All wind turbines and towers shall be set back from all structures and buildings, other than residences, that are in existence at the time of the application, or for which a building permit has been issued, a minimum of 1,000 feet, or 2.25 times the height, of the tower, including to the tip of the blade. The Town Board may, at its discretion, exempt minor structures such as walls, fences, tool sheds and similar minor structures from this setback requirement.