Replies

1. 
   matthew25 | Oct 02, 2023 07:47pm | #1

   Main things to consider:
   - Permeability - since you have impermeable polyiso outside of your WRB this is not a big deal for your situation unless you also have interior poly?
   - Thickness - the UT durability lab basically determined that longevity is correlated well with installed product thickness, with thicker WRB’s performing for longer, all else being equal. This is most relevant for liquid applied WRB’s.
   - UV exposure limits - read the spec sheet for this. For example, Risinger used to use Delta Vent SA a lot but if you look at the spec sheet it’s UV rating is only 50 days!
   - Accessory products - like flashing tapes or fluid-applied penetration flashings. Read the installation for the WRB you are interested in and see if they require accessory products to keep your warranty.

2. Expert Member
   Akos | Oct 02, 2023 09:21pm | #2

   Self adhered is only really need if you have board sheathing. With OSB/CDX, it is much cheaper (and quicker) to tape the seams and install regular house wrap. This would also give you flexibility of where the house wrap is located. I find when dealing with exterior rigid it is easier to have the house wrap over the rigid and go with outie windows. This keeps everything in plane and pretty close to a "standard" install.

   P.S. I've had good luck with VP100, relatively inexpensive, sticks great and holds up well to abuse.

1. 
   Patrick_OSullivan | Oct 02, 2023 10:33pm | #3

   I think this is good advice. The one thing I'll say is that every time you introduce a new "plane", you introduce something to think about.

   If you take one extreme (like Zip sheathing with no exterior insulation or Zip R-sheathing), your air and water sealing are in one plane. Easy to reason about. If you add a second plane (taped sheathing plus traditional WRB over it), you have two planes. One for air, one for water. You need to actively be thinking about this during install of things outboard of these layers. If you have taped sheathing, traditional WRB, and polyiso, you have three planes. The polyiso is a quasi-plane since things are probably not flashed to it, but it really depends on your window details. For instance... are you bucking windows out to the outside of the insulation?

   All these assemblies can work well, but I am constant champion of trying to fight against the unknown unknown (i.e. the things I wasn't smart enough to think through ahead of time) and installer error (because it's hard to police a productive crew on every detail).

   If I was using a self-adhered membrane, I think I'd go with VP100 like Akos mentioned. It's readily available and well regarded.

   One thing I'll say is that I commonly see it installed *horribly*. It's not so common in my part of NJ, but I see it on builds all the time alone the Jersey shore. Some of those installs are good. Sadly most of them seem to be "check the box" on an architect's spec for the product and the VP100 is looser to the sheathing than a good Tyvek install could be. It's sad, because these ocean adjacent areas could probably benefit from such a product and it really seems to be installer negligence working against them--bad install from the get go coupled with above acceptable exposure time of the WRB.

3. 
   woobagoobaa | Oct 05, 2023 09:11am | #4

   Another vote for VP100. Good value ... middle of the price range. But as mentioned, be sure the installer is following the instructions (ROLL IT!). The local Henry rep was super helpful, visiting my job site several times to coach the installers.

4. 
   steve41 | Oct 05, 2023 09:26am | #5

   I'm mostly curious about this- If this is foil faced polyiso on the exterior, wouldn't it be appropriate to diligently tape the seams and use it as the WRB? (without any additional SA WRB).

   Is there a rainscreen in the assembly?

5. 
   GregS_NH | Mar 13, 2024 08:24am | #6

   Thank you all for the input! For some reason GBA just notified me today of your responses, so I’m seeing them just now.
   Greg