low-e insulated glass

Insulated Glazing Unit or Insulating Glass Unit (commonly referred to as IGU) is a set of two or more lites of glass spaced apart and hermetically sealed to form a single glazed unit with an air space between each lite. Its most important function is to improve the thermal performance of glass when used in architectural applications.The most commonly found IGUs are double glazed, i.e. made with two lites of glass and are therefore also referred to as "double glazing units" or "DGU" (especially in Europe) but IGUs with three lites or more, i.e. "triple glazing" are sometimes used for in very cold climates. Insulated glazing may be framed in a or or in a . IGUs are also commonly used for .Insulating glass IGU made of is called insulated glass, which refers to heat insulation, not sound or electricity. A more accurate term is "insulating glass", since the glass itself has no insulative properties. It is the air space between the glass layers (lites) that provides the insulation. The space between the lites may be filled with or an inert gas like or which would provide better insulating performance. Typically the spacer is filled with to prevent and improve insulating performance. Less commonly, most of the air is removed, leaving a partial , which drastically reduces heat transfer through and . This is called evacuated glazing. Often the insulating quality is used in reference to where the gap is the insulating medium. The gap is usually 12mm to 20mm thick. The thickness does impact the insulating properties substantially. A 16mm air gap is considered the optimum thickness and is usually recommended by most users. In some situations the insulation is in reference to . In these circumstances a large gap improves the noise insulation quality or . 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. The heat and sound insulation of glazing may also be improved by the use of a film or coating applied to its surface. This film is typically made of polyester or metal, and may give the window a reflective appearance and effect. It may be used on single-glazed windows as an alternative to insulated glazing, or on the outside layer of insulated glazing to further improve its effectiveness. Such coatings may reduce fading of fabric and improve safety in case the glass breaks. Many of the films impart a color to the glass, typically blue, brown or gold, which may be used to enhance a building's architectural style. In automotive applications, where non-reflective and neutral-color tinted glazing is required, heat reflective properties are created using a nano-metre thick silver oxide layer within the windscreen. Insulating automotive glass is also called "athermic glass", "heat reflective glass" or "comfort glass". Secondary glazing is sometimes used as a cheaper alternative. It consists of a layer of glazing placed retrofitted inside the window, to provide sound and heat insulation. Plastic sheet may be used for heat insulation, but may only last for one season.