Effects of a Cool Roof System on the Mitigation of Building Temperature: Empirical Evidence from a Field Experiment

Abstract

This study aimed to examine the effects of a cool roof system on the building temperature mitigation using a field experiment under current climate conditions in Seoul, Korea. Particularly, this study analyzed which meteorological factors affect the performance of the cool roof system based on the results of a field experiment during four seasons at the study site with real-time changes in various urban meteorological variables. This study also examined the extent to which each meteorological variable affects a cool roof system. Automatic temperature data loggers were installed on the roof of a Dobong eco-class building with reduced experimental models that included both conventional and cool roofs. A multiple regression analysis showed that when applying the cool roof system with other explanatory variables being controlled, the surface temperature of the building roof decreased by approximately 5.6 degrees C, and the indoor air temperature of the experimental model decreased by approximately 0.56 degrees C. These temperature reduction effects are meaningful, as the annual average reduction effects include nighttime and daytime. In addition, the most influential weather condition variable for roof surface or indoor temperature is external temperature, followed by insolation and humidity. Finally, the surface temperature reduction values in the actual roof of the study site and those of the roof surface of the experimental model were different. This suggests that the effect of temperature change on cool roofs is related to environmental factors as well as roofing materials. Therefore, the study suggests that cool roof policies should consider not only solar reflectivity but also other building environmental conditions and roofing materials.