New home building, already slowed by high borrowing and materials costs, faces a further cost inflation this year as states and territories implement new building code requirements for a seven-star minimum NatHERS (nationwide house energy rating scheme) thermal rating.

But while the increase in thermal rating for new homes from six stars – codified in amendments to the National Construction Code, a blueprint of design rules – will create some extra upfront expense, there’s disagreement about how much it will cost.