We placed this half way in ground so that it could be removed for cleaning. Inside the barrell hubby hooked up a toilet float and plumbed into water line so that if water level in barrell went down it would refill by itself. Third, he plumbed pvc pipe to pump and up over wall with small holes drilled every half inch for water to fall on wall. Plug the end opposite the pump. We used fiberglass sheets along bottom fastened to bottom of wall with wire at a slant to return to the pump.
Water is pumped up, over through batting and returns to pump.
You can invest in the corragated core boards as found in green houses and such but this was less expensive. I place one cup bleach per week in barrell. Rest of the barn is as air tight as I can get it. Humidity has not been a problem, We can breed all year, and the buns stay at 70-80 degrees all summer. At the end of season we drain barrell remove pump cover wall with a tarp.