Spray foam insulation is ideal for crawl spaces due to its water-repellent properties and resistance to biological growth.
Insulation works by slowing conductive and convective heat flow, while radiant barriers and reflective insulation reduce radiant heat gain through reflective surfaces in contact with air spaces.
Faced insulation has kraft paper attached to it, which enhances its sturdiness and prevents it from falling. Unfaced insulation lacks this paper but performs similarly.