Will rainscreen gap on Zip and ZipR lose air tightness?
88Clayton
| Posted in General Questions on
I don’t think Zip is self sealing, so should I worry about losing air tightness when installing furring strips for rainscreen gap? If it’s an issue, what’s a strategy to maintain good seal?
Thanks!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Clayton,
It isn't a concern. Whether it's to attach furring or siding, sheathing always ends up full of fasteners. Builders have been using it successfully as the primary air-barrier, so there must not be much leakage through the holes they make.
I’ve seen nails flashed over with Liquid-Flash on Zip before, so that’s what got me wondering. I imagine my worries about furring strip penetrations would be lessened by use of Zip R, since the furring strip nail would likely not penetrate through the foam.
Clayton,
Without knowing your aims it's hard to say whether it's worth pursuing. Like very high levels of insulation, the returns for meticulous air-sealing diminish as you get to the potential small leaks. I think it's an open question as to whether spending the time to air-seal to beyond Passive-h0use levels makes any material difference to the way a house performs, from the point of view of longevity or efficiency. High performance houses routinely use the exterior sheathing as their air-barrier without sealing the nail-heads.
My aims are to get in the ballpark of 1.0 ACH50.
When it comes to sealing, I know there are definitely bigger fish to fry, but if I have the time, I’m not opposed to addressing the finer details.
Your comment about some Passive Haus projects not using it makes me feel better in the case that I don’t get around to it.
Thanks!
“I imagine my worries about furring strip penetrations would be lessened by use of Zip R, since the furring strip nail would likely not penetrate through the foam.”
Actually, the nails attaching furring strips would need to hit the studs so they would penetrate the foam. In the event that nail misses a stud, it should be removed and that hole sealed with either tape or liquid flash.
Clayton,
I've seen so many houses hitting Passive House or better levels of air-tightness with ZIP as the primary air barrier with furring strips fastened through it for a rain screen gap that I don't think this is a problem. Do a proper job installing and taping the panels and then put your energy towards all of the other, more tricky areas to air seal.
👍🏻👍🏻