Advocates for healthy homes say the government's budget its Warmer Kiwi Homes programme will leave thousands in the cold.
The scheme has been expanded to cover 90 percent of the costs of insulation or heating retrofit for low-income households.
The $56m investment is expected to cover an extra 9000 houses.
The chief executive of the Green Building Council, Andrew Eagles says that leaves half a million households in substandard housing.
