247, 269, 272 traditional materials 29, 272; traditional method–technique 15 training program 19, 38, 271 transformable structures 205 transition 1, 20, 88–91 transparency 31, 76, 80, 212, 220, 269, 272 transportation 10, 25, 47, 69–71, 75, 81, 136, 151, 182, 207, 234, 252, 257– 58, 271 trans‑scalar–trans‑scalar thinking 97, 106

treasure 246 two‑way feedback 76–77 un‑adjuvanted rammed earth 189 unconventional material 253 Uniclass 241 un‑sustainable system 91, 95 upcycling 103, 122–23, 176, 181, 186, 203, 206, 269, 272 upgrading 75 urban areas 7, 51, 203, 247; urban landscape 204; urban metabolism 8, 70; urban mining 25, 29, 34, 71, 204, 226; urban planning 63; urban resource centre 46 validation 101–02, 190, 194, 221 valuable resource 9, 272 value 79–81, 119–22, 224–25, 239; value chain 62, 91, 96–97, 108, 127, 206; value retention 103, 121 vernacular 13, 159, 183 virgin material 14, 25, 38, 75, 79, 82, 93; virgin resource 28, 31, 180, 272 voluminousness 70 walk‑through scanning 120 warehouse 26, 46, 51; warehousing 28, 252, 260 waste credits 119; Waste Framework Directive (WFD) 92, 97, 201; waste hierarchy 97–98, 103, 239, 243; waste management 24, 27, 41, 69, 74, 184, 206, 222, 272; waste minimisation 239; waste production 25, 27, 71; waste policies 97, 108; waste regulations 234; waste sorting 210, 213; Waste Trade Organisation (WTO) 80–81; waste trading 76 water content 191–93; water stress 115 ways of living 11 weather 146, 192–93, 207 web‑based platform 211; web scraping 48, 56, 59 wellbeing 208 whole life carbon 106–07, 231–32, 240; whole life cycle 231 wood construction industry 259 workability 256 workers 26, 31–32, 38, 134, 176, 206, 214, 217, 258 workflow 38, 54, 57–59, 61–64, 212 wrecking balls 30 zero waste 12, 18, 74