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Broken Window Seal: Signs, Causes & When to Replace Your IGU
A broken window seal causes foggy, cloudy glass and lost insulation. Virginia Glass Windows explains the signs of seal failure and your repair options in DC, MD & VA.
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Warning Signs
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Known Causes
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Solution Steps
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Professional Assessment
Common Symptoms
Foggy or cloudy appearance between the two panes
Condensation or moisture droplets trapped inside the glass unit
White or mineral deposit film on the inner glass surfaces
Window feels cold to the touch on the interior side during winter
Noticeably higher heating or cooling bills
Visible gap or separation at the edge spacer of the glass unit
What Causes This
Age and UV exposure breaking down the organic sealant compounds over 15 to 25 years
Thermal cycling — repeated expansion and contraction of the metal spacer stresses the sealant
Excessive moisture exposure from roof leaks, window ledge pooling, or sprinkler contact
Improper installation with insufficient sealant coverage at the factory or field
Physical damage to the glass edge or frame that breaks the seal perimeter
Low-quality glazing sealants used in budget window manufacturing
How to Fix It
Solution Steps
1Confirm the problem is a seal failure and not interior condensation caused by high indoor humidity
2Measure the existing IGU dimensions including glass thickness and spacer width
3Order a replacement IGU from a local glass fabricator — Virginia Glass Windows stocks common sizes for same-day service
4Remove the window sash and carefully extract the failed IGU from the frame
5Install the new IGU with fresh glazing tape or gaskets, ensuring proper support at the bottom
6Reinstall the sash and check operation, verify no rattling or movement in the new unit
When to Call a Professional
Any double-pane window with visible moisture or fogging between the panes
Windows older than 20 years where seal failure is likely in multiple units
When the window sash must be removed for glass access — this requires proper tools and technique
Skylights or specialty-shaped windows with broken seals — custom fabrication required
Commercial or multi-story properties where working at height is involved
Stay Ahead
Prevention Tips
Avoid power-washing windows directly — high pressure can force water into the seal perimeter
Inspect exterior window sealant (caulking) annually and reapply when it cracks or separates
Keep gutters clean to prevent water from overflowing onto window assemblies
Consider upgrading to triple-pane or high-performance IGUs in areas with extreme DMV winters
When replacing windows, specify units from manufacturers with 20-year or longer seal warranties
Common Questions
FAQs About This Problem
The seal itself cannot be repaired. The entire insulated glass unit (IGU) must be replaced. The glass panes are factory-sealed with argon or krypton gas fill, and once the seal breaks, the gas escapes. Only a new IGU restores the insulating performance.
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