Height exceptions. District building height regulations shall not apply to flagpoles, radio or television antennas, electric transmission towers or cables, wind electric-generating equipment installed by a residential customer generator or a farm customer generator in compliance with New York State Public Service Law § 66-l, spires or cupolas, chimneys, elevator or stair bulkheads, parapets or railings, or water tanks or cooling towers, provided that such structures in their aggregate coverage occupy no more than 10% of the roof area of the building. Barns, grain elevators and silos may exceed height limitations of this chapter, provided that for each one foot such structure exceeds 35 feet, the minimum yard requirements shall be increased by one foot but in no case may exceed 100 feet. The Planning Board may, as part of site plan review, waive height restrictions for wind electric-generating equipment installed for use in a commercial or industrial use.