The indoor thermal environment, air quality and occupant behavior in well-insulated and airtight houses in and around Tohoku district are investigated through questionnaire and field measurement. This report describes the results from the questionnaire survey conducted in summer of 1993 and winter of 1994, and thermal environment of 16 well-insulated and airtight houses in Morioka and Sendai by the field measurement in winter and summer of 1994. The number of houses investigated by the questionnaire survey is about 350. The well-insulated and airtight houses investigated have mechanical ventilation system and space heating system for a whole house. The main findings are as follows: 1. Indoor environment during the heating season of almost houses is thermally comfortable, compared with that of existing house in Japan. 2. The houses provide a comfortable indoor environment and also have a good influence on occupant' health. However, there are some problems related to dry feeling, which should be investigated in future. 3. During the summer, the room temperatures are stable compared with the change of the outdoor temperature in the day, but it doesn't decrease at night even if the outdoor temperature drops. It is possible to improve the indoor environment by cross ventilation with opening windows or night time ventilation.
