You wake up one morning and one of your double-glazed windows looks permanently foggy. It will not wipe clean because the mist is trapped inside the glass. This is one of the most common double glazing faults, and it is usually straightforward to put right.
What is actually happening?
A double-glazed unit is two panes of glass separated by a spacer bar and sealed around the edge, with a gas or dry air filling in the gap. Over time, the seal can fail. Moist air gets in, and moisture condenses on the inside faces of the glass.
Failure is more likely on older units, in windows that face the weather, and where a frame has been under strain.
Does it matter?
Misting does not usually make a window unsafe or let rain in, but it does mean the unit has lost much of its insulating performance. Over time the glass can also develop permanent staining that cannot be cleaned.
Can it be repaired?
The fix is to replace the sealed unit, not the whole window. A new unit is made to measure and fitted into your existing frame, which is usually much cheaper than a new window and takes far less time.
It is also a good opportunity to upgrade, for example to a more energy-efficient glass, a laminated safety pane or an obscure finish.
When a new window is the better answer
If the frame itself is rotten, warped or the hardware is failing, replacing the units alone is a false economy. We will take a look and recommend the option that makes sense for your property.