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?
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.
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-...
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.