US Patent 9458662 Energy-efficient fenestration assemblies

A fenestration assembly is described. The fenestration assembly includes: (1) a layer of film; (2) a frame having a first surface and a second surface, which is opposite to the first surface, the first surface substantially surrounding and having secured thereon the film and the frame having a thickness such that when the second side is fitted onto a window or a window frame, the thickness of the frame defines a space between the film and the window; and (3) wherein said film is a low-emittance film having an emissivity equal to or less than 0.35.