Abstract: A heating system for buildings including a fireplace with an open front hearth for burning firewood, a chimney extending from the upper portion of the hearth, a metal firebox being open in the front and closed on the sides and back, a plenum chamber within and surrounding the sides and back of the metal firebox and the chimney lower portion, a horizontal heat distribution chamber positioned in the building attic and communicating at one end with the plenum chamber, an air distribution duct connected to the other end of the air distributing chamber, the duct extending to discharge heated air to a place in the building remote from the fireplace, a fan placed in the horizontal air distributing chamber, and a return air duct extending from a selected place in the building and communicating with the plenum chamber lower portion so that the fan draws air through the return air duct, through the plenum chamber around the firebox where the air is heated, through the horizontal distribution chamber, and out through th