Effect of the Cool-roof System on Thermal Rooftop Environments

Abstract

The cool-roof system has emerged as a solution for the heat-island phenomenon through its minimization of the absorption of solar radiation. In the present study, an effect on the interior thermal environment was confirmed after the application of the cool-roof system on rooftops for the Cool Roof Campaign. The effect of the cool-roof system was measured according to the surface temperature and the indoor and outdoor temperatures that were recorded three times before and three times after the construction process, as well as on the first post-construction day. Through a determination of the thermal rooftop environment, the reduction ratio of the exterior-surface temperature was measured and the indoor and outdoor temperatures were compared. In addition, the interior thermal environment was evaluated by roof color with the colors green, white, and gray, and scale-model experiments were conducted under the same conditions. According to the results, the bright-color cool-roof system is highly efficient in terms of the reflection of solar radiation and the reduction of the surface temperature, and this is because of its higher reflectance and lower absorptance. Consequently, the use of the cool-roof system can decrease both the indoor temperature and the cooling energy in summer.