Assessing long-term effectiveness of passive cooling strategies in the built environment under climate change

Abstract

Urban overheating exacerbates energy demand, greenhouse gas emissions, thermal discomfort, heat-related mortality and morbidity and other severe physical and mental issues. Passive heat mitigation strategies, such as cool and green roofs, cool pavements, and urban greenery, have proven effective under current climatic conditions by reducing surface temperature of the built environment and urban air temperatures, improving thermal comfort, and decreasing energy demand for cooling. However, their long-term effectiveness is uncertain under future climate scenarios characterized by higher global temperatures, changing climatic patterns, and increased trapping of longwave radiation. This review systematically assesses 18 peer-reviewed studies that evaluated passive mitigation strategies under projected climate change. The results show that under high-emission scenarios such as RCP8.5, urban overheating levels may remain critically high even with large-scale implementation of passive cooling measures. In terms of building performance, cooling energy savings vary by climate and by scale of investigation, with the performance of cool roofs and green roofs declining by up to 60% and 25%, respectively. By highlighting the limitations of existing passive cooling solutions, this article underscores the need for novel, resilient designs and policies to ensure sustainable urban cooling in evolving climatic conditions.