OSB, hardware cloth, or ?

[Arky217]

I'm trying to determine what would be best (and reasonably priced) for supporting the insulation at the bottom of my floor joists.
It needs to be a rodent barrier, (insect barrier would be good also) and also would prefer it to be somewhat of an air barrier since the crawlspace has no walls.

1/4" hardware cloth has been mentioned as a good rodent barrier. The cheapest that I have been able to find, however, is $.40/sf. (and that is only .025 gauge). And, of course, it does nothing to keep out the air and insects. I suppose I could put it over Tyvek. That would solve the air barrier (don't know about the insects), but that would also jump the price up quite a bit.

I could use 7/16 OSB; it's fairly cheap at about $.20/sf, and I think I could install it tight enough at the edges to prevent rodents from gnawing through, but I wonder about it being a vapor retarder on the cold side of the floor. Of course, I suppose that I could take the trouble to drill a few small holes in it, but the holes might be a path for insects and a starting point for gnawing rodents.

The climate is mixed humid (western Arkansas). The floor is 2x8's with OSB subfloor, hardwood flooring. The insulation will be Roxul batts.

I'm kind of leaning toward OSB, but wonder if there are other options.

Any ideas come to mind.....

Thanks,
Arky

[nathan.principe]

is spray foam out of the question?  I guess that might not fit "reasonably priced" criteria, and that I can relate to.  Although they sell the kits for do-it-yourselfers

[MountainDon]

We used 3/8 CDX plywood. More costly than OSB, but I believe it handles exposure to humidity better. Like most wood products it is not rodent proof. But there are (I hope) plenty of easier to access places around to nest. If a rodent is determined it can chew through easily, they don't even need a corner or raised lip. They can simply start chewing at a flat surface if they want to. As long as you don't have a forgotten ham sandwich enclosed under the floor there should be little reason for a rodent to be so determined to chew through.

Foam is good insulation, but also makes nifty nesting materials when chewed into bits. My old boss back home found mice nests behind the foam sheet he had added to walls.

[considerations]

I don't know what size place you are planning/building but I had to buy a whole role of Tyvek to cover my 14 x 24...and I have about 1/2 of it left, so I've already "paid" for Tyveking over the floor insulation before finishing off with hardware cloth. 

That hardware cloth came in big roles as well, made it less expensive than the 15' rolls i normally see.

[Arky217]

is spray foam out of the question?  I guess that might not fit "reasonably priced" criteria, and that I can relate to.  Although they sell the kits for do-it-yourselfers

Well, I haven't actually priced it, but from what I've read, yes, it would probably be waaay out of the question for me price wise.

I was originally planning to dense pack cellulose at 3lb/cf for a cost of about $.80/sf for R-28, but what with buying the installation webbing, and stapling it in place with 100 zillion staples, it just seemed to be too much trouble, and was actually, material wise with the webbing, more than the Roxul. (Fiberglass is out of the question for me, for several reasons that I won't go into now)

The R-28 Roxul that I'm planning to use is $1.09/sf.

How does that compare to spray foam ?

Arky