I will be making one bat house this year from concrete and sawdust. I plan on using a 50/50% mixture. I have the plans and diagram for the mold already created to make a two chamber house that is 12" wide and 21" tall. I am not sure if this house has been tried in a climate such as Iowa's, but I am willing to give it a shot.
Next year (perhaps this summer) we will see if it is occupied and what times of the year the bats use it. The mold will be created from plywood and nails so I can easily disassemble the wood from the concrete house. I am planning on leaving the house the natural light grey color of the concrete.
Call me crazy, but since I have had successful nursery houses, I want to try some hibernation houses. The thermal dynamics of concrete are much different than wood, so I will be mounting this house on my own home for added thermal stability.
