In this study, we researched the thermal performance of well-insulated detached houses in Hokkaido. The heat loss coefficients of these houses are mainly around 1.3W/m2K. The space heating and hot-water supply systems use electricity in many of these houses. The results of our research are as follows: 1) Remarkably high temperatures were not found in these houses during summer. This is probably because of cross-ventilation and a small amount of solar heat gain. 2) The room temperature is stable throughout heating season, in spite of the high thermal performance. 3) The factors that influence the room temperature in each season were verified using multiple regression analysis. 4) The primary energy consumption of well-insulated houses with electric heating devices is greater than that of conventional houses equipped with fossil fuel boilers.
