Bat-Proofing Basics

When I moved into my house and I first vacuumed the fireplace, a large, stiff object was stuck in the end of the nozzle. I had vacuumed a dead bat, probably one that made a home in the chimney.

Horrified, I turned to Health Officer John Festa, who offers helpful tips for bat-proofing via the Village website. Festa and his staff remind residents that, should a live bat, enter a residence, leave it to the professionals. Leave the room where the bat is and call Animal Control at 973 763-3000 x7772.

However, once a bat is removed by Animal Control officers, or if residents suspect that bats are in the neighborhood, it's time to bat-proof. And Festa notes that the season for doing so is upon us: bats generally leave the area to hibernate around mid-November, so now is the time to seal a house against their re-entry in spring.

Bats tend to enter buildings near the roof line, and will happily roost in dark spaces that are generally undisturbed. Batproofing means creating barriers to their future entry once they leave the roost; it's important, though, not to seal them into a small area. So Festa's advice, via the Village website, is to let them leave home and then shut the door – or entry holes – behind them.

How do you know if bats are in the house?

Sometimes the only evidence of the presence of bats in a building will be an accumulation of droppings in one area of the attic, or droppings and rubmarks on siding at the bat entry opening. To confirm their presence and locate the openings used by bats' in the warmer months, observe from the outside for bats leaving in the evening, from one-half hour before until one-half hour after sundown.

How do I keep them out?

Once you have determined the principal entry points, you may seal all of the openings and crevices of over 3/8" not used by bats. Because bats cannot gnaw to enlarge an opening, a variety of materials can be used to seal an opening, including: l/4" hardware cloth, fly screen, sheet metal, wood, caulking, expandable polyurethane foam, or fiberglass insulation.

To block off the principal bat entry openings, either:

• seal the openings one evening after all the bats have been observed and counted while leaving, or

• hang one-half inch bird netting from above the openings with staples or duct tape, letting it extend, unattached at the bottom, to one foot below the openings (do not use in June or July). This allows the bats to leave but not enter again. After several days, the openings can be sealed, or
• seal the openings between November 15 and March 15, or

• some wildlife removal specialists, pest control companies, and other contractors provide permanent bat exclusion services for homeowners unable to complete the work themselves.

Are there other ways to bat-proof?

Occasionally, bats enter finished rooms from their roost area in the attic or wall spaces. Interior bat-proofing, such as sealing spaces around the attic door, will prevent the bats from accidentally entering living areas of the home until the bats can be excluded from the entire structure. Because fiberglass insulation is repellent to bats, insulating walls and attic will serve a dual purpose of energy conservation and bat control.

The only chemical registered for bat control in New Jersey is napthalene, which can be effective as a temporary repellent in very confined roost areas. The use of napthalene is no substitute for bat-proofing and does not guarantee that the bats will completely leave the building.

Other temporary methods include keeping the lights on in an attic bat roost area for 24 hours a day over several weeks when the bats return in the spring, or using fans to disturb the roosting bats with strong air currents. Sticky bird repellent applied around the bat entry opening can sometimes provide temporary control.

A healthy bat can live 30 years, the same length of time of my mortgage. I was happy to bat-proof, ensuring that those living in my house come and go through the doors, rather than the chimney.