Wall Assemblies for Different Control Layers

anukeen_sprout | Posted in Green Building Techniques on March 28, 2022 04:08pm

Hello GBA,

I am adding 400 SF addition to the back of my house in Oakland, California (Zone 3C). It will be part conditioned space, part unconditioned storage. I have several control layers overlapping, and I am trying to find the most efficient way to do this, but also make sure I don’t have any sandwiches. Please see the attachments for the control layers, which think correct. Please help me come up with the best wall details for these!

Proposed West wall detail, in to out:

5/8″ drywall, 2×6 studs + fiberglass batts, 1/2″ CDX (=shear wall), 1″ polyiso or similar (=exterior insulation), DensElement (= 2-hr Fire, Air seal, Waterproofing), Corru-vent furring strips, Hardie panels, Hardie board (board & batten). This seems excessive, no? Is there a more efficient way to do this?

Proposed middle wall, in to out: 5/8″ drywall, 2×6 studs + fiberglass batts, 1″ polyiso or similar (=exterior insulation), 5/8″ drywall. How to air-seal this assembly? I could use DensElement, but I would end up with a very uneven Prosoco mess. An additional layer of drywall on top of this? Should I also worry about moisture in this room?

Proposed East wall, in to out: 5/8″ drywall, 2×6 studs +NO insulation, 1/2″ CDX (=shear wall), Corru-vent furring strips, Hardie panels, Hardie board (board & batten). Can I just put the siding assembly directly over CDX? Should I waterproof? Air seal?

Please don’t be limited by my assumptions, and tell me the best way to do these assemblies. Also, even if there are best ways to do each of these individual walls, it’s probably efficient to repeat using a product when possible.

Thank you so much!