The transition to a circular built environment requires integrative models that operationalise circularity design, including resource flow circularity, design for adaptability (DfA), design for disassembly (DfD), and lifecycle performance. Current approaches often treat these aspects in isolation, limiting their effectiveness in guiding real-life design and policy. In response, the CIRLAB framework was developed as a multi-criteria model that integrates circularity and lifecycle indicators to assess and optimise building design. Its structure combines four composite circularity indices—DfA, DfD, Resource Longevity, and Circularity Flow—with embodied energy and carbon indicators. The model adopts a matrix of circularity criteria organised along two axes: building layers (Structure, Skin, Space Plan, Services) and levels of composition (Materials, Components, Systems, Whole Building). These criteria are synthesised into composite indicators through mathematical modelling. CIRLAB then applies the PROMETHEE II multi-criteria decision analysis method to incorporate lifecycle indicators, ensuring balanced designs, transparency, and flexibility in scenario comparison. This paper demonstrates the application of CIRLAB to a prefabricated wall element developed within the SUPRIM project. Prefabrication provides a suitable context to test the model, given its high level of control over material composition, assembly methods, and end-of-life strategies. The element is assessed against CIRLAB’s indicators, enabling a comprehensive evaluation of its adaptability, disassembly potential, material longevity, and circular flows, alongside embodied energy and carbon performance. Preliminary findings show that the model captures trade-offs and synergies between circularity and lifecycle indicators while highlighting opportunities for optimising design choices at the material, component and system scales. Testing CIRLAB on this prefabricated element demonstrates its value as a decision-support tool for designers and manufacturers, while also confirming its scalability to whole-building assessments. By bridging theoretical modelling with practical application, this work advances the operationalisation of circular economy principles in construction and supports their integration into future design and policy frameworks.