Before
Vented crawl space, 80%+ crawl humidity, visible mold on rim joist, sagging fiberglass.
Encapsulation
Removed fiberglass, sealed vents, installed 20-mil vapor barrier, closed cell foam on walls and rim joist, dehumidifier.
Results
Crawl humidity dropped to 48% within a week. Indoor humidity dropped from 60% to 45%. Musty smell gone in 24 hours.