The sheathing that was used for the prefabricated well panels was 7/16″ ZIP System panels. In a do-over I think we would stick with plywood for sheathing and happy a WRB over the sheathing. We ended up adding a WRB over the ZIP panels for three reasons:
- With ZIP panels we had a reverse-lap at roof/sheathing joints, and with that not surprisingly water leaking into the house.
- Many of the ZIP panel fasteners (nails) were overdriven, creating hundreds or thousands of holes in the WRB. The prefabricated panels were also assembled in Canada, loaded on a truck and trucked to Connecticut, unloaded, moved around, moved around again, hauled into place, and assembled. During that process some of the sheathing got pretty beat up.
- We planned to install rainscreen cladding with reveals, and did not want to have green sheathing visible behind the reveals, and the ZIP panels are also not rated for long-term UV exposure, I think your warranty is probably invalidated if you leave them exposed for more than 180 days.
The two main products we looked at for the re-wrap were Dorkin’s Delta-Fassade S (which was carried by Eastern Architectural Products, where we got most of our siding) and VaproShield’s RevealShield SA, which is what we ultimately went with and which we got through Cement Board Fabricators. Both of these products are designed specifically for rain screen applications where there are reveals, being black and UV stable. Also quite high performance, the RevealShield for example has a very high drying capacity (much higher than the membrane on the ZIP panels). Though I am not sure I totally understand the need for breathability, I guess maybe you want it to let the house dry out from when it was open to the elements, but as soon as you install closed cell insulation on the interior I don’t think the house is breathing any more.
The RevealShield comes in 5′ rolls with an integrated tape designed for a conventional horizontal application, and 5′ rolls with the fully self-adhered for which a vertical application is suggested, and which I thought would be a little easier for the crew (our roofers ended up putting it up for us) to install (the SA adds cost to what is already a pretty expensive WRB product). There is also VaproShield tape available that is UV resistant, and does not have the annoying white lettering on it that the ZIP tape has. I was a little concerned about having two WRBs on the house, but called Huber’s technical support and they said it was not uncommon and OK to add a WRB over the ZIP panels.
