you haven't told us what you are objecting too??? you need to be more specific for any sort of an awnser!! in principle you have the right to object, as you own the adjacent site.. why not explain the issue to your architect.
One of the most remarkable aspects of the Irish Planning system is that anyone can appeal any planning application anywhere in the country, as long as they make their observation within the five week period.
You can object but on what grounds? Unless something is going to infringe on your quality of life or cause issues for you with your own site I would be very wary of goi g down this route, he is entitled to achieve planning permission as you were when you bought the site.
I did point out my query was based on if I needed to. And yes if the proposed development was going to seriously impact upon us I would ' start off living in a house having objected to a neighbours permission'. I would not be in the habit of objecting for the hell of it.