If you’ve noticed cloudy patches or mist that you can’t wipe away, you’re not imagining it — it’s one of the most common questions we’re asked about older double glazing. Homeowners often wonder if it’s just condensation, whether it can be cleaned, or if a quick trick like a hairdryer will clear it. In this article we’ll explain what causes misty windows, why the problem returns, and the straightforward repair option that restores clear glass without the cost of replacing the whole window.
Why Do I Have Mist Between My Window Panes?
Misting between panes happens when the seal around a double‑glazed unit fails. That seal is designed to keep the space between the two panes dry and insulated. Once it breaks down, moisture can get inside the unit and you’ll see the familiar cloudy or foggy appearance — often worse in colder or more humid weather. Unfortunately, because the moisture is inside the sealed unit, it isn’t something you can clean off from the inside or outside surface.
1. You Can’t “Clean” Mist Inside Double Glazing
What you’ll notice: The glass looks cloudy, but no amount of cleaning makes a difference.
Why it happens: The condensation is trapped between the panes inside the sealed unit.
What to avoid: Quick fixes like heaters or hairdryers may seem to help temporarily on some days, but they don’t repair the failed seal.
The key point: Even if the mist disappears briefly, it will return because moisture can still enter the unit.
2. The Sealed Unit Can’t Be Repaired Once The Seal Has Failed
What it means: A double‑glazed unit is manufactured as a sealed system. When the perimeter seal fails, the unit no longer performs as intended.
What that affects: Visibility (cloudy glass), insulation (reduced performance) and sometimes the overall appearance of the window.
Good news: You usually don’t need a full new window — if the frame is sound, replacing just the glass unit is often the right solution.
3. The Quick, Economical Fix: Replace The Failed Glass Unit
How the repair works: We remove the old failed sealed unit and fit a brand new high‑performance specification unit into your existing frame.
Time and disruption: In many cases, a unit replacement takes around 20 minutes from start to finish.
Advantages: A refreshed look, clearer glass and improved energy performance — typically at a fraction of the cost of replacing the whole window.
Peace of mind: New units are backed by a guarantee (for example, a further 5 years on many replacements).
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