Abstract: An insulative window shade assembly of the roll-up type for windows or like openings comprises a flexible sheet of shade material essentially of the size in area of the window or other opening to be insulated. The flexible sheet of material in its inoperative position is contained in a header or casing mounted at the top of the opening and extending across the width of the opening. The casing contains a spring-actuated roller upon which the sheet of shade material is wound with the leading edge protruding through a longitudinal slot or opening in the casing. The system further provides two side guides or channels mounted at the sides of the window or opening, and in which the channels contain a pile fabric to seal the sides of the flexible sheet when unrolled to the operative or insulative position.