Finding a misty layer of moisture on the windows is a common sight in many Cheshire homes, especially when the outside temperature drops. However, there is a big difference between a bit of dew on the outside of the glass and finding condensation in between window panes.
At Northwich Glass, we have been a family-run business since 1959. Over our 60-year history, we have helped thousands of homeowners understand the health of their double glazing. If you can’t wipe the mist away because it is trapped inside the unit, it’s a sign that your window is no longer doing its job, and probably needs replacing.
What causes condensation between panes?
To understand why this happens, you first need to look at how an insulated glass unit (IGU) is built. Modern windows consist of two or three panes of glass separated by a spacer bar and sealed together to create a vacuum. This space is usually filled with an inert gas like argon, which slows down heat transfer between the inside of your home to the outside.
When condensation in between window panes occurs, it means the airtight window seal has been compromised. Moist air from the outside or high indoor humidity from inside has found a way into that gap. When the temperature of the glass drops, that moisture turns into liquid, leaving your windows looking permanently “fogged.”
Misted windows: what causes a seal to break?
Seal failure is the most common reason for misty windows and several factors can lead to a broken window seal:
- Age: Even the highest quality seals have a lifespan. Over decades, the materials naturally degrade.
- Temperature fluctuations: The constant expanding and contracting of the glass panes (known as solar pumping) can eventually stress the seal until it snaps.
- Poor installation: If the window was fitted incorrectly or the window frame doesn’t allow for proper drainage, standing water can rot the seals prematurely.
- Incorrect maintenance: Harsh chemical cleaners can sometimes strip away the integrity of the sealant over a long time.
Is it a serious problem?
While a bit of mist might seem like a purely aesthetic issue, it actually indicates significant energy loss. Once the seal is broken, the argon gas escapes, and your window loses its insulating properties.
This directly impacts your home’s energy efficiency. You may notice your energy bills rising as heat escapes more easily, or you might feel a noticeable chill near the window. Essentially, your double glazing has reverted to being not much more effective than an old single-pane window.
Fixing the issue: is a repair possible?
A common question we hear at Northwich Glass is whether you can simply “reseal” the window. While there are DIY kits or companies that offer to “de-mist” windows by drilling small holes to vent the moisture, these are often temporary fixes. They do not replace the lost insulating gas, meaning the thermal performance remains poor. Usually, once moisture has entered the unit, the internal spacer bar becomes saturated, and the fogging will eventually return.
When replacement is the best option
In most cases, the most cost-effective and long-term solution is to replace the insulated glass unit.
The good news is that you often don’t need to replace the entire window or the frames. If your frames are still in good condition, we can simply manufacture and install new glass units. This restores the energy efficiency of your home and provides a clear view again without the cost or disruption of a full installation. However, if the frames are warped or also showing signs of age, a full replacement may be more beneficial for your long-term comfort.
How to prevent future issues
While you can’t stop the passage of time, you can protect your windows by:
- Keeping humidity levels in the home under control using extractor fans in kitchens and bathrooms.
- Checking that the drainage holes in your window frame are clear of debris.
- Ensuring you choose a reputable installer. As of 2026, the quality of modern gaskets and warm-edge spacer bars has significantly improved, making current units much more resilient than those fitted 20 years ago.
Get a clear view again
At Northwich Glass, we understand that home improvements can feel daunting. Whether you are dealing with a single foggy pane or looking to upgrade your whole home’s thermal performance, our experienced team is here to help. We ensure that your installation is handled professionally and with minimal disruption so if you have noticed condensation trapped inside your windows, contact the Northwich Glass team today for expert advice and a professional assessment.
- Visit us: https://www.northwichglass.co.uk/contact-us
- Call our team: 01606 810 000
- Email: reception@northwichglass.co.uk
