It was also reported he was going to donate to the Christchurch earthquake recovery, but the sum of his donation has never been made public.
It was only early last year, when publicity surrounded the donation of $500,000 to Medicine Mondiale for the development of an incubator to save the lives of babies in developing countries, that his philanthropy was publicly outed.
After a modest childhood growing up in Ireland, Mr Green left school at 12 to become a drover, guiding cows to cattle marts.
But when the lorry arrived in Ireland and dried up the work, he moved to Australia to earn enough money to buy a lorry.
In Australia he and a friend, Barney McCahill, won a job digging trenches and laying water mains, before deciding to head back to Ireland, via New Zealand.
Once in New Zealand the two men won a tender to lay cables for the Post and Telegraph Department, followed by another to lay 21 miles of cable around Auckland City.
They then bought a digger and expanded into tunnelling, sewage and stormwater contracts, growing to become a major operator in infrastructure projects throughout the country.
The success of the business put both men on the rich list.
Since then he has invested in farms on the fringes of Auckland, land development, oil and gas exploration and shrewd investment in the stock market.
Last year, the NBR Rich List said he was worth $350 million - up from $220 million in 2010.
