Development of a simplified cool coating thermal model for predicting street canyon air temperature

Abstract

Thermal environment within a typical street canyon can be represented by the heat exchange interactions between the microclimate and built-up urban fabric elements, consisting of walls, roofs and pavement surfaces. Morphology of these elements, material thermophysical and surface solar radiation characteristics under the prevalent weather conditions determine heat storage, convective as well as radiative heat exchanges within the street canyon. Predicting these heat transfer mechanisms using thermal model can facilitate assessing air temperature within the street canyon. Therefore, in this study, an easy-to-use resistance capacitance based thermal model is developed and verified using real-scale experimental measurements under the tropical climate of Singapore. Furthermore, the impact of increased solar reflectance of walls and the driveway surfaces (by application of cool coating) on the street canyon air temperature is predicted. Increasing the solar reflectance of wall from 0.5 to 0.8 and driveway from 0.2 to 0.7 can reduce the peak air temperature up to 1.70°C and daily mean air temperature up to 0.85°C as observed in this study. The results of the proposed cool coating thermal model can be used in early-stage design by the designers and planners for assessing the thermal impact of cool coating implementation on the street canyon surfaces under any weather conditions.