Here’s a general guideline:

Summer (Hot and Humid)

Keep vents open: This allows air to circulate under your house, helping to reduce moisture buildup and prevent mold and mildew growth.

Winter (Cold)

Close vents: Closing the vents helps to prevent cold air from entering your crawl space, reducing the risk of frozen pipes and helping to keep your floors warmer.

Spring and Fall (Moderate Temperatures)

Open or close vents based on weather conditions: During mild weather, you can keep the vents open to allow for air circulation. However, if temperatures drop significantly, it’s a good idea to close them to prevent cold air from entering the crawl space.

Ultimately, it’s a good idea to monitor the humidity levels in your crawl space and adjust the vents accordingly. If you notice excessive moisture buildup, you may want to keep the vents open more often, especially during humid periods. Conversely, if you’re experiencing very cold temperatures, it’s best to keep the vents closed to prevent freezing.