A technique of building a
window whereby two sheets of
glass are used rather than the more traditional single sheet. The window is usually supplied as a
sealed unit and the two sheets of glass will typically be between half an inch and two
inches apart.
Double glazed windows have a number of advantages over traditional windows, predominately the fact that the air gap between the two sheets acts as a fine insulator. This results in reduced heat loss outwards, and reduced noise inwards.
A variety of different options are available for double glazed windows, including different materials for the frame (uPVC or aluminium are the most common) and different coatings on the glass itself to alter its refractive properties and solar gain.
Double glazing salesmen have a reputation, in Britain at least, of being notoriously pushy and using hard sell techniques.