In the early 1950s crawl space foundation vents were introduced to eliminate humidity in crawlspaces. Over time contractors and inspectors realized the vents that were installed to remove humidity in fact helped to increase the humidity level in most crawlspaces. They allow hot humid air in the summer months to enter the cool environment of a crawlspace. The humid air would condense and create higher humidity levels under your home.
This would eventually lead to mold and fungus growth. Now building codes are changing to allow builders to construct conditioned crawlspaces without crawl space foundation vents. Conditioning the crawl space is the practice of removing all components that cause moisture. ie: leaking pipes, broken dryer vents, ground water entering through the foundation, etc. A proper vapor barrier needs to be installed to prevent moisture from evaporating from the soil into the home.
After the clean space has been created the air in the crawlspace can be conditioned by one of several different ways depending on the crawlspaces individual situation. All components need to be in place or the desired results will not be achieved. Crawlspace Doctor has developed systems to properly condition crawlspaces.