is sun really the cause of shrinking foam?

[Fukien_Monk]

I'm insulating a post-and-beam log cabin with reclaimed barn beams (mid-1800s). Normally I'd go with blow-in, but for this project I had closed-cell spray foam applied on the outside. When it was installed, the crew said it needed to be covered within a year. A month later I started seeing cracks along some furring strips. Contractor came back and filled them with cans of spray foam, blaming it on sun exposure. After that I wrapped the place in house wrap rated for UV and figured I'd wait before siding it. Six months later I pulled the wrap off and there are a lot more cracks. I even noticed a big crack inside along a rafter. So here's my question: is it really reasonable to blame all this on sun exposure? If there's shrinkage happening on the inside too, that seems like a bigger problem with the foam itself. Anyone else seen this level of cracking with closed-cell?

 

[Passionfru1t]

@Fukien_Monk The contractor's explanation about sun exposure is only part of the story.
UV light primarily causes the surface of the foam to turn yellow, become brittle, and dust away. It doesn't cause the kind of deep, structural shrinkage that creates large cracks, especially not on the inside of the building.
What you're seeing is almost certainly a sign of a bad chemical mix when the foam was sprayed.
If the ratio of the two components is off, the foam won't cure correctly and will shrink dramatically, pulling away from everything it's attached to.

 

[Hermann Zapf]

@Fukien_Monk The contractor's explanation about sun exposure is only part of the story.
UV light primarily causes the surface of the foam to turn yellow, become brittle, and dust away. It doesn't cause the kind of deep, structural shrinkage that creates large cracks, especially not on the inside of the building.
What you're seeing is almost certainly a sign of a bad chemical mix when the foam was sprayed.
If the ratio of the two components is off, the foam won't cure correctly and will shrink dramatically, pulling away from everything it's attached to.

Thanks for explaining that! I'm new to spray foam and just helped my uncle insulate his workshop here in Missouri. We noticed some cracking too, but only on one wall. If the mix was off, is there any way to test the foam now, or do we just have to replace it?

 

[Passionfru1t]

hi @Hermann Zapf, from my experience, the easiest way to test the foam is to cut a small core sample out of a discreet area. A properly cured closed cell foam should be hard and rigid, and the cells should look uniform and dense.
If the foam feels soft, sticky, or has a crumbly or soupy texture, that's a sure sign the chemical mix was off. You might also notice a strange smell.

 

[slvr22_bd]

Thanks for explaining that! I'm new to spray foam and just helped my uncle insulate his workshop here in Missouri. We noticed some cracking too, but only on one wall. If the mix was off, is there any way to test the foam now, or do we just have to replace it?

Thought I'd also jump in. It's a huge problem if the mix was off and unfortunately, it's not something you can just patch over. The cracks and interior shrinkage you're seeing are clear signs of an installation or product failure, most likely an incorrect chemical ratio.

You can have the foam tested, but it requires a pro. An independent inspector can take core samples to test the foam's density and adhesion. These lab results would provide hard proof of a bad mix, which you'll need if you're going to hold the contractor accountable. Given the issues, it's very likely the foam will need to be removed and replaced. Patching won't fix the underlying problem, and the compromised foam will continue to shrink and lose its R-value over time.

 

[Alan]

I came in here because I was curious, wanted to know also if sun was the cause of shrinking foam, @Passionfru1t thanks for your detailed explanation on this. So the sun basically isn't meant to have that much of an effect, okay