Ireland needs a 'suitable amount' of the right type of housing supply as its population gets older, the ESRI has said.
It comes as a new report found the number of people per household in Ireland is larger than other European countries.
The growth is largely driven by a high fertility rate, a younger population and socio-demographic factors.
Report author Dr Conor O'Toole told Newstalk Breakfast there is a clear difference.
"We compared Ireland to the Nordic countries, to other western European countries, to Mediterranean countries," he said.
"What we saw was household size in Ireland was clearly larger than this other group of countries.
"From the last Census household size in Ireland is just over 2.7 - and the other countries in the main were lower than 2.5".
'Younger population'
Dr O’Toole said a number of factors help to explain the figures.
"Really in the main it's to do with demographics; we've got a younger population, there's a higher fertility rate in Ireland," he said.
"There's a lot more households with children than in other countries and that's really what's driving the main differences."
Dr O’Toole said as the younger population ages over time things need to change.
"Naturally that would mean household sizes would fall as the population aged," he said.
"But to let that happen we have to have a suitable amount of housing supply and the right type of dwelling for people.
"That's certainly one of the things we saw in the research - for household sizes to decline with the population, we need to have the right amount of housing supply".
A father with his two children. Image: Panther Media GmbH / AlamyThe ESRI report said Ireland's relatively high household size will likely persist "as long as favourable demographic features are present compared to other countries".
"We do find a role for higher housing supply to put downward pressure on household size, thus while changes in household size are likely to be driven primarily by demographics, changes in housing supply are likely to impact the rate at which this happens," it added.
Households in Ireland headed by over-65s are similar in size to their European counterparts.
In contrast, middle-aged and younger households are typically larger here.
