Misted double glazing: repair, not replace the whole window.
If the inside of your double-glazed window has gone cloudy, foggy, or you can see water droplets between the panes, the seal has failed. The good news is that we can replace just the sealed unit, not the whole window. Faster, far cheaper, and less disruption.
Most misted units we replace in Wallington cost £95–£180, supplied and fitted. Same-day measurement in most cases.
Why sealed units mist
A double-glazed sealed unit is two panes of glass separated by a spacer bar, sealed at the edges. The spacer is filled with desiccant that absorbs any moisture trapped inside. Over time (usually 15 to 25 years) the seal fails, moisture gets in, and you see condensation between the panes.
It cannot be cleaned from the outside or the inside. The unit has to come out and a new one put in. The frame is usually fine, so we keep the frame and replace just the unit.
Misted sealed unit: indicative costs (2026)
When to repair, when to replace the window
- Repair (just the unit): the frame is sound, the unit is the only thing failed. This is the common case. We measure the unit, order a replacement, and fit it in about 30 minutes per window.
- Replace the whole window: the frame is rotted, draughty, or the mechanism is broken. If your windows are very old, it can be cheaper long-term to replace the whole thing. We can quote both options and let you decide.
- Upgrade at the same time: when we replace the unit, we can upgrade to Pilkington K low-E glass for better insulation. The cost difference is usually £20–£40 per unit and the saving on heating bills is real.
What to do next
If you have one or two misted units, send us the rough size of the glass (height and width of the visible pane, in millimetres) and the frame colour/type (white uPVC, wood, aluminium). We will quote from that.
If you have several misted units (often the case if the windows are all the same age), it is worth a site visit. We can measure them all in one go and give you a single price for the lot.
Frequently asked questions
Can the condensation be cleaned out?
No. Once the seal has failed, the unit has to be replaced. There are companies that claim to drill a hole in the unit, drain it and reseal it. It does not work long-term. The unit will mist again within months.
Do you replace the whole window or just the unit?
Just the unit, in 95% of cases. The frame is usually fine. We take the old unit out, clean the frame, fit the new unit, and reseal it. About 30 minutes per window.
How long do replacement sealed units last?
Modern sealed units have a 10-year manufacturer warranty and last 20+ years. The desiccant and edge-seal technology is much better than it was in the 1990s and 2000s.
Got a misted window?
Send a photo with the rough size, or pop into the shop with the dimensions. We will quote same-day.