City-Scale Analysis of Green Roof Effectiveness in Reducing Local Surface Temperatures

Intensifying urban heat poses a significant threat to public health. To combat this danger, cities are increasingly implementing vegetated green roofs on buildings. This study develops an open-source, quasi-experimental method to evaluate the cooling impacts of green roofs across a city relative to nearby unvegetated roofs. This method, combined with publicly available data across a 14-year period, is applied to quantify the reduction in land surface temperatures (LST) due to green roofs in Washington, D.C. The results show significant variation in cooling performance among green roofs, indicating that not all green roofs reduce rooftop temperatures. The method developed in this study provides a low-cost approach for policymakers and planners to assess the cooling capacity of green roofs in their communities. It can aid in evaluating the effectiveness of green roof programs in mitigating urban heat, especially in resource-constrained situations or for large cities with numerous green roofs.