I'm building a medium sized hunting cabin... very much off-grid.  Most of the insulation I've added is faced R13 fiberglass but at the rear I'm using R15 Rockwool insulation batts because the generator is on that side and it helps deaden the noise.  My question is though, do I need to add something between that and the T&G pine that I'm putting up on the interior walls?

It's in the southern end of Missouri so Zone 4.  The exterior is OSB with house-wrap and then Diamond Coat shiplap siding.  I'm not there in July/August and won't be installing A/C anytime soon.  The main heating though is going to be ventless propane which I know puts out a lot of water vapor inside.  It's only occupied a few days each month so most of the time it's just going to be closed up and tracking the outside temp cycles.

Anybody with knowledge on this got some tips?  Most of the stuff I read is worried about A/C and warm moist air from outside condensing on the inside cool wall and insulation.  I think my biggest concern may be the other way around.  Warm moist air inside reaching the outer wall and condensing.  But I have also read not to place barriers on both sides which I think the house-wrap is right?  So I'm a bit confused now.

In your location, you won’t have moisture condensation issues as long as you don’t have vent free propane heaters running inside.

The house wrap is a liquid barrier not a vapor barrier. The wall will dry to both the outside and inside depending on the temp.

Just don’t use vent free fuel burning heaters inside.  They are ok for back up heat but never used as primary heat in a climate where it gets cold even if it gets cold only for relatively short periods of time.

You should add a vapor barrier right behind the TandG boards if the insulation doesn't have it.

Housewrap is not a vapor barrier.

It’s location dependent. OP doesn’t really need one in the location his cabin is. If he was farther north, then definitely would need one.

Got a map or diagram showing this break down?

This site will have a lot of the info you are looking for.  Don't let the name scare you off.  It's not a bunch of liberals but is all about building energy efficient and healthy houses.  

The warmer the climate, the less important interior vapor barriers are.  The colder the climate, the more important they are.  

The biggest issue for the OP is using vent free heaters as a primary heat source.  That's a big mistake because of the large amount of moisture they put into the air.  

https://www.greenbuildingadvisor.com/

For the time being I'll have to stick with the portable vent-free units.  With this seeing a max of 4 to 6 days of occupation a month I think it's reasonable that the moisture would get dried out over the down time but I'll look at the permanent heating being vented instead.  Those units are steeper in cost but given the condensation I was seeing from the roof on seriously cold nights I think that's probably going to be the right answer rather than try to barrier it out.

It hit 18 outside for a couple days while I was working and the roof underlayment was starting to drip.  The roof is green so morning sun quickly ended that, but that was a lot of moisture from just two Big Buddy heaters running on Medium.  

Thanks though.  I think it looks like I'll go ahead and leave the rock wool as-is.

I'm located near the very bottom of Zone 4 on this map.  Very close to AR border.

Have you thought about one of those vented diesel heaters?

I don’t think it would be great for long term but for occasional use they might be just right.

What size is your cabin?

https://www.amazon.com/VEVOR-8KW-Diesel-Heater-Air/dp/B0CFQNSCJ8

It's 1-1/2 story so about 720 sq feet with the loft but the non-loft side has a very tall ceiling.  Probably about 22' feet to the peak.   So an unfortunate amount of open air volume to keep heated.

To keep noise down I would hang drywall on that side and then the T&G over that.  

If not, it needs a vapor barrier if it is not the Kraft paper insulation. .