Homes in New Zealand are frequently becoming infected with mould. The latest House Condition Survey report found almost half of all New Zealand houses were damp and infected by mould.[1]

The study, conducted by the Building Research Association of New Zealand, looked at 560 houses across the country and weighted the findings to represent the total number in New Zealand.

The report found that many New Zealand houses lack adequate insulation and heating with 46 percent of bedrooms without heating and five per cent of homes without heating at all.

The World Health Organisation recommends indoor house temperatures don’t drop below 18 degrees to promote ventilation and prevent the growth of mould. But homes throughout New Zealand without heating are likely falling below that figure.

Mould is a type of fungi that thrives in cold and damp spots with poor ventilation. The most common moulds are black, green or white which can appear as a fuzz, stain or discoloration. Moulds affects human health in a number of ways and can trigger respiratory infections, asthma and allergic conditions.

The report found that mould grew most commonly in bathrooms but was also found in 20 per cent of living areas and bedrooms. Renters had it worse with 30 per cent of properties showing visible mould in the bedroom compared to the owner-occupied homes with 18 per cent.

Any mould should be removed immediately to prevent it from spreading throughout the house. To prevent the growth of mould, ensure the house is sufficiently insulated and heated. Use exhaust fans and sub-floor ventilation to prevent moisture from rising up.

If passed, the Healthy Homes Guarantee Bill which recently passed its second reading in Parliament, will see landlords forced to abide by specific warm and dry property requirements to protect renters from unhealthy conditions within the property.


[1] White, V. & Jones, M. (2017). Warm, dry healthy? Insights from the 2015 House Condition Survey on insulation, ventilation, heating and mould in New Zealand houses. BRANZ Study Report SR372. Judgeford, New Zealand: BRANZ Ltd.