Moderate Urgency
Condensation on Windows: Interior, Exterior, and Between Panes
Window condensation? Learn the difference between interior, exterior, and between-pane condensation, plus solutions from Virginia Glass Windows.
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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
Water droplets forming on the inside surface of the glass
Fog or moisture on the exterior glass surface in early morning
Condensation trapped between double-pane glass (cannot be wiped)
Ice forming on windows in winter
Water running down from condensation and pooling on the sill
What Causes This
High indoor humidity levels
Poor ventilation in bathrooms, kitchens, or laundry rooms
Single-pane windows with poor insulation value
Failed seal in insulated glass units (between-pane condensation)
Temperature differential between indoor and outdoor air
New construction materials releasing moisture as they cure
How to Fix It
Solution Steps
1Determine where the condensation is forming (interior, exterior, or between panes)
2For interior condensation: reduce indoor humidity with dehumidifiers and ventilation
3For exterior condensation: this is normal and indicates good insulation
4For between-pane condensation: the IGU seal has failed and needs replacement
5Use exhaust fans in bathrooms and kitchens
6Consider upgrading to double or triple-pane glass for single-pane windows
When to Call a Professional
When condensation is between the panes of double or triple glass
When interior condensation is severe and persistent despite humidity control
When condensation is causing mold growth or wood rot
When you need to upgrade from single to double-pane glass
Stay Ahead
Prevention Tips
Maintain indoor humidity between 30 and 50 percent
Use exhaust fans during cooking, showering, and laundry
Ensure adequate ventilation throughout the home
Open curtains and blinds to allow air circulation at window surfaces
Run ceiling fans on low to improve air circulation
Common Questions
FAQs About This Problem
No. Exterior condensation is actually a sign that your windows are well insulated. It occurs when the outside glass surface is cooler than the dew point of the outdoor air, typically on clear, calm nights.
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