"So we follow what happens a year later living in warm homes, and it's remarkable."
Mr Farrelly said it would be detrimental to the health of the community if the 7000 homes were left uninsulated.
"It's pretty raw what would happen. The number of children going to hospital with life-debilitating illnesses will continue, it's highly likely children will continue to die, and we know children are dying because of the houses they are living in," he said.
Northland District Health Board figures show people went to hospital for respiratory conditions 2346 times last year. That was up on 2100 times in 2014 - an 11 per cent increase - and 1846 in 2013.
Just more than half of those who went to hospital for respiratory illnesses last year were Maori, and just more than one-third were children.
Mr Farrelly said the Healthy Homes programme was one of the reasons Northland saw a major drop in cases of rheumatic fever last year.
Ministry of Health statistics showed admissions to Northland hospitals for first-time episodes of rheumatic fever had dropped from 15 in 2014 to five cases last year - the lowest number of recorded cases in at least 13 years.
In the past, health experts had compared the rheumatic fever rate in the region to that of a third world country.
The programme is funded by the Government through the Energy Efficiency and Conservation Authority, which gives $60 for every $40 raised locally. Foundation Northland, formally known as the ASB Trust, has been a major funder for Healthy Homes Te Tai Tokerau, donating $1 million each year. Other funders include Northland DHB, Top Energy and Northpower.
Mr Farrelly said as far as he knew funding was ending in June. "The question is, will the current funders continue to fund when the Government withdraws that funding? It was a partnership - it was a private, public, philanthropic partnership to make change. I think funders will be very, very disappointed and review what they're going to do if Government steps out and leaves the job half finished."
Mr Farrelly said the Healthy Homes programme was the most important project he had been a part of in his career in health. "Northland sits at the bottom for a lot of things, we have the worst this and the worst that, and we often don't have solutions. Here we have a solution that involves all of us together. We are really proud of what Northland has done in this area, I think of the whakatauki, 'with your basket and my basket, the people will be fed'."
Simon Bridges, Minister of Energy and Resources, said an announcement about the Healthy Homes programme would be made in due course.