Abstract: An open sided firebox is provided including an upwardly tapering upper bonnet portion. The lower end of an upstanding flue pipe opens downwardly into the interior of the bonnet portion and the upper end portion of the flue pipe is open for exhausting flue gases above the roof line of a building in which the firebox is disposed. A multi-walled outer housing encloses the firebox and includes a front wall having an opening therein through which the open side of the firebox opens. The upper portion of the housing tapers upwardly in cross section and encloses the bonnet. An upstanding flue liner is loosely disposed about the flue pipe and includes a lower end opening downwardly into the upper portion of the housing and an upper end sealed about the upper end of the flue pipe.