If you have crawl space vents, even the best crawl space vents out there, they’re going to let in humidity. After all, that’s sort of the point. The idea is to let outside air in so the air doesn’t become stale and stagnant.
However, while inviting in fresh air, crawl space vents also invite in humidity. That means you’re going to start seeing condensation pretty quickly.
It’s important to realize that even automatic crawl space vents have this problem. It doesn’t matter if you get to choose when the vents are open. As long as the vents have the option to open, you’re going to invite in moisture every time you open them.