I was thinking little brown or big brown. (We just got a bunch of big browns in a bat house at my aunt's house this year.)
I found one article that said big browns sometimes spend the winter in houses.
If they do spend the winter, they'll seem to be dead:
Quote:
The breathing of a hibernating bat is imperceptible, and its body cold to touch. Its heartbeat drops from roughly 400 beats per minute, when awake, to about 25 in hibernation, and its body temperature drops to within a few tenths of one degree of the surrounding cave.