I have the same humidity problem. I had a 50 x 64 x 20 foot pole barn put up to keep my RV, tractors, junk, etc. in. I put in roll up doors with concrete under them, with a gravel floor as I don't need concrete. I didn't insulate as I didn't expect the humidity problem. I try to keep the doors open as much as I can to keep the humidity down, but that isn't enough. The doors are 14' high and one 10x10. I can't find anything on the inet either about this problem other than ventilation.
I am presently putting in 2 2300 cfm exhaust fans in one end at the top that run on temp and humidity. On the other I am putting in 2 18x24 louvers. I am putting in 3 60" industrial ceiling fans, which I found at Home Depot for $70. They are also reversible but I can't find the cfm info on them. The gable vents I got at Lowes for $109 each, made by air vent.
I am thinking of removing as much gravel as I can and putting plastic under it, then putting it back down. I am wondering if it will decompose over time or get full of holes from the gravel left below and on top, or hold water. Think this will work? I have heard of putting down astro-foil, but that is super expensive.
Does anyone have any more suggestions? The humidity is so bad at times that you can see the 2x4 lines on the floor.
Thanks in advance.