What do you think about this article on Solitex Mento WRB vs ZIP systems?
rockies63
| Posted in Green Products and Materials on
An interesting product from 475.
https://foursevenfive.com/blog/why-solitex-is-the-best-wrb-solution/
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Replies
Scott,
It makes good case for using a sheet WRB rather than ZIP. It's less convincing as to why you should use Solitex over the others like Tyvek.
Making claims based upon some tests which may or may not be relevant. Meh. It's an advertisement. I'm not a fan of 475. They tend to use a lot of hyperbole and scare mongering. For example they link a 2010 GBA article about "cold OSB problem" which is probably irrelevant in 2019 when one considers exterior rigid foam, which 475 hates btw, of sufficient depth.
Huber states that with regards to ZIP sheathing the vapor transmission (per ASTM E96-B) is 12-16 perms.
https://blog.ansi.org/2017/01/explaining-water-vapor-testing-astm-e96/#gref
https://www.astm.org/Standards/E96
I agree, alot of fluff opinion and little fact.
Hi Scott,
I think the article raises some legitimate things to consider when designing or building an enclosure, like the differences in plywood and OSB performance characteristics, the ability to integrate a WRB with flashings in a shingle-style approach, etc.
The folks at 475 know their stuff. For example, I was on the phone with one of their sales reps the other day discussing vapor control. He has degrees in material science and architecture and is a Passive House consultant. He strongly recommended Intello for an interior vapor retarder, of course, but he spoke intelligently to other materials and methods too.
I think the assemblies 475 promotes do make sense. The thing is, they also make the most of the products that 475 sells. In other words, theirs is not the only or best way to build. Coming at it with the understanding that they are only going to promote the products they sell, I think you can trust their information, even if you decide to build differently.
By the way, I would write the same response for some other companies, including Huber and Benjamin Obdyke, based on my experience working with them. Some others, I would not.
I'd have to agree with Brian. I've used Pro Clima products and studied them, and they really are better than other options in many cases. I appreciate what the 475 gang is doing but agree that they can stray toward hyperbole, and some of their recommendations, such as unvented, dense-packed roofs, are dangerous if not implemented with 100% adherence to their list of requirements which nobody seems to read. But in the article, I see mostly accurate facts.
One fact I would dispute is the sub-1-perm rating for Zip. I believe (based on research and discussions with Huber reps) that it is sub-1 perm PER INCH of thickness. So in typical 7/16", 1/2" or 5/8" thicknesses, the perm rating will be roughly twice as high, just over one perm (dry). Intello's performance numbers and durability really are significantly better than readily available alternatives. Some have similar performance but lack durability, some are durable but lack Intello's wide perm swing.
Depending on the situation, Mento's superior performance may not be necessary. When there is exterior insulation, I'm happy with Zip as a WRB. When there is a deep rain screen and another product serves as the air barrier, I think Tyvek or even tar paper are fine. But when it's a demanding situation--no roof overhangs, panelized construction where insulated panels are exposed to weather, when the WRB has to double as the airtight layer--Mento really does perform. (We hit 0.12 ACH50 on a house I designed, using Pro Clima products and no spray foam, and I know of many similarly tight examples.)
Michael, what I can't understand is why would someone choose to use a separate product as the air barrier if the Mento product has superior performance? Don't most builders want to simplify construction and use less products and therefore not have to integrate them?
The main difficulty with all these construction layers (the sheathing, air barriers, moisture barriers, detailing and flashing around openings, transitions between building planes, etc) is getting them all to work together. If the Mento's can be the air and moisture barrier, and is a superior product in a demanding situation then shouldn't it be the best choice in all situations?
Scott, you might think so but every project is different and cost is always a factor.