Why Do Windows Get Condensation?
Where moisture appears—inside, outside or between panes—helps distinguish humidity, weather and seal-related causes.
Where the moisture appears is the clue
Condensation on the room-side glass is commonly related to indoor humidity, cold surfaces and limited air circulation. Exterior condensation can occur when efficient glass stays cooler than humid outdoor air. Moisture between panes usually indicates a failed insulated-glass seal.
Reduce indoor-surface condensation
Check indoor humidity, use kitchen and bath exhaust, keep air moving across the glass and avoid blocking warm air with heavy coverings. Persistent moisture, staining or mould warrants a broader moisture review.
Know when to inspect the unit
Fogging or droplets trapped between panes cannot be wiped away from either side. Record the affected unit, frame condition and any drafts or water entry before deciding between sealed-unit repair and full replacement.
Planning a Window or Door Upgrade?
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