nmachnai, Great question. Vented crawlspaces affect energy greatly. The vents allow un-conditioned air into your space and it seeps up into your living area. The solving is to close off those vents, add spray foam to the walls of your crawlspace ,add 10mil plastic and over lap 2 feet and use a great tape or the recommended tape for crawlspace underlayment plastic. Some recommend install the plastic up the walls, but I don't do this as the Closed Foam works as a vapor barrier. I would go up about 6 inches and have the plastic intergrate into the foam for a seamless seal.
After you do this, your home will be more energy efficient and the floors will be warmer in the winter, lower energy bills and over all, more comfort. I have added some links below, one of them videos on How to Do it. Good luck
David-
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