I'd guess that everyone who buys a house has a crawl space question. Recently I spent several days in my crawl space at my house of Stoney Creek in EHT. It should definately have a vapor barrier, some people go to a few inches of the edge some go all the way up the first block. I chose to go one extra step because I felt like the floors were cold, so I stapled up a 4 mil vapor barrier to the back side of the floor beams. I think it is warmer but I guess I'll have to wait until I see the gas bill in February. The most important function of the flow through air in a crawl space is to prevent moisture build up and thus "mold".