Is a lifetime guarantee real?

It is usually the lifetime of the product as defined in the terms, not yours, and it is usually limited to the frame. Read the definition. A clearly stated period on each component is worth more than the word lifetime.

My installer has gone out of business and a unit has misted.

Check whether you have an insurance-backed guarantee certificate, which is the route that still works. Failing that, the sealed unit manufacturer’s own guarantee may still supply the glass, and you would pay a glazier to fit it. See what misted double glazing costs to put right.

Does paying by credit card help?

For the deposit and for disputes, yes. Section 75 of the Consumer Credit Act can make the card provider jointly liable with the trader on qualifying purchases, which is a useful second route if something goes wrong early. It is not a substitute for an insurance-backed guarantee years later.

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What does a ten-year window guarantee actually cover?

A headline ten-year guarantee is normally several separate guarantees of different lengths: the frame from the manufacturer, the sealed units from the glass maker, the hardware from its own maker, and the installation from the installer. The installation part is the one that matters most and the one most likely to be short, and it is worthless if the installer stops trading unless it is insurance-backed.

Nothing on a window quote is as oversold as the guarantee, and the question that unpicks it is not how long, but who honours it.

The four guarantees inside the one number

Ask for them separately, in writing, and you will usually get four different answers:

The frame. From the profile manufacturer. Usually the longest, and usually covers discoloration and structural failure rather than anything likely to happen.
The sealed units. From the glass manufacturer, covering the seal failing and the unit misting. Commonly shorter than the headline figure, and the most likely thing to go wrong.
The hardware. Hinges, handles and locking mechanisms, from their own manufacturers. Often the shortest of the four, and the parts that actually wear.
The installation. From the installer, covering their workmanship: the fit, the sealing, the making good. Nobody else can honour this one.

A guarantee is only as long as the shortest part you care about. Ten years on the frame and a much shorter period on the sealed units is a reasonable offer, but it is not a ten-year guarantee against the thing most likely to fail.

The question that matters: who is still there?

An installer’s own guarantee is a promise from a company. If that company closes, the promise closes with it, and in a trade with a lot of small firms that is not a remote risk.

The protection against it is an insurance-backed guarantee, which is a separate policy from an insurer that steps in if the installer is no longer trading. It is normally issued through the competent person scheme, it costs very little, and it is the single most valuable piece of paper in the file. See insurance-backed guarantees.

A manufacturer’s guarantee usually survives the installer going under, but it covers the product only. Getting a replacement sealed unit free and then paying someone to fit it is a common and unwelcome surprise.

What to ask before you sign

Five questions, and the answers belong on the quote rather than in a conversation:

What is the guarantee period for the frames, the sealed units, the hardware and the installation, separately?
Does the guarantee cover labour as well as parts, or will a free part still mean a call-out charge?
Is it insurance-backed, through which scheme, and when will I receive the certificate?
Does it transfer if I sell the house? Most buyers will ask for it, and a transferable guarantee is worth having at that point.
What would void it? Painting a uPVC frame, fitting internal blinds into the frame and having someone else service the hardware all appear in real terms and conditions.

Independent of all of it, keep the FENSA or CERTASS certificate somewhere you can find it. Your solicitor will ask for it when you sell, and it is the one document a future buyer definitely wants.

Questions

Is a lifetime guarantee real?: It is usually the lifetime of the product as defined in the terms, not yours, and it is usually limited to the frame. Read the definition. A clearly stated period on each component is worth more than the word lifetime.
My installer has gone out of business and a unit has misted.: Check whether you have an insurance-backed guarantee certificate, which is the route that still works. Failing that, the sealed unit manufacturer’s own guarantee may still supply the glass, and you would pay a glazier to fit it. See what misted double glazing costs to put right.
Does paying by credit card help?: For the deposit and for disputes, yes. Section 75 of the Consumer Credit Act can make the card provider jointly liable with the trader on qualifying purchases, which is a useful second route if something goes wrong early. It is not a substitute for an insurance-backed guarantee years later.

Note This guide is general information about England and Wales, not advice about your specific property. TrustedGlazing is an introducer and does not install, survey or quote. Rely on your installer's survey and your local authority for decisions about your own home.