The primary feature in Casement Windows is that they are hinged on the sides of the frame and open from the side, usually to the exterior. Casement Windows that swing outwardly are typically the most energy efficient of window styles since the sash closes by securing firmly against the frame of the window. Another benefit of an outward opening Casement Window is that the ventilation or air passage is significantly improved due to the various angles of openings that can be obtained, thereby maximizing the ventilation. Screens are typically used on the interior of Casement Windows.