If you have concerns about damp or other issues in your rented home, see the Tenant’s Guide To Healthy Homes.

What is condensation?

  • It is caused when warm moist air, produced by ordinary household activities such as cooking and bathing, hits a cold surface, such as a cold wall or window.

  • If moist air cannot escape to the outside of your property it stays in your home. It moves around until it finds a cold spot where it can condense.

  • There is always some moisture in the air, even if you cannot see it. If the air gets colder, it cannot hold all the moisture. Tiny drops of water appear. This is condensation. You notice it when you see your breath on a cold day, or when the mirror mists over when you have a bath.

  • Condensation occurs mainly during cold weather, whether it is raining or dry. It does not leave a 'tidemark'. It appears on cold surfaces and in places where there is little movement of air. It can often lead to mould forming in corners, on or near windows, in or behind wardrobes and cupboards. It often forms on north-facing walls, as these are often colder.

Condensation is not the only cause of damp that can affect buildings

It can also come from:

  • Leaking pipes, wastes or overflows.

  • Rain seeping through the roof where a tile or slate is missing, spilling from a blocked gutter, penetrating around window frames or leaking through a cracked pipe.

  • Rising damp due to a defective damp course or because there is no damp course.

  • It can be difficult to be sure of the exact cause of dampness. Condensation-related dampness often leads to mould growth on wall and ceiling surfaces, furniture and even clothing.

How to avoid condensation

The following steps will help you reduce the condensation in your home:

  • Heat Your Home Effectively.

  • Have the right balance of heating and ventilation. Heating is used to keep the building warm. Ventilation allows moist air to escape from the building.

  • Central heating is designed to be in operation for long periods when the weather is cold. Either leave the heating on for long periods on a low setting or set the timer switch to turn the heating on in the morning and afternoon/evening for at least 7 hours each day. During this period, do not turn the heating on and off manually. Let the system's thermostat do this for you.

  • Other forms of heating, such as storage heaters, need to be manually operated. It is advised that these be left on low to moderate settings for long periods of the day.

  • Avoid having cold areas in the home. Ensure that the whole of the property is heated to a moderate temperature.

  • Try to produce less moisture. Some ordinary daily activities produce a lot of moisture very quickly.

  • Cover pans and do not leave kettles boiling.

  • Do not use paraffin and portable flueless bottled gas heaters. These heaters put a lot of moisture into the air. They may be against the conditions of your Tenancy.

  • Dry washing outdoors on a line, or put it in the bathroom with the door closed and the window open or fan on.

  • Do not dry washing on radiators.

  • Tumble dryers remove moisture from wet clothing. Tumble dryers must be vented to the outside. If your tumble dryer is part of the washing machine, it will be vented automatically. If it is just a tumble dryer, you will need to check the operating manual for advice on how to vent it.

  • Ensure that condensation which forms on windows is wiped dry as often as it occurs. This will prevent the condensation collecting on the windowsill and running on to the walls below. Wipe dry surfaces where moisture forms. This is to prevent mould from occurring.

  • Make use of extractor fans or cooker hoods where provided.

  • Try putting cold water in the bath before adding hot. This reduces the risk of steam being created.

  • If you have a combination boiler, adjust the thermostat at the boiler to get the hot water to a useable temperature without the need to add cold water.

  • How much moisture do you produce in your home?

  • Drying clothes produces 10 pints of moisture (6lbs of washing in an unvented tumble dryer).

  • Washing clothes produces 1 pint of moisture.

  • Having a bath produces 2 pints of moisture.

  • Cooking by gas for 3 hours produces 3 pints of moisture.

Ventilate to remove moisture

You can ventilate your home without making draughts:

  • Keep a small window or trickle ventilator open when someone is in the room.

  • Ventilate kitchens and bathrooms when in use by opening the windows wider. Leave windows open for half an hour after bathing or cooking to get rid of the moisture.

  • Close the kitchen and bathroom doors when these rooms are in use, even if your kitchen or bathroom has an extractor fan. This will help prevent moisture reaching other rooms, especially bedrooms, which are often colder. These are more likely to suffer with condensation. Keep bedroom doors closed to reduce the risk of moisture travelling to these rooms.

  • Where possible, position wardrobes and furniture against internal walls. Avoid placing furniture or heavy curtains in front of radiators.

Some words of warning

  • Never block permanent ventilators, for example: vents to windows, airbricks to walls and chimney breasts.

  • Do not draught-proof rooms where there is condensation or mould.

  • Do not draught-proof a room where there is a cooker or a fuel-burning heater, for example, a gas fire.

  • Do not draught-proof windows in the bathroom and kitchen.

First steps against mould

  • First remove mould growth by wiping down walls and window frames with a fungicidal wash. The was should carry a Health and Safety Executive 'approval number.' Follow the manufacturer's instructions precisely. Dry-clean mildewed clothes and shampoo carpets. Disturbing mould by brushing or vacuum cleaning can increase the risk of respiratory problems.

  • After treatment, redecorate using a good quality fungicidal paint to help prevent mould recurring. Note that this paint is not effective if overlaid with ordinary paints or wallpaper.

  • Take action and steps as suggested here to prevent condensation recurring.

  • The only lasting way of avoiding severe mould is to eliminate condensation and dampness.

Last updated: Wednesday, 24 April, 2024.