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Should I Replace or Repair My Double Glazed Windows?

Written By:

Reviewed By:

Leonardo David

Updated on

Measuring replacement double glazing

A double glazing replacement is an investment that improves the energy efficiency of your home while adding property value. However, double glazing can be expensive – as a homeowner or renter, you should thoroughly understand your options before paying for new windows.

  • New double glazing is typically more energy efficient, and it can save you hundreds of pounds during its lifespan.
  • Considering the high energy costs in the UK, an upgrade to A++ rated double glazing can save you over £180 per year. Over a 25-year period, you can save over £4,500.
  • You can expect to pay over £370 per window if you choose uPVC frames.
  • The top double glazing providers normally offer 10-year guarantee, but windows can last more than 30 years with proper maintenance.

If you’re considering a double glazing replacement, here you can read about your options and how to get the best deal.

We’ll also go over when to repair your double glazing, and replacements are not required.


You will find in this guide:


How much does it cost to replace windows?

Double glazing costs vary depending on several factors including your location, window type, window size, frame material, and what you need replaced. You will likely pay between £372 and £961 per window, assuming new glazing and uPVC frames, but specific costs depend on the windows you choose.

Generally, the most important factors that affect costs are window material, size, type, and installer. For example, large bay windows can cost thousands of pounds each, while a small casement window may cost just over £300.

What does a double glazing quote include?

Online window quotes include a preliminary cost estimate, based on details you give to the installation company. However, online quotes are not 100% accurate because they are provided before the installer inspects your home. For example, the installation company does not know the conditions of your wall and the exact location of every window. At best, online quotes are a rough guideline to compare window companies, but they don’t reflect the exact amount you will pay.

Make sure your double glazing replacement quote includes all the following costs:

  • Removing old windows
  • New glazing
  • New frames
  • Installation services
  • Final cleanup
  • Guarantees

Once you have a signed contract, the installer is not legally allowed to exceed the listed price.

How long should double glazing last?

The lifespan of double glazing is almost always determined by the frames and seals. uPVC windows can last between 10 and 35 years depending on their material quality, installation quality, location, etc.

You can expect the following costs for mid-range to high-end casement windows, according to the UK Federation of Master Builders:

Material  Cost  Typical LifespanCare Requirements
uPVC£372 – £96120-35 YearsLow maintenance
Aluminium£744 – £1,14730-50 YearsLow maintenance
Timber£1,147 – £1,82950+ YearsHigh maintenance
Composite   £2,046 – £3,59640+ YearsHigh maintenance

Your windows can reach their maximum lifespan if you provide regular maintenance, keeping them dry and clean, and making sure they are closed properly. If your glazing shows issues but the frames are still in good shape, you can replace only the glazing to save money.

Sealing – In many cases, the seal is the first part of a window to develop problems, and this can happen even if the frames have received proper care. Ideally, your window seals should last for 10-35 years while having a warranty of at least 5 years. High-quality windows are normally covered by a guarantee for 10 years or more.

Paint – Wood and composite windows require painting or finishing every 2-5 years to provide protection and prevent rotting. If this isn’t done, you will void the window warranty and they will fail much sooner.

Check Your Warranty Terms

If your glazing starts to fail and your windows are still under warranty, you could have them replaced or repaired free of charge. However, if the damage is due to improper care or usage, your warranty will be void. Although the exact terms vary by manufacturer, the following warranty terms are typical for high-quality windows:

Warranty   Length  
Hardware  10 Years
Workmanship  5-10 Years
Sealing  10 Years
Stain and Paint Finishes  5-8 Years

Benefits of replacing windows

When you replace old double glazing, you save on energy bills. However, this is just one of many benefits:

Save money – Modern double glazing offers significant energy savings. According to the Energy Saving Trust, A++ rated glazing can save over £180 per year, but your actual savings can be even higher with today’s rising energy costs. The energy efficiency of windows is described by their U-value, where a lower U-value indicates a smaller heat loss through the window – and higher energy savings. Old glazing has a typical U-value between 2 and 5, while modern double glazing has a rating of around 1.2. According to Everest, a leading window provider, an upgrade from 2.4 U-value to 1.22 U-value windows can save you £312 per year.

