Indoor air
Window condensation in BC winters
Condensation on glass is common in mild, wet coastal winters. It is not automatically a failed window — but ignored wet sills are a reliable way to grow mold on the frame and drywall below.
Warm indoor air holds moisture. When it hits cold glass, water appears. Coastal homes combine long heating seasons at moderate temperatures, high outdoor humidity, showers and cooking, and sometimes weak exhaust to the outside.
Condensation versus a leak
Condensation shows up on the coldest glass, often in the morning, and clears as the room warms and dries. It is worse in bedrooms and corners. Leaks follow storms or specific flashings and gravity — often one location tied to weather. Both can wet a sill. The repair path is different.
What reduces ordinary condensation
- Run bath fans during and after showers — and confirm they exit outdoors.
- Use the kitchen range hood when cooking moisture-heavy meals.
- Avoid sealing the house with zero outdoor air while generating indoor moisture.
- Wipe sills when you see standing water; do not let paint and drywall stay wet.
- Watch closets on exterior walls; cold corners show problems early.
A dehumidifier can help in chronic rooms. It does not replace exhaust for point sources like showers.
Single-pane and old frames
Older assemblies run colder. They will show moisture sooner. Upgrading glass helps; it does not remove the need to manage indoor humidity.
When it is more than “winter glass”
- Water between panes (sealed-unit failure)
- Soft or rotting sills
- Mold on the bottom of drywall that returns after cleaning
- Condensation with a strong musty smell from below the floor
Those need diagnosis beyond a towel on the sill.