Misted, draughty or sticking: how to tell when your double glazing needs replacing

Sponsored feature — this article is paid for by Perfect Wirral. Widnes Life produces sponsored content to help fund our independent local reporting. Advertisers do not influence our news coverage.

Most people don’t replace their double glazing because it fails outright. They replace it because it gets slowly, quietly worse — a bit more draught each winter, a bit more condensation each morning — until one day they notice the heating is running longer than it used to and nobody can remember when the back bedroom was last warm.

Sealed units have a working life. Twenty years is a reasonable expectation for a decent unit fitted properly, less if it has taken sun and salt air. The trouble is that the failure is gradual, so the point at which replacement makes financial sense passes without anyone noticing.

Here is what to look for, and what to ask before you let anyone quote.

The four signs that actually matter

Misting between the panes. This is the clearest one. If there is condensation inside the glass — between the two panes, where you cannot wipe it — the seal has gone. The gap is meant to be sealed and filled with dry air or argon. Once moisture is in, the insulating value is largely finished. Wiping the outside or inside does nothing, because the water isn’t there.

Worth knowing: a misted unit does not always mean new windows. If the frames are sound, the sealed unit alone can often be swapped, which is considerably cheaper than a full replacement. A good installer will tell you that. An installer who insists on full replacement for a single misted pane is worth a second opinion.

Draughts you can feel with your hand. Run the back of your hand slowly around the frame on a windy day, particularly along the opening edge and the bottom corners. Cold moving air means the gaskets have hardened or the hinges have dropped and the sash is no longer pulling tight against the frame. Sometimes that is an adjustment. Sometimes the frame has warped and it isn’t.

Windows that stick, drop or need lifting to lock. If you have to lift a door or shoulder a window to get the handle round, the frame has moved. This is a security issue as much as a comfort one — a multipoint lock that isn’t engaging fully is not doing the job it was fitted to do.

Condensation on the room side, every morning. This one is more ambiguous. Heavy internal condensation can mean failing glazing, but it can equally mean a ventilation problem — blocked or absent trickle vents, a tumble dryer venting indoors, a bathroom fan that stopped working two years ago. Rule out ventilation before you rule in new windows. Any installer who doesn’t ask about ventilation is skipping a step.

Repair, or replace?

The honest answer is that it depends on the frames, not the glass. Glass is replaceable. Frames are the expensive part.

If the frames are straight, the hinges are sound and the problem is one or two misted units, repair. If the frames have dropped, the seals have gone across the whole house, and the units are original to a 1990s installation, you are spending money on something you will replace within a few years anyway.

A reasonable rule of thumb: if the repair cost is approaching half the replacement cost, replace.

What to check before you sign anything

The glazing trade has a reputation, some of it earned. A few checks separate the firms worth having in your house from the ones that aren’t.

Ask who is actually doing the work. Plenty of firms sell the job and subcontract the fitting to whoever is available that week. Ask whether the fitters are employed, and how long they have been with the company. The quality of a window installation is almost entirely down to the fitter.

Get the guarantee in writing, and check who is backing it. A ten-year guarantee from a company that folds in year three is worth nothing. Insurance-backed guarantees exist precisely for this — they are underwritten by a third party, so the cover survives the installer. Ask which scheme, and get the certificate.

Check the certification. Replacement windows and doors must comply with Building Regulations. Registered installers can self-certify and issue you a certificate; unregistered ones cannot, which means you need Building Control involvement and a fee. That certificate matters when you come to sell — conveyancing solicitors ask for it, and its absence holds sales up.

Be wary of the discount that expires tonight. A price that is only available if you sign before the salesperson leaves is not a price, it is a pressure tactic. Reputable firms quote, leave, and are still quoting the same figure a fortnight later.

Get three quotes, and compare specification, not just the number. A cheap quote often has thinner profiles, a lower-spec glass unit or a shorter guarantee behind it. Ask for the U-value of the glass and the make of the profile system on every quote, then compare like for like.

About Perfect Wirral

This feature is sponsored by Perfect Wirral, trading as Perfect Conservatories, Windows & Doors, based at BMB Industrial Park on Docks Link in Wallasey.

The company installs windows, doors, conservatories and roofline across the Wirral peninsula and into Cheshire and north Wales, and has a showroom where the products can be seen and handled before ordering — which is worth doing, because glazing photographs considerably better than it sometimes looks in person.

They fit their own installations rather than subcontracting, and offer insurance-backed guarantees on completed work.

This is a sponsored feature. Widnes Life has not independently verified the claims made by the advertiser. Always obtain multiple quotes and check credentials before commissioning work.