I am advised by Revenue that data relating to the Home Renovation Incentive (HRI) is available from the statistics section of the Revenue website at http://www.revenue.ie/en/about/statistics/index.html. Specifically, the most recently available information on the cost of the scheme is in the Tax Expenditures section of the page at http://www.revenue.ie/en/about/statistics/hri-stats.html.
It should be noted that the value of the tax credits referred to therein is not reflective of the cost to the exchequer as not all credits have been claimed to date. Furthermore, it should be noted that tax credits claimed by an individual under HRI are generally split evenly over a two year period.