The indoor thermal environment and the residents' lifestyle in 8 thermally insulated prefabricated houses in the Kansai area were investigated. This report discusses the heating, room temperature, and usage of living space in these houses, comparing it with houses without insulation. The results are summarized as follows : 1) The residents of the prefabricated houses use kotatsus (tables with small heaters to warm the legs under the table and a skirt around the table to hold the heat in) and electric carpets because of the low temperature just above the floor level and additional heating apparatus because of the morning coldness. The room temperatures, however, are higher than in the houses without insulation. 2) In the houses without insulation, lack of heat retention causes the low temperature just above the floor level. In the prefabricated houses, it is caused by insufficient heater capacity and intermittent heating. 3) When the residents want to relax in the living room, they can't choose the seating style except sitting on the floor directly to use kotatsus or electric carpets because of the low temperature.
