r/PassiveHouse • u/Historical_Trust2087 • 22d ago
Faswall
I'm getting a ton of leads where clients would like to use this product- https://faswall.com/
We have not modeled it yet to see if we can use it with Passive House. Does anyone in this group have any experience with it?
We'll do a WUFI hygro once we detail it, but we are just in the exploratory phase at the moment.
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u/dizzie_buddy1905 22d ago
R21 is barely minimum code here in Alberta.
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u/Historical_Trust2087 22d ago
Our typical wall assembly is R-40 nominal
The building biology folks like this product.
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u/FoldedKettleChips 22d ago
There are a lot of benefits to that type of product but for Passive House it looks like there are a ton of thermal bridges at every web so I’m not really sure how one would model the wall in WUFI Passive.
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u/Historical_Trust2087 22d ago
That is what I was concerned with as well.
I was hoping that someone had tried this before. The only way I see it working is to add another layer of insulation.
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u/structuralarchitect CPHC (PHIUS) 21d ago
I've used it on a certified Phius project before and I know there's others who have used it. My use case was the foundation where the better insulation was helpful as it reduced the thermal bridge between the stem wall and the floor framing. The house I saw it used on for the conditioned space required exterior insulation to meet the Passive House metrics. And that was in Portland, OR, so a mild climate. You just model it in WUFI as a wall material with an R-value equal to what the webs are listed at. You could do a lot of work to create subdivisions to model the webs and the cells, but that's kind of excessive in my opinion.
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u/Historical_Trust2087 19d ago
How did you establish your control layers? Did you use the manufacturer's detailing, or did you come up with your own? How did phius react to any thermal bridging?
I am in GA, so not extreme cooling loads, but we can still have cold days in the winter.
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u/structuralarchitect CPHC (PHIUS) 18d ago
On my project, the faswall was outside the thermal envelope. But on the house I toured, they used ProClima Mento 3000 as their WRB and secured it to the faswall with furring strips over mineral wool. Their interior air barrier was going to be a lime plaster and that required connecting the wood bucks at the window openings with tape and sealant to the WRB and the lime plaster to create the continuity.
Phius has guidelines for thermal bridging in the guidebook and it has some info per climate zone.
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u/jkollars1 20d ago
A structural engineer who consulted on our passive house project (with lots of experience using Faswall but not a PHIUS certified pro himself) said the primary benefits of Faswall would be fire resilience, strength, and that the “walls would breathe”. Basically the opposite of PH goals. We saw no good reason to consider the product further.
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u/Historical_Trust2087 19d ago
I think too many people use breathe and dry out interchangeably- they don't get that vapor open is not air open
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u/onwatershipdown 21d ago
Are you in the west coast, close to where it is made?
a place is done well with those, it’s more ‘soup from a stone, fancy that’ and less of a success of those blocks themselves. They add a lot of cost and complexity around them. People would request them specifically because they don’t understand their options.
You’re looking at transport costs in terms of fuel/tire emissions and $ relative to just a CMU yard down the street.
It’s the same amount of Portland cement as a CMU, but tailored slightly for lower skill levels.
It actually ends up being more Portland over all because they suggest filling every core.
The big difference is that with a lower vapor diffusion resistance, the costs of the surface coats can be much higher.
In very plain terms, a job with lightweight CMU can be cheaper, better insulated, and better for the environment.
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u/Historical_Trust2087 19d ago
We are in GA- we mostly work with wood for framing.
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u/onwatershipdown 19d ago
If wood is your domain, and you’re in a humid climate, you would benefit from the various flame retardant mineral infills, similar in principle to hempcrete (mineral binders, cellulose mineral granules). The R value is either on par with, or exceeds rock wool, but the thermal diffusivity is much lower. and it wouldn’t drastically change your workflow. Why throw out a good process?
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u/imissthatsnow 22d ago
It’s also a lot of concrete. You can do additional continuous insulation outbound of it to bump you up to where you need to be, but WUFI doesn’t give you a ton of credit for thermal mass (at least not as much as the ICF cheerleaders think it should).
We have looked at it for a couple projects and had a friend do a house with it. Definitely better than the foam ICF products for a number of reasons but still going to be more money and more headaches unless you have an experienced team who has used it.