Abstract: A valve construction for use in duct work wherein a valve element extends obliquely across and in closing relation with a duct, pivot means mounting the valve element for swinging movement about a horizontal axis between its oblique closed position and an open position longitudinally of the duct, the pivot means being located relative to the valve element to urge closing of the latter and maintain the latter closed under fluid flow.

Abstract: In a building heating system having a furnace, the instant invention incorporates a furnace enclosure for spacedly enclosing the furnace, an inlet air duct for conducting fresh air to the enclosure space for supporting combustion in the furnace, a combustion products outlet duct extending from the furnace, radiant heating duct means extending from the combustion products duct in radiant heat exchange relation with building space, and flue means communicating with the radiant heating duct for exhausting flue gas.