I have a section 23 property (short term holiday/tourist rentals). My understanding (and my accountant) is that the relief can be written off against any Republic of Ireland/domestic rental income - ie residential, commercial or short term.
One word of warning re section 23 - be very careful ref the VAT situation, get good, experienced, informed advice, because you can open yourself to having your other rental income vatable, depending on what you do.
There's a bit of a minefield out there and not every professional (legal, financial etc) is fully up to speed on the tax and VAT implications of section 23.