Seonghwan YOON, Yasunobu ASHIE and Toshio ABE

Building Research Institute, 1 Tachihara, Tsukuba, Ibaragi, 305-0802 JAPAN

Introduction: There have been a number of studies on the passive cooling of the outer surface of buildings for the purpose of conserving energy without resorting to fossil fuels, and simultaneously, improving the indoor thermal comfort. In addition to this, the heat island phenomenon has been regarded as a problem (Ichinose et al., 1999). Thus, it is necessary to strive to reduce the thermal load of buildings on the urban environment. It is particularly important to examine thermal properties of finishing materials on the rooftop surface where the incoming direct solar radiation is great. For this reason, the purpose of this study is to examine the cooling effects by the evaporation and the reflection of solar radiation on the rooftop surface by conducting outdoor experiment and numerical calculation. In the outdoor experiment, various test pieces were installed on an existing rooftop to examine the change in the surface temperature on a clear, summer day. Next, numerical calculation was carried out assuming different states of insulation to clarify the influence of rooftop surface cooling on the thermal load both indoors and outdoors in summertime.