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92 posts
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Posted 29 Mar 11 9:40 PM
I would check with the Canadians who always use an exterior plywood or chip board. When I framed houses (1980's in Canada) they nailed the ply on the outside wall with no sealants. Then they wrapped it up with Tyvek building wrap on the outside of the plywood. Sometimes they would put a few inches of high quality styrofoam first, then building wrap. Things could be different now, so I would check with North Americans. Leo
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87 posts
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Posted 30 Mar 11 12:02 AM
Any north americans on here who would care to comment?
I think I will do as Dean and Lionsong suggest - and leave off the sealant and tape, and just wrap the ply in building wrap.
Cheers,
Ben
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92 posts
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Posted 30 Mar 11 8:40 AM
You could also consult the architect or planner who designed the resilient house (See first post on this threat) and ask their advice. There are also quite a few websites like Fine Home Building etc. I know that the Fine Home Building Site has the latest and greatest books on green and airtight building in North America. I agree with you and would err on the side of caution, unless I found better professional advice. Leo
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92 posts
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Posted 30 Mar 11 9:10 AM
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87 posts
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Posted 30 Mar 11 9:58 AM
I just emailed the architect from the Resilient House article so will see if he has anything to add. I can't imagine there will be anything wrong with wrapping in building paper over the ply - after all previously it was only single layer of wrap between my framing and cavity/cladding.
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80 posts
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Posted 30 Mar 11 1:48 PM
Can I ask, are you using a purpose-made air barrier product.. ie Ecoply 'Barrier' (7.5mm powdercoated), or just straight Ecoply? I ask because you may want to check the paperwork, it could be that warranties are dependent on by-the-book installation, which I'm pretty sure in the case of the Barrier product requires taping the joins at the stud. I know RAB requires this. If you're using straight ply you can do whatever you want (within code and reason), part of why I took this option.
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80 posts
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Posted 30 Mar 11 1:54 PM
I doubt you'd have any issues with wrapping the ply, but I think you may run into difficulties if you want to avoid taping the joins. A 3mm gap is usually required between boards at the stud to allow for expansion, and taping is (I believe) primarily required as a precaution against water ingress, not air. Of course, wherever air can get so usually can water.
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80 posts
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Posted 30 Mar 11 1:57 PM
Out of interest - we're also starting to see rigid air barriers used increasingly throughout Wellington also, especially in the more exposed areas (almost all of Welly really ;)). In any case, great to see!
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87 posts
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Posted 30 Mar 11 2:19 PM
I am not intending to use any tape - for the simple reason that prior to deciding I was going to use the Ecoply 'Barrier' solution I was going to have a standard timber frame + building wrap + exterior cladding.
Now it is simply timber frame + ecoply + building wrap + exterior cladding.
The only difference is the extra plywood layer to provide rigidity and bracing, as well as some additional R rating.
This is a far better solution the original, but the original got through council so I see no reason why this new method (without the tape) should have any problems.
BTW - I contacted the architect from the article at the top of this thread and he agrees with me.
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