I Glaze

The costs and savings for energy-efficient glazing will be different for each home and each window, depending on the size, material and installer. Double glazing should last for 20 years or more. Double-glazed windows have two sheets of glass with a gap between them, usually about 16mm, to create an insulating barrier that keeps heat in. This is sometimes filled with gas. Triple-glazed windows have three sheets of glass, but aren't always better than double-glazed windows: to choose the most energy-efficient window look for the BFRC rating and Energy Saving Trust Recommended logo.

Glass: The most energy-efficient glass for double glazing is low emissivity (Low-E) glass. This often has an unnoticeable coating of metal oxide, normally on one of the internal panes next to the gap. This lets in light and heat but cuts the amount of heat that can get out. In between: Very efficient windows might use gases such as argon, xenon or krypton in the gap between the sheets of glass.