In this paper, we report the experimental studies which were carried out in an experimental house with thermal insulation for its foundation walls, concerning (a) the indoor thermal environment and (b) the heat flow in the crawl space to the ground and to the floor, under the condition of crawl space heating. The main results which we obtained are as follows: 1. The temperature in the room ranges from 18 to 21℃, and that of the floor surface becomes over 23℃. 2. When a fan is put in operation in order to control a current of air in the crawl space, the flow of the heat towards the floor increases, but that towards the ground also increases out of the warm air blowing out zone. 3. It is suggested that most of the heat to the ground is brought by radiation from the lining of the floor.
