Condensation is the single biggest cause of mould in UK homes and it gets significantly worse between October and March. The good news is that reducing condensation does not require expensive building work — in most cases, changes to how you use your home make the biggest difference. Here is what actually works.
Produce less moisture in the first place
The less moisture you add to the air inside your home, the less condensation you will get. Some sources of moisture are unavoidable — breathing, cooking, bathing. Others are controllable:
- Dry clothes outside or in a tumble dryer vented outside — a single load of wet washing drying on a rack indoors releases around 2 litres of water into the air of your home. If you dry clothes indoors, do it in a room with a window open and the door to the rest of the house closed.
- Cover pans when cooking — a significant amount of the steam from cooking escapes into the kitchen air rather than being extracted. Lids on pans reduce the moisture load considerably.
- Vent your tumble dryer outside — a condenser dryer that exhausts into the room dumps large amounts of moisture into the air. Ensure your dryer is vented outside or is a heat pump model with a water tank.
- Do not block air bricks or vents — purpose-built vents in walls are there for a reason. Blocking them to reduce draughts increases condensation.
Ventilate when you produce moisture
Extracting moist air at the point where it is produced is far more effective than trying to remove it from the whole house afterwards:
- Use the extractor fan every time you shower or bath — run it during and for at least 15 minutes after. If your bathroom does not have an extractor fan, open the window during and after use and keep the bathroom door closed so steam does not migrate into the rest of the house.
- Use the cooker hood when cooking — a recirculating cooker hood that does not vent outside reduces cooking odours but does not remove moisture. If your hood recirculates, open a window while cooking.
- Open windows briefly after showering and cooking — a few minutes with a window fully open removes far more moisture than leaving a trickle vent open all day.
Keep a consistent background temperature
Cold walls cause condensation. A home that is heated intermittently — very warm when occupied, very cold overnight and when empty — has walls that never fully warm up. Cold wall surfaces condense moisture even when the air feels warm.
A lower but more consistent background temperature — 14 to 16 degrees overnight rather than dropping to 8 or 10 — keeps wall surfaces warmer and reduces condensation significantly. It may also cost less to run than heating from cold twice a day.
Pay particular attention to rooms that are heated less than others. A spare bedroom or a hallway that is not heated is a condensation risk — the cold surfaces in unheated rooms will condense moisture that migrates from the rest of the house.
Move furniture away from external walls
Furniture placed against external walls traps a pocket of cold, still air between the furniture and the wall. Warm moist air from the room cannot circulate through this pocket and the wall surface behind the furniture stays cold and damp. Moving sofas and wardrobes 50 to 100 millimetres away from external walls allows air to circulate and keeps wall surfaces drier. It is one of the easiest and most effective changes you can make.
Use a dehumidifier
A dehumidifier removes moisture directly from the air. In a home where condensation is a persistent problem despite good ventilation habits, a dehumidifier running in the rooms with the worst mould history can make a significant difference — particularly in bedrooms overnight, where breathing adds substantial moisture to a closed room for 8 hours.
Modern dehumidifiers are quiet, efficient and relatively inexpensive to run. A dehumidifier set to maintain 50 to 60 percent relative humidity removes moisture before it can condense on cold surfaces.
Check trickle vents are open
Modern double-glazed windows have trickle vents — small slots at the top of the frame that allow controlled background ventilation. Many people close these to reduce draughts, particularly in winter. Keeping trickle vents open provides a continuous low level of air exchange that reduces moisture build-up without creating significant heat loss. Check yours and make sure they are open going into the mould season.
If mould has already appeared
Reducing condensation prevents new mould growth but does not remove existing mould. Existing mould needs to be treated and cleaned before the conditions that caused it are addressed.
Black mould on walls — what to do →
