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What can I do to stop the condensation and black mould around my windows?

Mould growth caused by condensation is a warning that your heating, structural insulation or ventilation may need improving

Condensation occurs when warm moist air meets a cold surface

Provide some ventilation to all rooms so that moist air can escape, while also keeping your property reasonably warm

I have lots of condensation around my windows and black mould has started to appear.

What steps do I need to take? (MS)

Condensation occurs when warm moist air meets a cold surface, which means it often occurs around windows

MailOnline's property expert Myra Butterworth replies: Some properties suffer from condensation, with walls, ceilings and even floors damp and discoloured, often with mould growing on the surfaces.

We outline some of the steps that you can take to help ensure your home environment is as healthy - and as damp-free - as possible.

James Harrington, of chartered building surveyors Congreve Horner, explains: In simple terms, condensation occurs when warm moist air meets a cold surface. The risk of this happening depends on how moist the air is and how cold the surfaces of your rooms are.

Mould growth caused by condensation is a warning that your heating, insulation or ventilation may need improving

It is mostly an issue in winter when buildings become cold and windows are opened less, with moist air unable to escape.

Condensation occurs for short periods in bathrooms and kitchens because of the steamy atmosphere and quite frequently for long periods in unheated bedrooms, also sometimes in cupboards or corners of rooms where ventilation and movement of air are restricted.

It is important:

To prevent moist air spreading to other rooms from kitchens and bathrooms or from where clothes may be put to dry

To provide some ventilation to all rooms so that moist air can escape

To keep your property reasonably warm

How to reduce moisture to avoid condensation in the home

Good ventilation of kitchens when washing or drying clothes or cooking is essential. If there is an extractor fan, use it when cooking or washing clothes, and particularly whenever the windows show any sign of misting. Leave the fan on until the misting has cleared.

If there is not an extractor fan, open the windows but keep the door closed as much as possible to prevent the moisture spreading to other rooms.

After bathing, keep the bathroom window open and shut the door for long enough to dry off the room.

A lot of ventilation occurs in old houses through fireplace flues and draughty windows. But it doesn't occur in modern flats and houses unless a window or ventilator is open for a reasonable time each day and for all the time a room is in use.

Too much ventilation in cold weather is uncomfortable and wastes heat, and so all that is needed is a slight opened window or ventilator. About a 10mm opening will usually be sufficient.

Avoid the use of portable paraffin or flue less gas heaters if possible as each litre of oil used produces the equivalent of about a litre of liquid water in the form of water vapour. If these heaters are used, make sure the rooms they are in are well ventilated.

If you already have black mould, it needs to be cleaned with bleach and anti-fungicide solution

If condensation occurs in a room with a gas, oil or solid fuel heating appliance with a flue the heating appliances need to be checked as the condensation may have appeared due to the appliance flue becoming blocked.

Do not use unventilated airing cupboards for drying clothes. And if washing is put out to dry inside, open a window or turn on the extractor fan enough to ventilate the room. Do not leave the door open as this will allow moist air to spread to other rooms.

Try to make sure all rooms are at least partially heated to ensure that surfaces are reasonably warm.

Houses and flats left unoccupied and unheated during the day get cold, and so whenever possible, it is best to keep the heating on - even if at a low level. Even in a well-insulated house and with reasonable ventilation it is likely to be necessary during cold weather to maintain all rooms at not less than 15 degrees centigrade to reduce the risk of condensation.

Any sign of mould growth is an indication of the presence of moisture and if caused by condensation provides a warning that heating, insulation or ventilation – or all three – may require improvement.

If you do have black mould already, this needs to be cleaned with bleach or an anti-fungicide solution. And if the window reveals are redecorated you may consider mixing in some anti-fungicide solution in with the paint before it is applied to the walls to prevent future mould growth.


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