The following appurtenances attached to or part of a principal or accessory structure: a church, spire, belfry, cupola, dome, monument, smokestack, derrick, conveyor, flag pole, mast, antenna, aerial, roof tank, ventilating air conditioning and similar building service equipment, roof structure, chimney and/or parapet wall, provided that it shall be set back in conformance with the setback and yard requirements, plus one-foot horizontally for each foot in which it exceeds 40 feet in height above ground level. The principal or accessory structure to which it is attached may conform to setback and yard requirements with no additional setback, provided that the principal or accessory structure conforms to the height limitations of the districts.