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Not sure what to make of this foamed basement


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1886 farmhouse with stone foundation wall and wood joists, basement is obviously not a conditioned space. Someone spray-foamed the basement ceiling/underside of the first floor. Joist were original wood from 1886 I think, flooring appeared to be old floor boards where I could get a peek. I advised the client to get an opinion from a licensed insulation contractor because I thought they may have created a condensation issue which could rot the joists. Did I send my client on a wild-goose chase or am I right to be concerned on this one? Thanks (and yes, there was plenty of other stuff to report!))

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Hard to tell how thick the foam is, or what type, but I don't think I'd be concerned. If the foam is not thick enough to be above dewpoint on the warm side, or has gaps/voids/separations in it that allow conditioned air to condense on a cold surface, then it will be much less forgiving than it would be with fluffy (or no) insulation. If it's open cell foam, vapor can migrate into the foam until it finds a cold surface, under some conditions.

Some problems with spray foam can be impossible to see until there is a major problem and water comes running out. There are probably a lot more cases of sealed attics than there are floors, so it is fairly easy to find stories about attics with spray foam and moisture problems.

The main issue I see there is that it will be a nasty job to remodel, repair plumbing or wiring, etc. In the future, that insulation job will get damaged by tradesmen trying to do what they need to do, and it's unlikely it will get fixed. I would only spray-foam something like that if I had brought EVERYTHING completely up to date first.

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The foam denies ventilation to the underside of the floor boards. If the R-value is high, there won't be much thermal flux and therefore not much condensation above the foam in the first place but there still needs to be at least some ventilation through the floor boards, like cracks in the planking, to allow condensation to evaporate.

A lot of it has to do with climate.

Marc

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Yeah, that's a mess.

As a start, they should have cleared out any wiring not in EMT or conduit.

Get everything out of the way or accounted for, and blow in 6". There's formulas for figuring out where the dew point falls for any given region, but everyone backtracks to 6". It's silly to install less; this job has less.

OTOH, with that old growth timber, I wouldn't expect anything short of a complete saturation for years to cause any harm. What little condensation might occur wouldn't do much of nothing.

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Since no one else mentioned it, that foam needs to be covered or coated with an ignition barrier.

There is a furnace and uninsulated ducts in one of those pics. That basement is conditioned. If it were truly non-conditioned then the joists should be completely encapsulated in foam. What Kurt said about the old growth lumber, it's robust enough to handle more than a few insults.

FWIW, they would have gotten a better return applying that on the rim and down the wall to 2' below grade.

Where'd the 6" theory come from? In my climate 2" of ccSPF is enough to avoid dew point issues, 4" in ocSPF. Is it to marginalize the impact the applicator has on the outcome?

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The 6 inch thing came about (I think) from open cell foam; you need about 6" to avoid installing a VR.

Yes, I know it's calculable, but everyone around here has decided 6" is the magic number.

So, everything seems to revert to 6".

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