I've done a lot of reading on this topic. I'm doing some monitoring via a wireless Humidity sensor to make sure our crawlspace isn't a problem. The reason I have a concern is because I've found water on top of the 6mil polyethylene vapor barrier last year. The water doesn't get in via the normal methods (poor site grading, HVAC, leaking pipes) it is literally blown in via wind driven rain through the crawlspace vents during a few hellish wind/rain storms we have on an annual basis.

As a result of these storms I've literally had the insulation blown out from between the floor joist. As a result of this I've considered stapling another 6mil polyethylene vapor barrier to the underside of the floor joist. I'd just staple it up there but I'm afraid the wind would just blow it off when we get another monster storm. I'll probably nail/screw some strips of wood over them to keep it in place.

The goal is two-fold. Fist I hope to keep my insulation from blowing out again. Second, I'd like to insure that the crawlspace humity level can never cause a problem with my 3/4" solid wood floor installation.

Are there any problems with this approach?

Close in the crawl space, sealing it off. Moisture barrier over the soil and up the walls. and a dehumidification system running.

As Perry mentioned, that is a viable alternative, providing it is done correctly. Here's a web site that discusses it. I'm not sure who informed me of this site. Just don't remember. It could have been Perry (Floorguy).
http://www.crawlspaces.org/

Great resource Gary. Thanks guys... I think I'll pursue this further. It looks like a job I could do myself and it would certainly control mold and moisture under the house. Even without the wood floors it looks like a worthy effort.

I got my moisture meeter yesterday and measured the 3/4 plywood subfloor at 15%. For reference the 3/4" plywood work bench in my garage shop is at 13% so there is certainly higher moisture content in the floor as I would expect. RH in the house is at 40% right now.

Check the bottom side of the subfloor too.

Will do...