Clearing confusion about foundation vents and mold

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Dear Barry, I'm confused about foundation vents after reading your article emphasizing their importance. New studies, posted on the Internet at, state that foundation vents allow moist air to enter the crawlspace, causing condensation, fungus infection of the wood floor structure, and mold growth on sub-area surfaces. You say foundation vents prevent these conditions. They say the vents cause them. Who's right? --Kevin Dear Kevin, Having reviewed that Web site and the studies in question, I find that they conflict with common sense and the experiential knowledge of countless field professionals. Excess moisture in a crawlspace does not enter through vent openings. The primary water source is the soil itself. It is wetness due to ground water runoff, on or below the surface, from natural springs or over-watering of nearby landscaping. The way to prevent water intrusion into a crawlspace is by improving site drainage conditions to prevent wetness of the soil from m...