How long do double-glazed windows last?

Author: Mabel Glover  |  Last update: Monday, November 17, 2025

A double glazed window made today will typically have a lifetime of 25-30 years, and possibly more if they are installed in a sheltered location that is not subjected to extreme weather. Double glazed windows that are more exposed and regularly encounter weather can expect a lifespan of around 20 years.

How do I know when my double glazing needs replacing?

Clear signs of double glazing failure include:

Condensation forming on the interior of your window or between panes. Chips in the glass itself. Water is leaking through the frame. Your Energy Bills have risen disproportionally.

Is it worth replacing 20 year old double glazing?

Yes! Double glazing installations have an average lifespan of 15-20 years. Given this suggested longevity, older double glazing will likely be outdated and not provide the same level of energy efficiency and soundproofing as newer glazing.

What are the disadvantages of double glazing?

What are the disadvantages of double glazed windows?
  • Double glazed windows require the same cleaning as a single pane window. ...
  • Over time the window may need resealing and the efficiency of the glazing will wane. ...
  • If the glazing on the windows wears down over time you may need to replace the window or have them reglazed.

How many years do double glazed windows last?

A double glazed window produced today will have a lifetime of 25-30 years and more if fitted in a sheltered location and not subject to any extreme weather. A double glazed window that does face exposed weather will expect a lifespan of 20 years.

Double Glazing! The Little unknown Truths.

How to tell if your double glazing has failed?

How Do I Know If My Double-Glazing Needs Replacing?
  1. There Are Noticeable Draughts Around Your Windows. ...
  2. There Are Noticeable Chips or Cracks in the Windowpane. ...
  3. You Have the Irritating Problem of Condensation. ...
  4. Your Windows Have Water Leaking In. ...
  5. Your Energy Bills Have Been Increasing. ...
  6. Difficulty Using Windows.

Should I replace 50 year old windows?

Windows that are over 20 years old should be replaced. If you've lived in your home for decades and have never replaced the windows, they are likely original to the house. Replacing your windows will keep you up-to-date with the latest window technology. Older windows are likely to be made with pane glass.

What is better than double glazing?

Double- or triple-glazing

Triple glazing performs even better than double glazing to further reduce heating and cooling costs and is ideal for colder Victorian climates.

Do double glazed windows need to be sealed?

Failed double glazing can end up costing you more in the long run, as it's no longer effective if your window seal has failed. You'll lose money on energy bills. 20% of heat in the home is lost through windows and doors. Once your window seal has failed, cold air from outside is free to enter the home.

How much does a single double glazed window cost?

For a single double glazed window you can expect to pay £160 – £1,030, and up to £1,800 for bay windows with 3 panels. Are there any grants for double glazing in 2025? Several grants for windows could apply to residents in the UK, including ECO4, the Home Upgrade Grant, and Home Energy Scotland Grant and Loan.

How can you tell if double glazing is good quality?

Shine a Light – Wait until dark, go outside and have someone stand inside shining a flashlight towards the window. If you can see pinpricks of light escaping around the window, then there are obvious leaks. Thermal Camera – Having access to an infrared camera can also reveal hot spots from windows.

Can you replace double glazing without changing frames?

In short, yes! If your windows aren't as energy efficient as they used to be, you can replace the double glazed glass unit without having to replace the whole window.

What is the U value of 20 year old double glazed windows?

The lower the number, the better the energy efficiency is. Old single-glazed windows can have U-values of around 5.8 W/m2K, and older double-glazed windows can be around 2.8.

What is the best time of year to buy double glazing?

Double glazing companies often have sales at slower times of year such as January or July, when fewer people are in the market to buy new windows. This can be a good time to benefit from special offers and make decent savings on the cost of your new windows.

How can you tell if a double-pane window is bad?

How Do I Know if My Double-Pane Window Is Bad?
  1. You Feel a Draft. Run your hand around your window frame. ...
  2. You See Condensation. If water is condensing on the inside surface of your window, it's probably not the window's fault. ...
  3. Your Energy Bills Are Going Up. ...
  4. Your Frames Show Wear and Tear.

How often should house windows be replaced?

Home windows have a lifespan of 15-20 years. Once they reach this age, the seals start to weaken or fail, which leaves you open to drafts and water seepage. In addition, single-pane windows were the standard 15+ years ago. These windows lack insulation and are not as energy efficient as modern double-pane windows.

Can you reseal double glazed windows yourself?

Yes, you can reseal windows yourself, but it's a complex task best left to professionals. DIY resealing might not guarantee the functionality of your double-glazed windows, so for optimal results, hiring a window specialist is highly recommended.

How can you tell if double glazing has blown?

Common Signs of Double Glazing Failure
  • Fogging, Misting and Condensation. One of the most noticeable signs of a failing double glazing unit is the appearance of fogging or condensation between the panes. ...
  • Draughts and Temperature Fluctuations. ...
  • Increased Energy Bills. ...
  • Leaks. ...
  • Cracked Glass, Scratches and Chips.

Do new double glazed windows need vents?

Background ventilators are required on most replacement and new windows under Building Regulations.

How much heat is lost through double glazed windows?

Single-pane glass can lose up to ten times the heat of the same area of an insulated wall. Double glazing can reduce that heat loss by as much as 50%, while triple glazing can cut heat loss even further to around 20%.

Why is double glazing so expensive?

Expensive double glazing often features advanced technologies, such as low-emissivity (Low-E) coatings and inert gas fills between the glass panes. These innovations enhance thermal insulation, reducing heat transfer and contributing to a more energy-efficient home.

Is it worth tinting double glazed windows?

Heat passes much slower through a double glazed window than a single pane window, trapping heat in winter and keeping it out on hot summer days. Unfortunately, double glazed windows alone are not a shading device, which is exactly where window tinting comes in handy.

What time of year should you buy windows?

January and February weather doesn't inspire many homeowners to shop for new windows and doors, but that's exactly the time of year when you can save money on an order that will be ready for spring installation.

How much should you spend on replacement windows?

Our research shows that window replacement costs an average of $554 per window, depending on the window style, frame material, and brand you choose. However, replacement window costs can range between $100 and $2,500 per window.

How can I tell if my windows need replacing?

5 Signs Your Windows Need Replaced
  1. Do you ever find yourself asking, “do I need new windows?” ...
  2. Difficult to Operate. ...
  3. Uncomfortable Drafts or Poor Energy Efficiency. ...
  4. Single-Pane Windows. ...
  5. Fading Interiors. ...
  6. Outdoor Noise. ...
  7. Poor Curb Appeal or Outdated Style. ...
  8. Take a Step Toward Replacement Windows.

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