When Chuck Feeney sold Duty Free Shoppers, the multibillion-dollar business he had cofounded 36 years earlier, to Bernard Arnault, head of Louis Vuitton Moet Hennessy, he didn’t rush out and spend his $1.67 billion windfall on luxury. Instead, he turned full-time philanthropist.

“I became convinced that there was greater satisfaction from giving my money away and seeing something come out of the ground, like a hospital or a university,” he says, sitting in the Dublin offices of Atlantic Philanthropies, the foundation he created in 1982. “It just seemed logical to put the money to good use rather than putting it into a bank account and letting it accumulate and accumulate.”

Wearing a $15 digital watch and a crumpled shirt, he could easily be mistaken for one of the American tourists outside. “This watch tells me the time better than a Rolex. When you are 81-years-old, you don’t really need a lot of the trappings of wealth,” he says.

The Irish-American from New Jersey has spent most of his life doing everything he can to stay out of the limelight. This has included forcing recipients of $6.2 billion in donations from his Atlantic Philanthropies foundation to pledge not to reveal the source of their funds or risk losing them.

But following a decision in July by the charity to donate its final $1.3 billion by 2016 and wind up its global operations after 30 years of giving, he wants to talk about his philosophy of “giving while living”. Well, sort of. Shy and self-effacing, Feeney generally prefers asking questions to answering them; he evidently likes giving his money away better than giving interviews.

Feeney founded Atlantic Philanthropies when Duty Free Shoppers was expanding aggressively across the US, Asia and the Middle East. Two years after launching Atlantic, when he was on the cusp of becoming a billionaire, he secretly decided to sign over the vast bulk of his wealth and his 38.75 per cent stake in the company to the charity, leaving himself $5 million to live on.

The transaction was completed secretly in 1984 in the Bahamas and remained undiscovered for more than a decade, leading Forbes magazine wrongly to list Feeney as a billionaire and one of the richest individuals in the US.

Feeney was inspired by the essay Wealth by Andrew Carnegie, in which the 19th-century Scottish-American industrialist argued that the rich had a responsibility to distribute his wealth.

“It is logical for a US person to give their money away while they are alive as the government will take it from you when you die in taxes,” says Feeney.

Arnault might agree. This month, the French businessman caused an uproar when it emerged that he had applied for Belgian citizenship. One mooted explanation was the country’s favourable inheritance tax regime. “That guy [Arnault] is in the news today because he is trying to get residency in Belgium,” says Feeney, grinning. “You’d have to pay me to live there.”

Still, he defends the right of the wealthy such as Arnault to take “advantage of opportunity” in structuring their tax affairs. “Everybody sets up a structure that fits their purposes,” says Feeney, who based his own company and charity offshore, reducing their exposures to US taxes.

Is it hypocritical for tax exiles to become involved in philanthropy?

“I bet it is the government saying that,” he retorts.

Still, he is critical of the culture of greed and banking, which he says contributed to the financial crisis. “There is a need to fix certain things and make sure that excesses aren’t the norm,” he says.

He points to the ghost estates that blight the Irish landscape as evidence of the gross materialism that took over the country. But the Irish crash has not made him regret providing $1.5 billion in donations to the country. “It does seem unfair but that is what life is about,” he says.

Feeney’s philanthropic achievements have ranged from building hospitals in the US to increasing the number of nurses in South Africa. But it is probably in the education sector that the charity has had the biggest impact. This year Atlantic Philanthropies gave $350m to Cornell University, Feeney’s alma mater, to build a new high-tech campus on Roosevelt Island in New York. It has also pumped almost $1 billion into education projects in Ireland.

The educational focus perhaps reflects Feeney’s own experiences of charitable giving. “I was with a special services unit in the Korean war and when I got out the biggest thing I got was a GI scholarship,” says Feeney, who was the first person in his family to attend university.

Born into a working-class neighbourhood in Elizabeth, New Jersey during the Depression, Feeney says he saw how people struggled to make ends meet. To make a few dollars during his childhood he shovelled snow, cut lawns and caddied. “My claim to fame was I never lost a golf ball,” he says.

His entrepreneurial activity continued when he went to college, where he earned the nickname “sandwich man” for selling lunches to help pay his way.

When he travelled to Europe to study he spotted a gap in the market and began selling drinks, perfume and cigarettes to sailors on US ships stationed in Europe in the 1950s. “The Navy supply officers liked an American accent.

Feeney’s big break came a few years later when he won the concession to operate a duty-free business at Honolulu airport, which was on the cusp of a Japanese-led tourist boom. In the decades that followed, DFS expanded globally.

Aside from his philanthropic work, Feeney made an important contribution to the peace process in Northern Ireland. He became involved following an IRA bomb in 1987, which killed 11 people in Enniskillen, the town were his grandparents were born. At a time when Sinn FEin was ostracised due to its links with IRA violence, Feeney contacted Gerry Adams, the party’s leader, believing he was serious about pushing towards a peace process.

“We thought this guy could deliver what he said he could deliver. We were lucky to have Bill Clinton as president who bought the idea,” says Feeney, who funded Sinn FEin’s Washington office with a personal donation rather than a grant from his charity.

As he begins to wind down the activities of Atlantic Philanthropies, Feeney is turning his attention to persuading others to follow in his footsteps.

He is a signatory of the Giving Pledge, an initiative devised by Bill and Melinda Gates and Warren Buffett to persuade wealthy Americans to give most of their wealth to philanthropy. “There are only about 80 families signed up for this. We need a multiple of what we are doing to achieve our purpose,” he says.

But as he approaches his 82nd birthday, has his philosophy changed with age? “I can’t chase girls any more because I realise now that I can’t catch them,” he says. “I don’t think age has changed my outlook - you are supposedly older and wiser but have to roll with the pitch.”