Necessary appurtenant structures such as penthouses or roof structures for the housing of elevators, stairways, tanks, ventilating equipment or similar equipment required to operate and maintain the building, firewalls, skylights, towers, steeples, flagpoles, parapets, chimneys, wireless masts or similar structures may be erected above the height limits specified in Article III but no penthouse or roof structure or any space above the height limit shall be allowed for the purpose of providing additional floor space for residential use. In addition, water tanks, solar panels, solar collectors and related equipment, utility poles, windmills or towers may be permitted above the designated height limits.