Answer: The main sources of moisture are from:

  • Outside Air - warm, moisture-saturated air brought into the cooler crawl space from open vents can become a major source of excessive moisture in the crawl space. Why? When warm, moist air cools in the crawl space it no longer has the ability to hold as much moisture. When this very wet air touches a cooler surface the water vapor condenses (Dew Point) and water forms on those surfaces.

  • The ground - poor drainage in the crawl space can be the main source of moisture. This can be seen in some obvious cases as pooled water or poor drainage can just be adding to the crawl space moisture from the saturated soil caused by poor drainage.

  • The foundation - below grade foundations may not have properly designed drainage. This can be seen in moist cinder blocks or concrete foundation walls. The moisture from the saturated foundation adds to the crawl space moisture level.
     

Problems Created From Excessive Moisture
Excessive moisture can cause many structural issues to occur in your home and it can also lead to health issues caused by molds. These structural issues associated with excess moisture are reduced or eliminated by properly closing the crawl space:

bullet Insect Damage
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Air Quality Issues
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Wood Rot
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Swelling of Doors and Windows