High Density Foam -- Any Incidents of Cracking in Frame Walls as Studs Dry/Twist?

Just had a convo with a cold climate builder who said he has had concerns about the viability of the continuity of the air/vapour barrier created by using high-density foam in frame walls where budget dictates non-kiln-dried framing materials. Once the foam has set, and the wood starts to dry out, he has seen the studs twist and cup and significant cracks develop at the junction between the studs and the foam, and in some cases throughout the foam itself.

Although he didn't tell me if he'd done a before/after blower door test to see what the delta, his concern was enough to make him change products. He now uses high density foam on all non-framed walls where there is no issue with movement or shrinkage and the more flexible low density foam on framed walls. He's willing to take the hit on the lower insulation value and the additional vapour barrier requirement.

I hadn't bumped into this issue before and wonder if there are more people who have experienced this problem, and if so, is there any documentation, and if not, do you think there should be?

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...apart from installation issues, I mean. Have asked a few questions of one Net Zero builder who is using high-density foam and he pointed to installation QA/QC problems with +2" layers being sprayed, or layers are being sprayed without enough setting time between them if pulling and cracking are issues. He noted one incidence where a crap installation at the rim joists left gaps of 1 to 1.5 inches!

He didn't see much of an issue with air barrier being compromised, because spray foam would be in contact with sheathing and that is stable. I have a few phone calls with other Net Zero/Low Energy builders this week that are unrelated to this topic, but I know they have experience with high density foam, so I'll ask some more questions and report back on what I find.

Well if budget dictates one uses wet / green wood, said budget had better dictate drying time as no product should be installed until everything is dried out

The issue isn't the product, it is improper application

Shawna foam pulling away from the studs due to over application will cause spontaneous combustion or core burn. A poor mix will cause splitting of the foam and noxcious odors. See...






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