PURPOSE: To heighten the heting efficiency by heating a main building or the like with a waste heat energy from a nuclear power station once passed through a waste heat recovery type regenerative feed air heater while a part of exhaust is circulated.

CONSTITUTION: A heater 2 comprising a filter 4 for taking outside air, a feed air heater 5 connected to an energy feeder 7 and a regenerative heater 6 and a feed air blower 3 are connected to a main building 1 of a nuclear power station at a air inlet 1a and then to a filter 9, a blower 10 and a main exhaust cylinder 11 at an exhaust port 1b through an exhaust line stop valve 8. A regenerative feed air line 12 branched off between the exhaust port and the stop valve and connected to one end of a regenerative feed air heater while the other end thereof is connected between the stop valve and the filter 9 through a regenerative airing line 14. This enables effective utilization of heat energy generated in various parts of the main building. Thus, additional heating source can be created and lower the operation of the energy feeder accordingly.