Up to a third of a home’s heating is lost through single glazing, and having windows which are energy efficient can save energy use by around 20%.
To be thermally efficient, windows should be double glazed as a minimum and have a low emissivity glass, with a non-toxic, inert and insulating gas such as Argon between the panes.
Replacement double-glazed windows can achieve a Window Energy Rating (WER) of A+12, while for triple glazing the figure can be A+32.
Given this efficiency, upgrading your windows could save you as much as £450 on your annual household energy bills.
What is WER rating?
The British Fenestration Council devised this system to make a window’s effectiveness simple. Grades go from A to A, with A being the best grade. Anything higher than that is followed by a number, and anything over an A10 becomes an A+.
A couple of years ago, the A++ rating was launched for windows with a score of over A+20. Britain’s highest currently available grade is A+32.
Three key elements make up the rating – U value (or low heat loss), air loss through ventilation and solar gain.
This is about capitalising on solar radiation and reducing dependency on carbon energy for heating a home during the winter.
The number of panes, they type of gas between them, and the kind of coatings added, all influence the solar factor.
This is the technical way of measuring heat loss through a kind of building material. The lower the U value, the stronger the insulation the material provides. Modern double-glazed windows can achieve a U value as low as 1.4W /m²K, while triple glazing is even more energy efficient
This isn’t the same as ventilation, which is a controlled way of allowing in fresh air, and won’t affect energy efficiency.
Air leaks when the window frame has a weak point, such as at the seal, but for most modern units, they should be fully airtight, and have a zero L-value rating.
There is another benefit to replacement windows – sound insulation so that you enjoy more peace and quiet. Clearly, that could be more important if you live in a built-up area, near heavy traffic, or under a flight path.
The same things that affect energy efficiency in windows also affect noise cancellation – gas to fill the cavities, airtight seals and having more glass panes.
At Paradise, offering double-glazed windows in Oxford and the surrounding areas, we’re well placed to advise you on the energy efficiency of your home improvements. Get in touch today.