November 22

Why Do My Double-Glazed Windows Mist Up Inside?

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Why Your Double-Glazed Windows Are Misting Up Inside

If you’ve noticed a cloudy or foggy appearance inside your double-glazed windows, you’re not alone. Misted windows are a common problem for UK homeowners, and it’s often a sign that something’s gone wrong with the sealed glass unit—not just everyday condensation.

What’s Causing the Mist?

When condensation or fogging appears between the panes of glass in a double-glazed window, it’s usually because the airtight seal has failed. This allows moisture-laden air to seep in and get trapped inside the unit. Over time, this builds up and leads to that misty or foggy look that just won’t wipe away.

Why Seals Fail

There are a few common causes behind blown double glazing:

  • Age or wear: Most sealed units have a lifespan of 10-20 years before the seals naturally degrade.

  • Poor installation: If the unit wasn’t fitted properly, it may not stay airtight.

  • Thermal stress: Big temperature swings (like sun on one side of the window) can cause materials to expand and contract, eventually weakening the seal.

  • Faulty or poor-quality materials: Cheaper units don’t always last as long.

What You Can Check Yourself

Before calling anyone out, here are a few signs to look for:

  • Condensation between the panes that doesn’t wipe away from either side

  • White streaks or mineral deposits in the middle of the glass

  • Soft, spongy areas around the seal or frame (could indicate water damage)

Typical external condensation or fogging on just the inside face of your window glass (especially in the morning) is normal and not a sign of damage. But moisture between the two panes? That’s where a repair is needed.

Repair vs. Replace: What Are Your Options?

The good news is that you usually don’t need to replace the entire window. In most cases, the issue lies with the glass unit itself—not the surrounding frame. At Get Your Windows Fixed, we often replace just the failed sealed unit, which is a quicker and more cost-effective solution

However, if the frame is damaged, warped, or causing repeating seal failures, a full window replacement might be recommended. We’ll always tell you honestly what the best option is based on what we find during your survey.

Will New Glass Prevent It Happening Again?

Yes. Modern double-glazed units—especially those rated A+ for efficiency—use stronger seals and inert gases (like argon) between the panes to reduce the risk of misting. Replacing a failed unit can restore your window’s insulation and visibility, and stop unwanted heat loss through the gap.

How Much Does It Cost?

The price depends on the size of the glass and the type, but as a rough guide, replacing one misted unit starts from around £80-£150 for a standard window. Much cheaper than a full window replacement—and we always offer a no-pressure quote with no callout charge.

Why Choose Get Your Windows Fixed?

Our expert glaziers repair misted windows across the UK every day. We’re friendly, efficient, and clear in our pricing. We’ll quickly let you know whether your issue is repairable and give you peace of mind that your home is sealed and protected again.

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