PURPOSE: To effectively cool the interior of a room by a method wherein ventilating fans for supplying and exhausting the outside air to and from ceiling space and a ventilating fan for exhausting room air to the ceiling space are provided in the device to control room air temperature by ventilating the ceiling space and the room of a house.

CONSTITUTION: The ventilating fan 1 for flowing the air from the exterior of the house into the ceiling space S and the ventilating fan 2 for exhausting the air from the ceiling space S to the outside are provided at the walls W, through which the ceiling space S contacts with the outside air, of the general wooden house H. IN additin, the second ventilating fan 3 for exhausting the air within the room R to the ceiling space S is provided at a ceiling surface U locating to form the boundary between the interior of the room R and the ceiling space S. Copper-constantan thermocouples 4 and 5, which detect the tempeature differences between the outside and the ceiling space S and between the ceiling space S and the interior of the room R respectively, are provided and the power supplies to the respective ventilating fans 1W3 are controlled through a power source ON-OFF controller 6 with the outputs of said thermocouples 4 and 5.