A Complete Guide to Double Glazed Windows 2019

By 14 min read

You could save up to £115 per year by getting double glazed windows

Double glazed windows keep out the cold and noise

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Anything is only as strong as its weakest point. In the case of a house, this is the windows. If your windows are too thin and draughty, they’re letting the rest of your house down. It’s time to get serious and think about double glazing.

According to The Energy Saving Trust, up to 20% of a home’s heat loss is down to windows and doors. You can close them all you want, but one single pane of glass is not doing you any favours. Noise and heat will just pass through it like they own the place.

Double up the amount of glass between you and the outside world and you’ll enjoy a load of benefits, including cheaper energy bills, more warmth, and more peace. Here’s everything you need to know – and make sure to answer these questions to get bespoke double glazing quotes.

In this Guide:

Head straight to a specific section by clicking the links below

How does double glazing work?

It’s all about the air. The two layers of glass get the attention, but it’s the tiny pocket of air in the middle that does the job. This ‘air’ is argon, a very dense and non-toxic gas that cares only about keeping your house warm.

Glass is a great heat conductor, but that’s no use to you. The argon gas is there to keep it in check, acting as a barrier whenever heat tries to pass between the layers of glass. The air pocket in double glazed windows tends to range between 14-28mm (the wider the better).

On top of this, most double glazing also comes with low emissivity (Low-E) glass, where one of the internal panes is coated with metal oxide. This helps the glass hold on to the warmth that’s trying to escape, making the argon’s job a little easier. Teamwork makes the (double glazing) dream work!

How much does double glazing cost?

The cost of double glazing is hard to estimate because there are so many variables at play. It depends on the quality of double glazing, the frame material (e.g. uPVC, aluminium, wood), how many windows you’re fitting, the size of each window, the installation process… You get the idea.

For example, a 60x90cm casement window with a uPVC frame would cost around £500, while a fancy 180x150cm sash window with a timber frame would cost over £3,000. This is why personalised quotes come in handy, because they’ll give you a much more accurate idea of potential costs. It’s easy: just fill in the form at the top of this page, and our suppliers will get back to you with their best prices.

Take a look at this table for a general idea of double glazing costs for your whole home. These are prices for casement style uPVC frames:

Size of Property
Average Cost of Double Glazing
2-bedroom flat (4 windows)
£1,400 to £1,750
3-bedroom semi-detached (9 windows)
£3,000 to £3,500
4-bedroom detached (15 windows)
£5,300 to £6,000

For lots more information on double glazing prices, check out our wonderfully detailed page on double glazing costs in 2019.

How much could you save with double glazing?

Quite a lot, according to the Energy Saving Trust. For example, if you replace every window in a detached house with A++-rated double glazing, you’d save around £110-115 per year. Even with C-rated double glazing, the annual savings will still be around £95. In semi-detached and terraced properties, the potential savings drop, but they still make double glazing a worthwhile long-term investment.

Did You Know?

Double glazed windows will last up to and sometimes even beyond 25 years before throwing in the towel.

You can view the full details of the Energy Saving Trust’s findings here.

The energy efficiency of double glazed windows is represented by a grading system (a bit like school) created by the British Fenestration Rating Council (BFRC). The grades range from A++ to G, although you aren’t legally allowed to have windows worse than C-grade in the UK. The higher the Window Energy Rating (WER), the more expensive the double glazing will be.

What are the benefits of double glazing?

Here are the many joys that “going double” will bring to your life.

Reduced heat loss. This is the big one, because it means a warmer house in winter, cheaper energy bills, and a lower impact on the environment. Yes, that’s three benefits wrapped up in one.

Check out the thermal image below for a really exciting visualisation of what we’re talking about. The single glazed windows on the left are red because of all the heat they’re pumping into the outside world, while the double glazed windows on the right are smug and green.

Thermal Photo Of House

Less noise. If you live near a main road or the rehearsal studio of a death metal band, you’ll be really grateful for double glazing. The glass-air-glass combo is extremely effective at blocking out sound, so you can relax at home and pretend you live in a library. Plus, you can be less concerned about your own noise leaking outside.

