Probably, but you won’t know until you inspect your space. When your crawl space doesn’t have a dehumidifier and is not sealed, the moisture enters your space and causes joists and posts to soften and rot.

Sagging floors can be caused by many factors. Your joists or other wood structures in your crawl space may be damaged from fungal growth. Also, many homes are just built improperly, with widely-spaced support columns or poor footing that cause sagging floors. Another possibility is poor soil quality or improper compacting of the soil during construction.

In this climate, it is probably beneficial to have closed vents. Open vents allow moist, humid air into the crawl space. When that humid air mixes with the cooler air inside, moisture forms.

Mold spores are around us everywhere. Mold needs moisture, food and warmth to grow, however. Under your house, humidity and water can provide the moisture and, unfortunately, the wood framing of the house provides the food. Under the right conditions, mold can grow.

Most professionals agree that a humidity reading above 60% can bring about fungal growth and mold. Proper remediation of a dangerously humid space includes sealing the crawl space with an appropriate barrier and installing a dehumidifier to remove moisture in the future.