Maximum building height: 40 feet. However, structures not intended for human occupancy, such as silos, towers, chimneys, stacks, mechanical penthouses, etc., may exceed this limit up to a height of 60 feet by conditional use, in compliance with the provisions of §§ 110-306 and 110-328 of this chapter, provided the front, side and rear yard setbacks are increased by two feet for every one foot of structure height over 40 feet.