Condensation Control

CondensationCondensation is by far the most common cause of dampness. It affects both old and new buildings, but it appears to be a significant problem where the building has been modernised with the addition with double glazing and airtight conditions.

Condensation is directly associated with mould growth. It is this that the occupier sees first, and it gives an indication of the potential scale of the problem. The mould is usually found on decorative surfaces, especially wallpapers, where it can cause severe and permanent spoiling. In many cases, the mould and its spores ('seeds') give rise to complaints about health, and cause the "musty" odour frequently associated with a damp house.

The obvious places for condensation to occur are on cold walls, windows and floors, but it can also occur in roof spaces and in sub-floor areas where there is a timber suspended floor; in the latter case, it can lead to dry or wet rot enveloping in floor timbers such as wallpaper and porous plaster, the condensing water is absorbed into the material. Condensation is very much a seasonal problem, occurring during the colder months - October to April. During the summer, the problem is seen to go away.

During the winter, ventilation of the house is usually low (due to windows and doors being closed, draught-proofing takes place). This allows build up of water vapour in the house, which, in some cases is sufficient to cause condensation. This condensation becomes apparent from the following symptoms:

  • Water droplets form on cold, impervious surfaces such as glass and paint.
  • Slightly damp wallpaper (often not noticed).
  • Development of moulds, usually black mould.

One should also be aware that the problem can occur well away from the site of most water vapour production. E.g. water vapour produced in the kitchen may diffuse through the house into a cold bedroom where it will condense on cold walls.

Extractor fans should be considered to be placed in certain areas of the property to help withdraw the moisture when it is not suitable for windows to be opened. Coupled with ventilation, heating should be set or applied to give a low-level background heat. This will ensure no rapid changes to the environment, and will facilitate slight warming of wall surfaces over a period of time, thus reducing the risk of condensation other preventive measures could be:

  • Remove excess moisture sources - e.g. paraffin heaters, indoor drying of clothes.
  • Insulate cold surfaces.
  • Prevent possible water penetration.
  • Install a dehumidifier.
  • Use an anti-mould paint