Yes, I've thought of the rain shield as well - thank you for pointing that out. Cladding will be vertical cement board, so I'm thinking we can always do horizontal perforated or corrugated furring strips which would provide a rain shield for ventilation between cladding and WRB and also a nailing surface for vertically hung cement board. Not sure if that is common practice or not though. I love the idea of Zip - it's the installation that worries me. If you have good seals at the seams and penetrations, then no worries. Just need to inspect very closely as it is being installed whereas a wrap may have more forgiveness with the install - possibly. A decent middle ground between efficiency and forgiveness may be open cell - 1/2 cdx with taped seams (to increase air barrier), wrap, rain shield (furring strips that allow drainage/vent), cladding. This should create a good rain/air barrier while still having a good perm rate - creates a good seal while still preparing for perm/ventiliation when water does get behind the cladding.

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Posted by Turnblad85

Member since Sep 2022

1395 posts

Posted on 7/21/23 at 9:52 am to AyyyBaw

Can't say I've ever seen or heard of it done like that. First impression is thats a lot going on with a wall assembly. Its not easy to find a builder (if you're going to use one) who is willing to do unknown things. They like doing things they are used to with no learning-on-the-job surprises. Poorly installed zip or wrap is going to suck no matter what. Also, with the cdx sandwiched between wrap and foam, I'm not sure there is enough ability to dry if water gets between them. Tyvek has decent permeability but a few inches deep open cell is very little perm. That plywood may be wet for a long time before drying. I just don't know.

My personal favorite wall assembly accounting for cost and performance is: generous roof overhangs then cladding~rainscreen~zip (or zip-R)~rockwool insulation. But there are many ways to skin that cat and new products are being put out every day.

Seems like you're thinking things through and want a well built home. I'd suggest spending a little money and time on greenbuildingadvisor. Not sure how familiar you are with it but they are more building science oriented than "green" which is a bit misleading. Once you've formulated a thoughtful idea of what you want, you can ask questions and get good answers possibly even from authors and industry experts who love talking building science. Just be mindful to ask good specific questions. Not, "so whats a good way to insulate a home" .