Human Thermal Comfort: Modeling the Impact of Different Cool Pavement Strategies

Abstract

Cool pavement strategies could help mitigate the heat island effect and improve the outdoor thermal environment in hot climates. This study investigated the impact of cool pavement strategies on outdoor human thermal comfort. On the basis of the human body energy balance model and the thermal comfort model, the physiological equivalent temperature (PET) was selected to evaluate and compare the effects of different pavement strategies on the outdoor thermal environment for summer and winter in three climates (Sacramento and Los Angeles in California and Phoenix in Arizona). The pavement strategies evaluated included high reflectance, evaporation, high reflectance plus evaporation, and shading along with a baseline for control. The use of high-reflectance pavement reduced pavement surface temperature; however, increasing pavement reflectance increased mean radiant temperature, because of the increased reflected radiation hitting the human body, and consequently increased the risk of reducing human thermal comfort during hot periods by 3% to 8% in the three locations. Enhancing pavement evaporation and shading pavement with trees or other canopies were effective strategies for reducing pavement surface temperature and PET, helping improve human thermal comfort in hot periods by 3% to 28%. For some areas, such as Sacramento, where it is hot in summer and cold in winter, some cool pavement strategies (e.g., pavement evaporation or shading) used to improve the summer thermal environment might make the cold winter slightly colder. Therefore, strategies that can reduce summer hot temperatures but not reduce winter cold temperatures, such as enhancing evaporation or tree shading only in the hot summer, are desirable.