How Long Do Double Pane Windows Last?
The sealed glass in a double pane window usually lasts somewhere around 10 to 25 years before its edge seal fails; sun, water and how well it was installed move it to either end. The frame often lasts much longer, so when the seal goes, you can usually replace just the glass. Here is how to spot a failed seal, what wears it out, and how to get the most years from the glass you have.
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What actually wears out
A double pane window is two sheets of glass held apart by a spacer around the edge and sealed into one unit. The seal keeps dry air or an insulating gas in, and moisture out. That seal is the part with a lifespan.
The U.S. Department of Energy explains that in high-performance window glass the panes are separated by insulating spacers, and the space between them is filled with a gas like argon or krypton that insulates better than air. When the seal fails, that gas slowly leaks out and damp air gets in.
Signs the seal has failed
Haze or droplets between the panes that stay put when you wipe both sides. The surest sign.
White film or streaks
Minerals left inside when moisture comes and goes. They can’t be cleaned from outside.
Cold glass in winter
A pane that feels much colder than its neighbors may have lost its gas.
Warped reflections
A unit that has lost pressure can bow, so reflections look bent or wavy.
What shortens the life of the glass
Strong sun
South and west windows heat and cool every day, which works the seal hard.
Water sitting on the edge
Blocked drain holes or failed caulk let water soak the bottom edge of the unit.
Stress in the frame
A unit set too tight, or a frame that has shifted, presses on the seal.
Pressure washers and harsh cleaners
Spraying the edge of the glass or using solvents can break down the seal.
How to make the glass last longer
- Keep the drain holes clear. Most frames have small weep holes on the outside bottom edge. Clear them each spring.
- Fix caulk and glazing that has cracked or pulled away, so water can’t sit on the edge of the glass.
- Clean gently. Mild soap and water; no pressure washer near the edges.
- Aim sprinklers away from windows so they aren’t soaked every day.
- Watch for early fog. Light fog in the corners is the start; you can plan the replacement before it spreads.
New glass or new windows?
If the frames are sound and the windows open, close and lock well, only the sealed glass needs replacing. A new unit is made to fit the old frame, and can be ordered with low-E glass and gas fill.
Double pane window questions
More questions? Browse our glass repair FAQ or contact us.
How long do double pane windows last?
The sealed glass usually lasts somewhere around 10 to 25 years before the seal fails. The frame often lasts longer, so the glass can be replaced on its own.
How do I know if my window seal has failed?
Fog, droplets or a white film between the panes that won’t wipe off from either side means the seal has failed.
Is a failed window seal a big problem?
It is not dangerous, but the window insulates less, the fog usually gets worse, and the view clouds over. Most people replace the glass once it bothers them.
Can a failed seal be fixed without new glass?
Some services drill and dry the unit, but the seal stays broken and the insulating gas is gone. A new sealed unit is the lasting fix.
Do I need new windows or just new glass?
If the frames are solid and the windows work well, new glass is enough. New windows make sense when the frames are rotted, warped or drafty.
Windows fogging up?
Tell us how many windows and where, or call for a free estimate.