I live in Nashville, where it's quite humid. I moved into my first house last August and we have a stand-up crawlspace. Around the exterior of the crawlspace, the builder put in four vents. About a month after moving in, we started to see what looked like mildew and/or mold growing on the walls of the crawlspace. I had a “mold guy” come in and he recommended a dehumidifier. I had a friend of mine who knows quite a bit about DIY stuff come to my house and he recommended getting a humidistat fan instead. Before I rush out and buy one and put one in, what do I need to know about using humidistat fans? Are there certain factors that make them uneffective that I need to be aware of?
Either approach - a dehumidifier or a humidistat fan - is a good approach.
If you go with a humidistat, first make sure you have a vapor barrier across your entire crawlspace floor. You also need to ensure that the vents on the opposite sides of the crawlspace open, so that once the fan kicks on, it pulls air from the crawlspace outward.
If you opt for a dehumidifier, I personally just installed one from the Santa Fe Compact line and am very happy with it. The version I selected is designed specifically for crawlspaces. It's small - only 12 x 12 x 22 inches, yet hangs from the floor joists and takes out an impressive 70 pints of water each day.