Condensation affects millions of homes in the UK. It is closely related to how well the home is heated, ventilated, insulated and draught-proofed - and remedies often include improvements in heating and insulation, although there are simple things you can do to help cut down the problem.
Condensation can cause staining and mould growth, and can severely damage wall surfaces and window frames as well as furniture and clothes. The mould associated with severe condensation problems can also be a health risk.
Condensation, like all forms of dampness, is a particular problem because damp homes are harder to heat.
It is important to realise that condensation can occur in rooms some distance away from the source of moisture production. Warm moist air naturally moves to colder areas and will condense on cold surfaces. For example, a common problem in homes that are not centrally heated, is that moisture-laden air moves to unheated rooms (often bedrooms) and causes condensation.
What is condensation?
All air contains a certain amount of invisible water vapour and warm air can 'carry' more water vapour. If warm air comes into contact with a cold surface, the air 'gives up' its water as droplets on the surface. If you wear glasses you will know what happens when you come into a warm house from the cold outside. The same effect can be seen on a bathroom mirror when you have a hot bath - warm moisture-laden air chills on contact with the cold surface. This process can occur anywhere in the home.
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Why condensation is a problem
Condensation dampness causes staining and mould growth and can damage wallpaper, wall surfaces and window frames, as well as furniture and clothing.
The black mould, that is a familiar sight when there are severe condensation problems, can cause ill health in some people.
Condensation, like all other forms of dampness, makes houses difficult to keep warm. The reason being wet building materials lose heat more quickly than dry ones and also some of the heat input is being used to dry out the house.
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Where do you find condensation?
- Cold surfaces such as mirrors, single-glazed windows and metal-framed windows.
- Kitchens and bathrooms (where moist air is produced through washing, cooking, etc).
- Walls of unheated rooms.
- Cold corners of rooms.
- Wardrobes, cupboards (particularly built-in cupboards) and behind furniture against an outside wall.
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What can be done to reduce the risk of condensation?
To reduce condensation one or more of the following factors should be considered:
- Reducing moisture production
- Ventilation
- Heating
- Insulation
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Reducing moisture production
Moisture is produced in the course of day-to-day activities, but there are still a number of steps that can be taken to reduce moisture production:
- Keep lids on saucepans when cooking.
- Clothes should not be left to soak for longer than necessary.
- Tumble dryers should be vented to the outside.
- Bottle gas and paraffin heaters should be avoided.
- If producing steam in the kitchen or bathroom, open the window and close the door to stop moisture spreading through the house. (Draught strip bathroom and kitchen's interior doors).
- Cupboards and wardrobes will be less prone to condensation if doors are left open from time-to-time or if louvre doors are fitted.
- Clothes should always be thoroughly dried before being put into a wardrobe.
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Ventilation
If there is not enough ventilation, moist air will not be able to escape. However, too much ventilation makes a house draughty. Getting the balance right can be difficult!
Background ventilation can be given by air bricks and ventilators, (some of these are adjustable - but they should never be blocked) or by trickle ventilators fitted to window frames. If condensation is occurring against furniture (commonly a bed, if pushed against an outside wall, or a sofa in a bay window), move the furniture away from the wall and make sure air can circulate around the cold area.
In kitchens and bathrooms, extractor fans are a very good idea. Humidistat fans switch themselves on and off according to the dampness of the air. Ventilators, which can recover the heat from the air before expelling it, are also available.
Other measures for the kitchen and bathroom include opening windows when moisture is being produced and closing internal doors which should be draught proofed to prevent the moisture spreading to the rest of the house.
If condensation is a problem, care must be taken when draught-proofing the home. Too much ventilation (as draughts) can make condensation worse by making homes harder to heat. But if you seal off all the draughts, then the moist air cannot escape. If condensation is a problem and you want to draught proof your home, then it is worthwhile seeking further professional advice.
Never seal openings in a room where combustion takes place. Always seek advice.
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Heating
Condensation is most likely to be a problem in the home that is under-heated. The home may be unheated due to an inadequate heating system or not having enough money to heat the home.
If you cannot install or use a heating system, you may opt for individual fires/heaters. Of these, bottled gas and paraffin heaters should be avoided. They are likely to make any condensation problem worse. Remember also that on-peak electricity is very expensive, and it may be false economy to switch off your central heating and use electric bar fires or fan heaters instead.
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Insulation
Insulation is important in the treatment of condensation in three ways:
- It warms up the surface of walls, ceilings and windows - removing cold surfaces for the vapour to condense on to.
- It generally warms up the home.
- It can reduce heating bills, enabling people to heat their homes to a higher standard.
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Dehumidifiers
A dehumidifier is an electrical device designed to help condensation problems by removing moisture from the air. These should be used in areas where there is a risk of condensation. In general, they are not an ideal solution, but they can help in some cases. In cases of severe condensation, they are a useful temporary measure.
A dehumidifier draws in warm moist air from the room and passes it over cold coils, which causes water to collect in a moisture collector. The air that has been taken in is drier and cooler - the dehumidifier will then warm up this air and return it to the room.
- Dehumidifiers are less effective in poorly heated rooms.
- Moisture collectors may fill up quickly and need to be regularly emptied.
- Expensive to buy and cost money to run.
- They can be noisy.
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Dealing with Mould
For some people the microscopic spores produced by the black mould are a health risk. Remove mould using household bleach or a fungicide solution. If the mould is particularly bad, wear a facemask. The cleaned area may be over painted with a fungicide paint or covered with special wallpaper paste before redecoration. But unless the cause of the problem is treated, the mould will return in due course.
The most effective way to eradicate mould in the long-term is to eliminate the source of water to reduce the risk of condensation on surfaces.
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Fungicidal Washes
Cleaning with fungicidal washes can be effective. They can also be considered as a temporary measure pending lasting improvements.
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Fungicidal Paints
Some fungicidal paints now available may be capable of giving prolonged control and can be of value for redecoration. Indeed where damp conditions are slight, intermittent fungicidal paints may give an adequate period of protection. Fungicidal paints differ in effectiveness especially if conditions have not been improved to reduce dampness.
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Fungicidal Wallpaper Pastes
Pastes cannot be relied on to protect the wall covering itself from growth of moulds. The 'fungicide' is present solely to protect the paste during use and during the sometimes prolonged drying which can occur with various types of wall covering, for example, vinyl paper.
Fungicide pastes can be sprayed on to wallpaper surfaces to prevent mould growth.
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Anti Condensation Paints
These are not fungicidal paints and not intended to prevent mould growth directly. T hey work by forming a barrier to prevent moisture being absorbed on a paint surface or material, so avoid or reduce conditions suitable for mould growth. They may be considered as part of the overall strategy for reducing condensation mould growth.
Some of these products may be effective in keeping the mould at bay for a time, but in most cases the mould will grow back unless the condensation dampness which caused it is dealt with effectively.
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For more information about this and all other energy issues, please contact the Energy Efficiency Advice Centre.
Disclaimer
Please note that Energy Efficiency Advice Centres (EEACs) cannot be held responsible for third party products. While care has been taken to ensure that the advice contained on this webpage is accurate, it cannot replace expert advice in some cases. EEACs can accept no responsibility for any damage or loss incurred by reliance on the accuracy of this information.
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