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These is by far the most common cause of dampness experienced by tenants and householders, resulting in a large number of enquiries or complaints.

Condensation is caused by water vapour or moisture from inside the dwelling coming into contact with a colder surface, such as a window or wall. The resultant water drops (condensation) may then soak into the wallpaper or paintwork or even plasterwork. In time, the affected damp areas then attract black mould that grows on its surface.

Condensation mainly occurs during the colder months, whether it is rainy or dry outside. It is usually found in the corners of rooms, north

facing walls and on or near windows. It is also found in areas of little air circulation such as behind wardrobes and beds, especially when they are pushed up against external walls.

Note: Black mould is frequently seen on this type of dampness.

Most homes will be affected by condensation at some point. However, certain activities can increase the problem. Whether you are an owner or occupier or a rent-paying tenant, condensation and mould growth is often due to habits and lifestyle and is something that can be reduced or remedied by the occupant.

Cooking, washing, drying clothes indoors, even breathing – all produce water vapour that can only be seen when tiny drops of water (condensation) appear on colder surfaces such as walls, windows, ceilings or mirrors.

The ‘amount’ of condensation in a home depends upon three factors:

  • how much water vapour is produced by the actions of its residents
  • how cold or warm the property is
  • how much air circulation (ventilation) there is

Simply turning up the heating will not sort out the problem, this may only temporarily reduce condensation. All three factors may need to be looked at to reduce the problem.

The first sign of a problem is water vapour condensing on windows and other cold surfaces, which then takes a long time to disappear, allowing surfaces to become damp. The second indication is black mould patches growing on these damp areas.

Black mould

Mould spores are invisible to the human eye and are always present in the atmosphere both inside and outside dwellings. They only become noticeable when they land on a surface upon which they can grow and then multiply.

For mould to thrive and survive it requires four elements

  • Moisture – obtained from condensation
  • Food – such as wallpaper or emulsion paint
  • Suitable temperature – courtesy of the householder
  • Oxygen. – courtesy of mother nature

By dealing with the causes of condensation you will automatically deal with the problem of mould.

A six-step plan can help to reduce the amount of condensation and thus black mould growth in your home.

1. Produce Less Moisture

Ordinary daily activities produce a lot of moisture. To

reduce this:

a) Dry clothes outdoors. Avoid drying clothes indoors or if you have to, dry them on a clothes airier in the bathroom with the door closed and either an extractor fan on or a window slightly open.

b) Vent tumble driers to the outside (never into the home) or buy a condensing type.

c) Cover pans when cooking and do not leave kettles boiling.

d) Do not use paraffin or liquid petroleum (bottled) gas heaters. They produce large amounts of water vapour and are very expensive to run!

2. Remove Excess Moisture

Always wipe the windows and window sills of your home every morning to remove condensation. This is especially important in the bedroom, bathroom and kitchen – just opening the window is not enough.

3. Ventilate to Remove Moisture

It is important to remove condensation and excess moisture by ventilating rooms. You can ventilate a room without making draughts or causing it to become cold. To do this, you may only need to open the window slightly or use the trickle vent that can often be found on new UPVC windows. This allows warm (but moist) air to escape to the outside and let in cool (but dry) air.

a) Always ventilate or open a window when using the kitchen or the bathroom and close the doors to prevent moisture in the air from spreading to other parts of the house. Continue to ventilate these rooms for a short time after a shower, a bath or cooking, and keep the door closed!

b) Open bedroom windows for up to one hour as soon as you arise and throw back the sheets or duvets to air the bed and bedding.

c) Clear window sills of clutter that will restrict opening the window.

d) Leave space between the back of furniture and cold walls.

e) Ventilate cupboards, wardrobes and avoid overfilling them as this prevents air circulating.

f) Do not completely block chimneys and flues – fit with an air vent and make sure you meet ventilation requirements for any gas appliances in a room.

4. Heat Your Home a Little More

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 control the heating throughout your house and manage costs.

5. Insulate and Draught-proof

This will help keep your home warm and save money on your heating bills.

  • Insulate the loft up to a depth of 25cm)
  • Consider secondary or double glazing.
  • Consider cavity wall insulation.
  • Draught-proof windows and external doors. When draughtproofing, do not block permanent ventilators or rooms requiring ventilation.

6. Dealing with black mould

Black mould can grow on walls, ceilings, furnishings and even on clothes and toys, which can be depressing and expensive.

To kill and remove the mould:

a) Carefully remove excess mould with a damp cloth and throw away after. Or if possible use a vacuum cleaner and empty after. Do not brush mould as this releases spores into the air.

b) Wipe down affected areas using a fungicidal wash or diluted bleach remember always use rubber gloves and wear safety glasses.

c) Tea Tree oil is a natural antiseptic and disinfectant but it’s also great for cleaning especially on mould or mildew. Try a dilute of three to four drops of Tea Tree oil in two litres of water (hot or cold). Soak mildewed items in the solution or spray on to trouble spots using a plant mister. Wipe, then rinse off. Always ensure you carry out a test on small area of the fabric/material/surface beforehand.

d) After treatment redecorate using a fungicidal paint or wall paper paste – do not paint over using an ordinary paint.

e) Dry clean mildewed clothes and shampoo carpets.


Dealing with condensation is not easy. Only carrying out one or two of the above steps may not solve your problem. You need to do as many as possible every day, so that it becomes part of your habits and lifestyle.

producing activities

Our everyday activities add extra moisture to the air inside our homes. Even our breathing adds some moisture. One person asleep adds half a pint of water to the air overnight and an active person adds twice that rate during the day. The illustration below gives you some idea of how much extra water you could be adding to the air in your home in a day:-

  • 2 people at home for 16 hours 1.5 Litres
  • A bath or shower 1 Litre
  • Drying clothes indoors 4 Litres
  • Cooking and use of a kettle 3 Litres
  • Washing dishes 1.5 Litres
  • Bottled gas heater (8 hours use) 2 Litres
  • Warmth versus Ventilation

Striking the right balance between warmth and ventilation is important

and can be very effective. By opening windows or ventilating your home it may appear that you are losing some heat, but what you are actually doing is allowing warm moisture-laden air to escape and permitting cool dry air to enter your home. Dry cool air is actually cheaper to heat than warm moist air!


Remember – The advice is to ventilate for an appropriate period of time, not to leave the windows open all day.




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