Water on a window does not automatically mean a bad window. Moisture you can wipe from the room side, dew on the outdoor face and haze sealed between double glazing are different problems. Locating the wet surface first can prevent wasted cleaning or premature replacement.
- Wipe the indoor face
- Identify outdoor droplets
- Check for trapped haze
- Manage humidity or request seal assessment
Use a dry cloth to locate the moisture
If a dry cloth picks up water from the room-side glass, humid indoor air is condensing on a cold surface. Check whether curtains or furniture block air circulation across the pane. Use kitchen and bathroom exhaust fans during moisture-producing activities, and dry a wet sill so moisture does not linger.
If the room side is dry and droplets are on the outside, humid outdoor air may be condensing on glass cooled by indoor air. Do not lean out of a window to reach an unsafe exterior surface merely to remove temporary dew.
If neither exposed surface wipes clear
Persistent fog or moisture between the two sealed panes may indicate a failed glazing seal. ENERGY STAR identifies cloudy or damp space between panes as a reason to assess older double glazing. Lowering room humidity cannot wipe moisture trapped inside that sealed unit.
Photograph the haze and record the window maker, installation date and warranty. Ask the installer or manufacturer whether the glazed unit can be inspected or replaced. Do not assume the entire frame must be replaced without an assessment. Persistent dampness at the sill or wall also warrants a separate check for water intrusion.
A worked example
On a winter morning, droplets wipe off the room side and disappear later: start with indoor moisture and airflow. If both accessible surfaces are dry but a cloudy patch stays in the middle, document it and ask about the insulating-glass seal.
Common questions
Does inside condensation mean I need new windows?
Not necessarily. First check indoor humidity, ventilation and airflow at the glass.
Can I dry between-pane fog with a hair dryer?
No. The sealed cavity cannot be repaired by heating the exposed surface. Consult the window maker.
Is exterior condensation a defect?
It can be ordinary dew in warm, humid weather. Investigate separately if water is entering the building.
Official sources checked
This is general information; individual circumstances and product or agency instructions may differ.