Condensation on windows: what to check before repairs
Water on glass does not automatically establish a defective window.
Water on glass does not automatically establish a defective window. Identify where and when it appears before changing seals, heating or ventilation. A single photograph cannot distinguish every possible cause.
Locate the moisture precisely
Is it on the room-facing surface, outside or between panes? Photograph the area and describe it clearly. Moisture within a sealed glazing unit calls for advice from a window specialist. For room-side condensation, consider room use and air exchange as well as the window itself.
Keep a short observation log
Record the morning pattern, room temperature and humidity reading in a consistent location. Add showers, cooking, laundry drying and ventilation. A household meter can show a trend but is not a building-defect assessment. Compare several days using the same approach rather than unrelated readings from different positions.
Check normal operation
Do not block ventilation openings to remove draughts. Read the equipment instructions for filter care and ask the manager when needed. Heavy curtains or furniture may restrict airflow beside a window. Dry accumulated water, while recognising that wiping it away does not resolve its cause.
- Describe the exact moisture location.
- Record timing and room activities.
- Note heating and ventilation settings.
- Keep photographs and questions for the manager.
When to request investigation
Repeated wetting, mould or damaged finishes warrant finding the cause. Terviseamet recommends investigating moisture sources and involving building specialists where appropriate. Avoid concealing the problem with fresh paint before inspection. A shared apartment-building ventilation system should not be altered as one household’s experiment. Give the specialist your log so they can ask more precise questions and plan a useful assessment.
Related reading
Drying laundry indoors in autumn without a permanently damp room
Sources and verification
Information checked on 30 October 2026. Recheck the source before buying or visiting.
