How to tell if your double glazing has failed

Failed double glazing usually gives itself away in one of four ways. Misting or a permanent haze sitting between the two panes of glass, a room that has quietly stopped holding its heat, handles and hinges that have gone stiff or slack, and water finding its way onto the inside of the frame after a night of driving rain. Of those four, moisture trapped between the panes is the one that proves it outright, because that can only happen once the seal around the sealed unit has gone.

The better news is that a failed unit is very often not a failed window. In most cases the glass unit alone can be swapped and the frame, hinges and locks stay exactly where they are, which costs a fraction of a full replacement. Telling those two situations apart is the difference between a modest repair and a bill you did not need to pay, so the rest of this guide covers how to read the signs properly.

Misting between the panes is the sign that settles it

A double glazed unit is two panes of glass held apart by a spacer bar and sealed around the edge, with dry air or an inert gas in the gap. That seal is the whole design. Once it breaks, ordinary damp air gets into the cavity, and the moment the outside temperature drops the moisture in it condenses on the inner face of the outer pane.

That is why the haze appears and disappears with the weather, and why wiping the glass does nothing. You cannot reach it. If you can see cloudiness, streaking or little pooled droplets sitting between the panes rather than on either surface you can touch, the unit has failed and no amount of ventilation will bring it back.

It is worth being precise here, because this is where most people get it wrong. Condensation on the room side of the glass on a cold morning is not failure at all. That is normal household humidity meeting a cold surface, and it points at ventilation, drying washing indoors or an extractor fan that is not doing its job. The distinction matters enough that it is worth understanding what causes condensation between double glazing before you call anybody out, because one of those is a repair and the other is a habit.

A room that has stopped holding its heat

The second sign is slower and easier to miss. Once the seal goes, any insulating gas in the cavity escapes, and the unit loses a good part of the thermal performance it was made with. Nobody notices this on the day it happens. What people notice is that one room now feels colder than the rest of the house, or that a particular seat by the window is draughty when it never used to be.

If you want to check it without any equipment, wait for a cold morning and put the back of your hand near the middle of the glass, then near the middle of a window in a room that still feels fine. A failed unit reads noticeably colder. Doing that across the house takes ten minutes and usually finds the culprits.

Hardware that has stiffened, dropped or gone slack

Not every double glazing failure is about glass. A great deal of what we get called out to is hardware. Hinges that have worn so the sash drops and catches on the frame, handles that have gone loose, locks that need lifting and shoving before they will engage, and trickle vents that have seized open or shut.

We have found that people put up with a stiff window for a remarkably long time before mentioning it, and it is usually the cheapest thing on this list to put right. Hinges, handles, locks and patio door rollers are all replaceable parts. A window that has become hard work is very rarely a window that needs replacing.

Water getting past the frame

The fourth sign is water appearing on the inside of the frame or the sill after wind-driven rain. Before assuming the window has failed, check the drainage slots along the bottom of the outer frame. They are small, they collect dirt, moss and salt, and once they block the water that a window is designed to channel back out has nowhere to go but in.

Clearing them is a job with a thin piece of wire and five minutes. If the water keeps coming once they are clear, the seal between the frame and the brickwork is the next suspect, and that is a fitting problem rather than a window problem.

Why this coast is harder on double glazing than most places

This is the part that a national guide cannot tell you. Skegness, Winthorpe and the villages along this stretch sit right on the North Sea, and salt-laden air, constant wind and driving rain work on a window in ways they simply do not on a sheltered inland plot.

From more than 40 years of fitting and repairing along this coast, the pattern we see is consistent. Drainage channels silt up faster here because salt and fine sand get carried into them. Hinges, handles and lock mechanisms corrode sooner on exposed frontages, particularly on the seaward elevation of a property, where the same house can have perfectly healthy hardware on the sheltered side. And edge seals on units facing the prevailing weather tend to go before the ones round the back. If you are checking your own windows, start with the side that takes the weather and you will usually find the problem faster.

That exposure is also why the specification matters when the time does come, and why the best windows for coastal homes are not automatically the ones that suit a house twenty miles inland.

Repair or replace, and how to decide

Here is the judgement that saves people the most money. In our experience, replacing the failed sealed unit on its own works better than replacing the whole window because the frame usually has years of service left in it, the job is done in a fraction of the time with no making good to plaster or brickwork, and the cost is a small share of a full replacement. The seal is a consumable part of the window. The frame is not.

That holds while three things are true. The frame is sound and square, the hinges and locks still work or can be replaced, and the window is not so old that the whole thing is well past its service life. Where the frame itself has distorted, where several units on the same elevation have gone at once, or where the windows are old enough that you would be repairing them again in two years, replacement is the honest answer.

What we see that most installers do not

One genuinely useful thing about the way this business works is that we repair glazing fitted by other companies as well as our own. Misted units, locks, hinges, handles, door adjustments, patio rollers, trickle vents, child restrictors and leaks all come through, on installations we never touched.

That gives us a view across a lot of different products and a lot of different standards of fitting in the same few postcodes, which no installer who only services their own work ever gets. It is also why we will tell you when a repair is the right call. There is no version of this where quoting you for eight new windows you do not need is good for a family business that has traded in the same place since 1983 and relies on people locally recommending it.

If something on your windows has stopped working properly rather than stopped insulating, our repairs service covers most of it, including work carried out by somebody else.

When replacement genuinely is the answer

Where the windows really have come to the end, replacement brings a real gain rather than a marginal one, because modern units are a long way ahead of anything fitted twenty years ago. All our windows come A-rated as standard, and the energy rating scale itself is run by the BFRC, which is worth knowing so you can compare like for like between quotes rather than taking a salesperson's word for it.

Replacement windows in a home are covered by building regulations, and the work needs certifying. Piper Windows is a FENSA registered installer, so the installation is registered and you get the paperwork without arranging building control yourself. That certificate is easy to shrug at on the day and matters a great deal when a buyer's solicitor asks for it years later.

The short version

Look for misting between the panes, which proves seal failure. Look for a room that has lost its warmth, hardware that has gone stiff or dropped, and water on the inside of the frame after heavy rain. Then check whether the frame is still sound, because in most cases it is, and the fix is a new sealed unit rather than a new window.

If you are not sure which you are looking at, we will come and tell you honestly. You can get a free no-obligation quote, have a look at our recent window work, or ring us on 01754 898 998 and describe what you are seeing. We have been repairing and replacing glazing across Skegness and the wider Lincolnshire coast since 1983, and we would far rather save you a window than sell you one.