Longer eaves block direct summer sunlight and let in winter sunlight Mandatory energy conservation laws are 20-year-old standards. In Japan, it is mandatory to change indoor air every two hours as a measure against sick house syndrome. Although more frequent ventilation is now recommended as a measure against corona, ventilation raises the room temperature by letting hot outdoor air into the room in summer even if the room is cooled down, and conversely, in winter, the warmed indoor air must be thrown outside. In the winter, the heated indoor air has to be discarded outside. “The heat exchange system installed in this house has a heat exchange efficiency of 90%. So, for example, in winter, when the indoor temperature is 20 °C and the outdoor air is 0 °C the temperature of the room is 20 °C and the outside air is 0 °C. 20 °C °C air out of the room. but the heat exchange system allows the air to flow out at 0°C. However, the heat exchange system can reduce the air temperature to 0 Celsius The heat exchange system brings the outside air at 18 °C C to 18 °C and then brought into the room, resulting in a reduction of 2 °C In summer, on the other hand, the outside air temperature is 18 °C and the room is heated to 18 °C. Conversely, in summer, when the outside air is 36 Celsius. and the indoor temperature is 26 Celsius and the outdoor air temperature is 27 Celsius, to bring the air into the room at 27 °C, so 1 Celsius. This is the reason why the air conditioning system is so efficient.” These innovations have enabled the company to reduce air conditioning costs by 80%.   The installation of the air conditioner is also ingenious. In winter, a typical wall-mounted air conditioner is half buried under the floor to warm the floor, and air is blown toward the subfloor, with warm air coming out of the vents in each room. In summer, vents are built above the rooms so that cool air is blown from above by a summer air conditioner installed in a small room in the attic. By changing the location of the air supply between summer and winter, the rooms can be effectively heated and cooled. The Mochida residence is full of ingenuity. However, according to Mr. Mochida, the level of housing performance of the Mochida residence is common in Europe as housing that does not rely on air conditioning to reduce CO₂. The other day, an energy conservation law for housing was passed in Japan. “The new standard is almost the same insulation performance as the one proposed in 2011. It only made mandatory a standard that was already established 20 years ago. There are different levels of insulation performance, and our house is built to the strictest level, but under the current energy conservation law, it is not even close to the world standard.”