Dampness prevention in home must include measures against mildew

Press, 15 July 1987, Page 34

Dampness prevention in home must include measures against mildew

The Building Research Association of New Zealand has also produced a bulletin pertinent to builders and home owners keen to combat condensation and mildew. Bulletin numebr 244, produced in 1985, explains that condensation and mildew are mainly winter problems. A survey conducted by B.R.A.N.Z. discovered that at that time mildew occurred in 46 per cent of New Zealand homes. The survey found that one home in five has repeated or prolonged attacks and, in one in seven, condensation led to damp wall linings.

Condensation is widespread but is generally heavier in colder climates. It occurs on walls, ceilings and windows, and on any cold surfaces such as doors, mirrors, etc. Condensation can leave water stains and, if persistent, can promote mildew growth and help rot set in. Mildew occurs commonly in any type of building both in mild and severe climates. It occurs

on wallpaper, curtains, and ceiling linings, also on shoes, clothes and other items in cupboards. All air contains water vapour but can hold only a limited amount without becoming saturated. The higher the air temperature, the more it can hold. If there is too much moisture in the air for the temperature to cope with it, some will condense on cold surfaces. Mildew is primitive form of fungal growth which grows from spores that abound everywhere. It will grow in any home where humidity remains high, but will have difficulty surviving in one with low humidity. If there is no moisture available, mildew cannot grow. There are two ways to reduce humidity — by heating and ventilition. Heating will raise the temperature and allow the air to hold more moisture. Ventilation takes away the moisture to the outside. Constant ventilation is the most basic requirement and if there is not enough, the moisture cannot be removed from the air. However, too much ventilation is not the answer because it prevents the house from getting warm. Insulation helps to keep surfaces warm and so lowers the risk of condensation on these surfaces. Heating and insulation help lessen the chances of

persistent condensation and mildew but will not prevent them unles there is also enough ventilation. Ventilating a little (that is, having many windows slightly open) and all the time is preferable. If windows continue to steam up, then open them wider. Short bursts of vigorous ventilation help to flush out large quantities of moist air released from cooking, clothes-drying, showers, etc. Most people close doors when taking a shower or bath, and this helps prevent steam spreading to other rooms. Afterwards, opening windows while keeping the door shut allows the steam to escape to the outside. This can also be done in kitchens and laundries, when large amounts of steam are being produced. An extract fan over a stove or shower will help get rid of moisture provided that it discharges right outside and never into the roof space, underfloor space, wall cavity or other enclosed area such as a conservatory. Clothes driers can be vented so that the moisture is removed directly to the outside. Hints for control.— Make sure that there is some ventilation in all rooms at all times. Many windows slightly open are better than one window fully open. Keep the house warm, not too hot, and try to keep the indoor temperature in winter constantly 5 deg. C warmer than out-

side. A little heating kept on continuously does more good than a lot of heating during evening only. It is the combination of simultaneous heating and ventilating that works. For example, demisting the windows in a motor vehicle is done by venting and heating. Avoid large amounts of steam spreading through the house from such things as pots and pans boiling longer or harder than needed, clothes drying indoors and showers or baths. Open windows wider and close doors to other rooms if the production of large amounts of steam cannot be avoided. Vent clothes driers direct to the outside. Use windows as a guide and if too much moisture starts collecting, open them a little wider. Wipe the moisture off glass when condensation has occurred and then take the wet cloth away to dry out.

Provide permanent ventilation to wardrobes by such means as louvre doors, ventilators or leaving doors ajar. Cupboard heaters can also help in wardrobes where midlew is particularly likely to occur. Damp lumpy salt or sugar can be a sign the air in the house is too damp. Insulate ceilings of existing homes and ensure that new homes are insulated as required by the building code.