I am working on the design for a new Zero Energy Ready home design near Cleveland in Zone 5 and we are planning to use Zip-R sheathing with vinyl siding. The contractor and I typically put the outside of the wall studs in the same plane as the foundation, which will be a Monokast precast foundation system, with an EPDM sill gasket below the sill and regular blue sill seal between the sill and the rim joist. I’ve attached a preliminary detail showing this approach. The contractor has gotten blower door results below 1 ACH50 this way. The homeowner has done a good deal of research on his own. He thinks we could get even better air sealing if we put the face of the Zip flush with the face of the foundation, similar to “Scenario 3″ in the attached detail from Huber, leave the recommended 1/2” gap between the sheathing and the foundation, and use a high-quality tape between the foundation and the Zip R.
If this is actually a better detail I would be happy use it, but I am concerned about the possibility of moisture wicking up the tape and deteriorating the unprotected bottom edge of the Zip panel, even with the 1/2″ gap. Is this a valid concern? Would the high strength concrete of the foundation panels be less likely to absorb moisture than regular concrete? Opinions in general on using tape to continue the air barrier between the Zip and the foundation?