Why cover the earth with plastic Sheeting?
The majority of the water vapor that accumulates under a structure comes from the earth itself. Applying 6-mill. Polyurethane sheeting over as much dirt as possible reduces the evaporation rate into the crawlspace. I have never seen a crawlspace that was to dry, so cover it all and lap the plastic by several feet and then tape the loose edges. I like to take gutter spikes and stake the corners down so the plastic does not move around. You can live with a few holes. By the way, the water that accumulates under the plastic is a good thing. It is not in the air.