I have a house in a sub division where the majority of the trees at this particular house are shag bark hickorys. There is also a large old barn in very close proximity; both perfect bat habitat. To add to the already perfect bat habitat, the gable end vents are made up of louvers with screen wire on the back side. Bats were roosting in the louvered end vents. Screen wire was placed on the outside of the vents to keep the bats from roosting in the vents. This has worked very well except for the occasional bat that will roost on the outside screen. Does anyone have any suggestions for keeping even the occasional bat from roosting on the outside screen? There is only one particular vent I am interested in keeping all bats from roosting at as it is positioned directly above the back porch steps and a hot tub.

Mylar strips, monofilament line hung as a stand off, solid surface over the vent are just a few that come to mind.

Thanks for the suggestions; it is greatly appreciated. Is there any particular spacing on the monofilament line or Mylar?