Choosing Between Two Wall Assemblies
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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).
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Replies
Either assembly could work fine.
The VP100 should get better airtightness being self-adhered. I would save the Prosoco for joints and penetrations of the primary WRB rather than plywood seams in the field of the wall that will get fully covered with the VP100. I've never seen those two used in combination. Ensure they are compatible.
If you want redundancy, employ the "airtight drywall approach". Use the fluid applied Prosoco for the full depth of rough openings. Get a great seal to the foundation. etc. etc.