Height limits shall not apply to flag poles, chimneys, or cupolas, provided that the horizontal area of such parts does not exceed 0.1% of the ground area covered by the main building, and further provided that height limits shall not apply to roof mounted heating, air conditioning or other mechanical equipment except that such equipment, when visible when standing at ground level from a residential zone, shall be screened by a wall, cover or by other means and that such screening shall be in keeping with the architectural motif of the building.