At What Cost? an Analysis of the Green Cost Premium to Achieve 6-Homestar in New Zealand

In the green building industry there is an implicit understanding that the use of a green building rating tool will attract additional capital cost. This phenomenon has been well studied in commercial buildings, with mixed results, but has received little focus in the residential, single family context.

In New Zealand the local green building council advises the market that they have reduced the time and cost to implement their green building rating tool, Homestar, through modifications to version 4 of the rating tool, which include the use of a new 6-Homestar checklist.

This research investigates this claim using a comparative cost methodology to determine the potential additional capital cost commitment that would be required to achieve a 6-Homestar certification, utilising ten standalone and terraced house designs from the Hobsonville Point development in Auckland, NZ.

This research determines that there is an additional cost to achieve 6-Homestar of 3–5%. This is nearly double compared to previous research into Homestar and also finds that, for the houses reviewed, the use of the 6-Homestar checklist is less cost effective than other options. Therefore, in this instance the advice and guidance of the green building council is erroneous and misleading to the market.