Abstract: Radiator housing assembly, for a hydronic baseboard heater for heating a room or area, forming a part of an overall building or zone heating system having a master thermostat, said assembly having a damper which is positionable between open and closed positions in a controlled manner to regulate the flow of heated ambient air therethrough. The damper is adapted for automatic electrical positioning in response to a remote control device, such as an adjustable thermostat in the room or area to be heated in order to maintain the room or area at a predetermined desired temperature at or lower than the temperature setting on the master thermostat, thereby conserving energy.