Double glazing is a method of window glazing using two separate panes of glass separated by a thin void. The glass sheets are set into a frame, trapping the gas in between, to produce an integral window unit that is installed on site. There is a range of options for each component of the window, resulting in myriad combinations for the overall window unit.
The frame generally comprises one of three materials: aluminium, timber or PVC. The choice of material depends on the style of the house, the size of the window and the climate. Aluminium frames are great for modern homes with a streamlined look, while timber is more traditionally used on period-style houses. Timber is generally a better insulator than aluminium, and will help reduce heat loss through the frame. PVC is a relatively new option that provides the added benefit of being able to create window frames in almost any shape and colour.
Glass is available in a number of variations: plain, tinted or coated. The latter two aim to reduce the amount of heat that enters your house via the windows. Tinted glass is used to reduce the amount of UV light (and therefore heat) that enters the building. It also provides an architectural feature, giving the glass a coloured hue. Coatings are usually made of polyester or metal, and aim to reflect incoming UV rays, controlling the transmission of heat and/or light in a similar way.
The void between the glass sheets can be a vacuum or contain an inert gas. Argon, krypton and xenon gases are all capable of reducing the amount of heat convection through the window, with increasing degrees of efficiency. Argon is the most popular because it is the least expensive. In theory, a vacuum-sealed unit is the most efficient, but this method is usually limited to small sizes due to stability issues.
Double glazing technology can also be used in large-scale curtain walls. A curtain wall is a glazed facade that hangs separately from the structure of a building. These are commonly seen in commercial buildings, such as offices and skyscrapers, giving a seamless finish to the exterior of a building. Large sections of double glazing are prefabricated off-site and hung in specially designed framing components.
Double-glazed windows provide a thermal barrier, minimising the amount of heat that escapes or enters the home. This means that the amount of additional air conditioning needed to keep a home at a comfortable temperature is reduced, saving on heating and cooling bills. They also provide increased insulation without compromising views.