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As one of the globe's leading sectors for resource use and carbon emissions, the built environment could play a vital role in the circular economy (CE). This study aimed to understand and map the complex systems inherent to CE interventions in the built environment. We conducted a systematic literature review and thematic analysis to identify CE case studies in different cities around the globe that have considered systemic dimensions of CE and their interconnections and iterations. These include governmental, economic, environmental, technological, societal, and behavioral dimensions. The case studies informed a conceptual model that illustrates how CE functions in an urban setting. The model represents the interdependencies, flows, feedbacks, and unintended consequences that may result from the interaction between the CE research dimensions in cities. We hope to help policymakers, designers, and researchers to better understand how CE functions in urban settings, and to ethically design changes in the system to achieve circularity goals. The results suggest that meaningful stakeholder engagement is key to co-designing ethical CE interventions in the built environment. Finally, engaging disciplines like economics and decision sciences, and better understanding the role of public policies and human behavior are vital to future CE interventions in urban settings. 

The circular economy (CE) has emerged with the promise of conserving resources through approaches such as durability and extended product lifetimes. At the same time, buildings negatively contribute to resource use and waste production, making buildings a key target for CE strategies. However, the question of how durability and lifetimes affect the social and environmental impacts of building products remains largely unexplored. In this study, we applied environmental and social life cycle assessments (E-LCA and S-LCA, respectively) to a common building component, roof covering, to investigate the effects of durability and different lifespans, and the tradeoffs between social and environmental impacts. We tested different lifespan scenarios for three materials with different durability: thermoplastic polyolefin (TPO), zinc-coated steel, and galvanized aluminum sheets. The results suggest that it is critical to consider the tradeoffs of social and environmental benefits: steel had the most promising social performance, followed closely by aluminum, while the least durable material (TPO) had the worst environmental and social performance. However, the environmental impacts resulting from the production of aluminum sheets were significantly lower than the impacts from steel, which made aluminum the preferred choice for this case study. Moreover, product lifespans impacted the results in both E-LCA and S-LCA due to the number of replacements needed over the life of a 100- year building. We discuss key limitations of integrating E-LCA and S-LCA approaches, such as data aggregation and spatial issues, lack of standards on how to account for product durability, and concerns surrounding S-LCA results interpretation.