3 months ago, we turned a child's plastic playhouse into a coop. We covered the back window with chicken wire but the plastic shutters are open all day. I close them at night. The second window is their exit/entrance door. They too are the actual plastic shutters but I keep those open all day as well so the young chicks go in and out as they please. We have a wooden floor just below the windows, then another wooden floor as the base. The wooden base we call their basement which is where I keep the food and water. Nothing inside the plastic childs playhouse has been wet. I recommend chicken wire on 2 windows so the air can get through the entire coop.
The super nice thing about the plastic coop is no bugs digging in the wood, no smell from the poop in wood. Every 3 weeks I pull out the straw, use a garden hose and bleach on the entire coop. Open the windows and it dries in less than an hour.
THe plastic coop has worked out so well we are currently building an 8x8 plastic shed (from Lowes). I suggest you chicken wire a few windows and let the fresh air dry it all out.
We are trying to figure out how to insulate it. That is my problem.
good luck