Abstract: This invention is a device for use in increasing the efficiency of existing heating units. This heat exchanger consists of conduits for channeling the furnace or wood stove exhausts in an extended pattern. Cold air is pumped into the heat exchanger at a point at which the exhaust smoke is released up the chimney. The cold air is channeled around the smoke containing flues by a thermostatically-controlled fan and baffles found in the heat exchanger. This air exits the heat exchanger at a point at which the smoke enters it. This heat exchanger puts out temperatures in excess of 450.degree. F. As depicted in the preferred embodiment, only by way of example, the heat exchanger is extremely lightweight and made of galvanized steel with caps at either end to facilitate cleaning.