This crawl space had water collecting on top of the 6-mil liner. Standing water in a crawl space can come from the ground, rain, or condensation. The standing water slowly evaporates into the crawl space and is absorbed by the insulation and wood substructure.
Falling insulation is a result of the fiberglass absorbing the moisture in the crawl space and becoming heavier. The fibers of the material are damaged, and it begins to come apart and fall leaving the floors uninsulated.
This home was originally built open and later partially closed with panels between the piers. This leaves the foundation with a lot of gaps allowing moisture in and no true foundation walls. Because of this, we recommended the homeowner use spray foam on the floor joists. Their main goal was to keep the floors warm, so spray foaming the joists achieved this as well.
This Port Haywood, VA crawl space had standing water and no true foundation. The homeowners wanted to improve the insulation to make the floors warmer in the winter.