外断熱工法などを想定した“厚い壁”が日射熱取得量および年間熱負荷に与える影響に関する検討

谷口 景一朗
日本建築学会環境系論文集, 2019, 84 巻, 762 号, pp. 749-758
https://doi.org/10.3130/aije.84.749

Abstract
This study focuses on the renovation of apartment houses using the external insulation method which the number of cases is expected to increase in the future, and we conducted a systematic heat load simulation changing the window orientation, the window size (window-to-wall ratio), the window proportion, the type of glass, the thickness of the insulation, to clarify the annual heat load / the heat balance characteristics of each area and the factors that influence it. In addition, we prepared a basic data on the influence of the solar heat gain quantity and the annual heat load due to a difference of the location of window frame in “a thick wall” with thick insulation. Ultimately, the study deduced the following points.
 1) In Tokyo, it is necessary to consider a reduction of both the cooling load and the heating load depending on the type of glass used. In the case which the type of glass is a double low-e glass insulating type, the annual heat load can be reduced by decreasing the window-to-wall ratio with the main window direction set to the south.
 2) In Sapporo, it is important to consider mainly a reduction of the heating load. However, if the window-to-wall ratio is made too large, the cooling load will increase and the annual heat load will also increase due to the increase in the solar heat gain quantity in summer, so it is necessary to consider the appropriate window size.
 3) In Kagoshima, it is important to consider mainly a reduction of the cooling load, and when the window-to-wall ratio is reduced, the annual heat load can be reduced. In addition, as for the glass type, a double low-e heat reflecting type with a low solar heat gain coefficient resulted in the smallest the annual heat load.
 4) When a heat load simulation is conducted considering a solar radiation shading effect by “a thick wall”, even when the thickness of insulation is 50mm, the solar heat gain quantity is reduced by 25% which affects the cooling load and the heating load because of a difference of the location of window frame. Especially in Sapporo where the coldness in winter is severe and it is assumed that the external insulation method using thicker insulation (200mm in this study) is expected to be adopted, both the heating load and the annual heat load increase due to the solar radiation shading effect of the wall thickness.
From this study, it is suggested that it’s necessary to simulate shading devices in all openings and reproduce the influence of the solar radiation shading by the wall thickness. In the future, since the annual heat load is greatly affected by the insulation level of external wall or the internal heat generation quantity, we will add further verification, and we plan to develop a method to correctly predict the load reduction effect by the external insulation method.