Plan with confidence
Condensation on window glass: inside, outside or between panes?
Learn how the location of window condensation changes what it might mean and when to ask about a window repair.
First check which glass surface is wet. Room-side condensation, brief exterior condensation and moisture trapped between panes have different causes; persistent water between sealed panes merits an assessment.
Check where the moisture sits
Carefully wipe the room-side glass. If that clears it, the water was on the inside surface. If fog or droplets remain inaccessible between panes, the sealed unit may have failed.
Water on the outside surface can occur when exterior glass is cooler than the surrounding air. The appearance alone does not establish that a window is defective.
Consider room humidity and ventilation
Cooking, showering, drying clothes and everyday breathing add moisture indoors. Extractor fans, background ventilation and air movement all affect whether vapour condenses on a cold surface.
Do not block ventilation to address a draught without understanding its purpose. If you have concerns about air quality or persistent damp, seek appropriate property advice as well as window advice.
When a window assessment may help
Fogging between panes cannot be wiped from either side. A survey can check the sealed unit and the surrounding frame and explain whether glass replacement or broader work may be suitable.
Describe which windows are affected and whether the moisture clears when the room warms. Photos taken at different times can help the first conversation, but cannot replace inspection.
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General planning information updated 29 September 2026. Product specifications and the work for your home are confirmed in your quotation.