Condensation and mould

What is condensation?

Condensation is a natural occurrence. It appears when water vapour in the air meets a cold surface and ‘condenses’ – becomes liquid – and forms water droplets on the surface. This is what causes the mirror to mist when you have a shower.

What causes condensation?

  • Build-up of moisture

  • Cold surfaces and unequal room temperatures

  • Lack of adequate ventilation

Why is it a problem?

Condensation is a problem because, left untreated, it provides the right conditions for mould to grow. It can also affect plaster and cause woodwork to rot. It is unsightly and can cause unnecessary damage to your home or possessions. If you have black mould forming within your property, it is more likely that you have a condensation problem rather than rising or penetrative damp. The advice on this page should help resolve the problem.

Signs of a condensation problem

  • Mould or mildew occurring in winter rather than summer

  • Black mould in the corners of rooms, behind furniture and in cupboards

  • Moisture on walls, ceilings and cold surfaces, such as cold water pipes

  • Moisture on the inside of windows

  • Only outside walls affected, rather than walls between rooms

  • Clothes in cupboards and drawers have a musty smell or mildew on them

Dos and Don’ts

  • DO report any problems with extractor fans and heating systems

  • DO wipe down the inside of windows if they become wet with condensation

  • DO remove any mould growth with an appropriate mould and mildew cleaning product. Follow the manufacturer’s instructions

  • DO store clothes and arrange furniture to allow air flow around them

  • DO avoid placing beds and wardrobes against external walls - mould is more likely to grow behind furniture

  • DO NOT use bleach and water to treat mould - this is not as effective as a mould and mildew cleaning product

  • DO NOTover fill wardrobes and cupboards

  • DO NOT cover any vents

  • DO NOT disturb loft insulation – it causes ‘cold spots’ which lead to condensation

It is normal to find your windows misted up after a cold night, and does not necessarily mean you have a serious condensation problem.

How to stop condensation problems

Most problems are caused by the way we live or ‘lifestyle’. Making a few simple changes to the way we maintain our homes - or do household activities like cooking and laundry - can stop condensation becoming a problem. Think reduce, increase and control to prevent condensation becoming a problem in your home.

Reduce Moisture

  • When cooking, cover pans with lids, and keep the kitchen door closed.

  • Dry laundry outside whenever possible.

  • Do not put washing on radiators or in front of radiantheaters.

  • If you have to dry clothes indoors - put them in one room, close the door and leave the window open for ventilation.

  • Make sure tumble dryers are vented so that moist air goes outside.

  • Keep bathroom doors closed during use. Run cold water into the bath first and then add hot water. This can reduce steam by up to 90%.

Increase Ventilation

  • Always keep a small window or an air vent open when you are at home to reduce condensation build up. If you have trickle air vents, keep them open all the time.

  • If installed, use an extractor fan when cooking or bathing. Run the fan for 20 minutes after use so that moisture is cleared and keep the windows in the room closed. If a window is open the fan will draw air in from outside, rather than drawing the damp air out. Ensure your curtains or blinds do not obstruct the fan.

  • Don’t over ventilate your home in cold weather. This will reduce the temperature inside making condensation more likely as well as increasing heating costs. For security, make sure you close windows before you go out.

Control Room Temperature

  • If you have central heating, use the thermostat to set the temperature to between 18°c and 21°c.

  • Do not use the heating on a high setting for short periods of time. Heating your home for a longer time at a lower temperature will keep it warmer and cost you less.

  • Include any rooms that are not being used – radiators with thermostatic radiator valves (TRVs) will give you greater control over the heat from each individual radiator.

  • Bottled gas heaters produce high levels of moisture, so should not be used.

  • Do not place furniture against radiators as this prevents efficient circulation of warm air.

Where does more watervapour come from?

  • A bath or shower = 2 pints

  • Washing dishes = 2 pints

  • Bottled gas heater used for 8 hours = 4 pints

  • Cooking and using a kettle = 6 pints

  • Drying clothes indoors = 9 pints

When we breathe, we exhale water vapour. One person adds half a pint of water to the air overnight while asleep, and twice that when active during daytime.

Next steps

If you follow the advice on this page you should be able to keep condensation, and mould growth, under control. If mould growth persists - even after you have tried all advice given on this page – the next step is to contact us. Only then will we look in to what is causing the mould. Mould growth does not necessarily mean a property has a damp problem – it could be as simple as aging insulation, lack of insulation or a broken extractor fan. We will carry out an inspection and any appropriate work to correct the problem. However, if the condensation or mould is found to be caused by the ‘lifestyle’ actions listed in this leaflet, we may have to charge you for any work carried out by us.

Further advice

If you are still unsure about your condensation or mould issues, please contact the Repairs team on 01296 732600 or email: