Ever build or remodel houses with crawlspaces? Or put an addition on a crawlspace? Ever wonder about how to insulate them? Or how to keep them dry enough so the wood doesn't rot? I have. Here are my most recent thoughts. The Old Way Traditionally, moisture control in crawlspaces has consisted of screened vents to the outside—sometimes with an added ground cover of plastic film. The idea is to get outside air to carry away the moisture. The ground cover is there to slow the rate at which moisture enters the crawlspace air from the earth. The CABO and BOCA codes both require crawlspaces to have 1 square foot of free vent area for every 150 square feet of floor