Energy control sheet having insulative properties

In a window unit located in the external wall of a room, said unit comprising a plurality of transparent strata and including at least

• (a) a glazing unit having an inside face oriented toward the interior of the room and an outside face oriented toward the exterior of the room, said glazing unit comprising at least one rigid transparent stratum whose inner face coincides with the inside face of the glazing unit, and
• (b) a flexible, transparent energy control stratum which is located adjacent to said glazing unit or one of its component strata and which is a flexible, unitary multi-layer sheet material comprising a transparent-reflective metal layer bonded to a transparent polymeric support foil which has low transmission and high absorption properties with respect to infra-red energy in the 4-40 micrometer wave length, said metal layer being covered by a transparent polymeric protective layer and having a sheet resistance of less than 20 ohms/square,
• the improvement wherein (1) the transparent polymeric layer is selected from polymers which, in thicknesses on the order of 5-50 micrometers, transmit at least about 80% of the normal room temperature infra-red radiant energy in the wavelength of 4-40 micrometers,
• and (2) the energy control stratum is located other than adjacent the outside face of the glazing unit and is oriented so that the protective layer confronts an air space and does not contact any surface of the glazing unit,
• whereby said window unit not only effectively excludes externally originating heat and glare in hot weather but also returns to the room at least about 55% of the internally originating infra-red energy impinging on said window unit and thereby significantly improves the insulative effectiveness of said window unit in cold weather.