A window composed of two or more sheets of plate glass separated by a sealed air space. Introduced in 1944, Thermopane was the first insulated glass. The dead air space provides high thermal resistance. Lead strips were used to seal the perimeter of early insulated windows. When the seal is broken, moisture may condense between the two panes forming a haze. The fogging is remedied by drilling small weep holes at the bottom of the inner pane to provide better circulation. The insulation value is only slightly decreased.
Synonyms and Related Terms
double glazing; vitre isolante (Fr.);
Brand names: Thermopane [Libbey-Owens-Ford]; Twindow [PPG]
K.Konrad, K. Wilson, W. Nugent, F.Calabrese, "Plate Glass", in Twentieth-Century Building Materials, T. Jester (ed.), McGraw-Hill: New York, 1995.