Condensation Between Double Glazing: Does It Mean Your Windows Need Replacing?
Spotted a misty or cloudy window that just won’t wipe clean?
If you’ve tried the inside of the glass, tried the outside and the condensation still seems to be there, there’s a good chance the moisture is actually trapped between the panes of your double glazing.
That’s different from the everyday condensation you might wake up to on a cold morning.
Misting between double-glazed panes usually means there’s a problem with the sealed glass unit. But before you assume you need a house full of new windows, the good news is that one misted pane doesn’t automatically mean the whole window needs replacing.
Here’s what it means and what your options are.
What Does Condensation Between Double Glazing Mean?
Double glazing is made using two panes of glass with a sealed space between them.
That space helps to insulate your home and may be filled with air or an insulating gas such as argon. The unit is designed to remain sealed so that moisture from the surrounding air can’t get inside.
When that seal fails, moisture can enter the space between the panes.
You might notice:
a misty or foggy appearance
droplets of water between the glass
cloudy patches that come and go
a window that looks permanently hazy
The easiest way to tell is to try wiping the glass.
If the moisture won’t wipe away from either the inside or outside surface, it is likely to be within the double-glazed unit itself.
Why Does Double Glazing Mist Up Between the Panes?
Usually, it’s because the seal around the double-glazed unit is no longer doing its job properly.
Sealed units are designed to last for many years, but like most parts of a home, they don’t last forever.
Over time, seals can deteriorate. Weather exposure, age, movement and problems with the original manufacture or installation can all potentially contribute to a sealed unit failing.
Once moisture is able to enter the space between the glass, you start to see the familiar misted or fogged appearance. And unlike condensation on the inside of your windows, opening a trickle vent or using an extractor fan isn’t going to clear it.
If you’re not sure which type of condensation you have, our guide to condensation on windows explains the difference between moisture on the inside, outside and between the panes.
Does Condensation Between the Panes Mean I Need New Windows?
Not necessarily.
If the window frame is still in good condition and everything else is working properly, it may be possible for a glazing repair specialist to replace the failed sealed glass unit without replacing the complete window. That can make sense where the problem is limited to one pane and the existing window still has plenty of life left in it.
But it’s worth looking beyond the misted glass before deciding.
If the windows are older and you’re also experiencing draughts, damaged frames, stiff opening, problems with locks or generally poor performance, replacing one sealed unit might only solve one part of the problem.
That’s when it can be worth looking at the condition of the complete window.
When Might Replacing the Complete Window Make More Sense?
A misted pane on its own isn’t necessarily a reason to replace an otherwise good window.
But if it’s one of several problems you’ve started noticing, a complete replacement may be worth considering.
For example:
The windows are draughty. If you can feel cold air around the frame, there may be more going on than a failed glass unit.
They’re becoming difficult to open or close. Problems with hinges, frames or mechanisms can become more common as windows age.
The frames are damaged or deteriorating. Replacing the glass won’t solve a problem with the surrounding frame.
Several sealed units are beginning to fail. If multiple windows of a similar age are developing problems, it can be worth looking at the bigger picture.
The windows no longer perform as you’d like. Older glazing and frames may not offer the comfort or thermal performance you want from your home today.
You were already considering an upgrade. If you're planning to improve the look, warmth or overall performance of your windows, a failed unit can sometimes be the point where you decide it makes more sense to replace rather than repair.
There isn’t one answer that suits every home.
The important thing is knowing whether you’re dealing with one failed piece of glass or an older window that’s beginning to show several signs of wear.
Does Misted Double Glazing Affect Energy Efficiency?
If the seal in a double-glazed unit has failed, the unit is no longer performing exactly as it was designed to.
Modern double glazing relies on the sealed space between the panes as part of its insulating performance. Once that seal has been compromised, some of that performance can be affected.
That doesn’t mean a misted window suddenly stops insulating your home altogether.
But if the glass is visibly misted between the panes, it is a clear sign that the sealed unit has failed and is worth having checked.
This is particularly worth considering if the window is also noticeably cold, draughty or one of several older windows that are starting to cause problems.
Can Misted Double Glazing Be Repaired?
You may have seen services offering to “demist” double glazing by drilling into the glass and removing the moisture. That may improve the appearance temporarily, but it doesn’t necessarily address the failed sealed unit itself.
Where the frame is still in good condition, replacing the affected sealed glass unit is generally the more complete repair. Whether that is the right option depends on the age and condition of the rest of the window.
If you only have one failed unit in otherwise good windows, speaking to a glazing repair specialist may be your best starting point.
If your windows are older and you’re already dealing with several other problems, it may make more sense to compare the cost of repairing individual components with replacing the windows altogether.
Should I Check My Window Guarantee?
Yes - particularly if the windows aren’t very old.
If you know who originally supplied or fitted them, check whether the glass or sealed units are still covered by a guarantee.
A failed sealed unit can sometimes be covered, depending on the terms and age of the installation.
It’s worth checking before paying for any repair or replacement work.
What If the Condensation Is on the Inside of the Glass?
That’s a different issue.
If you can wipe the water away from the room-facing side of your window, it is more likely to be everyday condensation caused by moisture in the air meeting a cold surface.
That type of condensation is usually linked more closely to humidity, ventilation and temperature inside the home than to a failed sealed unit.
Our full guide to condensation on windows explains what causes it and some simple ways to reduce it.
How can I tell if condensation is between the panes?
Try wiping both sides of the glass.
If the window still looks misty, cloudy or has visible droplets that you can’t reach, the moisture is likely to be trapped inside the double-glazed unit.
Will condensation between double glazing go away on its 0wn?
The appearance may change depending on the weather and temperature, so a window can sometimes look clearer than it does on other days.
However, if moisture has entered because the sealed unit has failed, the underlying problem hasn’t repaired itself.
Can the glass be replaced without replacing the whole window frame?
Often, yes.
If the frame is still in good condition, a glazing repair specialist may be able to replace the failed sealed unit while keeping the existing frame.
Whether this is worthwhile will depend on the condition and age of the rest of the window.
Is misted double glazing a sign my windows are old?
Not always.
Sealed units can fail for different reasons, so misting alone doesn’t tell you the age or overall condition of the window.
However, if older windows are starting to develop misted units alongside draughts, damaged frames or problems opening and closing, it may be worth considering whether replacement makes more sense than continuing to repair individual issues.
Do I need to replace all my windows if one has misted up?
No.
One failed sealed unit certainly doesn’t mean every window in your home needs replaced.
Each window should be looked at based on its own condition, age and performance.
Not Sure Whether to Repair or Replace Your Windows?
If a window has started misting between the panes, the first step is working out whether the problem is limited to the sealed glass unit or whether the complete window is beginning to show its age.
If your existing windows are draughty, damaged, difficult to use or no longer performing the way you’d like, we can help you explore the replacement options.
At Doorquay, we supply and fit replacement windows across Dundee, Angus, Fife and Perthshire, with options to suit different homes, styles and budgets.
We’ll look at what’s currently fitted and talk through what you want to improve, so you can decide whether replacing your windows is the right next step for your home.
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