The provisions of this chapter with regard to height shall not apply to church spires, steeples, belfries, clock towers, noncommercial radio towers, flagpoles, chimney stacks, skylights, scenery lofts, antennas, water tanks, fire or parapet walls or roof structures for the housing of elevators, stairways, ventilating fans, air-conditioning equipment or similar equipment and structures, provided that such features shall be erected only to such height as is necessary to accomplish the purpose they are to serve.