Why Is My House Always Mouldy?

Mould growth is common in buildings which have condensation problems. Spores germinate on the surface of internal linings, often behind furniture or hidden within the linings themselves. Areas of poor air circulation increase the risk of condensation forming and can be undetected by the occupier. They feed on moisture such as condensation but some types of mould spores can feed on wall paper adhesive. Mould spores can germinate on any surface although the internal air conditions, thermal properties and extent of moisture all contribute towards the risk of mould germination. Modern professionals believe that mould is the 21st Century equivalent of asbestos in terms of health and safety risk. Mould spores can cause skin irritation and affect the human respiratory system. Heed this warning carefully, don’t ignore the mould germination and remember your health is at risk.

How do we stop the mould growth?

The risk of condensation and mould growth forming can be reduced by improving thermal insulation of the external fabric (walls / glass etc). Condensate will form on the coldest part of a room, single glazing, solid walls etc. Condensate is the excess vapour within the air, therefore regular air changes or air movement will reduce the risk of condensate forming. Warm air contains more vapour than cold air, therefore a rapid increase of air temperature will increase the risk of condensate forming on cold surfaces. The relationship between the internal air temperature and internal surface temperature is therefore a main reason condensation forms. If the external air temperature is cold, say below 5 degrees Celsius then the internal surface is possibly cold enough to be at risk of condensation forming, its then up to the internal conditions If the internal air and surface temperatures reach equilibrium then the risks of condensation forming is low.

For example, if you wanted to make condensation form within a property, wait till the external air is relatively cold, close all windows and doors to seal the accommodation and limit air changes. Switch on the heating and rapidly increase the internal air temperature. So obviously the reverse of this example should reduce the risks of condensation forming. Maintain regular air changes by opening windows and ventilating rooms and moderate your heating system. Low and constant air temperatures mean the surface temperatures will maintain equilibrium, rise and fall with the air temperature.

What should we do next?

Moderate your heating system and remember to ventilate rooms especially bathrooms or kitchens where high humidity levels are created. You should clean all signs of mould spores immediately using nitrates or chlorides to kill the germination although you may need to remove wall paper where spores are feeding on adhesive. It sounds easy to ventilate rooms and control the heating system but generally you are going to create a cool internal environment and most clients like to be cosy on winter evenings. You should consider improving thermal insulation, meaning the internal surface temperature is unlikely to drop to a level where condensation may form. Keep furniture away from external walls to ensure there is a regular air flow and try to balance the internal environment as constant rather than rapid changes or air temperature. If your nose is starting to itch, it might be time to open a window.


Produced By;

Gary Naftel BSc(Hons) MCIArb MRICS
Chartered Surveyor

The information in this Coffee Break article is intended for guidance only. The authors cannot accept any liability for any loss or damage which may result from the use of this article.