I am looking for opinions/advice used OSB, WRB..,  I will appreciate any input.  I am building a new house and tearing down an old one on the same property.  I feel fortunate that I will be able to reuse a significant amount of 2 x 4’s on the walls for rain screen over a total thickness of 3 or 4″s of EPS with staggered joints. My 2×6 walls will be Rockwool r23 batts. For the roof I plan on doing a 2 x 4 grid pattern over the the roof sheathing and 4″ of EPS again with staggered joints. This will leave me with a 3″ air space under my exposed fastener metal roofing. My roof system will be a parallel trusses  24″ deep filled with Spider Plus Fiberglass.  

I was also able to salvage a significant amount of OSB from portions of the roof and the second floor flooring which used two layers of 7/16″. I realize that 7/16″ is not typically used for roof sheathing, but with the 2 x 4 grid pattern I’m pretty certain I’ll be fine. I have plenty of time and I’m willing to fill holes in the OSB if necessary, but I would hope the WRB would suffice. 

Regardless of whether I use new or used OSB, I’m certain I’ll need a weather barrier on the OSB.  I was thinking of an adhesive roofing membrane and something as simple as roofing felt for the walls but using appropriate tape systems around doors and windows.

I have a hard time spending $45 on 7/16″ Zip System when it was less than half of that not too long ago.  I would also like an opinion on whether is should put a layer or layers of EPS on the between the drywall and ceiling.  Thank you