Abstract: A wood and coal burning heating unit is provided for heating a residential building or the like. The unit includes a firebox having a double wall on its rear and top sections, with the back chamber and top chamber, which are formed between the respective double walls, being connected in flow communication. Air is blown into the back chamber, flows through the back chamber and top chamber and is expelled through a substantially horizontal, rectangular opening at the front of heating unit. A plurality of elongate, upstanding fins are provided in the top chamber so that the air flowing through the top chamber flows along the upstanding surfaces of the fins. Heat is conducted through the fins from the inner top wall of the firebox and is then transferred from the fins to the air flowing along the surfaces of the fins.