This is a crawl space in an older home. It was very inefficient and unhealthy.
This picture is the same crawl after we conditioned it, this is extremely energy efficient and much healthier
When doing a conditioned crawl it is important to use sustainable products. We like to use a heavy 12 mil reinforced poly, sealing all the seams and penetrations with a heavy mil tape. We sprayed the walls with a closed cell soy based foam, this gives a nice monolithic seal to the perimeter walls.