Get a quote and call our team on

020 4587 8300

Request Quote
Blown Double Glazing - Misted Window Repair & Cost Guide


Blown Double Glazing – Misted Window Repair & Cost Guide

Myles Robinson
Written by Myles Robinson
Updated on 18th July 2024
Posted on 13th March 2024

Blown and Misted Double-Glazed Windows

Misted Windows Caused by Blown Double Glazing

Are you curious why your double-glazed windows aren't doing what they're supposed to?

Well, one of the possibilities is blown double-glazing!

Get a fixed quote

Dealing with blown double-glazing means misty windows and soaring energy costs.

In this guide, we cut through the fog to outline the why and how of failed double-glazing - covering detection, repair, and cost insights - with actionable solutions to restore your home’s comfort and efficiency.

Plus, we’ll share prevention tips to shield your windows from future fogginess.

Double-Glazing Windows Blown - Overview

  • Blown double-glazing occurs when the seal between the two panes fails, leading to condensation and diminished insulation, which can be repaired or replaced to restore functionality.
  • Key indicators of blown double-glazing include internal condensation, increased heating bills, and heightened noise penetration, urging the need for professional assessment and intervention.
  • Proper maintenance and regular checks of double-glazed window seals can prevent blown glazing while upgrading to A-rated energy-efficient glass during repair can enhance thermal performance and reduce energy costs.

Understanding Blown Double-Glazing

Before you jump to any conclusions, we will explain how double glazing works and what blown double-glazing means so you can determine whether this is the problem with your windows or if you have another issue entirely.

Blown double-glazing is when the seal between the two panes of a double-glazed window fails.

This failure allows moisture to seep in and condense on the glass’s cold surface, leading to misty windows, a tell-tale sign of blown double-glazing.

The effectiveness of double-glazing is rooted in its structure, which consists of two glass panes separated by a thermally efficient spacer bar.

This setup forms an insulating barrier filled with trapped air or gas that retains heat and wards off cold air.

However, when the seal fails, this insulating barrier is compromised, leading to decreased energy efficiency and the unsightly phenomenon of misted double-glazing.

Fortunately, a failed double-glazed unit is not a lost cause and can be repaired or replaced with replacement double-glazed units.

Taking prompt action to fix misted double-glazing restores your windows’ aesthetics, energy efficiency, and noise insulation capabilities, preventing your double-glazed window from failing.

For this reason, seeking professional double-glazing repairs is essential.

Signs You Have Blown Double-Glazed Windows

Early detection of blown double-glazing can save significant time and money.

What indicators should you pay attention to?

One of the most prominent signs is condensation between the window panes. This is usually a clear indicator that the seal has failed, allowing moisture to seep in and condense on the cold interior surface of the glass.

Another sign is a noticeable increase in your heating bills.

As the insulating properties of your double-glazing diminish, more heat escapes from your home, causing your heating system to work overtime and leading to higher energy costs.

Lastly, if you notice more external noise penetrating your home, it might be a sign of blown double-glazing.

The compromised insulation allows sound waves to pass through more easily, increasing noise levels inside your home.

So, if you notice condensation between the window panes, higher energy bills, and increased noise levels, it might be time to contact a professional to assess your double-glazing windows.

Effects of Blown Double-Glazing

As a homeowner, you should also learn more about the effects blown windows can have, which will make it much easier to spot if your home is having problems.

Blown double-glazing impacts more than just the inconvenience of misted windows. One of the most significant impacts is on your energy bills.

As the sealed double-glazed unit's insulating properties diminish, heat loss increases, leading to higher energy consumption. This affects not only your pocket but also your home’s energy efficiency.

Additionally, blown double-glazing can negatively impact the value of your property. Broken or damaged windows can decrease a property’s overall value, making it less appealing to potential buyers.

Therefore, promptly addressing any signs of blown double-glazing is in your best interest.

Moreover, the condensation between the glass panes of a blown window can cause further damage.

Over time, this moisture can lead to draughts, leaks, and reduced insulation, potentially damaging window frames and surrounding areas.

This underscores the importance of addressing blown double glazing as soon as it’s identified to prevent further damage and associated double-glazing costs.

Professional Assessment of Blown Windows

Now, even with this guide, we understand that not everyone will be confident evaluating the state of their windows, so calling an expert can be another great option.

Professional evaluation plays a vital role in addressing blown double glazing. Experts in the field can conduct an extensive inspection to identify any damage signs and accurately diagnose the cause.

Get a fixed quote

These findings can guide the most appropriate repair or replacement strategy, which often involves replacing the glass unit while retaining the existing frame.

Identifying the Cause

Blown Double-Glazed Window

The first step for professionals evaluating blown double glazing is pinpointing the cause.

Often, these issues can be traced back to manufacturing faults.

Such as damaged casement window seals from defective materials or faulty installation processes.

Installation errors are another common cause.

If the window is not fitted correctly or the seal is not applied properly, faults can develop in the double glazing, requiring a fix for double glazing condensation.

Moreover, chemical damage can lead to the gradual deterioration of window seals, facilitating moisture ingress into the unit.

Finally, a window's age can contribute to blown double glazing. Older windows are more susceptible to seal failure, resulting in foggy or misty windows.

High-quality double-glazed windows can remain intact for 15 to 20 years before experiencing blown glazing.

Windows 10-15 years old may have a wider gap between panes, making them more vulnerable to blown glazing.

Evaluating the Extent of Damage

After identifying the cause, professionals proceed to assess the level of damage to decide the most suitable course of action. This involves looking at factors such as:

  • condensation
  • broken seals
  • the age and condition of the window frame
  • the impact of rapid temperature changes

Professionals use a variety of tools and techniques in this evaluation process. These may include:

  • Smoke
  • Curtains
  • A flashlight
  • Thermal cameras
  • Specialised glazing tools include hand tools, vacuum lifters, and mini cranes.

