We installed about 1.5 inches of closed-cell spray foam over the foundation walls of this crawl space in Glen Allen, VA. At this thickness, the spray foam has an R10 value of insulation and acts as an air barrier and vapor retarder. We blocked out any open vents running along the crawl space wall, as these vents allow outside air and moisture to freely enter to crawl space, affecting the environment and relative humidity. With any insulation we install over the foundation walls, we always leave a 2-inch viewing strip at the top of the wall for termite inspectors. With these solutions in place, the crawl space is better protected from any outside influence penetrating through the foundation walls.