Abstract: A fireplace heat exchange system is disclosed which is connectable to an existing forced air heating system of a building. The heat exchange unit includes a housing or enclosure within which is disposed a firebox. The enclosure and the firebox define a heat exchange space. The firebox includes a front opening which is closed by doors. A plenum is positioned on top of the firebox for collecting combustion gases. A plurality of heat exchange fins are secured to the exterior of the firebox within the heat exchange space to channel the incoming air entering the housing around and over the firebox and to increase the efficiency and rate of heat exchange. An air control device is positioned adjacent the front of the firebox to control the amount of combustion air entering the firebox. A chimney connects to the plenum and a chimney damper limits the combustion gas flowing out the chimney.