The Energy Efficiency and Conservation Authority is adamant the Government's insulation scheme is making a difference, despite a report suggesting it won't work well for homes in colder regions.
The $347 million Warm Up New Zealand scheme, which started in July, has the aim of insulating nearly 200,000 houses over four years.
A confidential report commissioned by EECA, which has been obtained by Radio New Zealand under the Official Information Act, estimates the cost of bringing houses up to World Health Organisation standards would be about $10 billion.
The report's author, Otago University energy studies director Professor Bob Lloyd, says while the insulation programme has improved standards for underfloor heating, homes in colder regions also need costly wall insulation.
However EECA chief executive Mike Underhill says the programme is dramatically improving the comfort and health of thousands of people.
He told Morning Report that the average house in New Zealand, the insulation is a significant improvement, and, when coupled with the heating which is subsidised by the Government, will achieve the required standard.
Mr Underhill says it is also not a one size fits all scheme, and properties in the South Island get thicker insulation.
He says about 960,000 houses in New Zealand have either no insulation, or are not insulated properly. So far, 30,000 homes have been retrofitted with insulation, he says.
Energy Minister Gerry Brownlee says the findings are based on older standards for underfloor insulation, and he's satisfied the current package is adequate for anywhere in the country.