This homeowner had crawl space vents to help keep air moving in the crawl space in order to keep it dry. Instead, vents just act as a entry point for warm humid air and water seepage. Rather than air flowing in one vent and out another, it flows in through all vents and then travels up into the home. Humid air leads to condensation as its cooled in the crawl space during the summer. Vents hope to help but only make things worse.