| Double glazing is used in glass-paned windows, doors | | | | provides increased thermal insulation and may also |
| and conservatories as a means to insulate from | | | | reduce solar gain. Several types of coated glass are |
| draught, heat and cold, sound and direct sunlight. It | | | | available; for example, low emission, or low-E glass, |
| uses two panes of glass with a sealed gap, creating | | | | has a special metallic coating that helps prevent |
| a dead air space, providing thermal insulation. It also | | | | thermal loss and is frequently used in the glazing |
| helps reduce carbon dioxide (CO2) emission, a | | | | applications. |
| primary contributor to greenhouse gas emissions, | | | | Thermal conductivity is defined by the U-value. The |
| believed to cause climate change. Ordinary windows | | | | lower the U-value, the greater the insulating effect |
| use one pane of glass and do not have as much | | | | and the lower the rate of heat loss. A regular glass |
| thermal insulation, thus conducting more heat and | | | | pane has a U-value of 5.4;and twice-glazing has a |
| cold. It can cut heating loss by approximately 20 | | | | U-value of 2.6. Additional treatments to glass can |
| percent. | | | | lower the U-value and provide greater energy |
| Double glazed window or door frame material can be | | | | conservation. Low-E glass has a U-value of 1.8. If the |
| aluminium, timber or uPVC. Each material has a | | | | space between panes is filled with a gas other than |
| different thermal insulation value. Different types of | | | | air, lower U-values may be achieved. The U.K. now |
| glass are available, each with different safety and | | | | has regulations concerning allowable U-values for |
| thermal values. Float glass is a traditional standard | | | | windows and doors for both new construction and |
| pane that shatters into jagged shards when broken; | | | | renovations to existing structures. The U-value |
| it is usually not used in double glazing applications. | | | | calculation takes into account the material of the |
| Toughened glass has increased thermal properties | | | | frame, the window size and the type of glass. When |
| and greater strength, making it more resistant to | | | | considering installation of double glazed glass fittings, |
| impacts. When broken, it shatters into small pieces, | | | | the contractor should comply with these regulations. |
| making it safer. Laminated glass has a thin plastic | | | | Many contractors are certified by the Fenestration |
| layer between two sheets of glass, providing more | | | | Self-Assessment Scheme, or FENSA, insuring that the |
| strength and safety than ordinary glass. Coated glass | | | | installation complies with government standards. |