A university study suggests a law developed in the 1940s could force landlords to provide damp-free housing.
Researchers from the University of Otago and Victoria University of Wellington said New Zealand's Housing Improvement Regulations 1947 were developed to protect people from living in unhealthy homes but have hardly been used.
The group's study of tenancy tribunal cases in Dunedin and Wellington, published in the New Zealand Universities Law Review, found that in most cases where a tenant complained of damp or mouldy housing, the regulations were overlooked.
The researchers said the regulations could be used to make landlords install insulation, adequate heating, or ventilation.
They said in one case where the regulations were used, the tribunal ruled the tenant must be able to use and live in a house without mould developing, a decision upheld on appeal to the District Court.
The regulations come under the 1956 Health Act, which has to be complied with as part of the 1986 Residential Tenancies Act.