6 mistakes to avoid when buying double glazing

Investing in windows and double glazing can significantly enhance your home’s energy efficiency, security and aesthetics. Whether you’re a first-time buyer or looking to upgrade your existing windows, understanding the potential pitfalls will prevent costly errors.

Here are six common mistakes homeowners make when purchasing double glazing and advise on how to avoid them. You can then buy with confidence, getting value for money and long-lasting results.

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1. Don't get tricked by pressure selling tactics

Double glazing has a reputation for dodgy sales tactics, so make sure you don’t get caught out, or pressured into buying something you don’t want. 

Be wary of price conditioning, where a salesperson will ask you questions such as ‘what price were you thinking of paying?’ rather than telling you directly how much their products cost. 

Otherwise, they can use questions like this to assess how much they could get away with charging you. 

Be suspicious of anything designed to make you decide in a hurry, such as one-day only offers, or manager’s special deals. It’s unlikely that these actually represent value for money.  

Find out how to decide on the right products for you: Which is the best type of double glazing?

2. Don't fail to get multiple quotes and a proper contract

Always get at least two, ideally three quotes, from different companies before committing to any work being done. 

This gives you a clearer idea of a reasonable price, and can help discount any companies with dishonest practices. 

Be wary of quotes that are described as ‘starting from £xx’ as this will rarely be the price you actually end up paying. 

Make sure the quoted price is for everything, including installation, labour and any other costs, so that these don’t sneak in later.

 Additionally, ensure an insurance-backed guarantee and deposit protection is in place, as these will cover you if the company goes out of business, or failures to honour the warranty. 

If you’re unsure how much a reasonable quote should be, read our double glazing costs article, which includes average cost data from the Royal Institute of Chartered Surveyors (RICS).

3. Make sure you choose a reputable company

Picking the right company for the job is essential to getting a good end result, and we have lots of information to help you decide.

Check if the company is approved by FENSA (Fenestration Self-Assessment Scheme), a government-authorised scheme that monitors installers of windows and doors. 

Read our guide to the best and worst double glazing companies for an overview of the nationwide and regional options available.

Our survey of homeowners who had purchased double glazing found that half chose to use an independent company from their local area. 

You can use our Which? Trusted Traders tool to find a reputable trader near you, that has passed our extensive assessment process:

4. Know your rights to cancel an agreement

It’s important to understand the rights you have, and what happens if there are any problems, before you sign a contract and purchase new double glazing. 

Various laws offer you protection from the moment the contract is signed.

If you change your mind about what you are purchasing, your ability to cancel the agreement will depend on a variety of factors. 

For example, if the windows and doors are standard size, or made to measure for your property, alters your rights.

Read more: your rights when buying double glazing.

5. Don't jump to replacing windows before you've tried repairing

Before buying new double glazing, first check with your Local Authority Building Control, to find out when the double glazing was installed and if there is a warranty that is still in date. Warranties are often 10 or 20 years, and sometimes a lifetime warranty. 

Also see if you can repair common problems with your existing double glazing, before splashing out on new windows. If your double glazing is suffering from condensation, try increasing the ventilation. 

Trickle vents can be added to windows to allow some fresh air in without allowing the heat in your home to escape. You can open and close them to adjust ventilation.

If any seals are broken, these can sometimes be repaired without the entire window needing to be replaced. This is easier to do on frames where the seals, also known as gaskets, are separate, rather than built-in. 

Where the seal can't be changed on its own, sometimes the glass can be replaced instead of the whole frame. 

Everything you need to know about keeping your new windows in good condition: double glazing repairs and maintenance.

6. Think about your double glazing in context

 When making energy efficient changes to your house, ideally you should think about it from a whole-house perspective. 

This means considering how your double glazing interacts with your heating system, insulation and other measures such as solar panels. 

Ideally, you could improve multiple parts of your property at once, and see a combined impact on your energy use and bill savings. 

To help you decide on and track these important decisions, we’ve created a home energy planning service:

Make your property more energy efficient

Find out about our free home energy planning service

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