Abstract: A system for heating an edifice comprising a firebox, means for closing a fuel access opening to the firebox, a combustion air passageway opening into the firebox and extending to the outside of the edifice, and a stack connected to, and projecting vertically from, the firebox to convey combustion gases therefrom. A baffled air plenum chamber surrounds the firebox and a portion of the stack and is defined by a housing forming an enclosure around the firebox and stack. An upper air opening into the air plenum chamber is disposed at the upper side of the housing, and a plurality of lower air openings are disposed in the housing on opposite sides of the firebox, and are spaced downwardly from the upper opening.