Ah, yes, the old “breathing” myth. Although in other dryer climates, this building method has merit, it does not actually make sense in the South. Because our climate is conducive to mold and mildew, and because HVAC ducts often run beneath houses, it is imperative to seal and condition crawlspaces. This helps to eliminate mold and mildew, prevents buckling of the floors, and helps the HVAC run more efficiently.