Noise reduction – A window replacement is also an opportunity to choose glazing with better noise insulation. Acoustic double glazing can reduce noise levels by up to 75-95%, especially if you live in a noisy home. This may be worth the upgrade even if you plan to move, since reduced noise levels will increase the value of your home.

Style changes – A double glazing replacement also offers an opportunity to change the appearance of your home. For example, if you moved into another home and don’t like the windows, a glazing upgrade gives you the opportunity to choose another style.

Material changes – uPVC is the most common window material UK, but also the least valuable in the real estate market. If you want to add value to your home, you can choose a longer-lasting material like aluminium or timber. Some homeowners also prefer these materials for their appearance.

Upgrading to triple glazing – Triple glazing offers better insulation and soundproofing than double glazing, but its cost is also higher. While modern double glazing has a U-value of around 1.2, triple glazing has typical U-value of 0.8. Triple glazing is close to the U-value of a standard wall, which is 0.5. While triple glazing may not pay off the added cost with energy savings, it makes your home more comfortable thanks to its noise reduction properties. Triple glazing is also more effective at preventing hot and cold spots.

When to replace double glazing?

You might be wondering if you need a full glazing replacement or only certain repairs. While a complete replacement offers several benefits, as discussed in the previous section, repairs are much less expensive. The following are some cases where you should definitely consider a complete replacement:

Damaged Glass – If your glass is damaged, replacing it is the only option. However, you could save money by keeping your old frames if they are in good condition. Actually, most window frames are designed to have their glazing replaced if necessary.

Damaged Sashes – Unfortunately, if a window sash is damaged, you will most likely need to replace the whole window. This applies for rotting timber, warped uPVC, and discoloured or broken sashes. You might be wondering why the glass cannot be reused? Removing glazing from a window sash in one piece is very difficult, unless the seal is completely damaged.

Broken Sills and Jambs – If these components are damaged but the sash and glass are still in good condition, you can replace only the sills and jambs. In this case, you can save money by reusing the sash and glazing.

Fogging or Condensation – Fogging and condensation between the panes mean that the double glazing seals have been broken. This cannot be fixed in most cases, which means you will need a glazing replacement. However, it might be possible to reseal the window if the damage is still small.

Old Seals – Most seals will only last for 10-20 years, or a little as 5 years in some cases. You may be able to reseal your windows if there have not experienced fogging or condensation, but otherwise you will need a glazing replacement. You may be able to reuse the frames if they are in good condition.

Condensation on double glazing: When is it normal?

Double glazing can experience different types of condensation. When condensation forms on the surface of glass panes, it does not represent a problem. However, condensation between the glass panes normally indicates that the seals are damaged.

Exterior Condensation – Condensation on the outside-facing glass surface can be annoying, but there is no need to worry. External condensation forms when the outdoor air is humid and warmer than the surface of your windows – this can happen under various weather conditions. This is exactly like the condensation that forms on a glass with cold water. If exterior condensation is excessive, you can try opening a window for a few minutes to increase airflow.

Interior Condensation – Interior condensation is caused by the same physical principle as exterior condensation. This happens when the air inside your home is damp and a higher temperature than your windows. For example, interior condensation may form while you are cooking or taking a bath. In this case, you can also reduce condensation by opening a window, or you can wipe the windows with a towel.

Condensation Between the Glass – If your double glazing is fogging up, or showing water beads between the panes, the seal is damaged or worn out. You will most likely need a window replacement in this case. It might be possible to reseal the double glazing, but this can only be determined with an inspection by a qualified installer. In both cases, the only option is contacting your window provider.

Can I fix double glazing condensation by myself? – There is a common myth that you can fix condensation in double glazing by drilling a hole and allowing air to circulate. Unfortunately, this is a temporary solution and you will most likely have the issue again in a few months. You will keep repeating the “fix” when condensation shows up, making your windows less and less efficient each time.

Replacing single glazing

If your home still has single glazing, you can save money by upgrading to double glazing. For example, if you have not replaced your windows in 20 years, you could save over £300 per year with double glazing. Depending on the frames you pick, you could recover your investment in around 10 years.

Secondary glazing – If you have old single glazing but the frames and the glass are in good shape, you may be able to save money by installing secondary glazing. Here, the installer will place a second pane of glass against your frame and seal it. Secondary glazing is not as efficient as double glazing, since it does not include a layer of gas to buffer against hot and cold weather. However, secondary glazing can improve the energy efficiency of your home at a very reasonable cost.

