Insulated glazing
From Free net encyclopedia
Insulated glazing is a piece of glazing consisting of two or more layers of glazing separated by a spacer along the edge and sealed to create a dead air space or a vacuum between the layers. When it is made of glass it is called insulated glass. Insulating windows are usually double paned, but windows with triple panes or more are sometimes seen in very cold areas. It is mounted in a sash or frame as if it were a very thick piece of glass. The dead air space may be filled with air but an inert gas like argon provides better insulating performance. Argon (Ar) has an atomic mass of 39.9, which is much more than nitrogen (N2) and oxygen (O2) molecules, which have a molecular mass of 28.0 and 32.0 respectively. As a result, argon atoms move significantly slower than nitrogen and oxygen molecules at the same temperature. This reduces convection and decreases the energy transfer between one side of the glass and the other. Typically the spacer is filled with desiccant to prevent condensation and improve insulating performance. Less commonly, the air is removed, leaving a vacuum, which has no convection at all. This is called evacuated glazing.
Often the insulating quality is used in reference to heat flow where the gap between glazed sheets is optimum at about one centimetre. A larger gap allows for convection currents and negates the dead air space. However, in some situations the insulation is in reference to noise mitigation. In these circumstances a large gap improves the noise insulation quality or Sound transmission class.
Insulated glass may not be cut to size in the field like plate glass but must be manufactured to the proper size in a shop equipped with special equipment.