How energy efficient glazing works

Whereas in the past, window and door double glazing was literally two panes of 4mm wide float or toughened or laminated glass, separated by a 12mm to 20mm wide air gap and silver spacer bar, glass technology and warm edge technology now enable double glazing companies to put high specification double glazed sealed units into aluminium, timber or PVCu frames.

Anyhow, here is how energy efficient glazing works according to the Energy Saving Trust’s website:

“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. Energy-efficient windows come in a range of frame materials and styles. They also vary, depending on a) how well they stop heat from passing through the window, b) how much sunlight travels through the glass, and c) how little air can leak in or out around the window.”

According to the Energy Saving Trust, the following are just some of the benefits of fitting decent energy rated, energy efficient replacement windows:

  • Smaller energy bills: replacing all single-glazed windows with B-rated double glazing could save you around £170 per year on your energy bills.
  • A smaller carbon footprint: by using less fuel, you’ll generate less of the carbon dioxide that leads to global warming – typically, 680kg a year.
  • A more comfortable living environment: energy-efficient glazing reduces heat loss through windows and means fewer draughts and cold spots.
  • Peace and quiet: as well as keeping the heat in, energy efficient-windows insulate your home against outside noise.
  • Reduced condensation: energy-efficient glazing reduces condensation build-up on the inside of windows.

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.

Things the Energy Saving Trust suggests home owners should look out for when considering having energy rated replacement double glazed or triple glazed windows and/or doors installed:

  • Glazing panes: 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 the glass panes: Very efficient windows might use gases such as argon, xenon or krypton in the gap between the sheets of glass.
  • Spacer bars: These are set around the inside edges to keep the two panes of glass apart. For maximum efficiency, look for pane spacers containing little or no metal — often known as ‘warm edge’ spacers

Find out more about energy rated windows


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