Every autumn the same thing happens in homes across the UK. The heating goes on, the windows stay shut, and within weeks the condensation starts forming on cold surfaces — window frames, external walls, behind wardrobes, in bathroom corners. Left unchecked, condensation leads to mould. And mould, once it takes hold, is significantly harder to deal with than the conditions that caused it.
This guide covers the practical steps you can take this winter to keep condensation under control, prevent mould from forming, and deal with any patches that do appear before they become a bigger problem.
Why winter makes damp and mould worse
Condensation forms when warm, moisture-laden air meets a cold surface. In winter, the surfaces in your home get colder — external walls, window frames, corners and areas behind furniture that do not get much heat. At the same time, we produce more moisture indoors — cooking, showering, drying clothes on radiators, and simply breathing in a closed-up house. The combination of more moisture in the air and colder surfaces is exactly what condensation needs.
The rooms most at risk are kitchens, bathrooms, bedrooms (particularly external walls and behind furniture) and any room where clothes are dried indoors.
Ten practical tips for this winter
1. Ventilate when you produce moisture
The single most effective thing you can do is remove moisture-laden air at the point where it is produced. Use the extractor fan every time you cook or shower, and keep it running for at least 15 minutes after you finish. Open a window in the kitchen while cooking if you do not have an extractor fan, or have one that vents outside rather than just filtering and recirculating.
2. Keep a background temperature
A house that is allowed to go cold during the day and then heated rapidly in the evening creates the ideal conditions for condensation — the surfaces stay cold while the air warms up quickly and holds more moisture. Keeping a low background temperature of around 15 to 16 degrees during the day is more effective at preventing condensation than turning the heating off completely and then on again in the evening.
3. Do not dry clothes on radiators
A single load of washing contains around two litres of water, all of which evaporates into the air in your home when you dry clothes on a radiator. If you cannot dry outside, use a tumble dryer vented to outside, or dry in a well-ventilated room with the door closed and a window open. A dehumidifier in the room where you dry clothes makes a significant difference.
4. Leave space behind furniture on external walls
Wardrobes and sofas pushed directly against external walls block air circulation and create cold, still zones where condensation forms and mould grows unseen. Pull furniture a few centimetres away from external walls to allow air to circulate behind them.
5. Open windows briefly every morning
Even in cold weather, opening windows for ten minutes in the morning — especially bedroom windows — flushes out the overnight moisture build-up from breathing and allows drier outside air to replace it. Cold outside air in winter is generally much drier than warm indoor air, so a short burst of ventilation is effective even when it feels counterintuitive.
6. Use lids when cooking
Putting lids on pans significantly reduces the steam produced during cooking. Combined with the extractor fan, this keeps the moisture produced in the kitchen to a minimum.
7. Check and clear window drainage channels
Double-glazed windows have small drainage slots at the bottom of the outer frame that allow condensation to drain away. These block with dirt and debris over time. Check yours are clear — a blocked drainage slot leads to pooling condensation and eventually water ingress into the frame.
8. Deal with patches immediately
If you find a patch of mould, clean it promptly with an appropriate mould treatment product used according to the manufacturer's instructions. Wear gloves and open windows. Do not dry-brush or vacuum with a standard vacuum cleaner — this disperses spores into the air. If the patch keeps coming back after treatment, the moisture source has not been fixed — the problem is in the wall, the roof, the window seal or the ventilation, not just on the surface.
9. Check your extractor fans actually vent outside
Some older bathroom and kitchen extractor fans filter and recirculate air rather than venting it outside. These do not remove moisture from the room — they just remove some odour. If your extractor fan is recirculating rather than venting, it is not controlling condensation. Check where the duct goes, or feel for airflow outside when the fan is running.
10. Watch the warning signs
Condensation on windows every morning, a musty smell, dark spots in corners or on grout lines, or peeling wallpaper on external walls are all early warning signs. Catching them now is significantly easier and cheaper than dealing with established mould in spring.
If you are a tenant and your landlord is not acting
If you have reported damp or mould to your landlord and they are not responding within a reasonable time, you have legal rights. Under Awaab's Law, social landlords must investigate within 14 days of a report. Under the Homes (Fitness for Human Habitation) Act 2018, all tenants can take their landlord to court if the property is unfit for human habitation.
Your rights if your landlord is not fixing damp or mould →
Further reading
Why mould grows in autumn and winter → | How to reduce condensation → | How to stop mould coming back permanently → | Damp proofing vs ventilation →
