We place a higher-grade plastic, typically 12 mil, directly on the soil and tape the seams.
Any columns in the crawlspace are wrapped and taped as well
Then a 2” foam board is adhered to the outside walls of the crawlspace.
If you choose to utilize this method then you do not have to have fiberglass between the floor joists
We recommend having any water issues rectified in the crawlspace before encapsulation. You should also consider running a dehumidifier in the encapsulated area and have at least 25 CFM of air circulating in the space.
We provide this service for new construction as well as existing homes.