Dilemma: We have a covered porch that has a tong-in-groove pine ceiling. And we need to find a product that:
1. is easiest to maintain (ie TSP yearly and every 3-4 years new coat without sanding) and 2. best to deal with our damp/wet sea environment (ie mildew inhibitor?). Our painter wants to use spar varnish but our experience with similar houses near us that have used it, developed mildew/mold and the ceiling turned black rather quickly. So we would rather stay away from sealers and are leaning towards a stain or oil.

Here's a little house history:
We live in Maine on an island about 100 yards from the ocean. It is wet/cool/cold almost every morning and often the ceiling is wet or damp. Previous product was an oil-based stain, which was on for 12 years. We moved into the place four years ago and there was very little to no mold on the ceiling then. We TSP the entire house every year to combat the mildew.

They (painting contractors) had to sand the ceiling down to get rid of the existing mildew which wasn't that much, but it still indicates to me that there is mildew inside the wood. They suggested tong oil but that does not seem like a good mildew inhibitor and a yearly application for maintainence. I have talked to local paint vendors and they suggest either Sikkens 123 (which depending to who you talk to says its easy or hard to maintain) or a marine penofil stain, which contains a mildicide. Any other suggestions or comments about the above products?

Thanks.

It's not durable for exterior.

If there was any way for you to get a coat of Cetol 1 on the backside of the ceiling, it would help a LOT.
The idea being...your wood would be much more sealed-off from water movement into the BACKside of the ceiling.

>>> Same idea for wood siding shakes...If they're back-stained or primed, they last much longer.

Even the best mildicides are effective only for a year or two in that environment....

You're in FPE country!!
Their Marine Varnish is superb...spendy, but superb.
Very good info. on this FPE link...

Faron