The height limitations of this chapter shall not apply to church spires, silos, belfries, cupolas, and domes not used for human occupancy, nor to chimneys, ventilators, skylights, water tanks and necessary mechanical appurtenances usually carried above the roof level. Roof mounted equipment shall be screened from public view. Such features, however, shall be erected only to such heights as are necessary to accomplish the purposes they are to serve and then only in accordance with any other governmental regulations.