Re: Crawl space ventilation
No ventilation isn't good either. Microorganisms require available moisture, not necessarily liquid water. When there is no air flow then the water molecules settle into microenvironments where the microorganisms can use them to grow or amplify themselves. Your understanding of the limitations on open vent crawlspaces in the hot humid months of the year is correct though. I would recommend that you encapsulate the crawlspace then condition the air space. This will save you money in energy consumption and help promote clean indoor air quality. For more information check out these resources: www.solutionsiec.com/crawl_space_science.html, www.americanbasementsolutions.com/, and www.crawlspaces.org/. They discuss the science behind crawl spaces, current systems available, and more.
Jason Yost, CIEC, CMRS, WRT
Council-certified Indoor Environmental Consultant
Council-certified Microbial Remediation Supervisor
Water-damage Restoration Technician