I got mine at http://www.modernbeekeepingusa.comWhere can they be purchased from?
I live in Virginia. It's quite humid here as well in the summer. They come with a screened bottom board and I crack the top a bit to give a bit more airflow. You can also reverse the top and add a screen beneath it (like a travel screen) to give it more ventilation.I have never used them, but have heard they can cause moisture problems. If that is true, would not be a good idea in humid climate like where I live.