An international driving permit (IDP) is a translation of your driving licence and you must carry your driving licence with it when driving. When visiting in Ireland, a permit is only required if your driving licence is not in English. The permit itself does not grant any driving privileges.
There is a distinction between motorists with a foreign driving licence visiting Ireland and those living in Ireland. For non-residents, currently under the Convention on Road Traffic 1949 (Geneva Convention), drivers from Contracting States carrying a valid driver’s licence can drive on each other’s roads for up to a year when visiting.
If you are resident in Ireland, you must have an Irish/EU driving licence to drive here.