Public buildings, churches, temples, hospitals and institutions may exceed the height limit to a total height of seventy (70) feet providing all yards required in the particular district are increased one foot for each two foot in excess of the height limitation. Chimneys, church steeples, cooling towers, elevator bulkheads, fire towers, monuments, stacks, stage towers, or scenery lofts, tanks, water towers, spires, radio and television towers, grain elevators or other such architectural and mechanical appurtenances are exempt from height regulations.