New Zealand landlords will have to insulate their houses and install smoke alarms under legislation that's just been introduced to parliament.

Housing Minister Nick Smith announced the new rules in July and they'll be enacted through the Residential Tenancies Amendment Bill.

"The bill aims to make homes warmer, drier and safer for the million New Zealanders who live in rental accommodation, without imposing excessive costs," Dr Smith said on Thursday.

The insulation rules apply to social housing from July 1 next year and to private tenancies from July 1 2019.

Smoke alarms will have to be installed in all rental homes by July 1 next year.

The bill also allows authorities to take action against landlords whose houses are sub-standard in other ways.

"There are a small proportion of unsafe rental properties that have rot, unsafe wiring, leaky roofs and broken plumbing," Dr Smith.

When the rules were announced in July, landlords backed the changes.

The Property Investors Federation said the conditions were reasonable and wouldn't mean excessive rent increases.