Environmental impacts of circularity in the built environment: How do system boundaries affect decision support?

Life-Cycle Assessments (LCA) have become a common tool of decision support in the built environment regarding environmental impacts. The goal of this study is to investigate the influence of different LCA approaches and system boundaries on decision support regarding circular design strategies. Three different ways of applying attributional LCA (ALCA) and one consequential LCA (CLCA) are assessed using a case study of a wooden beam with either virgin or reclaimed timber. While the conclusions are not readily scalable, the case study's results indicate that using reclaimed material is environmentally beneficial when applying ALCA. However, when applying CLCA the reclaimed material performs worse than the virgin material. This highlights the potential pitfalls of scaling up solutions based on LCA results without considering the broader consequences. While the current ALCA approach is useful for declarations, it may not provide comprehensive decision support for driving a transition in the built environment.