A house with passive ventilation system in Morioka City was surveyed relating with indoor thermal environment. It was proved that indoor temperature was kept at about 18℃ all through the day in winter. Indoor thermal environment at the living room in winter was good. But the cold draft from the second floor flowed into the living room in the night. And relative humidity in the room was low in winter. Air change rate in winter was much, and it was necessary to adjust air change rate. Energy consumption was more than the average energy consumption in Tohoku district.