Windows · triage
Condensation on windows in the morning
The short answer
Inside-surface condensation on cold mornings is a sign of high indoor humidity. Run bath and kitchen fans, vent the dryer outside and keep humidity lower in cold weather. Fog between two panes is a failed seal, not humidity.
Repeated wetness grows moldWipe sills dry and watch for black spots or peeling paint around frames.
Every outcome on this card
This monthIndoor humidity is high
Lower it this month.
- Run bath fans during and 20 minutes after showers; use the range hood
- Check the dryer vents outdoors and humidifiers aren’t set high
- Measure humidity; aim for the lower end of 30–50% in cold weather
Warm, moist indoor air condenses on the coldest surface, often window glass.
WatchA failed window seal
Cosmetic and efficiency, not urgent.
- Check if the window is under warranty
- Ask for glass-unit replacement quotes Often cheaper than a new window.
- Log it
WatchOutside condensation
Normal on cool, humid mornings.
- Nothing to do It is common with efficient glass, whose outer pane stays cool.
Related
Written from
Original casaq guidance, updated 2026-10-05. General guidance, not a diagnosis; licensed-pro review pending. Severity levels: Emergency now / Today / This week / This month / Watch. Send a correction.
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