Crawl Space Repair - High humidity in the crawlspace
Mold needs 3 things to grow. The mold spores are always in the air, nothing you can do about that. The food source, which is anything that was once alive (wood, paper, plant life). Its hard to build a house without organic things like wood. The last component, and the easiest to control, is the moisture or humidity. Mold needs to "drink" just like other plant life. It gets water through the humidity in the air, therefore if you lower the humidity in the crawlspace, you will lower the chance of a mold outbreak.