Abstract: The objective of the present invention is to provide a system which allows efficient air-conditioning heat recovery during ventilation and is applicable to ordinary housing. In order to achieve the above objective, a central ventilation fan 110 is connected to a heat exchanger 120 via a ventilation pipe. Air collected in the central ventilation fan 110 is emitted via the heat exchanger 120 from a device after recovering heat from heated exhaust air from each room by the heat exchanger 120. On the other hand, the heat exchanger 120 is connected to a tank 130 via a water suction/drainage pipe. Water drawn up from the tank 130 by a pump 140 is heated by the heat exchanger 120 and then returned to the tank 130 again. The heat exchanger 120 uses the Peltier device to cool the exhaust air from the central ventilation fan 110, and heat water in the tank 130 at the same time, thereby efficiently transferring air heat from each room to water.