I just leave two of my (covered) top vents open. Works for me.
__________________ Happy Camping! ///// Richard D.
2006 4x4 Ford 250 SD / 2007 Flagstaff 827 FLS
One very patient wife and one furry child who travels with us. Forty-two years of trailering and camping, and I still have a blast.
We also use damprid along with a few small trash cans filled with charcoal, we do cover ours but leave the covered vents open also..this seems to work great for us,,,upon opening in the spring, we are dry and clean.. Sad that the season is coming to an end in a few short weeks, hope all of you had a great summer.
I leave the 3 covered vents open as well. I haven't tried this but I remember someone saying that they take Salt Pellets ( Home Water Softner Type ) and a couple plastic containers with lids and drilled [4 to 6] 1/2" holes in the top and sides to absorb moisture. The salt costs about $8 for a 40 lb bag and they used about 15 lbs in 4 containers. They place them inside the bathroom cabinet under the sink and under the kitchen sink as well as on the countertop and next to the bed. It may have been on the RV Today or RV Roadtrips show.