Nationwide only a third of the 36,000 homes retrofitted with insulation since the Warm Up New Zealand: Healthy Homes initiative began in September 2013 were rentals. It's estimated more than half of uninsulated properties are rentals.
Under the initiative, homeowners or tenants are eligible for free or reduced cost insulation if they have a Community Services Card and the house is occupied by someone under 17 years or over 65 years.
In some regions people at risk from illness linked to cold, damp housing are also eligible.
Green Party co-leader Metiria Turei said the party predicted the scheme would fail renters and this has been proven true.
"Landlords who are only interested in their immediate profit have no incentive to be good landlords."
She said a warrant of fitness scheme is needed to set a minimum standard for housing and hold landlords to account.
EECA said the initiative should appeal to landlords.
"Getting rental properties insulated is a no-brainer for landlords," said chief executive Mike Underhill.
"Landlords will end up with a higher quality property and tenants are more likely to stay longer in houses that are warmer and more comfortable."