What is the best way to do interior and exterior insulation in a cold climate?
I am planning a post and beam home build in Southern Colorado zone 7. Looking for help with clarification of how to layer wall insulation with water barrier and vapour barrier. Leaning towards rockwool as we are in a extreme fire zone. From the inside out I am thinking Drywall, Vapour barrier, rockwool, sheathing, 2" rockwool, tyvek, rainscreen, siding. Is this correct? It also appears there are a few rockwool products that can be used for exterior insulation and cavity insulation. Is one better then the others for my location and build? Thank you.
The wall assembly you list with a combination of interior and exterior mineral wool insulation will work fine. Mineral wool on the exterior of walls is in general a safer option that foam insulation as mineral wool allows moisture to pass through, where foam does not, see more here -
Which is the best rigid foam insulation panel?
If foam is thick enough it can work well as it takes on a similar role that a SIP wall would where the foam is the vapour barrier, but at only about 2 inches, exterior foam insulation can trap moisture in walls.
The only thing that I didn't get was when you said Tyvek, Rainscreen, Siding - I'm thinking you mean tyvek, 'strapping' and siding. And here is a page that may be of benefit about how to install siding so walls can dry.