Abstract: A solid fuel burning heater with improved efficiency in burning logs. A housing is divided by a louvered internal wall into front and back sections having combustion and heating chambers respectively. The louvered wall terminates below the top of the housing providing a crossover space through which hot, combusted gases flow from the combustion chamber to the heating chamber. A vertical heat transfer duct extends through the top and bottom of the housing and has open ends in free communication with external ambient air. Front and rear flues are connected to the combustion and heating chambers and these are interconnected by a main flue leading to a chimney. A damper is provided in the front flue. The combustion chamber comprises a primary combustion zone on a fuel-supporting grate and a secondary combustion zone above it. Adjustable draft openings at the front of the housing control air input to the combustion zones.