Why is condensation forming on the inside of my windows?
Warm humid indoor air is reaching a cold glass surface; persistent moisture can also reveal weak ventilation or localized air leakage.
Urgency: moderate
What this means
Measure indoor relative humidity and use kitchen and bathroom exhaust fans during moisture-producing activities.
Safe checks
- Dry the sill
- open coverings for airflow
- verify exhaust fans vent outdoors
- compare several windows and rooms.
Stop and get help if
- Investigate promptly if water damages finishes, mould-like growth spreads, or moisture appears between sealed panes.
Which professional to call
Contact the matched licensed or qualified trade if safe checks do not resolve the issue.
Find the relevant tradeSource and method
This answer combines HomeSOS's structured triage with safety boundaries supported by a public source. It does not replace inspection.
Health Canada: Home safety and indoor air guidanceReviewed August 12, 2026