Condensation and damp

We often get asked about problems with condensation and damp. Below are some facts about how to identify one from the other and tips on how to combat them.

What is condensation?

Mould growth on the window frame caused by condensation run-off

There is always moisture in the air, but basic household chores (such as cooking, taking baths, showers and drying clothes indoors) can produce up to 20 pints of water vapour each day within your home. If it can't escape this water vapour can build up in the air and when it gets cooler it will condense (turn back into water). It is important to remove this water vapour before it forms condensation. Poor ventilation and inadequate heating can increase the amount of condensation.

Examples of amounts of moisture produced in a 24 hour period include:

  • Washing clothes – 1 to 2 pints
  • Drying clothes – 6 to 12 pints
  • Cooking – 3 to 7 pints
  • Bathing and showering – 1 to 2 pints
  • Washing dishes – 1 to 2 pints

Two people at home all day will also produce three to five pints of moisture, while two people asleep for a night will produce another one to two pints.

What is damp?

Condensation mould growth on a window reveal and window sill

Damp can be caused by:

  • leaking pipes, wastes or overflows
  • excessive water spillages in the bathroom
  • leaks around the bath (edges need to be sealed to the tiles with silicone sealant)
  • not using a shower curtain or screen correctly
  • rain seeping through the roof where a tile is missing or cracked
  • rain spilling from a blocked gutter or entering around windows
  • ineffective damp proof course or in older houses there may not be any damp proofing
  • pooling of water against the house walls

This type of damp usually leaves a tidemark.

If you do not think the dampness in your home is caused by any of these and there is no tidemark, it is probably condensation.

How to reduce condensation

Condensation that doesn’t dry out or escape through adequate ventilation can cause mould to form on walls, windows sills, furniture, clothes, and cold water pipes, and can rot timber.

The following tips will help you to reduce condensation in your home.

Ventilate to remove moisture

  • Keep a small window ajar when someone is in a room (some UPVC double glazed windows have a trickle ventilator you can use instead). Some windows can be locked slightly open to allow ventilation.
  • Open windows when cooking, drying clothes and taking a bath or shower to allow fresh dry air to circulate through your home.
  • Where fitted, use an extractor fan in the kitchen and bathroom as these are effective and cheap to run.
  • If you don’t have extractor fans, open bathroom and kitchen windows when in use and leave them open for a short time once you have finished bathing or cooking to let the moisture escape.
  • Ventilate cupboards and wardrobes by leaving them open for a while or cutting a ventilation slot in the back of each shelf or behind each drawer.
  • Avoid putting too many things in cupboards and wardrobes as this stops the air circulating.
  • Leave a space between the back of the wardrobe and the wall to allow air to flow.
  • Where possible, position furniture against warmer internal walls.
  • Vent tumble dryers to the outside, unless it is the self-condensing type.

Controlling the moisture

  • Cover pans and simmer when cooking, and do not leave kettles boiling - this will also cut your fuel bills!
  • Where possible, dry your clothes outside on a line or in a well-ventilated room (with an open window or an extractor fan turned on).
  • Don’t dry clothes on your radiators as this puts a lot of moisture into the air. If you do have to use them, open as many windows as possible. Remember, covering radiators stops your room getting warm and dry.
  • Close kitchen and bathroom doors when in use to prevent steam going into colder rooms.
  • In cold weather, keep your heating on low all day throughout your home - this is important to help prevent condensation build up.
  • Wipe down surfaces where moisture settles.
  • Where fitted, use an extractor fan in the kitchen and bathroom as these are effective and cheap to run.
  • Ensure you use bottled gas heaters in a well ventilated room, as they put a lot of moisture into the air. Remember, you need to get written permission from your housing officer to use Calor gas bottles and heaters in your home.
  • Use a dehumidifier if you have one. These are cheap to run and the drier atmosphere they create will be easier and cheaper to heat.

Heating and insulation

  • condensation is less likely when the house is warmer, so use your heating if your home suffers from condensation
  • In cold weather, keep your heating on low all day throughout your home - this is important to help prevent condensation build up.
  • ensure your home is insulated to the currently recommended levels.
  • have a look at our energy efficiency pages for more tips on keeping warm, and advice about fuel bills

Things to avoid

  • Don’t block airbricks or vents in the wall.
  • Don’t completely block redundant fireplaces - a hole the size of two bricks with an open louvered (‘hit & miss’) vent covering it will keep the chimney aired and dry.
  • Don’t draught-proof rooms where there is condensation or mould.
  • Don’t draught-proof a room where there is a cooker or fuel burning fire, such as a gas fire.
  • Don’t draught-proof windows in the bathroom and kitchen.
  • Generally, draught-proofing your home is not a good idea if it is prone to condensation – it stops air circulation, increases condensation and it is not healthy for you and your family.

How to treat mould

To kill and remove mould, wipe down walls and window frames with a fungicidal wash, which is available from most DIY shops.

Dry-clean mildewed clothes and shampoo carpets. Avoid disturbing mould by brushing or vacuum cleaning as it can make existing respiratory problems worse.

After treatment, redecorate using a good quality fungicidal paint. This helps prevents mould re-occurring.

Condensation or damp still a problem?

If you follow these tips and guidance, but condensation, dampness and reoccurring mould growth is still a problem: