Double Glazing

Double Glazing describes windows that consist of two sheets of glass (triple glazing describes windows that consist of three sheets of glass).  

The purpose of Double Glazing is to insulate a building better. A great amount of heat is lost through window space as windows are thinner than walls. To reduce heat flow through the window space, Double Glazing windows are installed. A gap of air between the two sheets of glass reduces heat flow and helps keep a room warmer than the outside temperature.

The effectiveness of Double Glazing is dependent upon the distance between the two sheets of glass: if the distance between the two sheets is too great or not great enough, the Double Glazing will not be effective. Optimal performance is considered to be achieved at a distance of about 18mm.

The air in between the sheets can be almost entirely removed, creating a vacuum. This further reduces the conduction of heat. In addition, gases are sometimes used to fill the space instead of air.