How to buy double glazing Double glazing FAQs
How much money will I save on my energy bills by installing double glazing?
This thermal image shows the difference in heat loss between single and double-glazed windows (image courtesy of Horton Levi Ltd)
If you swapped all the single glazed windows in a three-bedroom house you’d save around £170 a year on your heating bill, as well as 680kg of carbon dioxide emissions. And double glazing should last for at least 20 years (so about £3,400 savings over 20 years).
The picture on the right is a thermal image showing the difference in heat loss between single-glazed and double-glazed windows. The house on the left has a single-glazed window where we can see more heat escaping - indicated by the bright yellow colours.
If you're considering installing double glazing, we can show you the best and worst double glazing companies, as voted for by customers. You can also find out how much you should expect to pay in our double glazing pricing guide.
My home isn't suitable for double glazing - are there any alternatives?
If you can’t have double glazing (for example if you live in a listed building) secondary glazing is an alternative. This works by fitting a second layer of glass inside your existing windows. It isn’t as effective as full double glazing but it could still save you around £105 a year on your heating bills.
What are the benefits of double glazing?
The benefits of double glazing are often stated as being:
• Energy efficiency and reduced heating bills
• Heat retention
• Noise reduction
• Increased security
• Reduced condensation
What is uPVC?
uPVC stands for un-plasticized polyvinyl chloride. It is the cheapest option of all double glazing materials, up to three times cheaper than traditional wooden frames, and also the most energy efficient.
It is available in a variety of colours and finishes (including wood effect), although white is the most popular. It is also recyclable and durable.
uPVC requires little maintenance other than a wipe with a soft cloth and at most a little washing up liquid.
Although they are more expensive, wood or aluminium frames tend to be the most visually pleasing.
What about timber double glazing?
Double glazed windows do not have to come in uPVC. Other materials are available such as aluminum and wood.
Timber is a greener option as it is a naturally renewable material. Many people feel wooden windows look nicer and more subtle than uPVC, particularly for traditional or period-style houses.
While timber windows tend to be more expensive and need maintenance, if properly looked after they can last a very long time.
What is the Window Energy Rating (WER)?
Double glazing should reduce condensation
Some window makers show the energy efficiency of their products using an energy rating scheme from A to G – like the one used for appliances such as fridges. The scheme is run by the British Fenestration Rating Council (BFRC). The required minimum rating to comply with Building regulations is C.
Is it worth getting A-rated windows?
The difference in energy saving between an A, B or C window isn’t huge. We calculated that getting B-rated windows instead of C-rated, or A-rated instead of B-rated, would save you around an additional 6.5% on your energy bills. And the cost of going up a rating is up to 10% extra per window, according to a Which? Local double glazing panel.
Should I use a Fensa or similarly approved installer?
You don’t have to, but it could make things easier. In England and Wales, Building Regulations dictate that new and replacement windows must meet a certain level of energy efficiency. You must get a certificate to show that your windows comply with these regulations. An installer registered with one of the self-certification schemes such as Fensa, BM Trada or Certass will issue this certificate for you. Otherwise your council will need to come and check the work.
For the Channel Islands, Northern Ireland and Scotland, contact your local authority for information on applicable regulations for windows. For more information see our guide to planning permission and building regulations.
Find out more about Fensa and other competent person schemes in the Which? Local guide to competent person scheme.
I had windows installed and some of the work is really poor. I contacted the double glazing company but it said that the problems are down to subcontractors, so I need to take it up with them. Is this true?
No. If a double glazing company uses subcontractors, it is responsible for its subcontractors' actions and standards of work. So if subcontractors fail to use reasonable care and skill or appropriate materials the double glazing company itself must arrange to have the problems fixed, and any claim you have will be against it, not the subcontractors.
The windows I had installed last year look terrible – the uPVC has gone from white to yellow. What options do I have for sorting it out?
The windows probably weren’t of satisfactory quality. This means that the double glazing company will be in breach of contract, and it’s likely that the windows will have to be replaced.
See our guide on your rights when buying double glazing to find out more on what you could do to resolve the problem.
A local double glazing company was running a special offer where if you buy the windows for the front of the house you get the windows for the back free. I went ahead, but two years on the frames are falling apart, and the double glazing company says it will replace only the front windows, as the ones at the back were free. Can it do this?
No. In practice, what you got was all the windows in your house replaced at a discounted price. As the frames have failed so quickly, it’s likely they were not of satisfactory quality, so the double glazing company is obliged to either fix or replace them.
- Find out what your rights are when buying double glazing
- See which companies score best in our double glazing satisfaction survey
- Find out how much you should expect to pay in our double glazing pricing guide