Causes of condensation and black mould


Guidance on the causes of condensation and black mould.

There is a difference between damp and condensation in your property and how it is caused.

Condensation is dampness formed when air containing water vapour is cooled by contact with a cold surface.

Why - warm air inside buildings is capable of holding varying amounts of moisture. When warm, moist air touches a cold surface, such as a window or external wall, it is then no longer able to hold as much water vapour. The air-borne moisture then turns into drops of water and collects on the cold surface. This is called condensation.

Condensation is caused by day-to-day activities, coupled with lack of ventilation and background warmth.

The average household produces around 14 litres or 24 pints of water vapour every day. This vapour is held in the warm air and must be allowed out of the property, otherwise condensation may form. The main sources of water vapour are:

  • Drying clothes
  • Cooking
  • Boiling Kettles
  • Bathing/showering
  • Unvented dryers
  • Washing machines

Condensation is different from damp. It is surface dampness and can be visible as black mould. It mainly occurs on cold walls inside and other cold surfaces such as tiles and cold-water supply pipes under sinks and hand basins. Condensation is usually worse during the winter.

Are you sure it is condensation?

Some forms of damp are caused by leaking pipes, a leaking roof or rising damp. Leaks often result in patches of damp coming through the plaster and wallpaper near where the leak is. Rising damp can be identified by a damp 'tidemark' low down on the inside walls.

Black mould

Small amounts of condensation can be found in most homes, but if you do not deal with it, and it is allowed to get worse, then black mould growth can occur. This can form on walls, surfaces personal possessions.

Black mould is almost exclusively caused by condensation and is usually found at the skirting level in rooms, in the corners of walls and ceilings or on cold surfaces. Mould can also appear on cold surfaces such as tiles and window sills or behind furniture where the air flow is restricted. Mould and mildew can also grow on furnishings, curtains and even clothes and shoes and can spoil wallpaper and furnishings.

Some damage may be permanent. JRHT will not pay for black mould damage to your personal possessions caused by condensation. You should check if you can claim this back from you home contents insurance.

Dealing with mould growth

If you see black mould, this can be removed by wiping down with detergents or proprietary mould removers. It can be washed out of fabrics but may leave stains or spoil colours.

The best way of tackling mould is to reduce the condensation levels and prevent it growing in the first place.

What can you do to prevent condensation?

It is your responsibility to prevent and address condensation in your home.

The amount of condensation depends on how much water vapour is in the air. Many everyday activities add to the water vapour level in your home, but their effect can be kept to a minimum.

Everyday activities that add to the water vapour level

Cover pans when you’re cooking

Don’t leave kettles and pans boiling longer than necessary

Keep the bathroom door shut and the room well ventilated.

When filling your bath, run the cold water first then add the hot – it will reduce steam by 90%

Drying clothes

Hang washing outside to dry whenever you can.

If you must use a tumble dryer make sure it's vented to the outside.

If you must dry washing indoors use the bathroom and keep the door shut and the room well ventilated

Do not hang wet washing on radiators all round your home – doing so is very likely to cause condensation problems

Heating your home Heating your home can help solve a condensation problem, but only if it’s used in addition to the other steps already described. Condensation forms more easily on cold surfaces. The best approach to heating in order to reduce condensation, assuming you have taken the other three steps, is to provide a minimum of background heating. This will warm your home, so there are no cold surfaces
Allow air to circulate

It is important to let air circulate around your home. To reduce the presence of mould on clothes or other stored items, do not store shoes etc underneath cabinets, pull furniture slightly away from walls, keep wardrobe doors and drawers slightly ajar, pull shelves away from the back of wardrobes, do not over fill rooms, cupboards or shelves or display cabinets.

Avoid cluttering rooms with personal possessions – too many personal items prevents air form circulating freely around your home and can cause condensation

Condensation can be a problem if it is not dealt with – it is your responsibility as a resident to take action to prevent excessive condensation in your home. If after having read this, you require further information please contact us on 0800 5870211.