Preventing condensation and mould growing in your home

Mould is a fungus caused by condensation. You may usually find it has grown in damp, unventilated areas of a home.

Mould can trigger allergic reactions and may also cause respiratory issues if not dealt with properly. Check your home regularly for condensation and mould to prevent health issues.

To treat mould, buy a fungicidal spray from large supermarkets or hardware stores and treat the affected areas as soon as you notice mould.

Keep an eye on this for a week and if it returns, treat it again thoroughly.

Condensation and mould growth

Condensation causes black mould growth and is often caused by habits and the way we live, and is something that can be reduced.

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

  1. how much water vapour is produced by those who live there
  2. how cold or warm the property is
  3. how much air circulation (ventilation) there is

All three factors may need to be looked at to reduce the problem.

Installation of double or secondary glazing with draught excluders can cause condensation unless acceptable ventilation, such as trickle vents to windows are also installed and used.

For mould to increase and survive it requires two elements:

1.    Moisture – obtained from condensation

2.    Food – such as wallpaper or emulsion paint

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

Types of dampness

Rising damp is caused by water rising from the ground into the home. The water gets through a broken damp proof course or solid floor.

Rising damp:

  • will only affect basements and ground floor rooms
  • usually leaves a ‘tide mark’ low down on the wall, up to 1m in height
  • is more noticeable in winter
  • if left untreated it may cause wall plaster to crumble and paper to lift in the affected area

Penetrating dampness may be found on external walls or in the case of roof leaks, on ceilings.

It appears because of a defect outside the home, such as missing pointing to the brickwork, cracked rendering or missing roof tiles or defective lead flashings.

It will normally appear as a well-defined ‘damp-patch’ and feels cold and damp to the touch.

Once the source of the water penetration has been found and fixed, the damp areas will dry out. It may be necessary to replace rotten timbers and plaster affected by the water leaking in.

Defective plumbing is caused by leaks from water and waste pipes.

The affected area looks and feels cold and damp to the touch.

Once the leaks have been repaired the damp areas will dry out and any damage caused will need to be repaired.

Condensation is by far the most common cause of dampness in the home.

It is caused by water vapour or moisture from inside the property coming into contact with a colder surface, such as a window or wall.

The affected damp areas then attract black mould over time that grows on its surface. It mainly occurs during the colder months and 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, beds, and sofas, especially when they are pushed up against external walls.

Five steps to reducing condensation and black mould growth

1. Produce less moisture

  • Dry clothes outdoors wherever possible. If you don’t have an outside drying area, dry them on a clothes airer in the bathroom with the door closed and either an extractor fan on or a window slightly open
  • If using a tumble dryer, vent it outside or use a condensing type
  • Cover pans when cooking and do not leave a kettle boiling unnecessarily

Try to remove the excess moisture by:

  • Wipe the windows and windowsills of your home every morning to remove condensation. This is especially important in bedrooms, bathrooms, and kitchens – just opening the window is not enough
  • Open windows slightly to allow warm (but moist) air to escape and let in cool (but dry) air. Dry cool air is cheaper to heat than warm moist air!
  • Always open a window when using the kitchen or the bathroom and close the doors to stop moisture in the air from spreading to other parts of the home
  • Keep the window open for a short time after you have left the room
  • Open bedroom windows for up to one hour after you wake and keep the door closed so damp air leaves the home
  • Keep furniture and bedding away from the cold, outside walls
  • Do not completely block chimneys and flues – fit an air vent

2. 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 your home.

Good heating controls on your radiators, room thermostats and a timer will help control the heating throughout your home and manage costs.

3. 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 270mm
  • Consider secondary or double glazing
  • Consider cavity wall insulation
  • Draught-proof windows and external doors. When draught proofing, do not block permanent ventilators or rooms requiring ventilation

If you have a low income and hard to heat home, you may be eligible for up to £25,000 of home improvements to cut your energy use and reduce costs. Visit to apply or call 0800 783 2503.

4. Kill and remove the mould

  • Carefully remove excess mould with a damp cloth or if dry use a vacuum cleaner
  • Do not brush mould as this release’s spores into the air
  • Wipe down affected areas using a fungicidal spray or bleach (protecting eyes and hands) and ventilate the room
  • Tea Tree oil is a natural antiseptic and disinfectant, but it’s also great for cleaning especially on mould or mildew
  • After treatment redecorate using a fungicidal paint or gloss paint before using emulsion paint

5. Household moisture

This is an idea of how much moisture is produced in a home:

  • Two people at home for 16 hours = 3 pints
  • A bath or shower = 2 pints
  • Drying clothes indoors = 9 pints
  • Cooking and use of a kettle = 6 pints
  • Washing dishes = 2 pints

Quick guide to preventing mould and condensation

The only lasting way to avoid severe mould growth is to eliminate dampness i.e., condensation.

Here are some tips to help prevent condensation and mould growing in your home:


  • Keep your home warm with a low background heat
  • Air any unused rooms frequently

Drying clothes

  • Whenever possible, dry your clothes outside
  • Do not dry clothes on radiators, use a clothes airer in the bathroom with the door closed and window slightly open


  • When cooking, keep the connecting doors closed and open windows
  • Put lids on pans and turn on any extractor fans


  • When the bathroom is in use, where fitted, always use extractor fans, close connecting doors, and open the window to let the air circulate.


  • Whenever possible, open windows to allow your home to air
  • Ensure double glazing trickle vents are left open


  • Leave a gap between sofas, chairs, etc. and outside walls
  • Avoid putting mattresses directly on the floor

If you have tried all the above advice and condensation or mould is still a problem in your home, report it to your landlord.