R-value
Spray foam has an R-value of 7 per inch while fiberglass is just 3 per inch
Fiberglass
Fiberglass insulation holds in moisture and becomes ineffective.
Spray Foam Insulation
Although the Spray foam insulation is not installed on the sub-flooring, it still works the same by being applied to all of the walls and working with the cleanspace encapsulation system.
Spray Foam
Spray foam insulation is closed-celled, meaning that it wont allow for water absorption unlike fiberglass insulation.
Wall View of Spray Foam
Spray foam on the crawlspace wall.
Messy Crawlspace
Falling insulation and moisture both make the crawlspace an unhealthy and inefficient space.
Insulation
While it is always good to have insulation in the crawlspace, some forms are better than others. For example, spray foam wont fall or hold in moisture like fiberglass and will ensure the energy efficiency of the home.