This invention absorbs available heat from the flue gas of an existing building's heating system and heat from the sun. The heat is absorbed and stored in a heat-collecting sphere of special design. The absorbed heat collected in the sphere is transferred, by the conventional refrigeration cycle, to the heat exchanger located at the air inlet to the building heating system. The refrigerant liquid is sprayed into the collecting sphere, as it absorbs heat, it evaporates and changes into a gas. The refrigerant compressor transfers the gas from the heat-collector to the heat exchanger. The existing heater fan draws air across the heat exchanger finned coil removing heat from the refrigerant. The refrigerant gas gives up heat and is condensed. The heated air combines with the existing furnace air to heat the existing building. The refrigerant liquid from the heat exchanger is transferred to the heat-collecting sphere spray nozzles.