To supply air having a fresh air temperature and humidity of outside air cleaned inexpensively to each room all the time, in ventilation of stagnant and staying contaminated air in the each room in a dwelling house excellent in sound insulation, heat insulation and functionality, and sealed as a result thereof.

The contaminated outside air is passed through water from a lower part of a water storage tank, a heater and a cooling plate are provided in the water storage tank to obtain a fixed temperature, the fresh cleaned air of the fixed temperature is obtained to be supplied to the each room, a water level sensor, a water quality monitoring sensor, a water supply valve and a water discharge valve are provided in the water tank, and those are functioned integrally, interlockedly with the water quality monitoring sensor, to control automatically the water temperature and water quality.