The best window seal replacement service diagnoses the actual failure point, repairs the seal rather than the whole frame, and uses installers who protect your warranty. Cloudy2Clear replaces failed window seals across England and Scotland for £120 to £500 per window, with seals that, once properly fitted, typically last 10 to 20 years.
Key Takeaways
- Window seal replacement at Cloudy2Clear costs £120 to £500 per window, depending on size and location.
- A failed seal can lose roughly 30% of a window’s insulating value, letting in draughts and moisture.
- Seals typically last 10 to 20 years once properly installed, trapping argon gas between the panes.
- Free consultations come with a no-obligation quote, and our engineers turn quotes around in under 20 minutes on site.
- Double glazing replacement carries a 25-year guarantee on the glass itself, separate from the PVC frame.
How Do You Know a Window Seal Has Failed?
A failed window seal shows up as condensation trapped between the panes, a persistent draught you can feel near the frame, or mould and discolouration building up along the edge of the glass. Any of these signs points to the seal, not the whole window unit, needing attention.
Condensation between panes is the clearest tell. It means moisture has got past the desiccant and spacer bar that are meant to keep the unit dry, and no amount of wiping the glass will clear it, because the moisture sits inside the sealed unit, not on the surface. Draughts often follow once the seal has broken down enough to let air through as well as moisture. Left long enough, you’ll start to see mould growth or discolouration creeping in around the edges of the glazing.
If you want the mechanics of what actually sits inside that sealed unit, we cover it in what a glazing unit is and how it’s built. Understanding the spacer bar, the desiccant, and the sealant helps explain why a failed seal behaves the way it does.
What Causes Leaking Double Glazing in the First Place
Leaking double glazing almost always traces back to a broken seal rather than a cracked pane. Once the perimeter seal degrades, the argon gas that insulates the unit escapes and moisture works its way in, undermining the window’s thermal performance well before any glass actually breaks.
Seals do a specific job: they keep insulating gas trapped, keep the unit airtight, and block water and moisture from getting between the panes. When that seal fails, roughly 30% of the window’s insulating value goes with it, and your heating has to work harder to compensate. That’s part of why proper double glazing care matters so much for UK homes and businesses, both for comfort and for keeping repair bills down. We go into the full detail on how seal failure connects to comfort, energy use, and cost in why replacing window seals matters.
Frame joints, sills, and the connection between the wall and the frame can also let water in, which is why any proper diagnosis has to check further than the visible glass.
How Much Does Window Seal Replacement Cost?
Window seal replacement at Cloudy2Clear runs from £120 to £500 per window. The exact price depends on the size of the window and where it sits on the property, with harder-to-access windows costing more to work on than a straightforward ground-floor casement.
Repair or Full Replacement: Making the Right Call
Minor seal issues, like an early sign of shrinkage or a small draught, can sometimes be checked and monitored yourself. Full seal replacement is a different matter. Getting the seal properly seated and airtight again is a job for professionals, because a poor reseal can undermine the warranty as well as the insulation.
If you’re trying to work out whether what you’re dealing with is a leak worth calling someone about, our guide on diagnosing and fixing window leaks walks through checking frame joints, sills, and rubber seals, and even covers a simple water test: pouring water slowly along the exterior frame and seals while watching for drips inside. For sealing gaps you’ve already confirmed, 100 percent silicone applied with a sealant gun gives a smooth, controlled result, and cleaning the surface first with rubbing alcohol or white spirit helps it bond properly. A basic diagnostic tool for this kind of check costs under £20.
Where the seal itself has genuinely failed inside the unit, that’s not something silicone on the outside will fix. That’s a job for full professional seal replacement, which protects your installation warranty in a way DIY work can’t.
When Does It Make More Sense to Replace the Whole Window?
Seal replacement solves the problem when the frame itself is sound and only the glazing unit has failed. If the frame has warped, the hardware is worn out, or the window is old enough that seal failure is just the latest in a run of issues, full replacement becomes the more sensible option.
We set out the signs that point toward replacement rather than repair in why you might need to update your double glazing, and our guide on how long double glazing actually lasts covers how seal lifespan fits into the bigger picture of when a whole unit is due for renewal.
How Cloudy2Clear Replaces a Leaking Window Seal
Replace the Pane, not the Frame!
That’s been our approach since Cloudy2Clear UK Ltd was founded in 2005, and it applies directly to seal replacement. Rather than pulling out a sound frame because the glazing unit inside it has failed, we replace the unit itself.
The process starts with a free consultation and a no-obligation quote, and our engineers turn that quote around in under 20 minutes once they’ve surveyed the window and taken accurate measurements. Installation itself is quick and clean, with minimal disruption to your home or business, and it’s carried out by engineers, not left as a DIY job, which is what protects the warranty on the finished work. Kirk Williams, our Operations Manager, oversees how that standard gets applied across jobs, and Cloudy2Clear is a member of Which? Trusted Traders. We work across the United Kingdom, including England, Scotland, London, the North West, and North East & Yorkshire, on both private homes and commercial premises.
Routine maintenance can reduce energy losses by up to 15% and prevent expensive repairs later, which is exactly why we treat seal condition as something worth checking before it turns into a full leak. Our care tips for extending double glazing lifespan cover what that maintenance actually looks like day to day.
Other Glazing Repairs We Handle Alongside Seal Replacement
A leaking window is rarely the only thing that needs attention on an older glazing unit, so we handle the related jobs under the same visit where it makes sense. Conservatory window repair addresses misted and draughty conservatory glazing specifically, since conservatories bring their own exposure to the weather. Broken window repairs cover cracked or shattered panes rather than seal failure, and locks, handles, and hinges repairs keep the hardware working and matched to your existing window style, which matters for security as much as function. Double glazed door repairs fix glass faults in front doors and patio sliders without replacing the whole door or frame, the same principle we apply to windows.
Frequently Asked Questions
Can a single failed seal be replaced without changing the whole window unit?
Yes. Seal replacement targets the failed perimeter seal and, where needed, the glazing unit itself, while the surrounding frame stays exactly as it is. That’s the core of our approach: replacing the pane rather than the frame whenever the frame is still sound and the fault sits in the sealed unit.
How long will a professionally replaced window seal last?
A properly installed window seal typically lasts 10 to 20 years, keeping insulating gas like argon trapped between the panes and blocking moisture from getting in. How long it lasts on your particular window depends on exposure to weather, direction the window faces, and how well the surrounding frame is maintained.
Can I fix a leaking window seal myself?
You can manage some surface issues yourself, like reapplying silicone around a frame joint with a sealant gun after cleaning the area with rubbing alcohol or white spirit. A genuinely failed seal inside the sealed unit is a different job, and full replacement is best left to professionals to keep the insulation and any warranty intact.
Does window seal replacement come with any warranty protection?
Professional installation is what protects warranty cover on seal replacement work, which is one of the main reasons full seal replacement isn’t a DIY job. Separately, our double glazing replacement carries a 25-year guarantee on the glass itself, distinct from the PVC frame, which is worth checking against whenever you’re comparing a seal repair to a full unit swap.
If your double glazing is misting up, feeling draughty, or showing that telltale condensation between the panes, tell us what you’re seeing and where the window is using the form below, and we’ll help you work out whether a seal replacement or a fuller repair is the right next step.
