Retrofitting existing buildings by the use of modular green roofs

• Modular green roofs can be effectively used to modernize existing buildings • Approach based on the nature-based solutions principles is versatile and replicable • Environmental benefits, technical and management feasibility support implementation • Economic aspects and management-related factors may hinder this process This study aimed to demonstrate how modular green roofs align with the Nature-based solution concept (NBS) and how their site selection process can be optimized to maximize benefits while minimizing economic costs. The implementation potential was assessed based on a set of legal, social, ecological, technical and economic criteria. The most important factors detected are environmental benefits, technical and management feasibility, building ownership status, and the condition of the roofing material. The proposed site assessment methodology provides a versatile and replicable tool that can be adapted to other urban contexts.