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Q. The crawlspace under my house has a vapor barrier and quite a few vents, so I don’t have any moisture buildup. But the floor of my house is uninsulated. So, should I close off the crawlspace vents during the winter to save energy?
A. In the South, moisture in the crawlspace is a year-round problem, so the vents should stay open. If you’re concerned about saving energy, a better solution would be to spend the money to add unfaced R-19 insulation between the floor joists. For the occasional freeze, you should also insulate any exposed pipes in the crawlspace.
In states where winters are moderate to hard, winter air tends to be much drier. So, closing crawlspace vents during the winter months is less likely to cause moisture problems and may slightly lower your energy bills. However, the walls of the crawlspace should be insulated (also with R-19), or closing the vents won’t make much difference.
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