When you vent crawlspaces you bring in hot, humid air and cause moisture and mold problems. This can evidenced by a foul smell or musty odors. Moisture moves to the cold surfaces. Venting crawlspaces made sense only when you had no air conditioning and no insulation and no crawlspace walls. - RLC Engineering Clemson, SC
From thermal, moisture, structural, occupant health, financial and operational standpoints, sealed crawlspace foundations perform better in my opinion than vented crawlspaces. Essentially all other building science experts around the country also hold this opinion.(Reference: Energy and Environment Building Association) - Craig Dewitt, PhD
Thousands of homes each year, in the Southeast, are built with vented dirt crawlspaces and yet virtually all building science experts agree that vented dirt crawlspaces are a bad idea.
The word “dirt” is the problem. The unsealed dirt allows mold, odors, moisture, wood rot, radon, and soil gases to make your crawlspace and home unhealthy. The foundation vents actually add more moisture to the crawlspace and cost you about 15% more on your power bill.
Mold is always in the dirt. Moisture and evaporation causes the mold to grow and allows ideal conditions for mold growth and eventual wood decay in the subfloor. In short the house actually becomes sick, which means people in the house can get sick.
Your house may be your biggest investment, but ask yourself this question:
“Which is more important, your home or the health of everyone living in your home?”
How does the unsealed dirt crawlspace do it’s damage?
Water in the crawlspace is not the main problem. Moisture in the dirt, from the foundation vents, and the water table underneath the house causes evaporation which increases the relative humidity. Now you add mold and other contaminants from the dirt floor of the crawlspace and you have created a toxic stew. Mold now has the three things it needs to grow – a food source (the wood floor), moisture, and adequate temperature. Foundation ventilation has proven to be a bad idea.
If this problem is not corrected, the wood floor will eventually begin to rot. In terms of health, however, the mold is your real enemy. It does not just smell bad; it can make you sick.
The areas in RED indicate the regions that will experience extreme benefits from a Sealed Crawl Space over a traditional vented crawl space. Areas covered by the BLUE portions are highly recommend for Sealed Crawl Spaces. Areas on this map shaded in GREEN will also benefit from a Sealed Crawl Space.