Vented crawlspaces are just one way moisture enters the home. The ground can release up to 18 gallons of water vapor into your crawlspace a day. Water vapor can also travel right through the porous foundation that your home sits on when there is a grading difference from the interior and exterior of the foundation wall. The solution to all of this is to seal the moisture out by closing the foundation vents and installing a ground and wall combination. Some homes also require dehumidifiers or air inducers.