Housing Minister Nick Smith says 18 deaths a year will be prevented under Government's plans to make insulation compulsory in all rental properties.
Another three lives will be saved each year from a further requirement for landlords to install smoke alarms, and $12 million will be saved in hospital admissions, Dr Smith said.
The minister revealed the figures in Parliament this afternoon under questioning by Green Party co-leader Metiria Turei.
She wanted to know how many children's lives would be saved if the Government introduced a Warrant of Fitness for rental housing, instead of just rules for smoke alarms and insulation.
Dr Smith said he could not provide these figures, because his official analysis did not break down into age groups.
However, he said that the Government's regime would save 21 lives in total a year. He also said that the biggest benefits would be for older generations, in particular those with influenza-like diseases.
"I think it is proper that we count the lives of all those that are saved, as well as children," he said.
The Greens and Labour want a WoF regime to be introduced for all rental properties, instead of the Government's narrower regime.
Mrs Turei said the Government's law changes would do nothing to improve cold, damp rentals because they did not include minimum standards for heating or ventilation.
Dr Smith repeated his concerns about a WoF system, saying that it would penalise landlords for minor issues such as the absence of warning stickers on glass panes.