Thanks for the link Joe. I have started on the interior bat house and it's going to be 3' long x 16'' tall and 10 1/4 '' deep, it's going to have 8 chambers 5-7/8'' chambers and 3- 3/4'' chambers. I'm not going to do an open design but instead when I groove the partitions I'm going to go ahead and groove the outside of the box too so they can cling to the outside of the house as well. I'm going with the closed design for 2 reasons- 1. because he thinks they also winter there and 2. when the barn lights were on there didn't seem to be a whole lot of dark places inside the barn, the one place that didn't get much light is where the 15 bats were and the few other dark areas I could hear them.
So I'm feeling pretty good about this project, I think I might just get some bats to use 1 or 2 of the many, many bat houses I've built.:?

