Selection of Circular Proposals in Building Projects: An MCDM Model for Lifecycle Circularity Assessments Using AHP

The circular economy (CE) in construction literature engages with individual CE concepts, mostly at the ‘macro’/‘meso’ levels, and lacks holistic frameworks of indicators for circularity assessments (CAs) to inform decision-making at the ‘micro’ (project) level. This article presents a model using the Analytic Hierarchy Process (AHP) for circular proposal selection in building projects based on a previously validated conceptual framework. The model involves twelve circularity indicators (CIs) classed under five themes relevant to building lifecycle stages. A questionnaire survey was used to establish the final weight vector of CIs. Participants acknowledged the immediate and prolonged effects of design on circularity and viewed waste as ‘design flaws’ but focused on aspirational design indicators relevant to achieving future circularity and missed opportunities for embedding circular materials in design. Moreover, UK participants showed distinctive behaviours towards CAs (proactive/reactive) based on work experience. ‘UK-Experts’ focused on ‘front-end’ design indicators, while ‘UK-Non-experts’ focused on ‘back-end’ waste management indicators. The findings indicate a partial transition to CE better described as a ‘recycle/reuse economy’. CAs and multiple-criteria decision-making (MCDM) techniques facilitate automated decision-making, which provides a new pathway to digital transformation within built environment. Future research will develop a decision-making tool and apply the proposed model in real-life projects.