The NZ Property Investors Federation surveyed members of its 20 affiliate associations around the country.

Those who responded to the survey owned 4096 rental properties, of which 88.7% were insulated.

And a third of the landlords who responded had installed a heater in their rental properties. Of those, 67% had put in a heat pump.

NZPIF executive officer Andrew King said the organisation had promoted the idea that it was good business sense to provide a warm, insulated rental property because it encouraged tenants to stay longer.

He said all rental property owners needed to accept that housing standards had changed and there was an emphasis on the importance of a healthy living environment in rental properties.

There are moves towards a warrant of fitness scheme for rental properties, and Labour MP Phil Twyford’s member’s bill, the Healthy Homes Guarantee Bill, was drawn from the ballot late last year.

It would require landlords to ensure their properties met a minimum standard of insulation and heating. King had previously said it was the better of the two options because it would not incur large compliance costs.

But he said the NZPIF was not backing any regulatory change to introduce compulsory insulation or heating standards at this stage.

King said: “We agree with the Children's Commissioner’s call to help children suffering health related illness through living in cold, damp homes. But before endorsing any regulatory changes aimed at rental property in New Zealand, we would need to be assured that these changes wouldn't reduce the supply of rental property, either now or in the future, and would not put strain on tenants through unnecessarily higher rental prices. Many tenants already cannot afford to heat their homes and higher rental prices would only make the matter worse."