Written by Seth Long, Damp Pro and Co · Last updated: 7 October 2026
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First locate the water
Wipe a small area of the room-side glass with a clean cloth. If the droplets clear, indoor air has probably condensed on that surface. If they remain, look from a safe position to determine whether the moisture is outdoors or inside the glazing unit. Do not reach out of an upstairs window or remove glazing beads to investigate.
The location matters more than the quantity of droplets on a single morning. Moisture indoors calls for checks of humidity, airflow and cold glass. Mist trapped between sealed panes is a glazing issue. External dew can form when the outer pane is cold in relation to outdoor air, without indicating that the room is excessively damp.
Why windows get condensation in the morning
Overnight, the air in a bedroom receives moisture from occupants while the glass may cool. Curtains or tightly fitted blinds can restrict circulation around the window, leaving the surface cooler than the rest of the room. When air meets glass cold enough for condensation, water appears even though no pipe is leaking.
Notice whether every window is affected or only one room. Closed doors, wet laundry and differences in heating or ventilation may explain part of the pattern. Morning droplets alone do not prove that windows need replacing. Check what happens after airing and whether moisture persists on adjacent walls rather than judging one photograph in isolation.
Remove pooled water without returning it to the room
Wipe glass, frames and sills when water accumulates. Use a cloth or suitable window-water collection tool, taking care around finishes, and empty collected water into a sink. Leaving a soaked towel to dry on a radiator simply puts the water back into indoor air. Avoid allowing puddles to sit against paint, seals or nearby plaster.
Open curtains or blinds after getting up where practical so air can move across the window. Leave existing trickle vents unobstructed and briefly air the room when it is safe and appropriate. Consider security and weather; prolonged airing that chills the room is not automatically more useful than controlled ventilation.
Check the moisture arriving at the window
Glass often shows a whole-room humidity issue before other surfaces do. Keep steam close to its source: use bathroom extraction, kitchen extraction that discharges outdoors and pan lids where practical. A recirculating cooker hood does not remove cooking vapour from the home. Keep wet laundry out of the bedroom if another suitable drying space is available.
Do not block intended air paths because the window feels draughty. Extraction needs replacement air to function, and reducing all ventilation can move condensation from glass to a colder corner. For a fuller plan covering wall surfaces and household moisture, see how to stop condensation. This window check is a starting point, not a reason to overlook the rest of the room.
Mould on windows and surrounding finishes
Mould on windows can appear on seals, frame corners, painted reveals or behind a blind where moisture remains. Check the material involved rather than treating every surface with the same product. A small patch on an intact washable finish may be suitable for careful cleaning according to a mould wash label; damaged plaster or extensive growth needs assessment.
Avoid dry brushing or mixing cleaners. Keep children and pets away during cleaning and follow the product precautions. If growth returns, removing it again will not explain why the reveal remains damp. Our black mould on walls guide covers cleaning limits and the importance of tracing moisture without identifying mould species from its colour.
Mist between panes and moisture outside
Persistent fog or droplets within a sealed double-glazing unit cannot be wiped from either exposed surface. It may indicate a failed seal, so contact a competent glazing professional for assessment. Increasing room ventilation does not repair that sealed space, and drilling or taking the unit apart yourself risks damage.
External condensation is a different phenomenon. The outside surface can cool enough for water vapour in outdoor air to condense, particularly under suitable weather conditions. Record whether it clears as conditions change. If water is entering around the frame rather than simply sitting on glass, investigate the junction and rainfall pattern separately; surface dew and rainwater leakage are not the same problem.
Need it sorted? Book condensation control
If indoor window moisture continues despite practical checks, book condensation control to assess extraction, airflow and cold spots. Damp Pro and Co offers free, no-obligation damp surveys for homeowners from its Ruislip base across West London and South Bucks. Tell us which side of the glass is affected and whether walls or frames also remain damp.
Request a visit through the quote form or call 07803 253337. A photograph taken before wiping can help explain morning window condensation. Mention any recent glazing replacement or changes to heating and room use so the recommendation considers how the home now works.
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Questions about this topic
Does water outside my double glazing mean the seal has failed?
Not necessarily. External dew can form on a cold outer surface. Moisture trapped between sealed panes is the pattern that calls for a glazing assessment.
Why is the window wet behind a roller blind?
A closely fitted blind can reduce airflow around cold glass. Check indoor moisture and ventilation, and allow circulation where practical rather than assuming the blind is the only cause.
Will wiping the glass stop condensation tomorrow?
Wiping prevents pooled water lingering but does not remove the reason droplets form. Moisture production, air exchange and surface temperature need considering together.
Should I report condensation after replacement windows?
Yes. Explain where water forms and whether intended vents are present and unobstructed. Replacement glazing can change airflow, so assess the room as well as the window.
Related guides
- How to stop condensation
Practical ways to stop condensation on windows and walls, from drying washing to extractor fans and ventilation.
- Black mould on walls
How to clean black mould safely, why it keeps coming back and how to find the moisture behind it.
- Mould in the bedroom
Why bedrooms suffer most: overnight moisture, wardrobes on cold walls and the habits that make a difference.