Height exceptions. The height limitations of this chapter, as shown on Schedule II of Article IV hereof,[1] shall not apply to the following structures: cliffside, cantilever-type and A-frame homes, church spires, belfries, cupolas, domes not used for human occupancy, chimneys, ventilators, skylights, water tanks, bulkheads and other necessary mechanical appurtenances usually carried above the roof level, parapet wall or cornice for ornament, extending above such height limit not more than five feet; radio or television receiving antennae or a public utility transmission tower or cable. No such uses shall in their aggregate coverage occupy more than 20% of the roof area on which located. This exception shall not apply in determining whether a structure is a Class A regional project by virtue of its height. Regional project jurisdiction shall extend to all structures over 40 feet in height, except residential radio and television antennae and agricultural use structures. For such jurisdiction, building height shall be measured from the highest point of the structure to the natural ground or finished grade, whichever is lower.