Why do double-glazed windows become misted?
15th of September, 2026
If you’ve noticed condensation appearing inside your double glazing rather than on the room side of the glass, it’s usually a sign that the sealed unit has failed.
It’s a common problem and often something that develops gradually. A window can look perfectly fine for years before a little misting starts to appear around the edges, eventually becoming cloudiness or visible droplets between the panes.
What causes condensation between the panes?
Modern double glazing is made using two panes of glass separated by a sealed space. The unit is designed to keep moisture out and provide an insulating barrier between your home and the outside.
Over time, however, the perimeter seal around the glass can begin to deteriorate. Once that seal is compromised, moisture can find its way into the space between the panes.
Because the condensation is trapped inside the sealed unit, it can’t simply be wiped away. You may notice it more during colder weather or after changes in temperature, and in some cases the glass can remain permanently cloudy.
Aside from affecting the view through your window, a failed sealed unit can also mean the glazing is no longer insulating your home as effectively as it should.
Does a misted window mean the whole window needs replacing?
Not necessarily — and this is the good news.
If the window frames themselves are still in good condition, it may be possible to replace just the failed glass unit rather than fitting an entirely new window.
The existing glazing is removed and a new sealed double-glazed unit is fitted into the frame, restoring the clear view while also helping the window perform properly again.
It can be a simple way to give otherwise sound windows a new lease of life without replacing more than is necessary.
When should you have misted glazing checked?
A small amount of condensation between the panes won’t usually cause an immediate problem, but once the seal has failed it won’t repair itself.
If you’ve started to notice misting, cloudiness or droplets that you simply can’t wipe away, it’s worth having the window looked at.
At Croft, we can assess your existing windows and advise whether a replacement sealed unit is all that’s needed or whether there are other issues worth considering.
If you have a misted pane or two at home, just get in touch and we’ll be happy to advise.