Flood Vents protect houses and buildings in floodplains by preventing hydrostatic pressure buildup that can destroy walls and foundations. This mitigation technique is referred to as Wet Floodproofing. Remember, compliant flood-proofing methods means lower flood insurance rates.
Vents that allow outside air to circulate under the floor in summer to prevent the moisture buildup that encourages mildew and rot. In winter, when the air is drier, the vents are closed to reduce the chance that the pipes in the crawl space might freeze.
The presence of moisture is what leads to mold, which can be bad for your health and costly to remove. According to the Environmental Protection Agency, the way to control mold is to control moisture. The main source of crawl space moisture is ground evaporation. Proper ventilation allows this evaporation to dissipate & only exhausts moisture from the crawlspace but replaces it with fresh, drier air providing moisture control. Ventilation also helps to remove strong odors and dangerous radon gas from the crawlspace.