Detailed information on new law regarding rent reviews guidelines and new rent pressure zone, can be found here.
This information is very useful and provided by PRTB.ie (rtb.ie) website, to guide landlords when they intend to increase the rent.
Important to note, New Tenancies that started after December 24th 2016, rents can be reviewed annually.
Tenancies that are existing tenancies as of 24th of December, rent reviews can be carried out every 24 months.
http://www.rtb.ie/search-results/news/article/2016/12/23/changes-to-policy-and-the-law