We put plastic in the crawl space of our 1960's ranch home about one year ago. The heated area is about 1100 sq feet, and had 5 permanently open vents in the crawl spce. We covered the dirt floor with 10 ml plastic , leaving an open area at the edges of about 1.5 feet all the way around. We live in atlanta. Now we have black marks around the nails of our oak floors in severl rooms of the house. I think these are moisture related. What is your advicce on how the ground plastic is supposed to be laid out. We did it following the advice of the local power company's energy audit. We hae not seen water on top of the plastic.