PURPOSE: To enable employment of the solar heat for heating in winter and also for cooling as occasion calls by accumulating the solar heat in pebbles and water having large specific heat and arranged under a floor and by turning the same into condensed CaCl solution.

CONSTITUTION: Water tanks 1 are arranged in series and the water inside thereof is made capable of circulating. Moreover, stone tanks 2 containing material such as pebbles having large specific heat are arranged in series so that the air inside thereof is capable of circulating mutually. Furthermore, the group of the water tanks and the group of stone tanks, both of which are constituted as mentioned in the above, are installed in parallel, inside of tanks 1 and 2 are arranged heat exchangers 3 respectively, which are connected in a zigzag manner by piping, and thus a closed circuit is formed. The device constituted in this way is arranged under a floor, the water inside the tank 1 is heated by a solar water heater 15 in the seasons from spring to autumn, heat exchange is made in the heat exchangers 3, and the heat is accumulated in the tank 2. Then, at the time of heating, air is sent from one end of the tank 2, taken out from the other end thereof and introduced into a room, while at the time of cooling, the air is introduced from the tank 1 into the room. In addition, the same effect can be obtained by putting water wherein CaCl is dissolved in the water tank 1.