How to buy double glazing: getting the right quote

Double glazing salespeople have a dubious reputation. Knowing common tactics and being one step ahead means you're far more likely to employ a reputable installer and pay the right price. 

To find out how much double glazing might cost for your home, visit our double glazing costs guide. 

We asked installers from nine Which? Trusted Trader double glazing companies how customers can make sure they are getting the right quote for the work they need. 

All of the traders have been installing double glazing for at least 10 years, while one has been in the industry for over 45 years. Every company has passed our comprehensive assessment process to ensure their work and practices are trustworthy. 

To find out more about the benefits of using a smaller local company and how we ensure Which? Trusted Traders are reliable, read our guide to independent double glazing companies. 

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Before you start

Before you approach any double glazing companies, make sure you have a good idea of what you want. You’ll be better informed and more in control, plus any quotes 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 options when it comes to buying double glazing. You could use:

• an independent double glazing company in your local area;
• 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 builder or joiner. 

If you're doing a home renovation, such as building an extension or converting your loft, you may find it's best to use your existing builder.  Your trader may be able to organise and buy double glazing for you, possibly at a trade price.

If you're choosing a specialist double glazing company, these are our top tips:

1) Do your background research

Using a company with a good reputation will give you peace of mind that they are installing your double glazing correctly. 

Jacob Gourd, from Ideal Glass, suggests what to look for: 'Prices can often vary depending on how busy an installer is. Most installers are most quiet in the winter months and may be willing to give discounts. For the most part, the quality of the product we provide is comparable across different companies, so don't fall for salesmen that insist their product is better than anyone else.'

Interaction with a good installer doesn't end once the window is fitted. 

Jacob said: 'Consider the online reputation of the company and look for evidence of their service when things go wrong after the installation. It is normal for products to need adjusting. Companies that are not responsive to aftercare are usually exposed in negative online reviews.'

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

Check whether its owners have changed the company name or it has been liquidated 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 recently had double glazing installed, 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. You can find a reliable trader by using our search tool:

2) 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 only looking at photos.

3) Get a number of quotes

Don't rely on just one quote – get at least three, if you can. This will give you a better idea of what a reasonable price is, and you'll get a feel for different companies' approaches.

We'd also suggest discussing the benefits of different systems when getting your quote or visiting a showroom. 

Tommy Rose, from Barnet Window Company, told us what a good quote process should look like:

• Get two or three quotes from established local installers and insist on clear written specifications. 
• Avoid inflated 'discount' pricing and focus on value rather than headline savings.
• While installers should give you advice, this shoudn't feel like pressure to rush into a purchase. A professional installer should explain options clearly and never rush you into signing immediately.
• Take time to check the frame system, glass specification, installation details and guarantees. A good quote should also clearly explain product approaches including material, style and layout.
• If those aren’t clearly listed, the quotes aren’t truly comparable.

When asked about avoiding dodgy quotes and sales tactics, the Which? Trusted Traders told us that reputable companies will offer their best price, first time, rather than haggling. Don't fall for any 'let me call my manager to see if I can improve the price' antics. 

Christopher Conway, from Evergreen Home Solutions, said: ‘If they can offer discounts after you reject the first quote, ask yourself why were they not willing to do this before.' 

4) 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.

5) Never use a cold caller

Sometimes double glazing companies will use cold calling as a sales tactic, and this is often a sign of an unreliable company.

Not all traders or companies knocking on your door or phoning you will be scammers. But we 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're tempted by an offer, don't agree to anything on the spot. Instead, take the trader's details and 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 doorstepping. They're also regularly checked to ensure they're meeting all our standards.

6) 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. 

Nick Trevenna, from Mike Martin Windows Systems, said: ‘Good practice is making customers aware early on how the installation will comply with building regulations. After the work is completed, the homeowner should receive the relevant certification, such as a FENSA or CERTASS certificate, together with their guarantee documents. The installer should also explain what the certification covers and why it is important for the property.’

Using a certified installer 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 local 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 an 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.

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

Double glazing quotes and side-stepping sales tactics

Not feeling feel pressurised, rushed or intimidated is important 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. 

Other might try to offer an on-the-spot discount that is only valid if the customer accepts immediately, or on the same day.

It's important to take the time you need to make a big financial decision so that you're confident with your choice of company and comfortable with the price.

Be wary of any salesman using any of these sorts of tactics, and don't let this persuade you to sign a contract there and then. After you have got quotes, take your time to think carefully and make an informed decision. This also means you’re likely to get a competitive price. 

Ensure each company gives you prices for exactly the same products and materials, so you can compare the quotes fairly. Compare the costs of what's included as standard and what is priced up separately as an optional upgrade or extra.

Nick Trevenna expressed the sentiment of all the traders we spoke to: 'Never agree to something on the spot. Time critical deals are a selling tactic and nonsense.'

Double glazing home surveys

James Gaft, from Balhousie Glazing gave us a detailed explanation of what to expect when a double glazing installer visits your home to measure up your windows:

'A professional home survey should provide reassurance that everything has been carefully checked and confirmed before manufacturing begins, helping ensure a smooth installation and the best long-term performance from the new windows or doors.'

1. Accurate technical measurements A surveyor should carefully measure every opening, often in multiple places, to account for any irregularities in the structure. Homes rarely have perfectly square openings, so these measurements ensure the new frames are manufactured to fit precisely.
2. Checking the condition of the surrounding structure The surveyor should inspect the surrounding brickwork, lintels and internal plaster to identify any issues that could affect the installation. This helps avoid surprises on installation day and ensures the new frames will be properly supported. 
3. Confirming the product specification The survey is also when the final details are confirmed — frame colour, opening styles, glass types, hardware, and any decorative features. This ensures what is manufactured matches exactly what the customer expects.
4. Identifying any practical considerations The surveyor should highlight anything that may affect the installation, such as restricted access, alarm sensors, blinds or shutters that may need to be temporarily removed.
5. Opportunity to ask questions A good survey should feel collaborative. Homeowners should have the chance to ask questions and clarify any details before the order goes into production.

If you don't feel comfortable with the details of the survey or how it is carried it out, ask further questions or look for another company. 

Double glazing contracts

Once you have chosen a company, it's legally obliged to provide you with certain information in writing. This includes: a description of the goods/services agreed; the total price, inclusive of any additional charges known at the start; when the installation 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 if a trader has discussed the contract with you at your home, but you agree to enter into this sometime later. 

What the company does 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 later than promised?
• 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 doesn't meet a satisfactory standard?

If you’re unhappy with the answers provided, you may be better off hiring someone else. 

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?

You should also agree a schedule of payments before any work begins. 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, but the final payment shouldn't be required until after the work is complete and you are satisfied. 

Visit our page on your rights when buying double glazing page to find out more about what should be included in a warranty and what to do if something goes wrong.

Should you tell your home insurance company about new double glazing or doors?

Yes, 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.