Help sort out the liquid applied WRB options
We are planning to go with a liquid applied WRB on our remodel, and I’m having a bit of a hard time picking between the different options, was hoping the collective wisdom here can help. I’ve read all the articles I can find on GBA but still hasn’t helped me understand the differences, including:
https://www.greenbuildingadvisor.com/article/liquid-applied-flashing
https://www.greenbuildingadvisor.com/article/liquid-applied-water-resistive-barriers
https://www.greenbuildingadvisor.com/article/housewrap-in-a-can-liquid-applied-wrbs
I was looking at Sto Gold and the Prosoco systems, but the price wildly varies and I’m wondering if people can enlighten me why. I’m fine paying more if a product works better, but I can’t tell from the marketing material and info in the articles.
For Sto Gold, a 5 gallon bucket is ~100-150.
Prosoco R-Gaurd Cat 5 is ~600 for the same size and coverage
Prosoco MVP is ~150.
I like that the liquid flashing from Prosoco doesn’t need the fiberglass mesh, which saves on installation labor, but that doesn’t justify the huge increase in the Cat 5 price, and is also usable with the MVP product which is much cheaper?
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This was my logic drafting out the plan for my yet-to-be-started house:
STPE, the newest technology, is a moisture-curing formulation originally used for car windshields. It allows all-weather installation and provides high permeability, but it’s not necessarily better in terms of adhesion, UV exposure, or durability, and it is quite expensive.
Ultimately I am planning to use Tremco’s fluid-applied system, which includes the ExoAir 230 product for the main body of the wall, along with the Dymonic 100 product for detailing. The Dymonic 100 polyurethane-based detailing product scored excellent results in the Walsh Construction wingnut testing, surpassing nearly every other sealant tested. And the ExoAir 220, a sister product to the ExoAir 230 I chose to use, was the only WRB that passed the UT Durability Lab’s nail sealability test (ASTM D1970). Had they actually tested the 230 product I’m sure it would have passed as well. The ExoAir 230 product can be sprayed with a standard electric airless paint sprayer, which was a big win for me wanting to do all of this work myself. Some of the other STPE products such as PolyWall’s BlueBarrier product required the larger gas spraying rigs which can run north of $10k to purchase. Of course, you could always roll the product as well, but I was planning on purchasing an electric sprayer anyway to paint the inside of my house. And I think the sprayed finish will result in a more even coating, especially around the hard-to-seal areas such as penetrations and inside corners.
For comparison 25 mils is the dried millage for the Tremco ExoAir 230 product. Most other liquid applied WRBs don’t get that high even on their wet millage thickness. Based on the work that the UT Durability Lab had performed I really preferred thicker products, they show that thickness was the number determining factor of durability.
I read the "results" of the UT study, but it's not clear to me they tested either the Prosoco R-Guard or Sto gold systems. There is a video by Matt Risinger that shows some impressive "lab" result from Prosoco's main lab, which includes not leaking through nails, but I take this with a grain of salt since it's seems mostly promotional.
Given it seems that ExoAir requires a much thicker application, what's the coverage by 5 gallon? Seems like it's in the ~150 range, but if covers 1/4 of the other products maybe it's the same price as the expensive STPE products?
Does anyone have any articles that talk about the different make-ups of these so I can learn the difference between STPE or other substrates?
There were two studies done by the group at UT. First was the nail sealabiliy test. Next is the ongoing exterior exposure WRB test. Also don’t forget about the Walsh Construction wingnut testing which pretty directly answers your question about STPE vs others when it comes to adhesion strength. Dave Nicastro was on a Build Show podcast with Risinger and that’s where he says thickness looks to be related to long term durability.
As far as price, sketch out your wall or at least a substantial portion of your wall and tally up the linear footage of seams between sheathing panels, as well as the overall square footage. Use the required accessory products for the seams (in the case of Tremco it would be the Dymonic 100) according to the installation instructions Using the stated product coverage for each system for both the main body and the seams, I found Tremco to be the cheapest but I grabbed those cost numbers several years ago before COVID inflation so I have no idea how it compares today. Tyvek’s fluid applied (which is STPE) was the next cheapest at the time but they require a certified installer it’s not something you can DIY. Pro Clima and Alumaflash both came next with peel-and-stick WRB’s. Let us know what you find with today’s costs!
Also, the Sto Gold Coat is NOT STPE. The only product Sto has that is STPE is their "RapidGuard" which is like a joint and seam filler.
Product Line STPE?
Blue Barrier System: Yes
Prosoco System: Yes
Pro Clima Fluid-Aplied No
Tremco System: No
Carlisle System: Yes
Grace Fluid Applied: No
Tyvek Fluid Applied: Yes
Henry Fluid Applied: Yes
Sto Gold Coat No
One of my concerns with ExoAir is the manufactures say it's not to be applied to the fireproofing materials. We are in a high fire zone, and therefore either need to do fire-rated plywood, densglass, or use fire rated siding. So it may not be the appropriate product for us.
I have not seen the same warnings on the STPE products by Prosoco.
Prosoco says the same thing, read page 2 here:
https://prosoco.com/Content/Documents/Product/RG_C5_PDS.pdf
"Chemical residues, surface oxidation, surface coatings or films may adversely affect adhesion. Pressure-treated wood or fire-retardant wood and other contaminated surfaces should be cleaned with an Isopropyl Alcohol wip and allowed to flash-off before application of R-Guard products."
The Tremco guide says it shouldn't be applied to "fireproofing" materials, not fireproof materials. DensGlass is definitely supported as that is one of the most common sheathing products used today and this is a commercial WRB product.
But even if you don't like Tremco, fine, consider one of the other brands out there like Polywall, Carlisle, Tyvek, or Henry. My main point is that Prosoco and Sto are not the only two options and you should probably shop around for prices after you determine if you are set on STPE or not. Prosoco is not the only STPE WRB.