Hi Rodger. I inspect in Calif. and I dont like a vapor barrier. As I see the problems that come from them. Excessive moisture to the soil. mold, fungus conndition. And then we get standing water on top and under the plactic. Unless you have a complete air tite sub-structure and control all exterior water condition its no good. Now If this is done then i can see one working. But i like to see a well ventilated sub-structure with lots of air to move all moisture out of the sub-structure. This also provides access to the soil/foundation for inspection as the years pass. One other problem is rats, cats, dogs, and other criters that make a mess on the plastic. Then the only way to clean that up is to take out all the plastic and install all new.

Please keep in mind im in Calif.
A lot dryer condition.

Best

Ron