Of the causes of dampness inside buildings, a leading cause is condensation, affecting both new and old properties and even those that have been modernised. Condensation is also connected closely with the growth of mould and this unpleasant sight is often the first sign of a problem.
The most common places that condensation appears are on cold walls and floors, but areas such as the roof space and the space between floors can also be vulnerable. The wooden timbers in the area often become damp and this makes them likely to be damaged by dry or wet rot.
So how does condensation come about? Firstly, it is important to understand that warm air holds more moisture than cold air. This means that when this moisture-filled air meets a cold surface the air begins to cool and cannot hold onto the moisture, depositing it onto the surface instead. This is known as the Dew Point – when the water ‘condenses’ from the cooling air and is visible as condensation on a surface.
When this surface is something impervious, such as glass or paint, little beads of water form and can be wiped away. But on porous surfaces, such as wallpapered or plastered walls, the water soaks into the surface. This absorption of water isn’t always visible and this is why a problem can go unchecked for some time.
The problems created by condensation tend to be worse at certain times of the year, namely from October to April when the climate is at its coldest. This is contributed to by the fact that, during the winter, we ventilate our houses less to keep the cold at bay – that is, windows are closed and draught proofing is in full use. This allows the water vapour to build up inside the house and causes condensation.
There are three main signs that condensation is present in a house: water droplets on glass and similar surfaces; mildly damp wallpaper; and the development of mould. The latter is usually found in spots where there is little airflow such as in the corners of rooms and behind free standing furniture, the junctions between floors and walls or floors and ceiling. The most common type of mould is black mould (Aspergillus niger).
Prevention and Cure
As with any problem, stopping it before it develops is the ideal scenario; and with condensation, the key element to preventing it is ventilation. Opening windows each day, even when it is cold, is important and even more so when you are cooking. Similarly, after a bath or shower, ensure the window is open to ventilate the area. In winter, maintaining a constant temperature in the house will also help prevent condensation.
If you notice that you have a condensation problem, then the steps to stop it before it turns into damp are based on similar principles. The aim is to remove moisture from the house and ensure that the air can flow so that any moisture that has accumulated can disperse. Drying clothes outside where possible is a good way to help with this and ensuring that air vents are unblocked allows them to do this job for you.