How to choose a double glazing installer
A quick, no-nonsense guide to hiring the right firm for your windows, doors or conservatory — and avoiding the common traps.
- 1
Check the accreditations
For replacement windows and doors, the installer should be registered with a Competent Person Scheme — FENSA or CERTASS — so the work is self-certified to Building Regulations and you get a certificate. TrustMark and Which? Trusted Traders are good extra signals. Ask for the numbers and check them.
- 2
Get three quotes
Prices vary widely for the same job. Get at least three written quotes that list the frame material (uPVC, aluminium, timber), the glass spec (double or triple, the energy rating), the guarantee length, and whether scaffolding and making-good are included.
- 3
Understand the energy rating
Windows are rated A++ to E under the BFRC scheme, and the whole-window U-value tells you how much heat is lost. A-rated or better is the sensible minimum for a modern home; ask what U-value you’re actually getting.
- 4
Read the guarantee — and who backs it
A 10-year guarantee is standard, but check whether it’s insurance-backed (so it still stands if the firm stops trading). Get it in writing before you pay a deposit.
- 5
Watch for the red flags
Be wary of high-pressure “today only” discounts, large upfront deposits, no written quote, no accreditation numbers, and prices that seem far below everyone else. A good local installer will happily give you references and let you take your time.
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