"The recipient must not, at the date of the gift/inheritance, be beneficially entitled to any other dwelling- house or to any interest in any other dwelling- house. The Revenue's view is that a dwelling-house means a building or part of a building being used or which is suitable for use as a dwelling."
I think this is what you're referring to. I think you're stretching it - you can try it on but I think you've lost your exemption because there are two houses.
Indicators like whether household charge, LPT and NPPR payments were made plus whether or not there are utilities connected may make it more obvious.
mf