Controlling condensation in your home

Condensation which occurs in your home is caused by warm vapour-laden air meeting a cold surface. When the air cools it cannot retail the moisture and some of it condenses on these cold surfaces, such as windows, mirrors and tiled walls.

The following rules can be used to minimise condensation: 

  • Keep all rooms warm and ventilated
  • Keep the internal kitchen door closed and window open when cooking
  • Keep the bathroom door closed and the window ajar when bathing or showering. Alternatively open the window immediately afterwards
  • If installed use an electric extractor fan when cooking, washing or bathing, particularly when windows show signs of misting. Keep windows and doors closed when the fan is in operation. Leave the fan on until the mist has cleared. This is especially important where extractor fans have been installed so as to counteract prevailing airflows within dwelling.

Don't use paraffin heaters or flueless gas heaters in unventilated rooms

Every litre of paraffin burnt can produce approximately one litre of water. Provide adequate ventilation where the use of these heaters in unavoidable. 

  • If possible keep heating on at all times in cold weather (intermittent heating causes condensation to be deposited as the air and surfaces cool)
  • Keep your heating on low if your home is unoccupied during the day
  • If condensation occurs in a room which has a heating appliance with a flue, check the heating installation immediately as the condensation might have appeared because the flue has been blocked.

Mould

Condensation can appear as black mould growth (mildew) on the walls of your property then it needs to be removed. If it is engrained in the wallpaper the only solution is to redecorate. If you have painted the wall prior to wallpapering, the simple remedy is to wash the wall with salt water solution to sterilise the wall. Simply add ordinary table salt to boiling water until the salt no longer dissolves. Use this solution to wash down your walls.

Dehumidifiers

There are various sizes of dehumidifiers commercially available that can be used to treat cases of severe condensation. They are very useful for drying our new buildings where parts of the structure are wet due to burst pipes or flooding. They are not normally suitable for a cure for regularly occurring condensation.

Drying clothes

Where possible, the drying of clothes inside the homes should be avoided. If a heated cupboard is not provided or used, occupants should be advised to restrict clothes drying within a dwelling to a room fitted with a extractor fan. When extraction is not continuous, controls should be provided to enable the extractor fan to be switched on for clothes drying. It is particularly important not to dry clothes in unventilated rooms, especially those kept at low temperatures.

It is essential that tumble driers are vented outside or are the condensing type. 

 

Curtains and internal blinds

The effect of a window or an internal blind on a window is to further reduce the window surface temperature and increase condensation on the glass. The use of trickle ventilators can help alleviate the problem. 

Roof ventilation

If roof ventilation is installed, ensure that it is not obstructed by insulation or goods stored in the loft.

Ceiling air tightness

It is important, from the point of view of energy conservation and to limit the risk of condensation in the loft, that airflow from the loft is minimised. To achieve this, the ceiling should remain well sealed.

If the householder installs products that penetrate the ceiling, the same precautions should be taken as above. The loft access trap can be a potential route for water vapour to escape into the loft space. It should be kept closed when access is not required.