An Integrated Decision-Support Framework for Sustainable Retrofitting of Post-War Residential Buildings to Support Urban Heat Island Mitigation

In recent decades, the intensification of the urban heat island (UHI) phenomenon has emerged as a critical challenge for European cities, exacerbated by climate change, dense urban morphologies, and the aging performance of the existing building stock. In this context, the renovation of post-war residential heritage represents a strategic opportunity to simultaneously enhance buildings’ energy performance and contribute to urban-scale thermal mitigation. This study investigates sustainable and integrated retrofitting strategies applied to residential buildings constructed between 1945 and 1990 in the metropolitan area of Milan. The research aims to evaluate how targeted refurbishment interventions can improve building energy performance and potentially support UHI mitigation through improved envelope performance and material selection. The methodology combines field surveys, archival data from public housing authorities, energy simulations, and multiple-criteria decision-making (MCDM) analysis, integrating economic, environmental, and performance-based indicators. Several retrofit scenarios are assessed across different building typologies. Results highlight that low-invasive and cost-effective measures, such as advanced glazing systems, roof insulation, and efficient heating system upgrades, achieve a favorable balance between energy performance improvement, economic feasibility, and intervention-related criteria. For buildings with larger dispersing surfaces, envelope insulation solutions using sustainable materials demonstrate increased effectiveness. Beyond individual building performance, the study discusses the potential indirect contribution of large-scale retrofit strategies to UHI mitigation through reduced building energy requirements and potentially lower HVAC-related anthropogenic heat emissions. The proposed operational framework supports public stakeholders in prioritizing interventions across a large building stock, offering a replicable decision-support tool for climate-resilient urban regeneration and for supporting UHI mitigation strategies.