Preventing dampness and condensation

Press, 7 April 1987, Page 28

Preventing dampness and condensation

Condensation and mildew are mainly winter problems, which a 8.R.A.N.Z., (Building Research Association of New Zealand), survey established occurs in 46 per cent of homes. One home in five has repeated or prolonged attacks and, in one home in seven, condensation leads to damp wall linings.

The information contained in this article

covers some aspects that builders and sub-trades may sometimes have to contend with. It is also considered that much of the information will prove useful for general guidance to householders.

Condensation is widespread but it 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 linins, also on shoes, clothes and other items in cupboards. Condensation is caused because all air contains water vapour but can only hold 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, some will condense on cold surfaces.

Mildew is a 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. There are two ways to reduce humidity — by heating and ventilation. Heating will raise the temperature and allow the air to take more moisture. Ventilation takes away the moisture t 6 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 unless there is also enough ventilation.

Providing adequate ventilation around the home provides an effective remedy when combined with proper heating and insulation.

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 there 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.

• 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 sdeg C warmer than outside. 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 and 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 leav-

ing doors ajar. Cupboard heaters can also help in wardrobes where mildew is particularly likely to occur. Damp lumpy salt or sugar can be a sign that 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.

• If mildrew grows on wallpaper, clean it down with a damp cloth and household bleach solution (1 part bleach and 4 parts water).

Try a small area to make sure that the bleach does not take the colour out of the wallpaper. If the colour is affected, try a fungicide solution available from a paint shop.

If stains cannot be removed in this way and repapering the wall is desirable, strip the old paper first. This is best done as follows:

Apply 2 or 3 costs of warm water to the wall-

paper by brush or roller at 5 to 10 minute intervals. Then remove the old paper immediately — it will usually come off quite easily. Some methylated spirits in hot water will help in removal of difficult patches. Next, paint the wall with a fungicide solution. Then when it is properly dry, rehang wallpaper using a paste containing a fungicide.