Officials believe a third of all rental homes won't be insulated in time for the deadline next week.
Landlords have had three years to do the work before the rule change, and now renters are being told to dob them in to Tenancy Services.
Officials told 1 NEWS about 150,000 rental homes still don't have underfloor or ceiling insulation. Those who fail to comply with the law change could face fines of up to $4000.
"I think landlords should be pretty conscious that there is a significant penalty here," Housing Minister Phil Twyford said.
However, if the underfloor or ceiling spaces cannot be accessed, landlords will be made exempt from the rule change.
Renters have been advised to approach their landlords in the first instance and tell them to insulate their home. If they fail to comply, they have been told to inform Tenancy Services.
There are 27 investigators around the country ready to begin inspecting next month, but they won't be able to get everywhere, meaning they will have to prioritise.
"We'll respond on a risk basis where there is the most likelihood of harm or the safety and wellbeing of the tenant is at risk," Housing and Tenancy Services manager Steve Watson said.
More rules around heating, ventilation and moisture will be phased in from 2021.