How To Get Bats Out Of Chimney: A Professional Exclusion Guide

Removing bats from a chimney requires a strategic exclusion process using one-way valves that allow bats to exit but prevent reentry. This method is the only humane and industry-compliant way to resolve an infestation, as it avoids trapping the animals inside while strictly adhering to seasonal maternity protection laws.

Mandatory Preparation and Exclusion Protocols

Before attempting to remove bats, you must understand that bats are ecologically vital and often protected by state and federal wildlife regulations. Mismanagement of an exclusion can lead to significant legal penalties, particularly if you disrupt a maternity colony during pup season.

• Essential Equipment:
  
  
  • High-quality exclusionary netting or specialized bat cones (polypropylene netting or PVC pipes).
  • Duct tape or heavy-duty adhesive tape for securing mesh.
  • Expanding foam or silicone sealant for sealing secondary entry points.
  • A sturdy ladder and proper fall-protection harness.
  • Personal Protective Equipment (PPE) including an N95 respirator, thick leather gloves, and long-sleeved clothing to prevent contact with guano or potential pathogens.
• Mandatory Prerequisite Knowledge:
  
  
  • Identify the species: Most house-dwelling bats in North America are colonial.
  • Seasonal awareness: Determine your local maternity season (typically May through August), during which flightless pups reside in the chimney and cannot leave. Attempting exclusion during this window will result in the death of pups and potential odor issues.
  • Legal compliance: Consult your state's Department of Fish and Wildlife to ensure your exclusion methods align with local statutes.
• Benchmarks:
  
  
  • Total project duration: Expect a 5 to 7-day period for full exclusion.
  • Estimated cost: DIY materials range from $50–$150; professional services range from $500–$2,500 depending on the complexity of the structure.

The Systematic Exclusion Workflow

Step 1: Conduct a Twilight Observation

Before installing any devices, you must pinpoint exactly where the bats are exiting the chimney. Spend an evening 15 minutes before sunset and 30 minutes after sunset watching the chimney stack from a distance.

1. Identify the primary exit point, usually a crack in the mortar, gaps at the chimney crown, or loose flashing.
2. Note the total number of bats emerging to estimate the size of the colony.
3. If bats are exiting from multiple sides of the chimney, you must design an exclusion device that covers every identified egress point.

Step 2: Seal Secondary Entry Points

Bats can squeeze through gaps as small as 3/8 of an inch. Before installing the one-way valve, you must close off all non-essential openings.

1. Inspect the roofline, ridge vents, and soffits for secondary access points that could allow the bats to relocate from the chimney into your attic.
2. Use professional-grade expanding foam or stainless steel hardware cloth to block these secondary gaps permanently.
3. Leave only the primary exit point—where the bats are currently emerging—completely clear.

Step 3: Install the One-Way Exclusion Valve

The goal is to create a physical barrier that functions as a trapdoor, allowing bats to fly out but preventing them from finding the opening to return.

1. Construct a curtain of netting or a cone of polypropylene mesh over the identified exit points.
2. Secure the top and sides of the netting tightly to the chimney masonry using duct tape or wood strips, leaving the bottom edge loose and hanging 12 to 18 inches below the exit point.
3. As the bats emerge at dusk, the mesh will guide them out; when they attempt to return, they will hit the mesh and be unable to find the entry hole behind it.

Pro-Tip: Ensure the netting is taut at the top so that when the bat crawls out, the mesh naturally hangs at an angle that directs the animal away from the chimney wall.

Step 4: Final Seal and Sanitation

Once you have observed no bat activity for 5 to 7 consecutive days, you can remove the exclusion device and permanently seal the chimney.

1. Perform one last twilight observation to ensure zero activity.
2. Remove the netting or cone device.
3. Seal the final exit point with high-grade mortar, silicone, or metal flashing.
4. Clean the base of the chimney of any guano using a HEPA vacuum and disinfectant, as bat waste can carry fungal spores like Histoplasma capsulatum.

Warning: Never use chemical repellents or insecticides. These are ineffective and can cause bats to drop dead in inaccessible areas of your flue, leading to severe odor issues and health hazards.

Technical Parameters of Exclusion Methods

Common Site Failures and Field Fixes

• Root Cause: The Bats Did Not Leave.
  
  
  • Actionable Fix: The exclusion device may be installed too tightly, blocking the exit. Ensure the netting is loose enough to allow passage but taut enough to prevent reentry.
• Root Cause: Presence of Pups.
  
  
  • Actionable Fix: If you hear high-pitched squeaking inside the chimney during summer months, abort the exclusion immediately. Wait until the pups are volant (flying) before resuming the process.
• Root Cause: Bats Relocated to Another Part of the Attic.
  
  
  • Actionable Fix: If you only seal the chimney but leave the attic vents open, bats will simply migrate. You must conduct a whole-house inspection and seal all potential entry points concurrently.

Frequently Asked Questions

Can I use mothballs to get bats out of my chimney?

No, mothballs (naphthalene) are toxic to humans and pets and are largely ineffective at repelling bats. Their use is an illegal misuse of a pesticide and will not force bats to vacate a colony site.

What should I do if I find a bat inside my living space?

If a bat enters your home, isolate it in a room by closing doors and windows. Open an exterior window or door to the outside, stay out of the room, and the bat will likely exit on its own once it senses the airflow.

When is the best time of year to exclude bats?

The best time is during early spring (before maternity season) or early autumn (after the pups have learned to fly). Avoid all exclusion activities during the summer maternity season to prevent the starvation of non-flying pups.

Is it necessary to call a professional for bat removal?

While DIY exclusion is possible, professionals are recommended if the colony is large, if you have height safety concerns, or if the chimney is located in a high-traffic area. Professionals also ensure compliance with local wildlife protection laws that protect specific bat species.

Protect your home and the local environment by ensuring your chimney is properly sealed through humane, seasonal exclusion methods. Contact a local wildlife management specialist if you suspect a large colony or require assistance with high-roof access.