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1 October 2020

How to buy double glazing

Avoid being overcharged for double glazing by reading our expert guide to getting double glazing quotes, side-stepping sales tactics and finding a reputable double glazing company.
Double glazing salesman talking to customer 478482
WhichEditorial team

Double glazing salespeople have a dubious reputation. But knowing their tactics and being one step ahead means you're far more likely to pay the right price. 

That's why we've spoken to experts and homeowners to get their advice on how to find the right double glazing company and get the best quote. You can click on the links below to head down to the section you're interested in.

To find out how much double glazing is likely to cost for your home, visit our double glazing pricing guide. Costs vary depending on whether you use a local or national company, how many windows you want installed, and the type of window and frame.

Before you approach double glazing firms: what you need to do

Before you approach any double glazing firms, make sure you have a good idea of what you want. You’ll be better informed and more in control, plus any quotations can be more tailored to your specific needs so you’ll get a better idea of the cost.

Trade shows or consumer home exhibitions are a good place to start. You’ll be able to see a wide range of double-glazed windows and doors in one place.

Look at the homes in your area too. What kind of windows do similar properties have? Is there a type that’s common in your street? At some point you may want to sell your home, so make sure the style you pick won’t put off potential buyers.

Finding a reputable double glazing company

There are a few different options when it comes to buying double glazing. You could use:

  • a well-known, recognised glazing company, such as Anglian, Everest or Safestyle;
  • a well-known DIY brand, such as B&Q, Screwfix or Wickes;
  • an independent double glazing company in your local area;
  • an independent builder or joiner. 

You're more likely to go down the last route if you're doing a home renovation, such as building an extension or converting your loft. If you're already working on a building project, your trader may be able to organise and buy double glazing for you, and possibly at a trade price.

Independents were rated highest in our survey, with a customer score of 84%. Rated lowest was big-name brand Everest, with 54%. 

One customer of an independent firm said:

Alongside independents and Everest, we also spoke to Anglian and Safestyle customers. You can compare all the ratings, both overall and for important sales and installation factors, in our double glazing company reviews

Top choosing tips from double glaziers

We've spoken to independent double glazing companies from around the UK to get the inside scoop on how to find the best company and avoid an unscrupulous double glazier.

Do your background research on the company

For a lot of people, one of the key reasons for choosing the company they did was because it had good reputation. 

We'd recommend using a company that's been around for 10 years or more – you can use Companies House to find out. This will also tell you whether it's in a healthy financial position, so less likely to dissolve midway through the work. 

Check whether its owners have changed the company name or liquidised at any point. If so, it could be a sign that it's unstable or not a reputable company.

It’s also worth talking to friends and neighbours who have had double glazing installed recently, especially if they have similar properties.

We've done the hard work for you – all of our Which? Trusted Traders have been through rigorous background checks, so you can be assured they're trustworthy. 

Check out previous work

Ask to see real examples of previous work. Don't just rely on testimonials on the firm's website or in brochures. 

If possible, speak to its customers about their experiences and go to see the work for yourself, instead of just looking at photos.

Get a number of quotes

In our survey, a number of people told us they chose the company because it was the only one they asked for a quote from - 19% for those who used independents and 25% of those who used a national brand. 

We wouldn't recommend relying on just one quote – get at least three, if you can. This will give you a better idea of what a reasonable price is. 

We'd also suggest discussing the technological benefits of different systems when getting a quote, or when visiting a showroom. That way you can get a feel for how knowledgeable and professional the company or trader seems. One homeowner said:

It's worth keeping in mind that if you do agree to a contract with a trader on the spot, you won't have the right to cancel once they have left your home. You can find out more about this in our section on double glazing contracts.

Check their contact details and availability

Great tradesmen are rarely available immediately, so if one has a totally clear diary, this could be a bad sign. It's also worth checking their contact details and paperwork. They should freely give their phone number (preferably landline and mobile), full company address and email.

Don't use a cold caller

Offering to install double glazing was the second most common tactic used by cold callers when we spoke to people back in June/July 2018 (1,645 Which? members).

