When we moved from our farm in Virginia to this smaller property (6 acres) in North Carolina the first thing we discovered is the little darlings, i.e. bats, were living on all the screens in the gable vents which meant that half of their bat poo and pee was coming into the house... That's not a good thing...
So I studied up on the problem and discovered that is a common problem with the little darlings and the fix is to build big triangles frames and mount hardware cloth (heavy screens) in these frames and mount them over the vents... There were seven in total (5 on the house and two on the garage attic) and that's how I spent my first winter here... Two I had to build scaffolding with ladder jacks to install...
I also purchased two bat houses which are rated to hold about 200 of the little darlings each and from the looks of their poo contributions below I'd say they both boxes seem to be fully occupied...