Roof-level features such as spires, belfries, cupolas, or domes not used for human habitation, chimneys, ventilators, skylights, parapet walls, cornices, solar energy systems, green or blue roof systems, water tanks or necessary mechanical appurtenances usually located on the roof level shall be excluded from calculating height. Flagpoles, monuments, transmission towers and cables, radio and television antennas or towers, and similar structures shall also be excluded from the height limits of this section but may otherwise be regulated in this chapter. Such features, however, shall be erected only to such height as is necessary to accomplish the purpose for which they are intended. No advertising device of any kind whatsoever shall be inscribed upon or attached to that part of any chimney, tower, tank or other structure that extends above the height limitations.