Choosing a double glazing installer

A good double glazing installer is registered with FENSA or CERTASS, offers an insurance-backed guarantee, gives a written quote with a full specification, and doesn’t pressure you to sign on the day. Get at least three quotes, check each firm’s registration and reviews, and compare the quotes like for like before choosing.

What every double glazing installer should have

• FENSA or CERTASS registration, so the firm can certify the work under Building Regulations. Check it on the scheme’s website, not just the logo on the van. See FENSA and CERTASS.
• An insurance-backed guarantee, which protects you if the firm stops trading. FENSA explains how it differs from the certificate.
• A fixed address and a landline, and a trading history you can check.
• Public liability insurance.
• Recent reviews from customers in your area, ideally with photographs.

Questions to ask a double glazing installer

1. Who will do the fitting: your own team or subcontractors?
2. Which frame profile and glass are you quoting, and what is the window energy rating?
3. Does the price include removal, making good, certification and VAT?
4. What happens if you find rot or a weak lintel?
5. How much deposit do you need, and when is the balance due?
6. What does the guarantee cover, for how long, and who backs it?

A firm that answers clearly and in writing is usually one that does the job properly.

Local firm or national brand

National brands advertise heavily and often price higher, partly to cover that. A good local installer using a well-known frame profile can offer the same window for less, with the owner on site. On the other hand, a national brand may offer a longer guarantee or finance. Compare the specification and guarantee, not the name.

Sales tactics to walk away from

• “Today only” discounts that vanish if you don’t sign on the first visit.
• Inflated starting prices followed by a big “manager’s discount”.
• Pressure to sign before you’ve seen a written quote.
• Large deposits, or full payment before the work is done.
• Vague specifications like “A-rated windows” with no frame or glass named.

These are common enough to have a name in the trade, and a genuine price will still be available next week.

Comparing quotes

Put every quote on the same basis: the number and style of windows, the frame and glass, what’s included, the guarantee and VAT. Our compare quotes tool does this side by side, and the quote checker shows whether a price is reasonable where you live. For the typical cost of a house, see uPVC windows.

After you choose

Read the contract carefully, including the cancellation terms; see your rights. Then follow the steps in how double glazing installation works. Ready to start? Get quotes from up to four registered local installers.