Energy-Efficient?

How much could you save?

By installing double glazing in an entirely single glazed house you could save the following each year:

Energy rating Detached Semi detached Mid terrace Bungalow Flat
A rated £130 – £175 £90 – £120 £80 – £105 £60 – £80 £50 – £65
B rated £120 – £160 £80 – £110 £70 – £95 £50 – £70 £40 – £60
C rated £120 – £150 £80 – £105 £70 – £90 £50 – £65 £45 – £55

These savings are for typical gas heated homes.

The benefits of energy-efficient windows

  • Smaller energy bills.
  • A smaller carbon footprint.
  • A more comfortable home: 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.

To get a better idea of how much you could save by replacing your windows, use the Energy Saving Calculator at the Glass and Glazing Federation’s website, developed with the Energy Saving Trust.
energy efficient

How energy-efficient glazing works

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 usually filled with Argon gas. Triple-glazed windows have three sheets of glass.

Energy-efficient windows come in a range of frame materials and styles. They also vary, depending on:

  • how well they stop heat from passing through the window
  • how much sunlight travels through the glass
  • how little air can leak in or out around the window.

What to look for

  • Glass: The most energy-efficient glass for double or triple glazing is low emissivity (Low-E) glass. This 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.
  • Pane spacers: 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.

Frame materials

For all frame materials there are windows available in all energy ratings.

  • uPVC frames last a long time and can be recycled.
  • Wooden frames can have a lower environmental impact, but require maintenance. They are often used in conservation areas where the original windows were timber framed.
  • Composite frames have an inner timber frame covered with aluminum. This reduces the need for maintenance and keeps the frame weatherproof.
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