Sealed Units explained

Sealed Units or otherwise known as Insulating Glass Units(IGU)

Even more commonly known as double glazing (or double-pane, and increasingly triple glazing/pane), consists of two or three glass window panes separated by a vacuum or gas filled space to reduce heat transfer across a part of the building envelope.

Insulating glass units (IGUs) are manufactured with glass in range of thickness from 3 to 10 mm (1/8″ to 3/8″) or more 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 used on both panes but special applications such as acoustic attenuation or security may require wide ranges of thicknesses to be incorporated in the same unit.

Thermal performance

The maximum insulating efficiency of a standard IGU is determined by the thickness of the space. Typically, most sealed units achieve maximum insulating values using a space of 16–19 mm (0.63–0.75 in) when measured at the center of the IGU.

IGU thickness is a compromise between maximizing insulating value and the ability of the framing system used to carry the unit.

Some residential and most commercial glazing systems can accommodate the ideal thickness of a double-paned unit. Issues arise with the use of triple glazing to further reduce heat loss in an IGU.

The combination of thickness and weight results in units that are too unwieldy for most residential or commercial glazing systems, particularly if these panes are contained in moving frames or sashes.

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