Circularity indicator for residential buildings: Addressing the gap between embodied impacts and design aspects

In the European Union, the built environment is responsible for more than the 25% of all waste generated, highlighting the need to adopt circular practices. To indicate the level of circularity, common indicators mainly focus on: 1) the amount of virgin materials, 2) the amount of unrecoverable waste, and 3) the product lifetime. However, a holistic methodology covering the macro (material impact), meso (supply chain) and micro level (design) is still to be fully developed. In this research, two indicators - the Building Circularity Indicator (BCI) and the novel Predictive BCI (PBCI) - combine the Material Circularity Indicator with Embodied Energy (EE), Embodied CO2 (EC) analyses and Design for Disassembly (DfD) criteria. A full and simplified version are tested for different case studies in different climate zones in the EU. EE ranges between 1.49 GJ/m2 and 7.60 GJ/m2 , while EC between 0.15 tCO2/m2 and 0.73 tCO2/m2 . In the full version, the BCI and PBCI ranges respectively from 0.23 and 0.28 to 0.04 and 0.10 with regard to mass, EE and EC. The simplified version ranges between 0.10 and 0.62, revealing to be a more accurate indicator when data are available for only a few dozen components. To enable comparisons among different buildings, results show how different interpretations of the DfD criteria affect the BCI, highlighting the need to indicate strict boundary conditions, a minimum number of evaluated components, and precise criteria on how the DfD criteria relate to either a material, a subcomponent/component, or its relationship to its context.