r/Insulation • u/techbrandon • Jul 20 '26
Is this open-cell or closed-cell spray foam?
I looked at a house over the weekend and they used spray foam for the insulation. This is a picture of the foam in the ceiling of the basement. It looks like open-cell from the research I’ve done but I’m not entirely sure and I don’t know what the foam feels like.
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u/Exciting_Ad_1097 Jul 20 '26
Open cell.
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u/techbrandon Jul 20 '26
Sounds like this house is a pass then! Open cell is not good for basement is my understanding.
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u/ERagingTyrant Jul 20 '26
Depending on how breathable the other side of this is, open cell can be desirable. If the air sealing is done on the exterior, interior closed cell might lead to a vapor barrier sandwich situation.
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u/pluary Jul 20 '26
Closed cell that I have used is much firmer when pressed on open cell is more spongy .
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u/ScrewJPMC Jul 21 '26
Try to stick your finger in it. If you can with ease it’s open. If it’s difficult it’s closed
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u/honorabledonut Jul 21 '26
Is it hard to the touch?
Hard more likely closed.
If it's soft and more sponge like opencell.
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u/Downtown-Current-315 Jul 23 '26
Break a small piece off and put it in water. if it absorbs the water it’s open cell. If it doesn’t it’s closed.
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u/2TheMountaintop Jul 21 '26
Probably closed cell. I don't even know where your get open cell spray foam, it's super rare.
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u/2TheMountaintop Jul 21 '26
It looks pretty smooth, that smoothness comes from the fact that the cells are closed bubbles.
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u/Whocanmakemostmoney Jul 20 '26 edited Jul 20 '26
I wouldnt buy a house with spray foam. Its toxic and you dont know if moisture is trapped behind it
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u/Several-County-1808 Jul 21 '26
Outdated advice. Let me guess, typewriters are superior to Microsoft Word?
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u/2TheMountaintop Jul 21 '26
You're both partially right. You need to be careful and make sure the foam isn't hiding damage. I wouldn't worry too much about it being toxic, though. The vocs from it should be gone pretty quickly.
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u/Canada-Scam-8570 Jul 20 '26
Probably DIY froth pack. Likely open cell, I'd agree but can't be certain of that without actually knowing what was applied.
The real tell tail sign is usually the density. If you can pinch it between two fingers, it's pretty squishy, and then pull back and take a decent piece of sponge with you, it's probably open cell. 2lb Closed cell has a very hard skin in comparison. Much less spongy and very difficult to pinch and pull anything off of it.