Facade: Wall assembly help needed
Hello. I have an attached wood frame row house in Brooklyn, NY on a 16′ wide lot about to undergo a comprehensive renovation. Our plan is to use 1/2 x 4″ primed and painted beveled cedar siding as the front siding material. Current proposed wall assembly is (exterior to interior) :
1/2 x 4″ WRC Bevel siding
Benjamin Obdyke Homeslicker (rainscreen)
Rockwool on exterior for CI
Solitex Mento 1000 (WRB)
5/8″ plywood sheathing
Rockwool batt between the studs
5/8″ sheetrock
Aqualock primer + regal select paint
I definitely want some type of exterior insulation and want to use WRC as my siding material. But how does the siding attach to the insulation layer ( weather Rockwool or exterior rigid foam). I originally wanted to use furring strips on the rockwool to attach the siding but i dont think i will have enough depth on the front exterior and i dont want my facade to stand proud of my neighbors. Thats why i thought of using the Homeslicker for some venting behind the wood siding as a space saver that still achieves similar objectives in terms of drying.
I was also considering using the ZipR sheathing since the insulation layer is behind the sheathing and i would be use the Homeslicker and directly attach the siding to the OSB. Would that work? I’ve heard very mixed things about ZipR which is why i’ve gravitated away from considering it.
Also, on the interior, could i benefit from using a “smart” vapor membrane like Intello or something similar?
The front facade is about 450 sq ft – so its not a huge amount of space so cost considerations are secondary to building a smart assembly with the highest quality materials.
Would really appreciate any comments from the community. Thank you, Armen
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Armen, exterior mineral wool and Homeslicker don't really go together. Homeslicker is a great product but it's not fun to install clapboards over it, as it is a bit squishy. Clapboards are best installed over vertical rain screen strips, which happens to also be a handy way to hold exterior mineral wool in place. If you go this route, where is your airtight layer? You should have one somewhere in the assembly. I think it's easiest to tape the sheathing seams; if you do that, you can use a standard WRB such as Tyvek. Alternatively, you can tape the Mento to create an airtight layer.
You could use ZipR instead of exterior mineral wool. Just make sure the foam R-value is enough for dewpoint control--in NYC, zone 4A, that means at least 16% of the walls' R-value should be in the foam. Thicker Zip-R can be tricky to install, but thinner types install just like regular sheathing--just make sure you get 1 1/2" nail penetration into the studs.
Adding a variable permeance membrane at the interior (Pro Clima Intello, Siga Majrex or Certainteed Membrain) is always good insurance. Not much moisture moves via diffusion, but some does. But it's not required by code in your zone as long as you have ventilated cladding.
Thanks for the feedback Michael.
Any experience with ZipR sheathing? I'm concerned about that assembly...with the polyiso being on the inside of the structural sheathing. Wont this reduce the sheer strength of the wall? If I used ZipR, I'd have the following assembly: WRC Bevel siding -> Homeslicker -> ZipR Sheathing 1" -> Rockwool comfort batt (stud walls)--> Intello --> 5/8" drywall
Do you have any experience with/thoughts on the the Proclima product line up (solitex mento, Intello, tescon vana tape) etc?
Thanks again
Armen, I have spec'd ZipR several times and have researched it pretty thoroughly, which is what my advice above was based on. I have not yet installed it myself. It has been tested and approved for shear strength, if installed per Huber's specs.
Again, I would not use Homeslicker with beveled siding, aka clapboards. If you're planning to use a form of beveled siding with a back that lays flat on the wall it would probably work.
Yes, I have a fair amount of experience with Pro Clima products. Mento (either Mento 1000 or Plus) can be made airtight. Intello is generally my favorite variable permeance membrane, and easy to get online from foursevenfive.com. Siga Majrex is also good, with somewhat different chemistry, available from sigatapes.com. Certainteed Membrain has performance numbers comparable to Intello but it is much less robust--while it would take a lot of effort to tear Intello with your hands, you have to be careful with Membrain to not tear it inadvertently. Tescon Vana is a good tape for almost all situations, but you can save a few dollars with Rissan on the interior. If you're going with a Pro Clima system, the best approach is to talk or online-chat with foursevenfive.com, as they know their products well and regularly release new ones.