New Zealand First has announced a policy to insulate more than half a million homes that have no or inadequate insulation.
The party says when the Government's Warm Up New Zealand insulation programme ends in June 2018 there will still be 530,000 homes that need insulation.
New Zealand First leader Winston Peters says his policy will address what he calls a "shocking situation".
"With so many young children and older people's health being put at risk, this is appalling. We want an end to what was reported last week - the story of a Kapiti family who said their rental property was so mouldy, damp and hard to heat that they would be better off living in a tent."
A one-year-old girl living at the Kapiti property had been admitted to hospital three times with respiratory problems and eventually ended up in ICU with bronchiolitis, according to RNZ.
NZ First's policy would cost $53 million a year over 10 years.
The Government's Warm Up New Zealand programme was due to end last month but has been extended a further year. It offers insulation grants for low-income home owners and landlords with low-income or high health-need tenants.
About 300,000 homes have been insulated through the programme so far.
From July 1, 2019, ceiling and underfloor insulation will be compulsory for all rental properties where it is reasonably practical to install. Landlords who don't comply could face fines of up to $4000.
Labour has argued that in addition to insulation requirements, properties should have minimum heating and ventilation standards. Its Healthy Homes Bill passed its first reading with the support of NZ First, United Future, Māori Party and the Greens, while ACT and National voted against it. It's now before a select committee, which will soon report back to the House before it has a second reading vote.