Of course, not all traders or companies knocking on your door will be scammers. But we would recommend turning these people away – you'll have no idea about the quality of their workmanship or whether they’re offering the right price. 

If you are tempted by an offer, take the trader's details without agree to anything. Then, in your own time, research the company and get a few quotes or second opinions.

All Which? Trusted Traders must sign up to our code of conduct, which prohibits cold calling and door stepping. They're also regularly checked to ensure they're meeting all our standards.

Use BM Trada, Certass and Fensa-registered glaziers

Choose a double glazing installer that is registered with a competent person scheme, such as BM Trada, Certass or Fensa. Membership means that companies can self-certify that their work complies with building regulations. 

It also means the work is covered by an insurance-backed guarantee if it's not compliant or the company goes bust.

An insurance-backed guarantee is issued by the double glazing firm. It means that the warranty they give on your installation (which could last 10 years, for example) will be honoured by the insurer should there be a problem down the line and you find that the company has gone bust.

In England and Wales, new and replacement windows must meet a certain level of energy efficiency. You need to get a certificate to show your windows comply with these regulations. An installer registered with one of the self-certification schemes 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.

It's also worth looking for and installer that's part of an Alternate Dispute Resolution scheme. Being signed up to one should make things a lot easier if anything goes wrong or there is a dispute. For example, the Double Glazing & Conservatory Ombudsman (DGCOS) is well-regarded in the glazing industry.

You can find out more about this on our your rights when buying double glazing page. 

All our Which? Trusted Traders automatically become part of one when they sign up to the scheme.

Find out about payment and insurance

Before you agree to any work, ask the firm about insurance. What happens if there’s accidental damage to your property or your neighbour’s car, for example?

Before work begins, agree a schedule of payments. This should be in writing in the contract. It’s not unusual to be asked for an upfront instalment, especially if it’s a big job.

Double glazing quotes and side-stepping sales tactics

Not feeling feel pressurised or intimidated was another important factor for our homeowners when choosing a double glazing company.

We've heard about instances of double glazing salespeople quoting a high price to begin with, and then dropping it over the course of their sales visit to encourage you to sign on the spot. The price you're quoted could drop by 75%, or more than £10,000, during a sales pitch.

This practice appears to be industry wide, as customers from all three big-name companies we've reviewed – Anglian, Everest and Safestyle – reported this happening to them.

Which? members can log in now to see examples of customers' experiences with the big-name companies, as well as tips on using your own tactics so that you can see what to avoid and how to get the best price. 

If you're not yet a Which? member, you can unlock our expert advice by joining Which? now.

Joining Which? or logging in will also give you access to our double glazing company reviews


What should I look for in a double glazing contract?

Once you have chosen a company, it's legally obliged to provide you with certain information in writing, such as a description of the goods/services, the total price (inclusive of any additional charges known at the start), when it will be provided and your rights to cancel – all of which it must adhere to.

However, in some circumstances the company isn’t bound to provide as much detail, and you won’t have the right to cancel. This applies if you’re getting made-to-measure double glazing, or if you enter into an ‘on-premises contract’ – which includes where a trader has discussed the contract with you at your home, but you agree to enter into this sometime later. 

What they do provide you with is still legally binding, so ask for as much as possible. Check your contract for the following, or ask the firm:

  • Are there penalties if the work is late?
  • Would prolonged bad weather affect the job?
  • What materials will be used and who will supply them?
  • Will you use outsourced labour?
  • What happens if any of the work does not meet a satisfactory standard?

Visit our page on your rights when buying double glazing page to find out more about what you should get in place with a contract to protect you, as well as what to do if something goes wrong.

Should I tell my home insurance company about new double glazing or doors?

You must tell your insurer about any changes to your home’s structure, habitability, security or value. Adding new doors or windows may help make your home more secure, for example. Changes like this may affect your buildings and contents insurance premiums.

You don’t need to tell your insurer about minor or cosmetic changes, however.

Our double glazing research

*In September 2018, we asked 2,155 Which? members about their experiences with buying double glazing, as well as the company they bought double glazed windows and/or doors from, and had them installed by, in the last 10 years. Quotes are from our 2018 and 2016 surveys.

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