Abstract: An automatic boiler damper comprising a solenoid valve secured to the pivot axis of a damper included within a stack utilized to vent a heating system. The solenoid is electrically operated upon the closing of a thermostat secured to the stack at a point immediately over the damper location. The damper is provided with a vent hole which enables the thermostat to detect the presence of heated stack gases in sufficient quantity and temperature flowing upwardly from the damper in the closed position, so as to enable the solenoid to open the damper and vent the stack gases through the stack. Heat is conserved thereby and cold drafts are not permitted to enter the stack as a downdraft.