I love seeing the bats coming out at night in the summer; I can see them in the front clearing, swooping around after moths. I've got a bat house, but I think that it's been vacant for years; I need to find a better way to attract them to my home.
Knock one of the screens out of your attic and they'll set up permanent residency in there. But, and this is a big but, they'll shit all over the place, you'll hear them crawling around, and many counties prevent you from doing anything to remove them or lock them out once they're in.
Source: was accidentally in this situation a few years ago. Our solution was to move. Okay, that's not really why we moved, but moving solved the problem. Enjoy the bats, new residents!