Workers who were building homes during the construction boom are among the country's new homeless, it has been claimed.
Focus Ireland said there had been a massive increase in the number of people looking for support after they lost their jobs due to the recession.
Joyce Loughnan, chief executive of the charity, said: "There are men coming in to our Coffee Shop who last year or the year before were working on building sites but then lost their jobs and got in to debt.
"They could no longer pay the rent and lost their apartment or flat, and some ended up homeless. We are trying to help them secure a home again and escape from being homeless.
"They are proud people and can find it very hard being homeless or asking for support."
The charity has launched a hard-hitting fundraising campaign to ensure it can cope with the growing demand from people who are homeless this winter. Charity key rings will be sold by volunteers in the coming week.
The campaign includes an admobile outside the gates of Government Buildings, featuring a poster showing a man sleeping in his car, with the headline: "I used to build homes. Then I lost mine."
Ms Loughnan added: "It's sadly ironic that despite the thousands of surplus houses that were built in recent years, up to 5,000 people are still homeless due to the lack of social housing."
Elsewhere, EBS Building Society has joined forces with the Simon Communities of Ireland to support 20 full-time volunteers on its six-month training programme.
Noeleen O'Callaghan, volunteer co-ordinator, said volunteers not only give their time and help those experiencing homelessness, but gain valuable skills for the future.