Double glazing typically lasts 20 to 30 years, but its lifespan depends on the quality of the sealed unit, the frame material, how well it was installed, and exposure to weather. In most cases, double glazing fails because the seal breaks down, not because the glass itself wears out.
How long does double glazing last on average?
Most double glazed windows last 20 to 30 years.
The glass panes can last indefinitely, but the actual sealed unit contains gas and moisture absorbing materials. Over time, the perimeter seal degrades, allowing air and moisture to enter. Once this happens, insulation performance drops and condensation forms between the panes.
Well made, modern sealed units often last longer than older ones thanks to improved sealants and spacer technology.
Does the frame type affect how long double glazing lasts?
Yes. The frame often outlasts the sealed glass unit.
uPVC frames
- Typical lifespan: 25 to 35 years
- The sealed unit usually fails before the frame
- Older uPVC can degrade from UV exposure
Aluminium frames
- Typical lifespan: 40 years or more
- Very stable with minimal movement
- Sealed units almost always fail first
Timber frames
- Typical lifespan: 50 years or more if well maintained
- Poor maintenance can dramatically shorten lifespan
- Often ideal for glass only replacement
What causes double glazing to fail?
Double glazing usually fails gradually rather than suddenly. Common causes include:
- Age related seal deterioration
- UV exposure breaking down sealants
- Thermal expansion and contraction
- Poor original installation
- Frame movement or building settlement
- Water ingress from blocked drainage paths
Once the seal is compromised, the insulating gas escapes and moisture enters the cavity.
Signs your double glazing is failing
Common warning signs include:
- Condensation or misting between the panes
- Cloudy or milky looking glass
- Draughts despite closed windows
- Higher heating bills
- Glass rattling inside the frame
Important distinction:
Condensation inside the room is normal and relates to humidity.
Condensation between the panes means the sealed unit has failed.
Can you replace the glass without replacing the whole window?
In most cases, yes.
If the frame is structurally sound, you can replace just the sealed glass unit. This:
- Restores clarity and insulation
- Is usually 40 to 60 percent cheaper than full window replacement (Read Guide Here)
- Causes minimal disruption
- Allows upgrades such as improved thermal or acoustic glass
Full window replacement is only necessary when frames are damaged, warped, or no longer secure.
Does modern double glazing last longer than older units?
Yes.
Modern double glazing benefits from:
- Improved spacer bars
- Better edge seal technology
- Higher quality gas retention
- Toughened and laminated glass options
As a result, modern sealed units generally outperform those installed 20 or 30 years ago.
How to make double glazing last longer?
You can extend the life of double glazing by:
- Keeping drainage slots clear
- Avoiding paint or sealant over frame vents
- Addressing failed seals early
- Ensuring correct installation depth
- Avoiding pressure washing around seals
Small maintenance steps can add years to a sealed unit’s lifespan.
When should you replace double glazing?
Replace the sealed unit only if:
- Condensation is permanent between panes
- Insulation performance has dropped
- The frame is still in good condition
Replace the entire window if:
- Frames are warped, cracked, or unstable
- Locks or hinges repeatedly fail
- You want a significant thermal or acoustic upgrade
Quick Answer
How long does double glazing last?
Double glazing typically lasts 20 to 30 years. Failure usually occurs when the sealed unit breaks down, allowing moisture to enter between the panes, rather than the glass itself wearing out.
Misted Windows? Don’t Replace the Whole Frame.
Restore your home’s clarity and insulation at a fraction of the cost.
Replacing just the failed glass unit is the smart, professional solution for blown windows.
