The before picture shows a crawlspace that typically has a 6 mil vapor barrier on the ground, which is easily punctured and torn. Also, the crawlspace is vented, which allows warm, humid air to condensate on ductwork that is in the crawlspace during the summer months. During the winter months, the vents and all of the gaps and cracks around the rimjoints/band allow cold, winter air to enter the crawlspace and cause frozen water lines, busted water lines, and extremely cold floors. In these types of conditions, wood can potentially mold, mildew, and rot.
The solution, which you will see in the AFTER picture, is to apply a 20 mil cleanspace liner over the earth and rolled upon to every pillar and all perimeter block walls, sealed at every seam with cleanspace tape. We then apply 2 inches of class II vapor barrier closed cell foam around the band board/rim joists, down the block, sealing up all crawlspace vents and down onto the cleanspace liner. This creates a crawlspace that is completely sealed off from all outside elements.