Abstract: An insulating, translucent panel useful as a storm window, a translucent wall within a building, or a skylight includes a polyethylene closed cell foam sheet adhered to a polycarbonate structural sheet. In one form of the invention, the two sheets are mounted within a frame which compresses the foam sheet edge so that the two sheets can be mounted in the frame without the use of screws. The polycarbonate sheet has parallel, closed channels disposed in a vertical position so that condensate drains to the bottom of the window assembly. A bottom frame member drains off the condensate.