WHAT IS CONDENSATION?
Condensation in a building usually occurs when warm air comes into contact with a cold surface. The air is cooled below its saturation point causing its excess water vapour to change into liquid water. The condensed water usually appears as water droplets or water film on non-absorbent surfaces such as windows or tiles. This form of condensation is described as surface condensation.
CONDITIONS FOR CONDENSATION
THE CAUSES OF CONDENSATION
The effect of moisture generation is further aggravated by the way houses are ventilated – it is theoretically possible to avoid condensation by adequate ventilation.
Up to about the late 1960s there was natural ventilation in many homes because of the lack of double-glazing, poorly fitting windows and doors, open fireplaces. Present attitudes have eliminated natural ventilation by the use of double-glazing, draught excluders, fitted carpets (preventing air movement up through suspended wooden floor boards) and the removal of open fireplaces with the introduction of central heating systems. To put it simply buildings have being effectively sealed and provided ideal conditions for condensation to occur.
Many houses remain unoccupied and un heated throughout the greater part of the day allowing the fabric of the building to cool down, The moisture producing activities are then concentrated into a relatively short period. This sudden increase in warm air can produce condensation as the air comes into contact with the relatively cold structure which is still warming up. Economic pressure – dramatic increase in fuel prices force many occupiers to under use heating systems not heat unused rooms and seal all draughts and reduce ventilation as described previously.
The main requirement for the development and growth of moulds 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. Moulds can be regarded as high 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 exceed 70% mould growth will be established.
There have been approximately 100 species of fungi detected in dwelling houses. The species most commonly encountered were Penicillium, Cladosporium, Rhizopus, and Mucor.
Condensation is an increasingly serious problem in dwelling houses and offices. It affects over 50% of buildings in the UK. Accompanying condensation there is an increase in the presence of mould growth and many of the household pollutants. Positive Pressure ventilation units along with complementary trickle ventilation are a cost effective way to control condensation and black spot mould problems.