WRB questions on a remodel
Hi,
I recently asked for some tips regarding my proposed roof assembly for a remodel of a ca. 1830 farmhouse in northern New York, zone 6. I am now looking for some feedback on the wall assembly. I plan to re-sheathe the house with zip wall sheathing. Mostly I am doing this because at some point the wind bracing was cut out of the frame of this timber framed home- don’t ask me why?!
After the zip wall is on and taped I plan to add 5.5″ of recycled polyiso and then install a 1×4 rain screen followed by cedar clapboard siding.
I plan on doing “outie” windows, so my question would be do I need to add another WRB on top of the foam to integrate the windows or do I just need to be creative and meticulous in detailing my window installation?
Is the zip wall overkill? Would it be wiser to use OSB sheathing and then a WRB between the foam and the rain screen? With 5.5 inches of foam I see a headache trying to secure housewrap after the foam, this is what motivated my decision to use the zip system.
I would prefer not to use housewrap over foam so any ideas on installing the “outie” windows properly would be of great help.
Thanks for all the help,
Mike
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Replies
With an "outie" window you really need to integrate the flashing with a suitable drain-plane material, and reclaimed roofing iso ain't it. Martin informs me that there are some aluminum-faced iso products that can be detailed to meet a WRB spec, and even 1/2" goods would likely be adequate (and if nothing else, easier to air-seal than fiber-faced iso.) The foil facer gives it a small thermal performance boost too (not that it would be easy to measure with 5.5" of iso on the exterior.)
Zip sheathing isn't necessarily overkill, since it's dead-easy to air-seal, and could be a time/schedule saver, if not an overall cost saver. Making the structural sheathing the primary air barrier is usually the most durable, least likely to get messed up during construction (and beyond.)