Basement window installer Materials include the window itself, as well as the goods needed to construct a window well, such as screws, tools, timber, concrete, insulation, caulk, moisture barriers, tarps, shims, and more. The kind of window determines the cost of an egress window more than the size. In the event of an emergency, an egress window must be at least 20 inches wide by 24 inches high and large enough for an adult to escape through. For basement egress windows, casement windows are the most preferred choice.