An Oireachtas committee has heard that a lack of construction workers threatens Ireland's ability to hit climate targets.

The Joint Committee on Environment and Climate Action is continuing its consideration of the National Retrofitting Plan.

Seamus Hoyne, Dean of Flexible and Work Based Learning at the Technology University of the Shannon, pushed for new ways of attracting workers to the sector, and to "change the messaging" used.

Construction work is now using "cleaner systems" with more digital components, and the "imaging" of recruitment needs to reflect this, he said.

And he warned that "the challenge of upskilling our workforce cannot be underestimated, given the resource constraints that exist at present".

"Scaling up apprenticeships" is also critical, Mr Hoyne said, and added that they can lead to many opportunities, rather than being "a dead-end", as was often thought in the past.

He noted that many workers left the sector and the country during the pandemic, and Ireland is now competing with states right across Europe to encourage them back to our shores.

"There are now five fully registered one-stop shops" providing retrofitting, Mr Hoyne said, according to his latest information.

He was responding to Christopher O'Sullivan, Fianna Fáil, who asked if 19 such facilities will be enough to meet demand.

"In general, it should be, if there is an equal [geographical] spread", Mr Hoyne added.

And he said that the registration process has been made "rigorous" to avoid risks.

New skills are needed for those who are retrofitting older buildings, Dr Caroline Engel Purcell, Head of Research at Carrig Conservation International Ltd, said, such as understanding how moisture moves through older structures.

And Dr Cathy Daly, an Archaeological and Ethnographic Conservator with the University of Lincoln, warned that using modern retrofit materials risks damaging older buildings.

Natural insulating materials work best, but there is "confusion" over the relevant SEAI grants, she said.

Dr Daly added that the construction industry does not grasp the value of these traditional materials, such as hemp.

16% of private homes in Ireland were built before 1945, she noted.

Having studied the relative benefits of demolition versus retrofitting, Dr Daly said, "The greenest building is the one that is already built".

But she cautioned that, "It may be years before we truly understand the impact of retrofit works being undertaken today".

Dr Daly said that research in England had found that poor retrofitting work had rendered homes "uninhabitable and it's very expensive to put right".

She was responding to Sinn Féin Deputy Réada Cronin.