Crawlspace Vents Should You Vent Your Crawl Area? Cupping is when the wood begins to twist up on the edges due to extreme moisture on the bottom of the flooring boards, not an excellent thing. What makes this even worse is to suppose that there was enough moisture in http://waylonogiln.blogkoo.com/picking-out-fast-systems-for-sub-floor-ventilation-fans-16085527