All,

I am in the process of building a home with my wife. We’ve found a great design-build firm that loves the idea of building an energy efficient home in Northern Virginia. Right now, we are trying to determine optimal building enclosure for performance and cost.

The two options we are thinking of are:
Wall assembly 1:
1. 2×6, 16 O.C” with 3/4″ plywood or 23/32″ Advantech sheathing (which one is better?). Seal all sheathing, nails, and rough openings using prosoco joint and seam, and fast flash.
2. Henry Blueskin VP100 WRB;
3. 2″ Rockwool Comfortboard 80;
4. 1×4″ for drainage plane;
5. Hardie siding.
6. 5″ of Rockwool insulation in wall cavity.

Wall assembly 2:
1. 2×8, 24 O.C” with 3/4″ plywood or 23/32″ Advantech sheathing (which one is better?). Seal all sheathing, nails, and rough openings using prosoco joint and seam, and fast flash.
2. Tyvek Commercial WRB;
3. 2″ Rockwool Comfortboard 80;
4. 1×4″ for drainage plane;
5. Hardie siding.
6. 7.25″ Rockwool insulation in wall cavity

We are very interested in designing the roof detailed in this article:
https://www.jlconline.com/how-to/insulation/an-airtight-lid-the-easy-way_o#:~:text=Conventional%20vented%20attics%20are%20one,creates%20a%20tight%20air%20seal

How can we make either building enclosure option better? Our goal is to build in redundancy for water management and air control so we aren’t relying on a single layer/system for water and air control (Our goal is to get under .5 ACH).