crawlspacemoisture

And probably mold.

While many, many vented crawl spaces don't have a 'problem', there are plenty out there that can have amazing issues. when you stop and think about it, crawl spaces are bathed in humidity year round, and the thinking is the humid air outside is better than what's beneath the home. The idea that every crawl space be treated with an antimicrobial is good, but limited. Crawlspaces that perhaps 'circulate' poorly attract bugs. The insulation can get saturated. Wood moisture levels over about 16% will grow fungi regardless of whether there's a treatment on it or not, and I see houses every week that have moisture levels high enough to rot wood. An antimicrobial won't fix that. To answer the OP, Advanced Energy did a couple of studies - one focused on the hot, humid south and a 2nd in multiple locations across the country, on sealed crawl spaces and their benefits. CrawlSpaces.org However, you may consider this 'unbiased' and pushing a technology. I don't, but YMMV.