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EPS as a water-resistive barrier (WRB) and air barrier?

M_Vaupel | Posted in Green Building Techniques on

I plan to build using rough cut 2×6 studs.  I plan to sheath it with 2.5” R10 EPS, covered with 30 lb felt. The asphalt felt will be tacked down with 3/8 verticle shims over each 16” oc stud to create an air gap, then horizontal strapping to attach board and baton rough cut cedar as siding. interrior side will have let in corner bracing to prevent racking, 475 intellos membrane with dense pack in the stud bays.

My question is what is the best, most resilliant way to air seal the EPS joints? Tape? Spray foam? A mesh tape with a fluid applied barrier? What sticks well to EPS and stays flexible over the long haul?

Also, I have wondered if asphalt driveway sealing products  (crack sealing viscous liquid and the more fluid surface sealer) have ever been experimented with as an inexpensive wrb and air barrier?

Thank you
Mike Vaupel
Berlin, VT

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  1. GBA Editor
    Martin Holladay | | #1

    Here are links to two previous Q&A threads on this topic:

    "Taping EPS foam"

    "Siga Wigluv vs 3M 8067 Flashing Tape"

    In both threads, the consensus seemed to be the Siga Wigluv would work.

    In one thread, Michael Maines noted, "I heard this from my local Siga rep: 'All of the Siga tapes will stick to EPS without primer. As long as the tape will not have long term UV exposure.' And from my Pro Clima rep: 'You'll definitely need to use PRIMER RP on any foam. You could use it with an all-around tape like TESCON VANA, or try our new COMPEGO tape that adheres especially well to low energy materials like poly and many foams, with a plastic carrier film that's vapor retarding.'"

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