Structure of multilayered unit for windows

The structure of a multilayered unit for windows, comprising a plurality of planar members;

• at least one flexible film disposed therebetween and spaced from two of the planar members;
• spacers solely defining the clearance between opposing planar members;
• and a sealing member for sealing the spaces defined by the planar members at substantially their entire peripheral edge portions said flexible film extending at least over that region of said planar members which forms a window, and the planar members present on at least one side of the flexible film being transparent or semi-transparent, characterized in that the structure includes a resilent stretching member separate from said spacers for stretching the flexible film taut by imparting thereto a force having at least a vector component thereof acting at right angles to the plane of the film, so as to tend to push said film away from said stretching member, each of the spacers opposing each other on each side of said film having a space formed therein which faces the flexible film and further wherein the stretching member is located in at least one of said spaces and is substantially shielded from sunlight by at least one of said spacers.