Energy Efficient Double Glazing Windows

Energy Efficient Double Glazing Windows

For many homeowners, the desire to improve the appearance and comfort of their home is balanced by a wish to be as environmentally friendly as possible. Because installing double glazing onto a home is one of the biggest investments anyone can make in their property, how can you achieve both aims without the costs running away from you?

In this article, we’ll look at:

  • the advantages of eco-friendly double glazed windows
  • what the energy ratings you see for double glazing actually mean
  • how double glazing makes your home more eco-friendly
  • choosing the right time to get double glazing for your home
  • finding a double glazing installer you can trust

If you’re budgeting for eco-friendly double glazed windows, how much will you need to have save up or take out on a loan?

Property typeNumber of double glazing panes to be installedInstallation Prices
Small or terraced house8£4,100-£4,600
Large terrace or medium-sized house10£5,200-£5,800
Large house (including detached)15£7,600-£8,500

These prices are indicative. They’re just there to give you a ballpark figure for your personal situation. It’s always best to ask three or four installers to quote you so that you get the double glazing you want at the best possible price. We’ll tell you how to do that later in this article.

What are the advantages of eco-friendly double glazed windows?

Warm winters

For homeowners looking to benefit from additional insulation, double glazing is an effective and attractive addition to their property. Because of the way double glazing is manufactured, it actually captures natural heat and keeps it inside your home during the winter months.

Cool summers

Double glazed homes need far less air conditioning. This is because it stops a large percentage of the sun’s rays from getting into your home on hot summer days – much more so than single-panel units.

Utility bill savings

Because double glazing keeps your home warm in winter and cool in summer, you’ll spend a lot less on gas and electricity bills than you are now to keep your property at a temperature that’s comfortable for you. If you have double-glazing in your home already which is over 10 years old, the technology behind them has advanced so quickly since then that, by replacing your existing windows with the latest in double-glazing, you’ll still notice a difference on your utility bills.

Safety and security

Double glazed windows, particularly those manufactured in the last couple of years, are a lot harder to break into because the panes of glass are sealed much tighter than ever before and the frames holding the glazing are a great deal tougher too.


If you live by a busy road or in the middle of a city or a town, the noise from outside, particularly at rush hours, school closing times, and on weekend nights can severely impact on the satisfaction you enjoy from living where you live. Double glazing blocks nearly all the noise from outside getting into your home.

Less condensation

How does condensation in your home occur? It’s caused by ventilation issues affecting both your home and your windows.

If you do nothing about condensation, then it can build up quickly causing damp and mould, both of which have been proven to have a negative effect on people’s health.

If you see condensation on the outside of your window, don’t worry – that’s actually a good thing and there’s nothing wrong with your windows. It means that your double glazing is helping to keep your home warm when it’s colder outside.

A major warning sign is if condensation starts to appear between your panes. If that’s happened, then this means that, almost certainly, there is a gap in the seal of the window somewhere. This gap will have caused all the insulation gas to have leaked out, reducing the overall insulating properties of your windows.

Completely recyclable

Most current double glazing is completely recyclable – that’s both the glass and the frames. In addition, many manufacturers have stopped using steel and lead in the production process making your double glazing even kinder to the environment.

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Window energy ratings

Each window range manufactured in Britain in recent decades has received a rating ranging from A to G on its energy efficient properties. Under current UK law, all windows now must be manufactured to a C rating at the very least.

The ratings for each type of window are provided by one of the following organisations – CERTASS, the British Standards Institute, and the BRFC. Each of these organisations measures energy efficiency in its own way however most industry experts agree that it’s safe for homeowners to assume and believe that an “A” rating from one organisation means that a window is better than one rated “B” by another organisation.

The organisations use the following three measurements when deciding how to rate a particular type of double glazing:


G-value measures the amount of heat gained by calculating the solar energy which passes through the double-glazed panels being tested.


The L-value measures the amount of air leaking from a particular double glazing panel – in other words, how much heat is being lost by warm air that’s escaping?


The U-value measures how much solar energy is transmitted through a double glazing panel – in other words, how much heat does the window capture?

How the energy efficiency of the windows you choose directly affects what you pay your utility company

The better the energy efficiency of the double glazing you choose for your home, the more you’ll save year on year on your energy bills.

