Condensation Between Glass Panes: What It Means and What to Do
There are two very different types of condensation on windows, and knowing which one you've got saves a lot of wasted effort. This guide explains the difference and what to do about the one that actually needs a glazier.
Between the panes vs on the inside surface
Condensation on the inside face of the glass, on the room side, is normal household condensation caused by moisture in the air meeting a cold surface — better ventilation, trickle vents or extractor use usually helps.
Condensation or misting that appears between the two panes of a double glazed unit is different entirely. It means the airtight seal around the edge of the unit has failed, and moist air has got into the gap between the glass. No amount of cleaning, ventilation or heating will remove it — the unit itself needs replacing.
Why the seal fails
Double glazed units use a spacer bar with a desiccant inside to keep the gap dry, sealed at the edges. Over ten to twenty-plus years, or sooner with a poor original installation, that edge seal can degrade and let moisture in. Once the desiccant is saturated, misting appears and gets worse over time.
What replacing the unit involves
The good news is that a failed seal is a glass problem, not a frame problem. We remove the beading, lift out the failed unit, fit a new one to match your existing thickness and spacer size, and re-bead it — all without disturbing the frame, hinges or handles.
- Frame, hinges, handles and locks are left completely untouched
- New unit matched for thickness, spacer bar colour and glass spec
- Old unit removed and recycled
- Typically a 30–60 minute job per unit once the glass is on site
Can it be prevented?
There's no way to 'unseal' or repair a failed unit — it's a manufacturing seal that either holds or doesn't. Choosing a quality unit with a warm-edge spacer bar when replacing does reduce the risk of an early repeat failure, which is the spec we fit as standard on residential units.
Want a professional to handle it?
Get a quoteCall Mark on 07535 916982 or request a callback.
Related repairs we handle
Covering Central London and out to the M25
See also
- For ventilation, see trickle vent replacement.
Frequently asked questions
Can I dry out condensation between the panes myself?
No — there's no way to remove moisture from inside a sealed unit without replacing it. Drilling 'weep holes' or similar DIY fixes don't solve the problem and can make the unit worse.
Does misting mean the whole window needs replacing?
No — in the large majority of cases it's just the glass unit that's failed. The frame, hinges and handles are unaffected and stay exactly as they are.
How do I know if it's room-side condensation or a failed seal?
Room-side condensation wipes away and comes back with humidity; misting between the panes never wipes away because it's on the inside faces of glass you can't reach, and it tends to be a permanent haze or fog.
Will a new unit mist up again?
Not under normal circumstances — a properly fitted, quality sealed unit should last many years. We fit warm-edge spacer, argon-filled units as standard to reduce the risk of early failure.
Call Mark on 07535 916982 or request a callback.