Permitted exceptions to height regulations. Chimneys, cooling towers, cupolas, silos, fire towers, steeples, water towers, spires, communications towers or necessary mechanical appurtenances may exceed normal height limits provided that no tower, other than a church spire or farm silo, shall exceed the height regulations by more than 40%. No tower shall be used as a place of habitation or for tenant purposes. No sign, nameplate, display or advertising device other than one identifying the manufacturer of the structure or the geographic location shall be inscribed upon or attached to a chimney, tower, tank or other structure which extends above the height requirement.