A couple of years ago I received a distressing call from some tenants saying there was a bat flying around inside their house. To make matters worse they had just brought home their newborn baby and were afraid this bat might have rabies and attack their baby.
We asked the tenants to remove the baby from the house and immediately contacted several pest control vendors to find one who works with bats and would be able to come out right away and help us resolve this problem. We had a selected vendor come out, evaluate the problem, and provide an estimate of what it would cost to exclude bats from the house.
Unlike most houses this one had open beam ceilings that continued past the exterior wall and supported large overhangs. This was an older house with small openings where the beams met the exterior wall allowing bats at certain spots to enter the interior space between the sheet rock and the roof and make nests. Inside the house the beams were covered with sheet rock creating vaulted ceilings with minimal insulation. By watching at dusk for bat activity and examining the sides of the house near the openings for staining and the ground beneath the openings for bat guano, we determined several areas that needed to be treated for bat exclusion.
We notified the owners of the problem and their response was that it wasn't necessary to pay to have an expert treat for bats and that it would be more cost effective to have their handyman plug all the openings with caulking. We communicated this to the bat exclusion vendor and were told this approach would only drive any bats nesting in the house into the house interior in search of an exit.
Because of this situation we decided to do some research on bat exclusion to educate ourselves and the owner as to the best and most cost effective approach to satisfactorily resolve this issue. First we found out that only approximately 0.5 percent of bats are rabid. While this is a very small percentage of the bat population you still don't want to run the chance that this bat inside your house may be rabid. Secondly bats need access to food and water so they are going to normally exit to the outside of the house--not the interior. Plugging holes on the exterior of a structure will keep the bats out, but will also drive those trapped inside to find other exits, usually into the inside of the house or, if no exit is found, to eventually die.
Instead of plugging the holes we built cones around the exterior openings using soft window netting and staples. The trick is to design the cones so that the bats can get out of, but not come back into the opening. Since the owner wanted to use his handyman I instructed him on what openings to plug and where and how to construct the cones. We then had a bat exclusion expert come and inspect the work and verify that it was done correctly.
Since then we have had no problems with bats. Upon review we agreed with the owner that although it was a great learning experience about bats and bat behavior it probably would have been more cost effective to have a professional do the entire job.