Based on the actual measurement results covering a period of approximately twenty-seven months, we have clarified the indoor thermal environment and energy consumption characteristics of a well-insulated and airtight residential house, located in a temperate region. We have also made clear the potential for further energy savings. The key points are as follows: (1) Heating starts when the daily average outdoor temperature falls to 15℃ or lower, and measured values for the coefficient of heat loss and energy consumption efficiency, heating of the house, were similar to the original specifications. (2) When the daily average outdoor temperature ranges from 15 to 25℃, neither heating nor cooling is required. (3) Cooling starts when the daily average outdoor temperature exceeds 25℃ and the energy consumption for it can be kept low even in fierce heat. (4) For further energy saving, it is important to optimize the air-conditioner capacity according to air-conditioning load. At the same time, in a temperate region where humidity is high in summer, the selection of optimum dehumidifying methods is important.
