How can we combine urban cooling strategies to effectively cool cities over the entire diurnal cycle?

• Published in: Building and environment 2023-08, Vol.242 (1), p.110524, Article 110524
• Main Authors: Anand, Jyothis, Sailor, David J.
• Format: Article
• Language: English
• Subjects: Building thermal storage; Cross-limited timber; ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; Radiative cooling; Reflective roofs; WRF analysis
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2023.110524

The urban heat island effect generally peaks in the night/evening hours and, in some cases, an urban cool island effect during daytime has been reported. These patterns are observed mainly because of the widespread use of impervious and thermally massive materials (like concrete and asphalt) in the built environment and their ability to store energy during the daytime and release it at night. Unfortunately, most urban cooling strategies, such as cool (white), green, and blue spaces, provide better thermal performance during the daytime than at night. Hence, such solutions are not ideal for nighttime heat mitigation. In this study, we investigate the effect of the thermal storage capacity of existing buildings on nighttime urban air temperature for a hot arid city—Phoenix, and a hot humid city—Atlanta. The study uses regional scale atmospheric modeling to compare the nighttime urban cooling capability of thermally light buildings (Cross-laminated timber buildings in this case) with concrete buildings. The results show that the adoption of thermally light buildings reduce nighttime air temperatures, and slightly increases daytime air temperatures. On the other hand, cool roof adaption could reduce urban air temperature significantly during the daytime and slightly at night. Therefore, together with cool roofs, thermally light buildings may be able to cool the surrounding air by an average of about 1 °C throughout the diurnal cycle, providing thermal comfort and reducing cooling demand during all hours. •Most urban cooling strategies perform better during the daytime.•The urban heat island effect generally peaks in the night/evening hours.•Urban nighttime air is warmed due to the buildings' thermal storage capabilities.•Reducing the thermal storage can provide cooling an average of ∼1 °C at night.•Thermally light buildings with cool roofs can cool the urban air always (∼1 °C).