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?

edit to original post:

…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 resulted in shrinkage and pulling that 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.