The chief executive of the Irish Council for Social Housing has said up to 10,000 social homes in the non-profit sector could be in need of retrofitting.
Speaking to RTÉ's Morning Ireland, Dr Donal McManus said that for local authorities the figure is likely to be in the tens of thousands.
A huge retrofitting programme is part of the Government's Climate Action Plan announced earlier this week.
The aim is to end the use of fossil fuels for home heating, and the plan will include new insulation, heating systems, and renewable energy sources in order to upgrade the energy efficiency of older properties.
Dr McManus said a few thousand homes have already been upgraded using SEAI grants.
He said a certain amount of housing stock in the non-profit sector is very old and will cost more to upgrade.
He said: "The Government did a study a number of years ago and identified 2,000 local apartments that would need deep retrofitting, and that would be costly.
"For shallow retrofitting, we'd find it's maybe in the low thousands."
Dr McManus said he thinks everyone involved in the retrofitting of social homes needs to come together and work out a plan.
He said that if the aim is to move towards zero carbon emissions, then there will be a greater cost in the long run.
Dr McManus added that the issue he would like to discuss with the Government is who pays for the upgrade works.
He cited a European programme called Energy Sprung, where the housing association and government each pay a part of the cost, and the tenant also contributes as part of a savings plan.
He said that if the Irish Council for Social Housing was given an idea from Government as to what the regulations and finances will be, its members would be ready to begin upgrading works quite soon.
Meanwhile, Professor John Fitzgerald of the Climate Change Advisory Council said home owners and tenants will need to be reassured that they will save money by retrofitting their homes.
Speaking to RTÉ's Today with Sean O’Rourke, Prof Fitzgerald said a carbon tax is essential, but it is only the first step.
"If you want people to spend lots of money on retrofitting their homes, you must be able to tell them they'll save a load of money from doing so," said Prof Fitzgerald.
"If a carbon tax is there, then they will save a load of money."
Prof Fitzgerald said he would like to see the Oireachtas Committee recommending a trajectory where the carbon tax is raised gradually until 2030, beginning with the next budget.
He said this would reassure people that if they invest money retrofitting their home, they will save money in the long run as the carbon tax rises.