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A man holding a window. SAM Conveyancing talks about the signs of double-glazing failure

Signs of double glazing failure

(Last Updated: 19/07/2024)
6 min read
Key Takeaways
  • One of the most common indicators of double-glazing failure is fogging or misting of the window, indicating a broken seal.
  • Top Tip: Triple-glazing is heavier than double-glazing which can lead to additional strain on the window frames and walls, so make sure you have this in mind when replacing your failed double-glazing windows.
  • Schedule regular checks with professionals who can maintain your double-glazed windows.

Double-glazing window panes can be a fantastic addition to any home, providing better insulation, reducing noise, and helping to save on energy bills.

But like all good things, it doesn't last forever. Here's what you need to know about double-glazed units, the signs of failure, and how to keep those windows in top shape.

What is double-glazing?

Double-glazing involves two panes of glass separated by a layer of air or gas, usually argon, sealed together in a single unit.

This setup offers superior insulation compared to single-pane windows, helping to keep your home warm in winter and cool in summer. It's a common feature in many UK homes and a real asset for energy efficiency.

Signs of double-glazing failure

Double-glazing condensation

When the seal around the double-glazing glass unit fails, moisture can seep in, and condensation forms between the panes. The only permanent fix is to replace the double-glazed unit. You might try a dehumidifier temporarily, but it won't solve the root problem.

A misted double-glazing window pane. SAM Conveyancing can help you identify if you need energy efficient windows.

Seal deterioration

A sealed double-glazed unit deteriorates over time due to weather exposure or poor installation. If the problem is caught early, resealing might be an option. However, in severe cases, full replacement double-glazed units will be necessary.

Cracks and poor installation

Cracks can occur from impacts or natural wear and tear. Poor installation can lead to gaps, improper sealing, and subsequent issues. Cracked glass usually needs replacing and if the installation was subpar, you might need a professional to re-fit the window correctly to ensure proper sealing and alignment.

16% of homeowners discover defects

In our recent survey, 16% of homeowners found defects; including 2% who were able to pull out of a bad purchase, 7% who were able to negotiate a better price, and sadly, 7% of homeowners who did not get a survey and discovered defects after the purchase.

12 of the 39 who remembered how much these defects cost to remedy spent over £5,000

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Fogging and misting

Fogging or misting inside the glass (condensation forming) indicates failed seals. This reduces the insulation efficiency and visibility, leading to increased heating costs and a compromised view.

Increased energy bills

A noticeable spike in energy bills could be due to your double-glazed windows no longer providing the right amount of insulation for your property. The costs rise because your heating system works harder to maintain indoor temperatures.

Cracks, scratches, chips:

Visible damage to the glass affects not only the appearance but also the functionality of your windows leading to potential safety hazards.


Feeling draughts near your windows even when closed. This also suggests that the seal has deteriorated or failed, leading to a loss of heat and increased energy bills.

Difficulty opening and closing windows

If you’re noticing that your windows are hard to open or close, they could be warped or misaligned. This is often due to moisture ingress and seal failure.

Noise from the outside:

Increased noise levels from the outside are a sign that your windows are not providing the same level of sound insulation as before.

A contractor performing double-glazing repairs. If your sealed unit looks like it has excess moisture, SAM Conveyancing's surveyors can help you.

Prevention and maintenance

Regular inspections

Tip: Regularly inspect your windows for signs of wear and tear. Look for any signs of condensation inside double-glazing, damage, or deterioration.

Benefit: Early detection of issues can prevent more severe problems and extend the life of your modern double-glazed windows.

Ensure proper ventilation

Tip: Proper ventilation can help reduce condensation and moisture build-up around your windows.

Benefit: Prevents mould growth and maintains the integrity of your window seals.

Seal and glass replacements

Tip: Replace any damaged seals or glass panes as soon as possible.

Benefit: Keeps your windows functioning efficiently and prevents further damage.

Benefits of blown double glazing replacement

Improved energy efficiency, enhanced comfort, and a reduction in heating costs. Plus, it can even boost your home's market value.

Professional maintenance services

Tip: Schedule regular maintenance with professionals who can thoroughly check and maintain your double-glazing units.

Benefit: Professional insights and services can tactically tackle potential issues, ensuring long-term functionality.

If you keep an eye out for signs of your double-glazed window failing and maintain your windows well, you can ensure your windows continue to serve you effectively for years to come.

Three panes of glass, otherwise known as triple-glazing. Learn if you need to replace your double pane window with the help of SAM Conveyancing.

Problems with triple-glazing

Triple-glazing offers even better insulation than double-glazed windows but isn't without its issues.


Triple-glazing is more expensive to install but is considered to be thermally efficient. The higher initial investment might not be justifiable if the climate or your insulation needs don't warrant it.


Triple-glazing units are heavier. This can lead to additional strain on the window frames and walls, requiring more robust structures surrounding your windows.

No return on investment

The difference in insulation between double and triple glazing is less noticeable in milder UK climates. You might not see a significant enough improvement to justify the extra cost.


Even triple glazing can suffer from condensation issues if not properly installed, leading to similar maintenance and potential replacement concerns as with double glazing.

Whether you stick with double glazing or upgrade to triple glazing, knowing what to look for and how to address issues will keep your home warm, comfortable, and energy efficient.

Noticed damp around your windows?

Don't let condensation and damp become a bigger problem for you, our specialist surveyors can help you with your next steps.

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