Circularity – not so straightforward: A review of methodological choices in LCA for circular renovations of buildings

Life cycle assessment (LCA) is a crucial tool for evaluating the environmental impacts of building renovation strategies, particularly within the context of the circular economy (CE). However, its application to circular renovation projects presents methodological challenges. This systematic review aimed to analyse these challenges and potential inconsistencies. The review was conducted following PRISMA guidelines, using the Scopus database for literature retrieval. A total of 176 papers were included in the review. Key findings indicate a lack of consensus in terms of methodological choices, including approaches for impact allocation of multiple cycles, the choice of reference study period, the applied approaches to dynamism, the inclusion or exclusion of existing building impacts and the approach to biogenic carbon accounting. Variations in methodological approaches affect LCA outcomes, thereby influencing decision-making related to the environmental impacts of renovation strategies. Notably, many studies failed to acknowledge or scrutinise the potential biases introduced by their methodological choices. To illustrate these implications, a hypothetical renovation scenario is used to demonstrate the effect of different methodological choices. No single approach was identified as universally correct, as the choice of methodology depends on the goal and scope of the LCA. Nevertheless, best practices were identified for applications within the context of the circular economy.