Cr John Bain was the only councillor not in favour of the funding. He said that although he supported the project, he struggled with the process and wanted to be responsible with ratepayers' money, because he believed all Northland residents were "indirectly" ratepayers.
His proposal to ensure that 20 per cent of HAC admission fees and future donations would be funnelled back into the IGR, was defeated at voting.
Cr David Sinclair quipped that not everyone was a cyclist but the Twin Coast Cycle Trail had received $900,000 because it was a boost for the region.
Under the terms of the agreement, the $1.5m would be paid towards HAC through IGR Impact Investment, over two-and-half years from the start of construction.
Once built, the centre would be handed over to the Whangarei Art Museum Trust , a Whangarei District Council-controlled organisation.
NRC's conditions included a formal commitment from the museum trust that should HAC ever be sold to a private operator, the $1.5m investment would be repaid on the settlement of sale.
The funding application was made by Northland Inc, which had originally asked for a loan investment. However, NRC chairman Bill Shepherd said a loan would contravene terms of funding set down by the district council.
A delighted Mr Trass said his plan B was "to panic" had the funding not been approved.
There were moments he was concerned because "some NRC and WDC councillors still hadn't accepted the referendum, and were trying to undermine the project".
Northland Inc chief executive David Wilson said the agency had been working to support the project for more than three years and was tasked with supporting projects which would boost the local economy.
"It's a good project with a vital cultural aspect. We now have a good offering of quite intriguing and important cultural stories."
He and the team at Northland Inc had been working on boosting off-peak, all-weather tourism products across the region.
Mr Shepherd said the HAC would complement the Twin Coast Tourist Discovery revitalisation project - also funded via the IGR.
In the meeting agenda, regional council staff said PNT contended that the commitment to no additional ratepayer funding for the Hundertwasser project was a commitment specific to district council funding as set out in their pre-referendum submission to the WDC 20/20 Inner City Revitalisation Committee.
The commitment of no more ratepayer funding was given by former WDC chief executive Mark Simpson.