What is a Crawl Space? A neutral low ceiling foundation space commonly unconditioned, sometimes used for storage. Most homeowners have issues with cobwebs, water stains, spiders, drafts, and some without concrete or gravel and water management interior drainage system resulting in soggy dirt floors. Crawl space encapsulation materials are installed to prevent moisture mold mildew and rodent issues. The moisture barrier also creates a clean durable finished space suitable for storage and climate control. Crawl Space Encapsulation done right includes a thermal barrier using insulation. Common insulation materials installed are spray foam around seams and box sill, and a vapor barrier over gravel or dirt floors. If the floor is concrete, no vapor barrier is necessary.