Insulated glazing

Insulating glass (IG) consists of two or more glass window panes separated by a space to reduce heat transfer across a part of the building envelope. A window with insulating glass is commonly known as double glazing or a double-paned window, triple glazing or a triple-paned window, or quadruple glazing or a quadruple-paned window, depending upon how many panes of glass are used in its construction.

Insulating glass units (IGUs) are typically manufactured with glass in thicknesses from 3 to 10 mm (1⁄8 to 3⁄8 in). Thicker glass is used in special applications. Laminated or tempered glass may also be used as part of the construction. Most units are produced with the same thickness of glass on both panes but special applications such as acoustic attenuation or security may require different thicknesses of glass to be incorporated in a unit.

The space in between the panes provides the bulk of the insulation effect. It can be filled with air, but argon is often used as it gives far superior insulation, and sometimes other gases or a vacuum are employed.

History

Possibly the earliest use of double glazing was in Siberia, where it was observed by Henry Seebohm in 1877 as an established necessity in the Yeniseysk area where the bitterly cold winter temperatures regularly fall below −50 °C, indicating how the concept may have started:

One of the peculiarities of this part of the country is that it is a land of dear glass. You rarely see a window with square panes.