Based on the evaluation, a decision will be made on whether a repair or full replacement is necessary. If there is damage to:

  • hinges
  • locking mechanisms
  • handles
  • gaskets
  • sealing
  • rust
  • drafts
  • damaged hardware, such as screws and locks that impact its functionality

In some cases, the sealed unit may be fully replaced.

Minor issues might be manageable with repairs, whereas severe structural problems will likely necessitate a full replacement to prevent further issues.

Repair Blown Double-Glazing

If you are confronted with blown double-glazing, there’s no need to panic.

It is often possible to repair misted double-glazed windows without replacing the entire window, which can save homeowners time and money.

While renewing the entire window’s seal is a potential solution, it doesn’t effectively resolve the existing misting or condensation between the panes.

Instead, replacing the glass unit is the preferred action for a lasting resolution.

Professional glazing companies follow a standardised process, including a thorough damage assessment, to repair blown double-glazing effectively.

Additionally, they typically offer a guarantee on the replacement glass unit, ensuring long-lasting results and reassuring the customers.

When repairing or replacing a foggy double-glazing unit, it’s also a good time to consider upgrading to A-rated energy-efficient glass.

This enhancement can not only improve thermal performance but also potentially result in decreased energy expenses.

Get a fixed quote

Blown Window Replacement

Misted Double-Glazed Window

A full window replacement might sometimes be required if repairing the blown double glazing isn’t enough.

This is often advised when encountering severe misting issues or structural damage or when planning to upgrade to more energy-efficient glass.

By replacing the entire window unit with a new, energy-efficient one, you can enjoy enduring benefits such as:

  • Improved insulation
  • Decreased heating expenses
  • Enhanced visual appeal
  • Potentially augmented property worth.

Double-glazing companies will likely do this as this won't be covered under window grants, but these installers will likely offer various payment methods to make things easier.

And the good news is, often, there’s no need to replace the window frames when addressing blown double glazing. If the frames are in good condition, simply replacing the glass units is adequate.

Cost of Repairing or Replacing Misted Windows

After going through what a blown window is and what you can do to repair it, the next most important thing is obviously the price of it.

You might wonder about the cost of repairing or replacing misted windows. The cost is influenced by factors such as:

  • The type of window
  • The material of the frame
  • The location of the property
  • The size of the window

Typically, you can expect to pay anywhere from £50 to £200 per window, depending on these specific conditions and requirements.

The costs for replacing misted windows in old fenestration systems or timber double-glazing are generally higher.

This is especially true for properties with older fenestration systems or timber double-glazing, particularly when the units are secured with putty instead of wooden beads.

Conversely, replacing misted windows with modern energy-rated aluminium or uPVC double-glazing is a more straightforward and frequently less expensive procedure for homeowners in the UK.

You can also see the cost of double-glazing a 2-bedroom house to get a better idea of what the replacement costs might end up being.

Double-Glazed Window Maintenance

Although repairing or replacing blown double-glazing is important, preventive measures are always more beneficial.

Regular maintenance for double-glazed windows plays a paramount role in extending the lifespan of your windows and preventing blown glazing.

Checking the seals on your double-glazed windows regularly, preferably every five years, is an integral part of your maintenance routine to maintain their functionality and insulating capacities.

In addition, keeping your home well-ventilated can help prevent condensation from forming inside your windows. Remember, condensation is a common precursor to blown double glazing.

By taking these preventative measures, you can save yourself the time, money, and hassle of dealing with blown double-glazing and fix double-glazing condensation issues.

Get a fixed quote

Misted Double Glazing Repairs - Our Verdict

With this guide ending, it's time for a few final thoughts on blown double-glazed windows and how to fix them.

Blown double-glazing is a common issue that can affect a home's aesthetic appeal, energy efficiency, and noise insulation.

It is caused by the failure of the seal between the glass panes in a double-glazed window, leading to condensation and misting.

By understanding the causes and signs of blown double-glazing, you can take the necessary repair or replacement steps.

Regular maintenance will help you extend the lifespan of your windows and maintain your home’s comfort and value.

Remember, prevention is better than cure; a little attention now can save you significant time and money.

Frequently Asked Questions

Is blown double-glazing less efficient?

Yes, blown double glazing is less efficient due to damage to energy efficiency, increased energy consumption, and heating bills. The noise insulation is also compromised.

Does blown double-glazing cause dampness?

Misted Window

Yes, blown double-glazing can cause condensation, which, if left untreated, can lead to dampness and mould.

This can pose a risk to your family's health.

Does insurance cover blown double-glazing?

Yes, blown double-glazing is usually covered under your household building insurance.

However, if the blown double glazing is caused by attempting to remove Georgian and astragal bars, then it most likely won't be covered by warranty, as window bars shouldn't be removed.

Can you repair the blown double-glazing?

Technically, blown double-glazing can be repaired by renewing the seal on the entire window, but this won't eliminate the misting or condensation inside the panes, so it's not recommended.

What is blown double-glazing?

Blown double-glazing occurs when the seal between the glass panes of a double-glazed window fails, leading to misting and condensation.

Get a fixed quote

Written by
Myles Robinson
Myles Robinson Marketing Director
Posted on: 13th March 2024
Topic: Advice

Myles is dedicated to sourcing and fitting the best composite doors and windows. His mission is to offer our customers exceptional deals on energy-efficient composite doors, focusing on reducing costs while making sure the most advanced technology is readily available for installation. This commitment is what motivates Myles in the door industry.

More articles

Build Your Doors & Windows Online Design Online Here ➜