Condensation and mould in your home

Condensation is something that can happen in every home but there are some basic things you can do to prevent/reduce this from happening. If condensation persists and is not managed, this will result in black mould appearing.

Condensation is caused by water vapour or moisture from the air inside the home which has cooled and come into contact with cold surfaces such as:

  • windows;
  • metal window frames;
  • cold pipes; and
  • on the inside surface of external walls.

This can cause damage to your home, for example by the water droplets (condensation) soaking into and spoiling paintwork, wallpaper and plaster.

Condensation usually occurs during cold weather, whether it is damp or dry outside. If condensation occurs regularly and is not wiped off, it will lead to mould growth which appears as black spots. This is usually found in corners of rooms, north-facing walls, and on or near windows. It is also found in areas with little air circulation such as behind wardrobes and beds, especially when they are pushed up against external walls.

Most homes will be affected by condensation at some point; however, certain activities can increase the problem. Mould growth is often due to habits and lifestyle and is something that can be reduced or alleviated. Cooking, washing and drying clothes indoors all produce water vapour that can only be seen when condensation appears on colder surfaces such as walls, windows, ceilings or mirrors.

Did you know that you add extra water to the air inside your home on a daily basis, which causes condensation? Even your breathing adds some moisture. One person asleep adds half a pint of water to the air overnight and during the day adds one pint of moisture:

  • two people at home for 16 hours - 3 pints of water;
  • one bath or shower - 2 pints of water;
  • drying clothes indoors - 9 pints of water;
  • cooking or using the kettle - 6 pints of water;
  • washing dishes - 2 pints of water; and
  • bottled gas heater (8 hours use) – 4 pints of water.

The amount of condensation in a home depends on three factors:

  • how much water vapour is produced in the home;
  • how cold or warm the home is; and
  • how much ventilation there is in the home.

Turing up the heating will not solve the problem, this may only temporarily reduce condensation. All three factors may need to be looked at to reduce the problem.

Black mould spores are invisible to the human eye and are always present in the atmosphere both inside and outside the home. They only become noticeable when they land on a surface where they can grow and multiply.

The following advice can help to reduce the amount of condensation and black mould growth in your home: 

  • Dry clothes outdoors. If you have to dry clothes indoors, use a clothes airer in the bathroom with the door closed and either an extractor fan on or a window slightly open.
  • Vent tumble driers to the outside (never into the home) or buy a condensing type.
  • Cover pans when cooking and do not leave kettles boiling.
  • Do not use paraffin or liquid petroleum (bottled) gas heaters. These produce large amounts of water vapour and are very expensive to run.
  • When removing excess moisture, always wipe the windows and windowsills of your home in the mornings to remove condensation. This is especially important in the bedroom, bathroom and kitchen. Opening the window is not always enough, though opening bedroom and living room windows for 1 to 2 hours every morning will help.
  • Always ventilate or open a window when using the kitchen or the bathroom and continue to ventilate these rooms for a short time after a shower, a bath or cooking. If you have extractor fans, then ensure that these are turned on as well.
  • Leave space between the back of furniture and cold walls. It is best to allow at least 10cm to 15cm space.  
  • In cold weather, the best way to keep rooms warm and avoid condensation is to keep low background heat on all day rather than short bursts of high heat when you are in the house. Good heating controls on your radiators, room thermostats and a timer will help.
  • To add to these measures, a really good way to manage condensation and mould would be to buy a domestic dehumidifier. These can be bought for a reasonable price at many high street stores or online.

If you do find black mould in your home, it can be quite easily treated. Using a cloth, wipe down the areas of mould using an anti-fungicidal mould spray, which are available from most supermarkets. After treatment, redecorate using a fungicidal paint or wallpaper paste – do not paint over the area using an ordinary paint. 

Origin Housing have also created a video, showing their 3-step-guide to tackling condensation  here