Furniture stays colourful. Do you ever find yourself staring at your faded red sofa and wondering where it all went wrong? With double glazing, the sun’s UV rays will find it twice as hard to enter your home and drain the colour from your furniture. You can be confident that your future home decor will stay brighter for longer.

Durability. Double glazing is an investment, so you need it to last for a long time. Fortunately, most double glazing comes with at least a ten year warranty, and will usually last around 25 years. Now that’s loyalty.

Improved security. Opportunistic burglars tend to go for the easy targets, but a house with double glazed windows is basically a fortress. When windows are harder to break, people with bad intentions will just go and find a single-glazed alternative. What’s more, your windows will be less prone to damage from wayward footballs and windswept pigeons. All of this will help your insurance premiums, too (mainly the burglar thing).

Increased house value. Like any major home improvement, double glazing will add a few pounds to the resale value of your property. Not only will it help new owners with their energy bills, but it also gives the property a more modern look. At the very least, you’re giving people a head start before the triple glazing craze arrives.

What are the disadvantages of double glazing?

Double glazing comes with a handful of downsides, but there’s a solution for each of them.

Hotter summers. A boiling hot summer is what everyone craves until they’re actually experiencing one. Double glazed windows are good at keeping heat inside, but in the warmer months, this isn’t ideal.

Fortunately, you can buy windows with a UV protective coating, which reduces the amount of heat that can enter in the first place. Plus, you can always try the good old fashioned technique of opening your windows.

Risk of damp. When you don’t have proper ventilation, damp comes knocking. If you upgrade from some draughty single-glazed windows to some airtight double glazing, your house is suddenly going to become a lot less ventilated. Moisture in the air will give up trying to escape and start a new life as damp on your walls (especially in winter).

A popular solution is to get window frames with ‘trickle vents’, which help the air circulate through your house a bit better. Again, just opening a window will help.

Difficult to repair. The airtightness of your double glazing is very important, as the layer of argon gas between the two panes needs to stay intact. Unfortunately, if this is compromised and condensation starts to appear between the panes, there isn’t much you can do except replace them.

The best way to avoid the problem is to make sure you get your windows professionally installed. DIY installations are much more likely to go wrong, and you’ll struggle to get a warranty if you decide to go lone wolf.

Expensive. Double glazing isn’t cheap.

Parting with all that money for thicker windows might feel sad, but you’ve got to treat it as an investment – the amount you save on your annual energy bills will bring you a seriously satisfying return over time.

Let’s sum up the pros and cons of double glazing:


  • Reduced heat loss
  • Less noise
  • Furniture stays colourful
  • Durability
  • Improved security
  • Increased house value

X Cons:

  • Hotter summers
  • Risk of damp
  • Difficult to repair
  • Expensive

What frames should you choose?

No window is complete without a frame (no really, it just wouldn’t work). There are three different options for you to choose between, each with their own pros and cons:

(£) uPVC is the white plastic material that you see in homes all across the UK. It’s not particularly attractive, but it’s practical, easy to clean, and the most affordable of the three.

(££) Aluminium is the next step up, costing a bit more than uPVC but offering something sleeker, stronger, and more durable. It comes in a range of fun colours, and you can even apply a woodgrain finish to pretend you’ve got something more fancy.

(£££) Timber is the classiest option, but you’ve really got to pay for it. It always looks impressive and it’s great for traditional houses – just be ready for a fair bit of maintenance.

You might also be interested in: Which double glazed windows are best?

How long does double glazing last?

Double glazing is with you for the long haul, but not the forever haul. Over time, the gas between the panes gradually leaks out, and the windows become less effective. That’s why it’s important that argon is non-toxic.

Most double glazing warranties are at least ten years, but they can often extend up to twenty years. It just depends on the quality of the windows and who you’re buying them from. After they’ve been installed professionally, double glazed windows will sometimes last beyond 25 years before they throw in the towel.

Installing double glazed windows

If you think you know how, doing your own double glazing installation will obviously be cheaper in the short term, but there are some serious disadvantages. Most importantly, you’ll probably invalidate any warranty you have on your windows, and you’re much more likely to face problems further down the line.

It’s best to get in touch with a professional installer and do things the proper way.

Will double glazing improve your property’s value?

Certainly! If anything, it’s just about keeping up with everyone else; in 2014, a report from Nationwide showed that the percentage of UK dwellings with double glazing had grown from 30% to 79% since 1996. Upgrading your windows is a very sensible thing to do, which is probably why the Brits love it so much.

Here’s how double glazing will help to boost your property’s value:

• Increase its energy efficiency and reduce energy bills

• Keep it warmer in the winter

• Update its appearance to something more modern and desirable

• Improve security (and decrease insurance premiums)

• Lessen its impact on the environment

Of course, you don’t have to upgrade your windows all at once. It’s an expensive procedure, so some people target the coldest rooms and take things slowly. Either way, any amount of double glazing will improve your property’s value.

Receive a Bespoke Double Glazing Quote for Your Property Get Quote

Should you go for triple glazing?

People just won’t stop adding new layers of glass. Triple glazing obviously comes with more benefits than double glazing (it’s thicker and warmer), but it’s not necessary unless you live somewhere extremely cold. For example, triple glazing is taking off in the Nordic countries, but it might be quite an excessive investment in the UK.

Generally speaking, the jump from single glazing to double glazing is much more significant than the jump from double glazing to triple glazing. If you’re thinking of waiting for something better, European scientists are currently working on quadruple glazing, so hold tight.

You might also be interested in:

How much does triple glazing cost? and What is secondary glazing?

Additional tips and advice

In this section:

Head straight to a specific section by clicking the links below

Energy efficient window rating labels

The BFRC scheme is the system used in the UK to rate the energy efficiency of windows. This will make it clear to you how energy efficient the windows you are thinking of using are. The ratings scale from A to G and use a traffic light guide to make it easier to understand.

How long does it take to install?

The time required to install double glazing differs from house to house, and the exact time is dependent on the size of the house and the style of windows chosen. Though, on average, it takes three to five days to fit an entire house with new double glazed windows.

Do you need planning permission?

You do not need planning permission to replace or add new windows to your home unless you live in a listed building.

What to look for when choosing a double glazing company

When choosing a double glazing company it is important to choose one that is not only local to you, but also has a good track record with past window installations. Look for a company that can show you their previous work and designs.

Additionally, it is important to choose a double glazing company with a team that is professional and knowledgeable in all areas of window installations; choosing to buy double glazing is a big decision so it is important to have an expert on hand to help and guide you through the process, offering their expert opinion and answering questions throughout.

By filling out the form at the top of this page, you will receive a free, no obligation quote from a local, trusted installer.

Top tips when dealing with a double glazing company

When looking to upgrade your home and install double glazed windows, it is important to get quotes from more than one company so you can make a comparison. Additionally, using a local company is beneficial as you are able to meet them face to face and ask any questions you may have.

Before you approach a double glazing company, have a rough idea of what you require; this will allow them to give you a tailored and specific quote from the start and will make the whole process quicker.

Most importantly, when choosing a double glazing company ensure you see examples of their past installations so you can have an idea of the type of work they do and whether it is right for you and your home.

The Eco Experts make choosing an installer easy and safe; simply fill out the short form at the top of the page to receive a tailored quote from a trusted installer in your area.

How do you maintain double glazing?

Double glazing should be easy to maintain, but be sure to follow these top tips:

Keep your home well ventilated to avoid the buildup of condensation on the inside of the windows. If condensation starts to appear between the panes of glass it may well mean that the unit has a fault; you should contact the installer immediately if this occurs.

You should clean your windows regularly, ensuring the frames are clear of any dust, dirt or dead insects. A vacuum cleaner will be the best thing to use for this. To clean the actual windows, a vinegar and water solution will be all you need to keep them sparkly clean.

We’re sure you can’t wait to do your house a favour and go double. We can help you find the best price from trusted installers in your area. Just fill in this form to get started.

Jonathan Whiting
Jonathan Whiting

An eco hero with a head for numbers, Jon’s data visualisation skills are legendary. Whether it’s determining what countries will survive climate change or the animals most at risk from it, he has the planet’s best interests at heart.