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:
Air Quality Issues
Swelling of Doors and Windows