Why foundation vents fail in Middle Tennessee summers

Vents were sold as a drying strategy. In a mixed-humid summer they are an intake. Outdoor air at 80 percent relative humidity hits wood that is cooler than the yard. Water leaves the air and stays on the joists.

Spring Hill's clay adds a second moisture load from below. Vents do not cancel soil vapor. They add to it. That is why Crawl Space Insulation that stays in the joists of a vented crawl fails, and why encapsulation closes those vents on purpose.