wall stack up
Last Post 19 Oct 2015 07:04 PM by HP Home. 5 Replies.
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TguyUser is Offline
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12 Oct 2015 10:43 AM
Looking for feedback on a straightforward wall stack up for zone 5, 3000 elevation. L&P siding, zip wall then open cell foam. House will sit on a crawl space, one story. Thoughts? I need to keep it simple as the local trades in my area are old school. thanks BTW 2x6 walls
Bob IUser is Offline
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12 Oct 2015 06:51 PM
Sounds pretty minimal. Does it meet local codes - ("code" meaning the crummiest building you legally can build)? What is your crawl space floor? Crawl space walls? Roof/ceiling? What minimal amount of air changes are you willing to have? Why aren't you doing a rain screen? (or are you testing failure rates?) Is there more wind than at lower altitudes? If so are you taking that into consideration for how you build your house? (can't tell from your description) You're writing to a "green building" site so it seems like you would be looking for a home a little better than minimum?
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
jonrUser is Offline
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12 Oct 2015 07:39 PM
There is a lot to be said for rigid foam (like EPS) reducing thermal bridging by the studs.
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13 Oct 2015 02:04 PM
OK I give up, of the many possibilities that come to mind, what do YOU mean by "L&P siding"??

With open cell foam you'll want to put a layer of MemBrain under the gypsum to limit wintertime moisture loading of the OSB. ($100 for an 8' x 100' sheet from Menards, comes in sheets up to 12' wide.)

Alternatively, you could use 1.5" ZIP-R and forget the MemBrain, and get a bit of thermal break and higher wall performance. It goes up just like regular OSB sheathing, but takes longer nails, with slightly tighter spacing. With open cell foam it wouldn't need an interior side vapor retarder, but with R23 rock wool or something you'd still want the MemBrain.
Bob IUser is Offline
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13 Oct 2015 02:08 PM
I assume he's referring to Louisiana Pacific Smart Side; a manufactured clapboard made, I understand, from a material identical to Advantech.
Bob Irving<br>RH Irving Homebuilders<br>Certified Passive House Consultant
HP HomeUser is Offline
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19 Oct 2015 07:04 PM
Posted By Dana1 on 13 Oct 2015 02:04 PM
With open cell foam it wouldn't need an interior side vapor retarder, but with R23 rock wool or something you'd still want the MemBrain.


Why is this? I thought per code if you have sufficient exterior insulation that no vapor barrier was necessary.
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