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Assembling an unvented roof in very humid weather

jamesboris | Posted in Green Building Techniques on
I’ve framed 6 or 7 roofs — but now I’m building my first unvented one, in Zone 2A. The assembly:
1) tongue & groove roof deck, exposed to interior (air-sealed at top plates) [done]
2) Solitex Adhero [done]
3) 7” polyiso
4) 5/8” ply
5) high temp peel & stick underlayment
6) standing seam roofing (There is no 2×4 strapping above the UL– I read a dozen debates here and decided against it, mostly based on the logic of Malcolm Taylor & Michael Maines).
For my case, Martin and others often strongly advise waiting for dry weather before installing the foam, plywood, and underlayment – to avoid sealing moisture into the assembly. I’ve read that even without rain, it can be dangerous to install in high humidity.

I’m confident that we can get it all installed in 1-2 days (I’m the lead laborer on this)… but we tend to run at 90%+ humidity this time of year. Morning dew runs the gutters. It gets hot by mid-morning, which dries any dew, but it stays humid.

Any advice? Is humidity itself an issue here, or am I okay if I just wait til the dew dries? And tarp overnight if we take more than a day. I don’t wanna be dumb/impatient here 🙂 Thanks!

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