Patching the Thermal Hole of Windows

Materials research is being applied to the significant reduction of undesired heat gains and losses through apertures. This paper summarizes the background and recent progress supporting the development of vacuum and electrochromic windows at SERI. Evacuated glazings now under investigation feature a thin-film, transparent infrared reflector, spherical glass spacers, and laser-welded edges. Webelieve that these features will result in an overall glazing R-value of 10 or more, maintainable over architectural lifetimes. Technical issues discussed include thermal and mechanical stress, optimal spacer configuration, and gaseous diffusion. The electrochromic work has concentrated on achieving large differences in the transmissivity of window glazing by using thin, transparent films thatrespond to small electrical potential by becoming, reversibly, partially colored or opaque. Color memory, bleaching rates, and alternative transparent solid-state conductors are discussed.