Mould and condensation issues

Ever noticed condensation running down your walls in the bedroom, bathroom and kitchen? Has this in turn created damp problems?

In high humidity rooms condensation can easily occur where there is not enough air circulation or where non-breathable paint has been used to seal up the room. Bathroom and kitchen paint is probably the worst thing that you can use in your bathrooms and kitchens because they seal up the room thus trapping moisture inside and this then can form condensation and damp problems.

Inadequate ventilation is also another major cause of the problem. The smallest (and cheapest) fans are the ones that are usually fitted in bathrooms and kitchens. They are not always the best choice, because they are the absolute minimum required, and this is not always enough. The issue with larger fans is that they use more energy and also increase heat loss. So getting the right size is important.

Where the extractors face is also important. If they are west or south facing they are likely to get blown shut by the wind and hence not be able to extract air properly. So it is worth placing them on the north or east walls to get the best performance and also to stop the incessant slapping of the vent’s flaps.

If you are worried about heat loss then this can be partially remedied by using room based heat exchange extractors. However you do need to have a fairly airtight room / house for these to be anywhere near efficient.

A house needs good ventilation and in many homes this comes from trickle vents in the windows and so these should be kept clear.

Many people also dry their clothes on radiators. This just adds large amounts of moisture into the internal atmosphere and so should be avoided.

Condensation is also caused by cold spots in the house. This might be on walls, or on the windows (windows are less thermally efficient than walls). This is way radiators are commonly placed under windows to prevent condensation. So if there are cold spots then condensation is more likely here. This is a structural issue and should be addressed.


Ensure that you have adequate ventilation in the house (appropriately sized extractors in high humidity areas) and that they are fitted onto a north or east facing wall. If you have a breathable house (many of the older buildings with solid walls are intrinsically breathable) then by using breathable paints onto the lime plaster then the walls will help to control the relative humidity in the house.

Do not dry clothes on radiators (unless you provide adequate ventilation).

Where you are redecorating existing painted walls, you can use clay or chalk paints to help to ease the problem as they actively absorb and release moisture as humidity levels change.

Insulate where cold spots occur (or cure the underlying structural issue like thermal bridging). Where this is difficult you can use products like insulating paints or thin insulation like aerogels or insulating plasters.

Where these solutions are difficult to do you might want to use anti-mould paints / treatments just to stop the formation of mould.

For more advice and products please call the Eco Home Centre on 02920373094.


Rounded Developments Enterprises Ltd have endeavoured to ensure that the information contained in this report is accurate. However, Rounded Developments Enterprises Ltd. accepts no liability for the use of this information.

Statement of Vested Interest

Rounded Developments Enterprises Ltd are a well-recognised supplier of a range of sustainable building products and as such have a commercial interest in some of the recommendations contained within the report. In some cases, cost estimates have been given on the basis of current quotations for similar equipment supplied by Rounded Developments Enterprises Ltd, and may not be the only equipment available. However, it is our opinion that the study offers an appropriate level of detail in view of the resources available and information provided. The authors have no expectation of any order being placed with them and would welcome questioning of the choice and costs of any equipment.