Abstract: Window unit (2) includes a window casing (4) having a plurality of flexible plastic sheets (6) mounted on spring rollers (30). Sheets (6) can be unrolled into an operative position where they are spaced in front of a transparent window panel to act as storm windows. Rectangular sealing frames (8) are movable in casing (4) between a first position in which the frames (8) are spaced apart to receive the plastic sheets (6) therebetween and a second position in which the frames (8) are pressed together to trap and seal the plastic sheets (6) therebetween. Frames (8) are movable manually by elongated shafts (50) which pass through key hole slot (56) in window casing (4).