Re: need plans for proven bat house *LINK*
Gary Smyth
I'm a bat fan, but bats will drive you bats mostly because they don't recognize that you are trying to help them. It took three seasons (and several tries) to get them to try out new quarters. Some bat houses worked and some remained vacant.
Posts near water are better than buildings as the bats need water and there are insects there. On buildings (even set out) droppings somehow always get onto siding. Even a single resident will donate enough streaks to make you wish that you didn't select a building where people reside.
Several types were made and what finally worked for me was old weathered barn siding, It was warm enough and rough enough and had no chemicals in the wood.
See link for Bat Conservation and Management site.
https://batmanagement.com/blogs/bat-roosts/how-to-choose-a-bat-house-location