The crawl space vents allowed in rain water, moisture, humidity, and who knows what else. The vents should always be sealed.
You can see the damage from the water. HomeSpec installed a crawl space drainage system and a sump pump to solve the water issues.
The pipes in the crawl space were very rusted.
An Algonac homeowner contacted HomeSpec about repairing his wet crawl space with rusted pipes and water damage.