I am convinced that a client of mine is the victim of a shoddy crawl space ceiling insulation job, and that he should have it done right. He too in convinced.

So, the question is how best to address it. 

The crawl space is only 200 sf, located below a single-room addition, with ducts in the floor. There are plenty of penetration through the floor and the sill boxes. Air is the least of our worries (it's the darn critters he wants to keep out, and reduced leakage is a bonus). The existing faced fiberglass batts (R-19) are showed into between the joists, with the kraft facing in the wrong direction. The batt insulation is only 5 years old, and it's condition has not been compromised. 

The following is my proposed approach to the problem. Remove the existing batt insulation, apply a flash coat of closed-cell spray foam, cut batts to fit properly, install wire supports to keep batts flush with floor, and install a layer of house wrap to underside of joists to protect batt insulation. Sound like a winner to you pros?

Thanks in advance!

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For the cellulose and rigid I wouldn't worry about the foaming of penetrations unless they are big enough to have a blow out in the living space.


For the fiberglass and rigid, I think foaming the perimeter to seal off any leaks would be good, but probably nothing other than that.

Good luck out there.

Thanks, and thank you for your input Cory!

Housewrap as your blowing barrier makes a lot of sense, though it's like wall papering a ceiling getting it in place!!

I dunno about the foam board. Where I come from (cold climate) that might work with unfaced EPS board. But If you use foil-faced Thermax, that leaves you with a vapor retarder on the cold side of the assembly, doesn't it?? Great idea in an A/C-dominant climate. But that's a really bad idea here in Wisconsin.

Don you raise a couple of good points.
As to your points about the rigid foam, the foil facing would be on the cold side, but with Thermax you have foil facing on both sides. Also, I always do all within my power to achieve an effective air seal, which has eliminated any condensation-related issues in the past. Nevertheless, I am going to think further about the points you have raised.


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