Mildew and condensation

Press, 12 June 1986, Page 15

Mildew and condensation

A typical family of four produces 8 to 9 litres of water vapour a day through breathing and perspiring. Cooking, dishwashing, clothes drying, indoor plants, showers and baths also generate moisture.

No wonder that the Building Research Association reports that 45 per cent of houses in New Zealand have mildew — a tiny white fungus caused by dampness and condensation.

Wet building materials can also be a major source of moisture.

In an average house, it has been calculated that 2500 litres of water vapour can be released by a concrete floor as it cures. Timber framing while it is drying can release up to 200 litres of water.

Ground water evaporation has been shown to be a major source of water vapour in all houses and a contributor to roof cavity condensation in brick veneer houses.

There is a common misconception that con-

densation only occurs in cold climates. In fact, many warmer coastal regions of New Zealand suffer the same condensation and mildew problems as experienced in colder parts of the country, although climate is the determining factor. The building industry has, during the last few

years, made a concerted effort to ensure that new houses are insulated and the problems of condensation resolved. "Condensation is a people problem,” says Mr Kevin Golding, product development manager of Winstone Wallboards, Ltd. “Modern building trends are toward tighter construction practice and small living spaces with electric heating. “Some of the worst cases of condensation are in small home units where couples shower in

the morning, go off to work and when they return in the evening they turn on all the electric heating. All the moisture generated cannot get out

of the building. "Good living practices will overcome condensation problems and there may be no need for further building regulations. “If everyone heated their whole house evenly and ventilated it by opening windows and using air extractors, the problems would diminish.

“What is needed is an understanding of the principles by home owners as well as designers, builders and building regulators,” says Mr Golding. It has been found, for instance, that moisture in the roof space of houses is largely caused by ground water evaporation. The installation of polythene ground cover has resulted in almost total drying out of the roof space in all houses studied by B.R.A.N.Z. in the Invercargill area.

Moisture sources need to be controlled, ventilation increased and the building designed and built to allow a controlled moisture flow.