During site surveys of properties suffering from foundation movement, we always encounter other building problems. In this house, there was a concerning amount of mould growth in some areas of the building. Mould growth can trigger significant respiratory problems for the young and elderly, particularly those with asthma.
Mould growth is caused by condensation and condensation is caused by the presence of too much moisture in the air. Mould growth will occur if the relative humidity remains above 70% but will grow at an increasing rate at over 80%. High relative humidity results in condensation at higher internal air temperatures.
Condensation can be prevented or at least controlled by consideration of four factors – moisture generation, ventilation, heating and insulation.
In this bathroom, there was no extract ventilation – Building Regulations requires that all bathrooms are fitted with mechanical extraction of 15 litres/second minimum. Although, we did not enter the attic space, it is most likely that there is little or no insulation either.
In the bedroom, the likely cause is poor background ventilation and poor insulation in the attic. The vent is partially blocked on the outside after the walls were re-dashed some while back. Building Regulations require a minimum background ventilation of 5000mm2.
In many dwellings where resources are limited, condensation can be reduced by simple behavioural patterns and DIY works such as opening windows during showers (purge ventilation) and leaving them open for about 15 minutes after, not drying clothes on radiators and ensuring vents from dryers are connected to the exterior of the building.