Yes, well, confusion can easily arise unless you keep up to date with this stuff.
Before the An Bórd Pleanála case referred to in the archiseek link I posted I was told by our local planning officer that one velux to the rear was considered exempted development, two was pushing it and they would not be considered exempted development on the front.
Things change in planning all the time, which is why I advise people to take advice from a building professional.
Building Regulations OTOH have been law since 1st June 1992.
There is no excuse even for laypersons for not knowing about them, whatever about interpreting them - leave that to professionals is my best advice.
You can read about them here:
http://www.environ.ie/en/TGD/
Finally Health and Safety law affects work practices everywhere.
Wander over to the Self-Build Faq and read a little of this [still] unfinished work.
ONQ.
[broken link removed]