Ceiling pine panels

Hi guys, most likely a really dumb question, but neither the carpenters working on the project nor the wisdom of the www could provide me with an answer (so far).
We decided to get our cathedral roof insulated and covered with new timber wood panels. So the simple question is: Is varnish, oil, or nothing?
In my opinion, it is currently pretty bright and could be a tint warmer/ darker, but this will done in time anyway. It's 140 sqm of a cathedral roof, so a pretty big job, and I don't wanna do it for nothing...(or worse, to do it wrong) If it needs treatment, a single coat option without additional sanding would be preferred...
Cheers Krischan