US Patent 9322209 Insulating window panel

An insulating window panel for removable installation into a custom size window opening recess includes longitudinally extending frame pieces configured with joints for interconnecting the frame pieces to form a frame around a transparent flexible glazing sheet. Each frame piece has a longitudinal keder channel with a slot that opens out of a glazing side of each frame piece. The glazing sheet has edges corresponding to the frame pieces; and a keder formed on each of the edges, with a corner cut that spaces apart intersecting kedered edges, all being shaped and sized for sliding each keder edge into the keder channel of each corresponding frame piece such that the frame pieces form joints at the corner cuts and the frame pieces are pulled together at the joints by tension relative to the glazing sheet. Preferably a weatherstrip surrounds the frame perimeter with compressible fins for sealed but removable installation.