The table below gives you a rough guide to the savings on offer for different types of property if all of that property’s existing glazing is replaced by new double glazing with different energy ratings.

energy ratingAvg quoted price per windowELECTRICITY BILL SAVINGS PER ANNUM (estimated, full house fitting)
Large semi or detachedMedium-semi or end terraceTerraced houseBungalowApartment
A ++N/A£105 to £120£85 to £115£70 to £90£65 to £80£45 to £60
A +N/A£100 to £125£80 to £105£65 to £80£60 to £75£35 to £45
A£540 to £660£95 to £110£70 to £75£55 to £70£55 to £70£35 to £40
B£290 to £460£90 to £105£70 to £75£55 to £60£55 to £65£35 to £40
C£240 to £360£80 to £95£70 to £75£55 to £60£55 to £65£35 to £40

What is low-E glass?

As we’ve seen, all double glazing in the UK allows homeowners to save money on the utility bills. Different grades of double glazing produce different levels of savings.

There are two companies in the UK manufacturing something called “low-E glass” – you might hear an installer refer to it as “coated glass”.

Low-E glass is coated with a transparent metal which reflects heat back into your home and it lets both light and heat from the sun to come in from the outside. Low-E glass is produced by Pilkington (they use a “hard coating” method) and Saint Gobain (they use a “soft coat” method).

Low-E glass can work out at up to 25% more than standard glass (sometimes called “annealed glass”). This bigger upfront investment in your new eco-friendly double-glazing will however result in significantly lower energy bills for years and years after installation.

How do you know it’s time to get eco-friendly double-glazing?

If there’s condensation on the insides of your window or between the panes, that’s a strong sign that you need to change your double glazing for a newer, eco-friendly alternative straight away. Likewise, if too much noise is getting into your home, your double glazing is almost certainly starting to fail.

What else should you look out for to tell you it’s time to invest in new double glazing for your home?

Do your windows look tired?

Your window frames are exposed to the outside 24 hours a day, 7 days a week and no matter how tough your existing double glazing, that exposure is going to subject them to wear and tear.

More often than not, you can give them a quick clean to refresh their appearance. But damp and mould will start to build up around the frames if your window panes are cracked. And, as we mentioned earlier, if they are cracked, the gas that used to provide the insulation that kept your home cool in summer and warm in winter will have leaked out meaning that you’re no longer protected.

Rotting wooden frames

Wooden frames are durable, attractive, and long-lasting, particularly on older properties. However, as with all other natural substances, they are prone to wear and tear and, in the case or wood, rot. If your window frames are starting to rot, cold air will be getting in, warm air will be getting out, and the whole frame may eventually become unstable and dangerous.

It’s difficult to open and close your windows

Another sign that your existing windows or double glazing is reaching the end of its life is if you struggle to open and close them, they slam themselves shut, or, no matter how hard you try to, they don’t fully close.

It’s inconvenient and annoying when your windows don’t behave as they should when you’re trying to use them in standard and expected ways. What’s worse is that this also presents a major safety and security risk to the people in your home.

Your home feels freezing

If your home feels colder than it should be, that might be a warning sign that your current windows are draughty and cold air is getting in. With all types of window, as they start to get older, the seals start to fail and it’s this failure which allows the cold air in.

The colours of your furniture are starting to fade

Ever wondered why, over time, the colours on your sofa, carpets and furniture start to fade? Most of the time, the problem is caused by your windows.

Modern double glazing stops this because it stops the powerful uV rays from the sun from getting into your home and it’s these rays that causes your furniture to fade.

Getting the best quote

If now is the time to replace your existing windows with the latest in eco-friendly double glazing, the best way to do it at the cheapest possible price is to get 3-4 reputable installers in to quote you for the work.

CompareCompanies work with installers up and down the country, all certified by CERTASS and/or FENSA to make sure that they are completely compliant with all necessary building regulations and that all their work comes with insurance-backed guarantees meaning that, if anything happens to the company, you’re still protected.

By filling in the form on this page, installers will get directly in touch with you to find out what you want. They’ll offer you advice, guidance, and expertise on all areas of installing eco-friendly double glazing in your home.

Our service is completely free and you don’t have to accept any quotes you receive from the installers we introduce you to.

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