Can I replace double glazing by myself?

Unless you are a professional window fitter or glazier, the answer is no. Glazing is very difficult to seal and easy to break, and mistakes can cost you thousands of pounds. Also consider that window manufacturers will normally void their warranty if glazing is not installed by a professional.

Can I buy double glazing by myself?

If you purchase double glazing directly from a window manufacturer, you may save around 20-30% in some cases. However, this can backfire because you must look for a glazing installer anyway. In addition, many window installers offer deals if you purchase glazing with fitting services included. The best recommendation we can give is always comparing multiple quotes, and taking the time to read what is included in each quote.

When to repair double glazing?

In many cases, you can choose to repair your double glazing rather than having it replaced. This may be a good choice, especially if your windows are less than 10 years old. On the other hand, a full replacement is likely a better option if your glazing, frames or seals are near the end of their lifespan.

Resealing double glazing – A competent glazier or fitter may be able to reseal your windows in some cases. This means removing the old putty and adding a new desiccant and putty around the glass panes. However, this method will not work if you have argon double glazing or a similar gas-filled window.

Overhauling and draught reduction – A draught-proofing procedure will typically include resealing, new sashes, and other repairs as necessary. This is the best option if your windows are mostly in good shape, but you are getting drafts or condensation.

Retrofitting old frames – Retrofitting old frames is the cheapest way to upgrade double glazing. Since you don’t have to purchase new frames, you can cut project costs by over 50%. However, this is not possible if your frames are very old, damaged, or not deep enough for double glazing.

What are double glazing inserts? – Double glazing inserts are installed around the frame of a window to add extra sealing to the window. However, these fixes are temporary at best, and will not seal your window for long.

Is repairing the best option? – Repairs can represent a waste of money if your windows are damaged or near the end of their lifespan, since you have to replace them in a few years anyway. Generally, repairs are recommended if your windows are not very old, and their damage is not extensive.

How long does it take to replace double glazing?

Replacing double glazing will typically take 2-3 weeks in total, and about 8-12 hours of actual window fitting.

  • Survey to provide an accurate quote = 1-2 hours
  • Measuring windows and openings = 1-3 hours
  • Removing Existing Windows =Between 30 minutes and 2 hours per window
  • Fitting and sealing the windows: About 1-2 hours per window
  • Finishing and adding trim: 30-45 minutes per window
  • Cleaning up debris and tools: 2-3 hours
  • Total: 12 – 26 hours for a 4-window installation

Multi-story homes will take longer to fit, as you might expect.

Will a double glazing replacement save me money?

Double glazing will reduce your energy bills, in some cases by more than £200 per year. However, energy savings alone are unlikely to pay off the full cost of a double glazing replacement – unless your windows are very old, or you can get an excellent deal. However, a double glazing upgrade also brings other benefits: you will increase the value of your home, while improving comfort and reducing noise levels.

If you are concerned that your double-glazed windows may not pay themselves off, here are some quick recommendations:

  • Make sure you know the energy rating of your current windows.
  • Look for uPVC windows with low-E glass to maximize your energy savings.

How to save on double glazing replacement costs?

If you are replacing double glazing, it is important that you get the best possible price. While double glazing can be expensive, here are some tips that can help you achieve a much lower cost:

Know what you need – Double glazing sales representatives are often tasked with charging you as much as possible, which means you might get a ridiculously high quote. You may see quotes drop by as much as £10,000 in a single meeting, and even then, the offer could still remain overpriced. Make sure you know what you need, what it should cost, and why you need it – so that a sales representative cannot talk you into a more expensive option. To make sure you have time to research, don’t accept any “today-only” offers.

Using old frames – Retrofitting your old frames can save you a great deal, even if you want to replace your old glass with higher quality glazing. Just make sure that the frames are in good shape and deep enough for double glazing.

Written By

Ollie Smith Photo

Ollie Smith

Ollie is the director of Ecopreneurist, with a string of successful publishing brands under his belt, he aims to make the world a better place by showcasing only the best, unbiased and reliable content on the web!

Reviewed By

Leonardo David Photo

Leonardo David

Leonardo David is an electromechanical engineer, MBA, energy consultant and technical writer. He has also been writing articles about energy and engineering topics since 2015.

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