Beads of water on the glass, damp window sills and mould on cold corners all start the same way: warm, moist indoor air meeting a cold surface. Here is how to read the pattern and fix it, cheapest step first.
Condensation on windows and cold surfaces happens when warm, moist indoor air touches glass, frames or walls that are cold enough to turn that moisture into water. Cooking, showering, drying washing and simply breathing all add moisture. Wipe the glass, vent the moisture at the source, keep the home steadily warm and check for look-alikes such as leaks before you buy any equipment.
Look at where the water is. Condensation on the inside of single or older double glazing, on metal frames, on tiles and on the cold corners of external walls points to moisture in the room air. It is usually worst on cold mornings and in bedrooms, kitchens and bathrooms, and it clears as the day warms up.
Water between the two panes of a double-glazed unit is different: that means the seal has failed and the unit needs replacing. Water on the outside of the glass is also normal on clear, cold nights and is not a damp problem. Damp patches that do not clear when the room warms, or that grow after rain, are not condensation, so see our guide to telling the damp types apart.
Start with the free steps and only move down the list if the problem is still there after a couple of weeks.
Ashford Borough Council's flood risk assessment describes the geology of the area's catchments as predominantly Chalk, with outcrops of Gault Clay, Lower Greensand and Weald Clay along the south-west margins, and notes that the East Stour rises on the Weald Clay. That is context, not a diagnosis: it does not tell you your windows are the cause, so measure before you decide.
A cheap room thermometer and humidity meter, read at the same time each morning for a week, will show which room is the problem. BRE describes monitoring temperature and humidity over time as an effective way of diagnosing damp.
If the window sills are wet because a gutter is overflowing, a seal has failed or a roof is leaking, a dehumidifier is the wrong tool. The same goes for rising damp, which needs a specialist survey, and for mould that is already established: existing mould must be cleaned off, using suitable products with gloves and a mask, and large areas need a professional. A Dryzen system also needs a loft to mount the unit, and it is not suitable for rented homes unless the landlord authorises the changes.
A Dryzen system is a loft-mounted dehumidifier with insulated ductwork to the central area or stairway of the home. Each unit covers 150 square metres and extracts 12 litres a day, uses about 20 pounds a year in energy and has an activated carbon filter. The smart app shows temperature and humidity (it needs 2.4GHz Wi-Fi and internet). The free survey will tell you honestly whether it suits your home or whether the fixes above come first.
Occasional misting on a cold morning is normal. It becomes a problem when it is there every day, runs onto the frames and sills, or leaves mould. The glass is only the place where the moisture shows first, so look at how much moisture the home is producing and how well it escapes.
Yes. Council guidance recommends wiping condensation off glass and frames with a dry cloth, because standing water on frames and sills is where mould tends to start. It treats the symptom, so pair it with the steps above.
No. Short, regular airing plus extractor fans and trickle vents where you have them is the usual advice. Keeping the home steadily warm also helps, because warmer surfaces are less likely to collect condensation.
Sources: GOV.UK: Understanding and addressing the health risks of damp and mould in the home; BRE: Diagnosing the causes of dampness in buildings; Stoke-on-Trent City Council: Damp, mould and condensation; Ashford Borough Council: Strategic Flood Risk Assessment (2014)
Last reviewed 2026-10-05. General guidance only; this is not a survey of your home.