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Factsheet on Condensation & Damp

All houses can be affected by condensation and it can cause mould, leave a musty smell and damage clothes, furnishings and decoration. The advice below should help you prevent condensation before it becomes a problem and identify the differences between condensation and damp.

What is condensation?

Condensation occurs when moisture in the air gets cooler and tiny water droplets appear on surfaces e.g. when your mirror mists over after you have a bath. It usually happens during cold weather and appears on cold surfaces and places where there is little movement of air; for example in corners of rooms, on or near windows and in or behind furniture.  If left untreated black mould will begin to grow.

What causes condensation?

There are three main causes of condensation in a house:

1. Rooms that are too cold and inadequately heated, creating lots of cold surfaces.

2. The production of too much moisture from cooking, washing, showering, clothes drying, etc. - all result in moisture laden warm air which will lead to condensation in the coldest parts of the house.

3. Inadequate ventilation of the steam produced at source, which keeps it all in the sealed envelope of the house. Houses with double glazing and no open chimneys are effectively hermetically sealed boxes, with little or no ventilation to remove excess moisture when it is produced. Through the daily routine of showers, baths, boiling kettles, cooking, drying clothes and breathing a person will produce approximately 4 pints of water per day and ventilation is needed to remove this from the home.

How to prevent condensation

By following the simple steps below you can considerably reduce condensation by producing less moisture and keeping your home well ventilated and heated.

1. Maintain a minimum temperature in all your rooms, especially bedrooms and bathrooms – temperatures should not be allowed to fall below about 18°c.  If you are out all day leave some heating on to keep the house warm.

2. Minimise the amount of steam you produce when cooking and washing and always vent this to the outside, for example by opening a window or using the extractor fan if you have one.  Always confine steam to the room it is produced in by keeping internal doors closed.

3. Keep the bathroom door closed during and after bathing. Open the window (or use the extractor fan if you have one) straight after bathing, in order to get rid of the moisture.

4. Dry clothes outside if permitted, or in a room with the window open and the door shut. Vent tumble driers outside if they’re not condenser versions.

5. Keep all rooms ventilated by slightly opening windows and keeping doors shut, particularly when the room is in use. Double glazed units often have trickle vents fitted which should be left open. This helps release any moisture and prevents it spreading around your home.

6. Don’t block airbricks or window vents. Keep trickle vents open all year around.

7. When going to bed, close the bedroom door and keep a small window ajar or when getting up, open the window and keep the door closed for a couple of hours to get rid of the moisture produced overnight.

8. Wardrobes and other large items of furniture should not be placed directly against external walls. Pockets of trapped air can lead to serious surface condensation and mould growth on the walls and furniture. Leave space between the back of the furniture and the wall. Leave wardrobe doors open slightly. Put floor-mounted furniture on blocks to allow air to circulate underneath. Do not overfill cupboards and wardrobes.

9. Open a window and shut the doors of any rooms affected by condensation.

10. Make sure blinds, shutters, curtains are not left closed permanently as this will create a barrier between them and the window with condensation occurring causing water to form on the inside of the window and mould on the window frame, window ledges and surrounds.

Left untreated nuisance condensation can cause mould to grow.  If this happens you must remove mould by washing the surfaces affected with a fungicidal mould remover, following the manufacturer’s instructions.

What is damp?

Damp is different from condensation. Damp occurs when a fault in the building’s structure lets in water from outside. There are two main types of damp:

1. Penetrating damp - this occurs if water is coming in through the walls or roof (for example, under a loose roof tile) or through cracks.

2. Rising damp - this occurs if there is a problem with the damp proof course. This is a barrier built into floors and walls to stop moisture rising through the house from the ground. The usual evidence of rising damp is a ‘tide mark’ on the walls that shows how high it has risen and sometimes an accompanying musty smell.

We understand that all houses are different and, therefore, some may be more susceptible from condensation than others and this could be due to their age, style of build, location, type of windows, heating, ventilation etc., but we ask that you follow these reasonable simple steps to keep on top of this.

It is your responsibility as per the terms of your lease to manage and deal with condensation, but if damage is caused to the property by condensation/mould that has been ignored and neglected, then it will become your responsibility to rectify the situation at your own expense.