A framework for strategic planning of spatially cumulated green roofs to reduce urban heat

Cities and their residents are becoming increasingly vulnerable to the impacts of climate change, particularly rising temperatures. Green roofs, as part of multifunctional green infrastructure, offer a promising strategy to lower ambient temperatures by utilizing often underutilized roof space. However, research has largely focused on individual buildings, frequently overlooking aggregated spatial cooling effects. To address this gap, this study introduces a GIS-based framework to delineate Impact Areas (IAs) that account for the cumulative effects of green roofs, thereby supporting strategic city-scale planning for urban heat mitigation. It combines a feasibility analysis, which assesses four indicators, with a geostatistical hotspot analysis to delineate IAs where green roofs can provide the greatest cooling benefits. For the feasibility analysis, the study integrates two data options: 1) specific data from the space heating model (not yet widely available) and 2) openly accessible sociodemographic and building age data. The framework was applied to the City of Wuppertal, Germany, using both data options. For Wuppertal, three IAs were consistently identified across both data options, overlapping with zones of high heat exposure and highlighting the need for targeted climate adaptation. The framework's modular design enables transfer to other cities and allows for flexible adjustment, e.g., by incorporating data on specific vulnerabilities to further prioritize implementation areas. Resulting IAs can inform higher-level planning and support targeted engagement with policymakers and building owners. This approach is an important step toward strategically planning and leveraging the cumulative effects of green roofs as an integral part of multifunctional green infrastructure.