‘Super cool roofs’: Mitigating the UHI effect and enhancing urban thermal comfort with high albedo-coated roofs

Abstract

This paper focuses on the impact of three types of roof retrofitting: green, high albedo-coated, also called ‘cool roofs’, and recently developed ‘super cool’ materials—in mitigating the effects of summer urban heat islands (UHI) and enhance overall urban thermal comfort. Human thermal comfort was considered in terms of physiologically equivalent temperature (PET), calculated by combining on-site field measurements with ENVI-met microclimate modelling and the RayMan model. The main environmental parameters addressed were roof surface temperature, ambient air temperature, and mean radiant temperature. The results show that the performance of the super cool roofs surpassed the cool and green roofs at reducing average ambient air and mean radiant temperatures, and the super cool roof had the lowest average PET during the day. However, all the roofs shortened the duration of strong thermal stress by 1 h compared to the conventional roof. This work contributes to the understanding of how roof retrofit technologies can be evaluated at the neighbourhood scale, assisting strategic decisions on building envelope retrofitting for sustainable cities.

Keywords

• Cool roof
• Mean radiant temperature
• PET
• Thermal comfort
• Urban heat island