Building height. No building shall exceed a height of 40 feet. In determining the height of any building, elevator or escalator penthouses, cooling towers and other structures on the roof, which house mechanical or other equipment, shall not be taken into account, provided that they do not exceed a height of 10 feet above the roof to which they are attached and provided, further, that such structures are appropriately masked or screened as determined by the Planning Board at time of site plan approval.