How to Deal with a Blown Double-Glazed Window: Repair & Cost Guide
A blown double-glazed window occurs when the seal between the two glass panes fails, allowing moisture to seep inside and causing unpleasant condensation. This damages both the window’s appearance and its insulating performance.
In this detailed guide from Home Windows, you’ll learn how to spot a blown double-glazed window, understand the common causes, weigh your repair or replacement options, and manage associated costs.
Identifying Blown Double-Glazed Windows
Early detection saves money and hassle. The clearest sign of a blown window is condensation trapped between the glass panes, creating a foggy or misted appearance that won’t wipe away.
Other indicators include:
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Increased heating bills due to heat loss through compromised insulation
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Noticeably higher indoor noise levels as the soundproofing fails
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Visible moisture or droplets forming inside the window unit
Acting quickly after spotting these signs can prevent damage worsening and additional costs arising.
Common Causes of Blown Double Glazing
The main culprit is typically seal failure – over time, window seals can degrade due to exposure to weather, UV rays, and temperature fluctuations. Older windows (15-20+ years) are particularly susceptible, as materials naturally age and lose effectiveness.
Improper installation or damage from storms can also compromise seals, allowing water and air ingress. Lack of maintenance and poor ventilation can accelerate the problem, underscoring the importance of regular window inspection to catch issues early.
Effects of Blown Double Glazing on Your Home
Beyond aesthetics, because of how double glazing works, blown glazing impacts:
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Energy efficiency is compromised when heat escapes more easily, forcing your heating system to work harder and hike energy bills.
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Property value with foggy, misted windows can reduce curb appeal and may signal neglect to potential buyers.
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Structural health from moisture inside glazing can lead to mould growth, wood rot, and compromised window frames, possibly causing costly repairs.
Repairing Blown Double-Glazed Windows
Professional Repair Services
Experts use specialised equipment to assess damage and often restore misted windows without full replacement. Professional repairs can extend your windows’ life, improve their insulation, and maintain property aesthetics, usually at a lower cost than full replacement.
DIY Repair Options
Some homeowners attempt moisture removal using kits that drill a small hole in the glass unit to dry out trapped condensation with desiccants. While this can work for minor fogging, it requires precision and care. DIY solutions carry risks including worsening damage or voiding warranties, so weigh benefits carefully.
Replacing Blown Double-Glazed Units
When damage is severe or persistent—such as cracked glass, broken seals beyond repair, or compromised window frames—replacement is often the best solution.
Replacing just the sealed glass unit can be more economical when frames are sound. Full window replacement is advised if frames are warped or rotted. New units restore strong insulation, reduce energy costs, and improve comfort and home appearance.
Costs Associated with Blown Double Glazing
| Service Type | Typical Cost Range (per window) | Notes |
|---|---|---|
| Professional Repair | £50 – £200 | For moisture removal & resealing |
| Double-Glazed Unit Replacement | £50 – £150 | Glass unit only, frame intact |
| Full Window Replacement | £200 – £600+ | Includes frame & glass |
Consider potential energy savings when deciding repair vs. replacement—well-sealed windows reduce heating bills significantly over time.
Preventing Blown Double Glazing
To protect your windows:
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Regularly inspect seals and frames for damage or wear
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Maintain good home ventilation to control indoor humidity
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Avoid harsh cleaning chemicals that degrade seals
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Invest in high-quality units and timely replacements before major failure occurs
Warranties and Guarantees
Most reputable double glazing products include at least a 10-year seal warranty. Installation performed by certified professionals often comes with insurance-backed guarantees for added peace of mind, protecting your investment if issues arise later.
Repair Blown Double-Glazing — Our Thoughts
Blown double glazing affects more than appearance—it undermines your home’s comfort and efficiency.
Fast identification and action are vital to keep energy costs down and avoid expensive repairs.
Whether you hire a pro or try minor DIY fixes, knowing the options—and the costs—puts you in control. Regular maintenance and buying quality double glazing upfront are key to avoiding blown units altogether.
