Window insulation

Window insulating apparatus, comprising:

• (a) a plurality of panels formed of low heat-transfer material, the sum of the areas of the panels being approximately equal to that of the window opening, each panel being generally rectangular and being arranged in the window opening with the length extending horizontally, the panels being arranged in side-by-side planes and slidable vertically from an upper storage position where the panels lie side-by-side to an operative position where the panels are arranged in a step-like condition,
• (b) an extruded element applied to the upper and lower edges of each panel, each element having a sealing surface which mates with a similar sealing surface on an extruded element applied to the immediately adjacent panel,
• (c) a pair of side frame members having vertically extending guiding elements for guiding the panels between the upper storage position and the lower operative position,
• (d) first adjusting means for moving the side frame members toward and away from each other, and
• (e) second adjusting means for moving the vertically extending guiding elements for the outermost panel in a direction transverse to the plane of the window to maintain the desired degree of sliding friction for the outermost panel.