Moulds and mould growth can appear on any damp surface such as plaster, wallpaper and timber and is associated with condensation and lack of ventilation problems in many buildings. It is unacceptable because of appearance (unsightly growths of various colours - greens, yellows, pinks, black, grey or white), odour (musty and damp), and fears of health and hygiene considerations (particularly in food processing industries).
Moulds are simple fungi from several groupings in the fungal classification system. A typical life cycle is shown in figure 5 where spores are produced under asexual and sexual reproduction. It is sexual reproduction of fungi which allows genetic modification to adapt and tolerate changes in the environment such as humidity, temperature and food requirements.
There are three principal features common to the broad range of mould fungi:
1. Simple food requirements: The ability to exist on non-nutrient materials such as building plaster and brick which have traces of contaminating organic matter.
2. Produce large numbers of spores which can allow rapid adaptation to particular environments.
3. Can grow extremely quickly under suitable conditions.
The main requirement for the development, spread and growth is a source of moisture although food, oxygen and a suitable temperature are also important. It is available water which is critical to mould development and different materials at the same moisture content often have different water availability.
Moulds can be regarded as hydrophilic fungi (tolerating high water availability) although individual species have their own optimum requirements for moisture. In most situations where surface condensation occurs and the relative humidity of the internal atmosphere exceeds 70% mould growth will be established.
The susceptibility of materials to mould growth will vary as mentioned previously. For instance it has been demonstrated that mould will develop on cheese and leather at 76% RH. It will not develop on wood below 85% RH nor on cotton or glass below 96% RH. The longer surfaces are under conditions of high moisture or local high humidity the greater the probability of mould growth developing. In a number of structures there may be a local or adjacent high humidity at the walls of the buildings sufficient for mould growth whereas the internal environment may not be experiencing relative humidity above 70%.
There have been approximately one hundred species of fungi detected in dwelling houses. The species commonly encountered were Penicillium, Cladosporium, Rhizopus, Mucor. Fungi specifically encountered on paint and plaster were for example Cladosporium cladosporioides, Aspergillus niger, Penicillium purpurogenum and Mucor plumbeus.
The appearance of mould growth in buildings often suggests poor standards of property maintenance and/or domestic activities encouraging condensation. Prolonged exposure to mould growth will cause disintegration and disruption of certain painted surfaces. Paper and certain fibre building fabrics may also be softened and deteriorate as some mould species are capable of digesting cellulose.
In America Moulds can be referred to Toxic Mold (without the u) and has been subject to many high profile insurance claims and studies relating to health impacts.
We offer a variety of solutions to deal with mould growth:
Anti-Mould Paint Additives
Heat Recovery Ventilators
If you are uncertain as to how best to deal with your mould outbreak please send us your pictures or contact us to discuss your specific requirements.