As you can see this vent needs some TLC. Besides the TLC, the vent is closed which can lead to problems such as excessive moisture in the crawlspace. We recommend keeping vents open except during extended periods of temperatures below freezing. When the temperature dips many homeowners close all their vents until spring. If you feel you must close vents in the winter only close a few. Keep a vent open on each side of the crawlspace as a bare minimum. Also, during extreme cold weather keep a light bulb lite in the crawlspace to generate some heat to prevent frozen pipes.
I am a full-time home inspector servicing all of South Carolina.