The height limitations of this chapter shall not apply to church spires; farm structures when permitted by other provisions of this chapter (e.g., silos, barns, etc.); belfries, cupolas, penthouses and domes not used for human occupancy; chimneys, ventilators, skylights, water tanks, bulkhead and similar features; utility poles and standards; and necessary mechanical appurtenances usually carried above the roof level. Such features, however, shall be erected only to such height as is necessary to accomplish the purpose they are to serve and then only in accordance with any other governmental regulations.