Height requirement exceptions for certain building appurtenances. The height limitations of this chapter shall not apply to church spires, belfries, cupolas, penthouses and domes, not used for human occupancy, nor to chimneys, ventilators, skylights, towers, water tanks, similar features, and necessary mechanical appurtenances usually carried above roof level. The provisions of this chapter shall not apply to prevent the erection above the building height limit of a parapet wall or cornice for ornament (and without windows) extending above such height limit not more than five feet. Such features, however, shall be erected only to such height as is necessary to accomplish the purpose they are to serve and subject to the Wisconsin State Building Code.