Little to no additional cost
A study by consultants Aurecon, with costings by quantity surveyors Kwanto, found the cost of meeting a 6 Homestar v5 rating compared to the latest Building Code energy efficiency requirements was between 0-1.3% depending on where you are in the country.
The report found the cost, excluding fees, of building to Homestar 6 varied from no additional cost for a 2 bedroom terrace in Christchurch and Wellington, to a maximum of 1.3% extra for a 4 bedroom standalone home in Christchurch.