Apparatus for controlling the delivery of air in a forced air distribution system having a source of air under pressure (4), a duct system to deliver the air, and a plurality of ports (8) in the duct system with each port defining an air delivery zone (16). The apparatus includes a vent member (20) associated with each of the ports which is movable between an open position to admit air to the zone and a closed position to block air from the zone. Independent actuator units (50) are provided to move the vent member between the open and closed positions controlled by a central control system. Thermostats in each air delivery zone communicate with the central control system (80) to control operation of the actuators units and the source of air under pressure which generally comprises heating or cooling equipment such as a furnace or air conditioning unit.