PURPOSE: To facilitate mounting work, maintenance as well as inspection, improve appearance, reduce noise and prevent the invasion of outside air and noise by a method wherein the heat exchanges and ventilations of a plurality of rooms are effected by respective independent one set of an fan unit and a plurality of heat exchanging units.

CONSTITUTION: The ventilating unit is provided with the fan unit 1, consisting of ventilating blades 12, air feeding blades 13, a motor 14 and electric dampers 10, 11, and a plurality of heat exchanging units 15, provided with heat exchanging element 32. The fan unit 1 and respective heat exchanging units 15 are connected by ducts and a plurality of rooms can be ventilated or can effect heat exchange simultaneously or independently. The fan unit 1 is provided in a space behing a ceiling and the heat exchanging units 15 are connected detachably to the fan unit 1 through the ducts 34, 36 and duct mounting boards 33, 35. Accordingly, the mounting work, exchanging of equipments, maintenance and inspection may be effected easily. On the other hand, the size of an opening on the ceiling is small, therefore, the indoor appearance of a room may be improved, the invasion of the outside air and noise may be prevented by the electric dampers 10, 11 and the noise in the room may be reduced.