So after long research it seems to be needed to somehow insulate between the metal ribs and whatever you install on top of the ribs to avoid thermal bridge between the rib and whatever wood you use, the idea is to minimize the thermal transfer that metal has and avoid passing that as much as you can to the wood.
After reading many papers about house insulation in different countries and standards it seems to be necessary to leave a gap between the metal stud and the insulation and the idea is to touch as little as possible any metal stud so there is this weird cladding systems and brackets that you can buy for metal studs but the problem with the buses is that space is limited so I searched for a solution for limited space that you can install in between the metal ribs and the furring strips that I plan to install on top and I found this :
is meant to be installed on top and it supposed to give better performance than most products and is compresible so it can be use in like a sandwich setup for lack of another word.
Please keep in mind that I'm driving my bus to Alaska in winter with the family so -30c or lower could be possible so any idea to insulate better is welcome and please do not try to convince me to not do the trip because I'm not going to listen.
The bus will be sprayed with injected foam after the frame is up and then cover with some plywood or other kind of wood finish.
so a couple of questions :
1.- what do you think about thermablock, could it help ? any other product you know ?
2.- what about an air gap in between the ribs and the frame ?
3.- should I use stainless steel self tapping screws instead of just steel ?
Any other suggestions ?