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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Considering the small size of the job, is there a minimum number that the insulation guy is going to charge for the job? I would determine that with different comparisons of thicknesses of the foam.

Does the crawl space have a floor? Is it ventilated? Do you have moisture coming up? 

Hello Bruce.

Slab floor. Ventilated like you've never seen before. There are large openings at the perimeter for easy access to the space. The accesses are closed up with steel gates (of the aesthetic kind), so sealing up the space at the walls is not an option. No moisture coming up.

No minimum charge for job, just "get it right." My goal is to get the homeowner the best bang for his buck. This is why I'd like to get the flash coat of foam (about an inch) to the floor.

Thanks Bruce.

If cost isn't an option, why not go with a full thickness of foam and get rid of the f/g? Eventually, moisture will gather in the f/g, wire supports will fail and the homeowner will have a problem again.

You raise a very legit point Bruce, but then we are also talking about a job cost near $2,000 versus $600. Also, this means that we'd be throwing out good insulation, and I hate "wasting" things.

Also, won't the house wrap serve to significantly reduce the moisture build-up in the fiberglass?

I'm sure the house wrap will reduce the moisture penetration substantially, as long as it is installed properly. But I don't know if it will prevent all moisture penetration over a period of years. Especially if there are critters involved. Any chance of bats nesting under there? I am flying blind here a bit, but if the h/o paid for decorative iron gates for his crawl space, I'm not sure that he would flinch at an informed proposal for foam for an additional $1400.00.

If I were you, I would lay down options for him to decide, and tell him what you would do if it were your home, and why; while setting aside the cost considerations. People are not always easy to read, and I have often been surprised when homeowners bite on quality over cost after a good sales presentation. Who knows, he may like the foam so much that he calls you back to do the whole attic next year.  

Good points Bruce.

I'll give it a shot.

One last issue: the ducts in the floor. I was going to have rigid insulation installed below the flex duct (the ducts sit just above the underside of the floor joists). Any suggestions? Thanks!

That makes sense to me, I would hit the rigid foam with the foam as you pass by, mainly to seal the edges and have a uniform finish.

Here's a great article for your resource: http://www.greenbuildingadvisor.com/blogs/dept/musings/building-unv...

Also, will there be any negative fumes emitted from the spray foam application?  http://www.greenbuildingadvisor.com/community/forum/green-products-...

Thanks for the article Carlos.

The new product I'm using is supposed to emit no VOCs that would be considered negative fumes. In the past that has been one of my main concerns with respect to spray foam.


Sounds like a winner to me, you can skip the wire supports the house wrap should support the insulation just fine. Another option would be to skip the fiberglass and spray foam, and fasten ridgid foam (thermax) to the joists then dense pack with cellulose. The foam and dense pack is just a sweet way to go. You reduce the thermal bridging of the joists, get a good air seal, and have a nice finished R-value.

Cory, the approach you mention is the balls! I typically do just what you recommend. In this case I want to avoid tossing the fiberglass, and the homeowner is concerned with accessing the pipes, ducts, etc.

Thanks for the advice Cory!
Cory, for future reference, when you go the rigid and dense-pack cellulose route do you also hit the main penetrations through the floor with foam sealant, or would you just consider that over-redundant?

And, same question with respect to fiberglass and rigid (vs. cellulose and rigid).



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