This chapter presents the results of the transdisciplinary research ‘SOSLabs. Research-action laboratories for urban sustainability’, a project that has proposed, within three Action Research Laboratories, the construction of a transcalar model for the assessment of sustainability in programming, planning, and urban design activities in support of public territorial government interventions. Specifically, the research developed in SOSLab3 has been aimed at defining a methodology to pursue the objectives of the SRSvS (Regional Sustainable Development Strategy) in circular building, which is essential for integrated territorial management. The proposed method focuses on disused public heritage, which still awaits coherent and sustainable reuse programmes. This is caused by delays during the decommissioning process, difficulties in allocating management responsibilities, and the lack of reuse strategies that recognise the centrality and unexpressed potential of the structures. Furthermore, the study aims to analyse and optimise the cultural, social, economic, and technical processes that link heritage conservation to its reinterpretation through compatible reuses supported by the development of local communities. Thus, the protocol tested seeks to make the sustainability of the reuse processes related to changes in the functions, ownership, and management of historical public assets measurable. To monitor the sustainability of this redevelopment process, this protocol also codifies a specific ‘index of priority’ to verify the historical and cultural compatibility of the redevelopment programmes, considering performance improvement and efficiency, socio-economic impact, governance, and inclusion levels.