Out of a total housing stock of 2m homes, almost 290,000 were empty that night.
Just over one in five of all vacant dwellings were holiday homes, accounting for 59,395 dwellings. This compares with 49,789 vacant holiday homes in 2006.
Of the remaining 230,056 vacant homes, 73.2% were houses and 26.8% apartments.
Leitrim had the highest overall vacancy rate at 30%, followed by Donegal (29%). South Dublin had a vacancy rate of 5%, the lowest in the country.
National Institute of Regional and Spatial Analysis director Rob Kitchin said the Department of the Environment expected a generous base vacancy rate of 6% in a properly functioning housing market.
He pointed out that in Apr 2011 there was an oversupply in the State of 110,365 units, plus 17,872 units under construction, as reported by the department’s unfinished housing survey and which are not counted in the census.
The vacancy rate excluding holiday homes is in excess of 15% in nine local authority regions: Leitrim, Longford, Ros-common, Cavan, Mayo, Sligo, Donegal, Kerry, and Galway county.
Only one local authority had a vacancy level, excluding holiday homes, below the base rate of 6%: South Dublin. There were five others with rates below 10%: Fingal, Dún Laoghaire-Rathdown, Kildare, Wicklow and Meath.
Mr Kitchin said: “Unfortunately, the areas of high vacancy/oversupply coincide with the areas of low or negative population growth, which would suggest that they will suffer ongoing issues of oversupply for many years. Areas where there is low vacancy will start to correct in the coming few years as long as demand and supply are allowed to harmonise.
“That is, we do not start to build until all excess housing has been taken up by purchasers. The lack of consumer confidence and access to credit, coupled with present weak demographic demand, will dampen this process.”
More than one in four occupied dwellings in Ireland were built in the decade leading up to Census 2011.
While detached houses comprised 42% of the total and remained the most popular dwelling type, the numbers of flats and apartments increased by 27% between 2006 and 2011.
Almost 475,000 households in Ireland were renting on census night last year. This is a significant increase since the last census in 2006, when just over 300,000 households were renting. The biggest increases were in Laois (up 88%) and Fingal (up 81%).