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Arky217 12-29-2010 11:56 AM

Floor joist insulation
I am still pondering what would be the best way to insulate my floor joists.
My house is in western Arkansas. It has a pier/post foundation and will have no skirting. In other words, the perimeter of the foundation will remain open. The bottom of the joists are about 3 to 4 feet above the ground and are on 19.2" centers.
The subfloor has not been installed on the joists yet; it will go down after the house is dried in.

Unless I come up with a better solution, my current plan is, after installing the subfloor, to glue/staple polypro mesh to the bottom of the joists. I would then dense pack blow cellulose between the joists through strategically cut slits in the mesh. Following that, I would cover the mesh with 1/4" hardware cloth for rodent protection and to support the cellulose.

Since the foundation is completely open and the location is on a high, dry ridge, I don't anticipate the underfloor moisture problems that are sometimes associated with an enclosed crawlspace.

One concern, however, is what would happen if there were a water leak in the house and some of the insulation were to become soaked. I have read that cellulose has good wicking properties and would wick excessive moisture to it's surface. I just don't know if it would do it fast enough to prevent the joists from starting to rot.
I do know from experience that fiberglass batts do not wick well, and tend to hold wetness for quite a length of time. For that, among other reasons, I have ruled out fiberglass batts. Besides, they seem to be about twice the price of the cellulose.

I've read that sprayed foam may be the best insulation, but for me it's too expensive and the house is probably too remotely located to get a spray rig in.

Hard foam sheets, sealed at the edges with cans of aerosol spray foam is another method, but again it's very expensive compared to the cellulose. Also, what would happen if water became trapped between the foam sheets and the subfloor ?

Anyone know of a reasonably priced solution that may be better than the cellulose ?


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