The short answer
Double glazing typically lasts 20–35 years, though the sealed glass units inside the frames may start to mist from around 10–20 years. The frame usually outlasts the glass: when a sealed unit fails, you can often replace just the glass rather than the whole window. Lifespan depends on the quality of manufacture and installation, the frame material, the level of exposure, and how well the windows are maintained. These are typical illustrations — many windows last longer, some less.
How long double glazing lasts is really two questions: how long the frames last, and how long the sealed glass units last. They are different components with different lifespans, and understanding that helps you plan repairs and replacement sensibly rather than assuming a misted pane means the whole window has failed.
Lifespan at a glance
- Whole window (typical) 20–35 years
- Sealed unit before misting 10–20 years
- uPVC frame 20–35 years
- Aluminium frame 30–45 years
- Timber frame (maintained) 30–60+ years
- Main enemy Seal failure & exposure
Frame lifespan by material
The frame is usually the longest-lived part of a window. Good-quality uPVC typically lasts 20–35 years before it becomes brittle or discoloured. Aluminium, being a metal with a thermal break, often lasts 30–45 years. Well-maintained timber can last several decades — 30 to 60 years or more — but only if it is repainted or restained every 5–10 years to keep water out; neglected timber can rot far sooner. See uPVC vs aluminium vs timber windows for how the materials compare more broadly.
| Component | Typical lifespan | Note |
|---|---|---|
| uPVC frame | 20–35 years | Low maintenance |
| Aluminium frame | 30–45 years | Very durable |
| Timber frame | 30–60+ years | Needs repainting |
| Sealed glass unit | 10–20 years | Before misting risk |
Why the sealed unit fails before the frame
The sealed glass unit — two panes bonded around a spacer bar with a gas or dry-air gap — relies on its perimeter seal staying airtight. That seal is under constant stress from temperature swings and ageing, and after 10–20 years it can fail, letting in moisture that shows as misting between the panes. This is the most common reason a double glazed window appears to “fail” long before the frame is worn out. The good news is that a single failed unit can usually be swapped while keeping the frame — see misted or blown double glazing.
What shortens or extends the life of your windows
Several factors influence how long your windows last. Exposure is a big one: south and west-facing windows take more sun, wind and rain, and coastal salt air is harder on frames and seals. Standing water from blocked drainage holes accelerates seal failure. On the positive side, keeping drainage clear, cleaning frames and glass, lubricating hinges and locks, and repainting timber on schedule all extend life. When the time does come, replacing at 20–35 years brings a better energy rating and a fresh guarantee — see signs you need new windows. This is general information; the lifespan of your specific windows depends on their quality, installation, exposure and upkeep.
Compare double glazing quotes
When your windows reach the end of their life, comparing quotes helps you get a fair price. Use our service to reach FENSA or CERTASS registered installers in your area.
Frequently asked questions
How long should double glazing last?
Double glazing typically lasts 20–35 years overall, with the frames often outlasting the sealed glass units, which may start to mist from around 10–20 years. Quality, installation, exposure and maintenance all affect the figure.
Why has my double glazing failed after 10 years?
Most likely the sealed unit’s perimeter seal has failed, causing misting between the panes. This is common from 10–20 years and can usually be fixed by replacing just the glass while keeping the frame.
Do uPVC or aluminium windows last longer?
Aluminium frames tend to last longest, often 30–45 years, while good uPVC lasts 20–35 years. Well-maintained timber can outlast both, but only if it is repainted or restained regularly.
How can I make my double glazing last longer?
Keep the drainage holes clear, clean the frames and glass, lubricate hinges and locks, and repaint timber frames on schedule. Avoiding standing water around the seals is one of the simplest ways to extend a window’s life.
Sources & further reading
- Glass and Glazing Federation (GGF) — window lifespan, sealed units and maintenance guidance
- Energy Saving Trust — double glazing performance and longevity
- FENSA — replacement windows, guarantees and registered installers
- GOV.UK / Building Regulations Approved Document L — thermal standards for replacement windows
This is general information, not advice for your specific property or installation. Lifespan varies with quality, installation, exposure and upkeep. Replacement windows should be fitted by a FENSA or CERTASS registered window installer. We are an independent information and introduction service, not an installer.