Abstract: Apparatus is provided for use in the method of conserving energy by operating a ventilating and air conditioning system in a high rise building in a manner to permit operation of a heating and cooling unit at a reduced percentage of full capacity while adequately heating or cooling the atmosphere within the building. The method is accomplished by cycling area air supply and return dampers between fully-open and intermediate-open positions to selected floors or parts of floors within the building. The dampers are cyclically operated by electro-pneumatic actuators which are operatively connected to a central control apparatus for cycling according to a pre-determined pattern.