I do have a vapor barrier. The crawlspace has vents but they are
sealed. I also have two high capacity vent fans on one side of the
crawlspace, and two 'moisture scrubbers' on the other side of the
crawlspace. Also have a french drain with a sump pump. I had all this
put in because I was having huge problems with moisture, with lots and
lots of mold growth. I even had soggy insulation on all the a/c ducts
down there. All this seems to have dryed things out okay (though I
haven't gone through the hot part of the summer yet, so we'll see), but
there is still an area in one corner that still seems to be staying a
bit damp. So I thought a dehumidifer in that area, drained to the sump
pump, might help.