When I was a kid, I spent summers near a bat mega-cave (now several-times decimated from white nose) and the researchers liked to say "if you find a bat in your house, it's likely a teenage boy bat with poor judgment." Kudos on your open-door, dim-lights, let-escape strategy, which is what I was taught by bat-conservationists. I'm generally surprised that the houses here don't support more bats. We plan to get a bat house as soon as we're able.