The Short Answer (And Why It Matters)
Quality double glazing has two life expectancies, not one. The frames typically last 30-35 years. The sealed glass units inside them typically last 15-25 years before the perimeter seal starts to break down. That gap is why so many UK homeowners think their windows are "finished" when they actually only need new glass.
If your home was double-glazed in the 1990s or early 2000s - the height of the UK installation boom - you're now squarely in failure territory for the sealed units, even if the frames look fine. That's exactly what we see across most of our Essex and East London call-outs.
Lifespan by Frame Material
| Frame material | Frame lifespan | Sealed unit lifespan |
|---|---|---|
| uPVC | 25-35 years | 15-25 years |
| Aluminium (powder coated) | 40-50 years | 15-25 years |
| Hardwood timber | 40-60 years (well maintained) | 15-25 years |
| Softwood timber | 20-30 years | 10-20 years |
| Composite (timber + alu) | 50+ years | 20-30 years |
What Actually Shortens Lifespan
1. Quality of the Original Installation
The single biggest factor. Sealed units packed badly, drainage slots blocked or omitted, frames not squared - these mistakes manifest 10-15 years later as premature seal failure. Budget installations from the boom years are now failing in huge numbers; quality installations from the same era are still going strong.
2. Orientation and Sun Exposure
South- and west-facing windows take the brunt of solar gain. The seal expands by day, contracts by night, and over thousands of cycles the bond fatigues. East- and north-facing units typically last 30-50% longer in the same property.
3. Drainage and Water Pooling
Every uPVC window has small drainage slots along the bottom of the outer frame. Block them with paint, dirt or sealant and water sits against the sealed unit edge - exactly the worst place. We cover this in our spring maintenance checklist.
4. External Sealant Failure
The bead of silicone between frame and brickwork is the first defence. Once it cracks, water finds its way into the cavity, and from there to the sealed unit's seal. A 30-minute resealing job every 7-10 years can add a decade to unit life.
5. Frame Material Choice
Timber frames that aren't repainted every 5-7 years allow moisture into the rebate. uPVC and aluminium are far more forgiving, but they're not invincible - dark colours absorb more heat and can warp slightly in heatwaves.
How to Extend the Life of Your Windows
- Wash frames with mild soapy water twice a year - never bleach or solvents
- Clear drainage slots with a cocktail stick every spring
- Lubricate hinges and lock mechanisms annually with light machine oil
- Check the external silicone bead each spring and re-do if cracked
- Replace cracked or shrunken rubber gaskets early - they're cheap and easy
- Repaint timber frames every 5-7 years
The Key Takeaway
When your sealed units fail at 15-25 years, the frames almost always have another decade or two left. Replacing the units alone restores full thermal performance, removes the misting, and costs a fraction of full replacement. We cover the typical 2026 prices in our double glazed unit cost guide.
If your windows are showing signs of misting or you're not sure how much life is left in them, we offer free assessments across Essex and East London.