Tier 2 reduces the amount of materials and simplifies the design. It's similar to Tier 1, but with the sheathing removed and replaced with cross bracing. The framing can be wrapped with waterproof, airtight, and vapor open SOLITEX MENTO membrane as a temporary WRB.
Tier 2 removes not only the sheathing, but also the labor associated with installing it, and makes the assembly even more robust, healthy, and resilient.