The Cost of Replacing a Blown Window

All you need to know about repairing and replacing blown glass windows, including costs of materials, labour and time frames.

Replacing a Blown Glass Window

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A complete guide to replacing a blown a window

When your view is obscured by a blown glass window, it makes sense to get them replaced. If you have decided to replace your blown window, use this guide to help you understand what’s involved in the process. This guide will give you a clear understanding of the costs involved and the time frames that you can expect.

What is involved in replacing windows?

Over time double glazed windows may become cloudy, largely because the seal between the two panes of glass has begun to leak. The problem is called a blown window and may be particularly bad when temperatures drop. The non-toxic gas that is sealed between the two window panes is the key to the glazing’s energy efficiency, so if you have a blown window, your double-glazing will not be functioning properly either.

But what does window replacement entail?

What should you expect when planning to carry out your blown window replacement? If you have a blown window, it may not be necessary to replace the entire window, you may find that you can replace the double-glazed unit on its own.

To begin the work, your tradesman will measure the glass unit carefully and order the replacement. The glass that arrives will have been cut to fit into your window frame and account for all of the frame-fixing measurements. Next, the old unit with the blown window will be removed and the new one installed.

After the new window is fitted, you may find that you need to employ additional tradesmen to paint or decorate the space around the window, or possibly the entire wall that surrounds the window.

It is possible to replace a blown window yourself, but as this is a technical job that must be done accurately, you may find it easier to employ an experienced tradesman to do it for you in less than half the time. Moreover, if your window is located within a load-bearing section of wall then the risks are even bigger.

If your window is not installed properly, its lifespan will be short, so it is worth getting an expert window fitter to do it for you. Poorly installed windows will leak, let in draughts as well as noise and will not work effectively as an insulator.

Further, it is very easy to easure up the space for the window incorrectly and end up with a window that you cannot use. In addition, you will also need to know the type of glass that is needed, including the correct thickness, whether the glass is toughened or tinted etc.

There are many different types of windows around, so it is worth doing some research. For some newer models of glazing, anti-theft blocks can slow things down and cause your installation to take longer.

When your new window is in place, you will find that the room requires more ventilation than before because your fresh windows will be more airtight and retain more moisture. With this in mind, you may want to install double glazed windows that have trickle vents, so that there is an effective level of ventilation. Additionally, you may find that there is further work required to the area around the window.

Therefore, as you calculate the cost of replacing your blown window you will want to consider the specific type of window that you need as well as other tradesmen that you may want to be involved, such as plasterers, painters or decorators. You will also need to consider the time to carry out the initial measurements and clean up the area when the job is complete. All of these factors will affect the final cost of the work.

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Cost of replacing a blown window?

The average cost of replacing a blown window is around £60 - £400, depending on whether you need to have the entire window replaced or just the double-glazed unit repaired.

The price is going to vary depending on the size of the panel you are replacing and the ease of access to it. The cost to repair a sash window is going to vary depending on the condition of the unit and the number of panels that need replacing. It can be common that when a window blows that the frame may need additional repair work or replacing. This is an additional cost you may need to bear in mind depending on the condition of your window.

Your tradesman will usually work at a cost of around £100 – £150 per day.

Below are some estimated costs of hiring a specialist to replace a double glazed blown window:

Description Avg. Cost Duration
Replace a small blown double glazed window - opener £60-£90 1-2 hours
Replace a blown sash window £50-£120 1-3 hours
Replace a standard blown double glazed window £150-£300 1-3 hours
Replace typical uPVC 3 panel bay window £600-£850 2-6 hours

Cost Breakdown Calculator For Replacing a Blown Window

Individual costs of replacing a large blown glass window - Total Cost: £300






Waste Removal


Given the right factors, most double glazed windows will usually last for around 20 years, some may even last as long as 30. Therefore, it is worth ensuring that you choose a good quality brand and have your windows properly installed so that they last for a long time.
Yes, around 10% of your home’s heat is lost through your windows and doors. Although replacing your windows with Double glazing can be an expensive outlay, by swapping to more energy-efficient double-glazed windows you can save hundreds of pounds annually, as well as keeping out unwanted noises too. The insulating gap between the two sheets of glass that create the double glazed window stops warm air from escaping from your house so quickly. You can even get triple glazed windows with two gaps positioned between three panes of glass for extra insulation. Low emissivity glass is the most powerful type of glass for double glazing. Low emissivity glass features an invisible coating of metal oxide on one of the internal panes of glass that adds an extra layer of energy efficiency to its performance. The British Fenestration Rating Council have created an energy efficiency rating to make it easier to see how effective different types of windows are. The rating ranges from G to A+ and includes the performance of both the glass and the frame that make up the window unit. The best-rated windows may display the Energy Saving Trust Recommended symbol to make them easier to identify.
Yes, double glazing windows is a popular and easy way to add value to your home.
Traditional wood is still a popular option because of its classic aesthetic and robust quality, however, the long-term damage from rot and heat is a downside. Fibreglass is often chosen as a more long-lasting alternative to wood that is also easy to maintain. Vinyl is the most cost-effective and energy-efficient option. Available in a wide range of different styles and colours too, vinyl is a great choice for replacement window frames.