How Long Do Double Glazed Windows Actually Last?
Double glazing is one of the most common home improvements in the UK, yet many homeowners in {location} are unsure when their windows need replacing. Salespeople will tell you it's time for new ones, but what does the evidence actually say? Here's an honest look at window lifespan.
The Realistic Lifespan
Modern double glazed windows installed by a reputable company should last 20 to 30 years. Some premium aluminium frames can exceed 40 years. However, the sealed glass units inside the frames often have a shorter practical life than the frames themselves.
The sealed unit — the two panes of glass with gas between them — is the component most likely to fail first. When the perimeter seal degrades, moisture enters the gap and you get the cloudy, misty appearance that's impossible to clean. This typically happens after 15 to 25 years, though poor-quality units can fail within 10.
Signs Your Windows Need Replacing
- Misting between the panes: This means the seal has failed and the insulating gas has escaped. The window is no longer performing as designed.
- Draughts around the frame: Worn seals and gaskets let cold air in. Sometimes new seals can fix this without a full replacement.
- Difficulty opening or closing: Dropped hinges, worn gearing or warped frames can make windows stiff or impossible to secure properly.
- Visible damage or rot: Cracked frames, discoloured UPVC that's gone chalky, or timber frames with wet rot all indicate the window is past its best.
- Excessive condensation on the inside: While this can be a ventilation issue, it sometimes points to windows that no longer insulate effectively.
Can You Repair Instead of Replace?
In many cases, yes. If the frames are sound but the sealed units have misted up, a glazier in {location} can replace just the glass units for a fraction of the cost of full window replacement. New hinges, handles and gaskets can also extend the life of otherwise good frames by several years.
Full replacement makes sense when the frames themselves are damaged, warped or so outdated that they don't meet current energy standards. If your windows are pre-2002, they almost certainly fall below current Building Regulations minimums.
How to Make Your Windows Last Longer
- Clean drainage slots at the bottom of the frame twice a year to prevent water pooling
- Lubricate hinges and locking mechanisms annually with a silicone-based spray
- Keep rubber seals clean and replace them when they crack or shrink
- Don't paint over UPVC frames — it can trap heat and cause warping
What to Do Next
If your double glazing in {location} is over 15 years old, have a FENSA-registered installer inspect them. They can tell you whether you need full replacements, new sealed units, or just some maintenance. Get three quotes and don't let anyone pressure you into replacing windows that still have years of life left.