Moisture

According to the Energy Efficiency and Conservation Authority, about 45% of our homes suffer from problems associated with moisture.

High moisture levels are associated with health problems including asthma, eczema and headaches.

With good ventilation (including venting bathrooms and dryers outside), insulation and reduced water use, you can keep your home drier and healthier.

Why does moisture matter?

High moisture levels:

• encourage the growth of moulds, fungi, dust mites and mildew which can be harmful to your health
• make your home harder to heat which can also contribute to health problems for you and your children
• can cause rot and other deterioration of your home and its contents
• make your home less comfortable to live in.

Up to 15 percent of New Zealanders are allergic to moulds, spores and their toxic by-products that grow in most households. The allergies appear as asthma, headaches, eczema and sneezing fits. Damp homes are associated with increased numbers of doctor visits for respiratory problems such as asthma.

Causes of high moisture levels

High moisture levels can be caused by:

• condensation - when warm air comes into contact with a cold surface such as a window, roof space or wall
• dampness getting into the home from outside - especially from damp ground beneath the house
• water released from household activities such as washing, cooking and even breathing
• water released from unflued gas heaters.

In new buildings, some moisture is trapped during the construction process. Wet timber may also have been used. This will dry out eventually over the first year of the building's life, as long as the house is properly heated, ventilated and insulated.

Dealing with moisture

Reducing moisture levels in your home involves:

• eliminating or reducing sources of moisture
• ensuring that air can circulate so that moisture is removed.

Keeping moisture out

Moisture often gets in from under the floor, especially if water pools under your house or the soil is always damp. You can prevent this by:

• covering the ground under the house with heavy polythene, even under a new concrete slab foundation
• fitting underfloor insulation
• ventilating enclosed sub-floor spaces
• dealing with surface run-off or underground water that promotes damp air.

Also, it's not a good idea to use air from an uninsulated roof space for ventilation. This air is likely to be full of moisture.

Avoid unflued gas

Don't use gas heaters unless they're vented outside and don't use gas cooktops without an extractor fan. Burning gas releases moisture inside your home and also emits other pollutants which can be unsafe or you and your family.

Insulation

Insulation helps keep the air inside your home warm. It also keeps surfaces warm so moisture won't form on them when it gets cold outside. An insulated room will have fewer problems with condensation on walls and windows.

There are legal minimum requirements for insulation in new homes and renovations - it's worth exceeding these requirements if you can to get a drier, more comfortable home.

A warm home is usually a drier home so using passive heating or mechanical heating to keep your home warm will also help to reduce moisture.

See insulation and passive heating for more.

Ventilation

Effective ventilation will help to remove moist air from your home and bring in cleaner air that's healthier to breathe. See ventilation for more detail.

Extract moist air

The most significant sources of moisture in your home are the kitchen, bathroom and laundry.  All these rooms should have extractor fans to remove moisture. Vent to the outside not into the roofspace. Your dryer should also be vented outside.

Reduce water use inside the home

The less water you use in your home, the less damp it will be. If you use a drying rack, put it outside whenever you can - otherwise the moisture will evaporate inside your home, resulting in condensation.

See easy ways to save water for other water-saving tips.