How to Compare Double Glazing Warranties
A ten-year guarantee means nothing until you know who backs it and what it covers. Here is how to read a window warranty before you compare it with another.
Key takeaways
- Ask what is covered, for how long, by whom, and whether it is insurance-backed.
- Frames, glass units, hardware and installation are usually covered by different terms.
- A guarantee from a company that stops trading is worth nothing unless it is insured.
- Compare warranties only after comparing scope and price, never instead of.
Two installers can both advertise a ten-year guarantee, and one can be materially better than the other. The difference is in four questions: what is covered, for how long, who is legally on the hook, and what voids it.
The three guarantees in every window job
| Cover | Typically covers | Usual length |
|---|---|---|
| Profile manufacturer | Frame profile against discolouration and defects | 10 – 20 years |
| Glass unit manufacturer | Sealed unit failure and misting | 5 – 10 years |
| Installer | Workmanship, installation, watertightness | 5 – 10 years |
| Hardware | Handles, hinges, locking mechanisms | 2 – 10 years |
Many quotes present all of this as one “10-year guarantee”. Ask for the breakdown, because a ten-year workmanship guarantee with a five-year glass unit cover is a different product from the reverse.
Is it insurance-backed?
An insurance-backed guarantee is underwritten by a third party, so it survives if the installer goes out of business. It is the single most valuable line on a guarantee document and the one most often missing. Ask directly: if you close tomorrow, who pays to fix my windows? If the answer is a shrug or a trading history, the guarantee is a promise rather than a protection.
What voids a guarantee
- Work carried out by someone else, including repairs and adjustments.
- Failure to maintain the windows as instructed, such as not clearing drainage slots.
- Damage from building work, extreme weather or accident.
- Removing or altering the frames, hinges or locking hardware.
- Not reporting a fault within the stated notification period.
How to compare two warranties
| Check | What good looks like |
|---|---|
| Workmanship cover | 10 years, in writing, on the contract |
| Glass unit cover | At least 10 years against misting and seal failure |
| Insurance backing | Named underwriter, with a policy document available |
| Response times | Stated service call-out commitment |
| Transferability | Transfers to a new owner if you sell |
| Exclusions | Short, specific, and written in plain English |
The bottom line
Compare the scope first, the price second and the warranty third, but do read all three. A cheap quote with an uninsured five-year guarantee is not the cheapest window you can buy; it is the one you will replace soonest.
Frequently asked questions
Ten years on frames and installation is the market standard, with at least ten years against sealed unit failure. Shorter cover is acceptable only if the price reflects it.
A third-party underwriter stands behind the guarantee, so it remains valid if the installer ceases trading. Ask for the named underwriter and the policy details.
It should. Sealed unit failure is the most common claim, and glass unit cover of ten years is typical on quality products.
Many are, which is useful at sale. Check the terms and keep the certificate and FENSA documentation with your property paperwork.
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