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wall system for natural wood frame in high desert  RSS feed

 
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Hi
Hoping to get some opinions.
We are building a fairly conventional house but want to build with natural materials both for environment and health. I am in zone 3 high desert so we are mixed/dry.  I wanted to post  my wall to see if I am missing anything important. It is positioned for passive solar heating and cooling and natural ventiliation ( I won't have a HRV system). I am most concerned about preventing mold and having decent air.
I am not able to do earthen wall's (though that was my first choice) . now it is wood frame.
So. From the outside working in I have
#1 wood shiplap siding (painted)
#2 3/8" air gap
#3 furring strips
#4 Housewrap (this is my biggest question. I don't really want to use tyvek and can't use felt paper. Wonder if I need it?)
#5 plywood taped to increase some air barrier.
#6 2×6 studs
#7 rock wool cavity insulation
#8 shiplap interior wall ( either painted with a natural type paint or beeswaxed)

Does anyone see any potential problems with this design? 
Thanks
 
pollinator
Posts: 401
Location: Southern Arizona. Zone 8b
40
bee bike fish greening the desert solar woodworking
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A couple notes:

It's hard to get a good air seal with ship lapped boards unless you caulk it constantly.

Have you considered "Board and Batton" for the inside walls?  I think it looks nicer than ship lapped, but that's a personal preference.



 
Tamara Heinemann
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Thanks Peter.
No. I've not looked at board and batten. I will check it out though.
I read somewhere I could focus my air sealing on the exterior plywood. Taping and caulking. That was my first defense hoping to not have to worry so much about interior air sealing. But these sorts of things are why I posted my ideas to see others opinions.
Again thanks.


 
Peter VanDerWal
pollinator
Posts: 401
Location: Southern Arizona. Zone 8b
40
bee bike fish greening the desert solar woodworking
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The main reason that Tyvek is popular is that it allows water vapor to pass through it without allowing water or wind to pass.  This helps to keep the inside of the wall dryer.

Taped plywood is less permeable so it's more likely to end up having water condense on it.

If where you live experiences even short periods of hot humid weather, then condensation inside the wall may be a concern.  If the hot, moist air gets through the ship lap it could condense on the cooler plywood within and now you have water inside your wall where it will cause mold, fungus, etc.

I live in a desert that experiences a monsoon season where the humidity can reach 100% at night.  When they first started building stucco houses decades ago one of the major problems they had with it was humid air getting through holes, cracks, etc. and condensing inside the wall where it would rot out the wood framing.  Tyvek (or similar products) inside the stucco, but outside the wood framing, was one of the ways they solved this problem.
 
Posts: 14
Location: Colorado Frontrange
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I recommend taking a look at http://www.greenbuildingadvisor.com/, which has a ton of content about walls, air and water vapor, insulation, etc. involved in home building. And there's a Q&A section where you can ask specific questions and usually get a lot of feedback.
 
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