Condensation Control Nottingham & The East Midlands
Aspergillus mould growth is associated with high relative humidity (condensation) rather than rising damp. The wall areas generally affected are cold surfaces (outer walls) and poorly ventilated areas (corners of rooms, behind furniture and inside fitted cupboards).
Mould growth can cause throat irritations and may aggravate existing illnesses such as asthma. To prevent mould spreading it should be removed using a fungicide wash and the appropriate safety precautions followed.
Relative humidity is the amount of water vapour in the air expressed as a percentage of the amount it can hold at a given temperature. Relative humidity has to reach 80% on the surface of a wall for mould to grow. Relative humidity should ideally be around 55-65%.
In order to eradicate the mould growth, it will be necessary to reduce relative humidity. There are four elements to consider in doing this:
Cold surfaces attract condensation. This is because condensation forms on surfaces that are at a specific temperature in relation to the ambient room temperature. This is known as the dew point.
The dew point is around 6-11 degrees cooler than the ambient room temperature. If a surface is cold to the touch this is usually a good indication it will attract surface moisture and mould growth.
There are a number of ways the insulation value of a wall surface can be improved including the application of polystyrene wallpaper backing or thermal boards. Thermal boards may also be a good option for lining the back of the wardrobes if relocating them isn’t really an option.
Anti-condensation paints are also available which reflect heat and contain a fungicide to prevent mould growth.
Current building relations regarding roof insulation exceed that present in most properties and it would therefore be advisable to upgrade the insulation if this is the case in your property.
It may be possible to control/reduce the condensation problem by modifying any one of the above factors but usually it requires a combination of measures possibly taking in to account all four of the general factors mentioned.
Room temperature (and particularly the surface temperature of walls) should be increased where possible. Unnecessary changes in temperature should be avoided. Every time the temperature changes there will be a risk of condensation forming as relative humidity increases. This is because warm air can hold more water vapour than colder air. Additional radiators or other forms of (dry) heating could be fitted in particularly cold areas such as bays.
Ventilation should be improved but critically without lowering the room temperature. For example, moving furniture (such as the wardrobe) away from outside walls to allow free air movement. Fitted cupboards and large items of furniture are best located away from external walls. Where this is not possible, consideration should be given to fitting ventilation grills to the upper and lower parts of built-in units.
Ventilation can be improved by installing ‘Passyfier Vents’. These are a type of air brick that prevent the cold blasts of air associated with standard air bricks. ‘Passyfier Vents’ allow the higher air pressure associated with damp air to dissipate at a constant rate. They are silent in operation, making them particularly suitable for bedrooms and living rooms. The cost of supplying and fixing these vents is enclosed
Extractor fans with humidity sensors should be fitted in the kitchen, bathroom, utility rooms and cloakrooms.
Water Vapour Levels
Excessive water vapour in the air results in the formation of condensation. This occurs because relative humidity tends to rise as air temperature cools.
This is particularly the case at night. The average family introduces around 12 litres of moisture each day simply from domestic activities and breathing. Half of this moisture accumulates throughout the day, whilst half can be attributed to cooking and bathing. Warm, moist aid permeates throughout a property due to the air pressure differences associated with internal variations in temperature and relative humidity, eventually coming into contact with cold surfaces and often resulting in condensation.
Extractor fans should be switched on during cooking and bathing. Clothes should not be dried on radiators etc. Trickle vents can be fitted to window frames and windows should be opened when possible. A de-humidifier could be used to extract excessive water vapour from the air (again, this may be incompatible with the use of air bricks).