Getting the bats out of your attic is only half the job. Once they are gone, you are left with what they left behind: piles of guano, urine-soaked insulation, and a smell that does not go away on its own. I have cleaned up after bats more than once, and I will tell you straight: skipping this step is the mistake most people make, and it is the one that comes back to bite you. If you only have the sound to go on, the attic noise identifier narrows it down in three questions.
Why the cleanup matters
Bat guano is not like mouse droppings. When it dries out and you disturb it, by sweeping it, vacuuming it, or just walking on it, it releases a fine dust that can carry the spores that cause histoplasmosis, a lung infection that starts off feeling like the flu and can get much worse. Small kids, older folks, and anyone with a weak immune system are the most at risk.
Guano and bat urine also soak into insulation and wood. You cannot clean soaked insulation. It has to come out. And the longer the colony was there, the deeper that contamination goes.
One more thing worth knowing: bats are protected in a lot of places, so removal is a job for exclusion, never trapping or killing. That part should already be done before you start cleanup. If it is not, finish it first, or you will be cleaning the same attic again next season.
Gear you need before you start
Do not go up there in a t-shirt and a dust mask. Here is what I wear:
- A respirator, not a cloth mask. An N95 is the minimum for a small job. For a big colony or an enclosed attic, step up to a full-face respirator with P100 filters.
- Disposable coveralls with booties, so you do not carry guano dust back into the house on your clothes.
- Nitrile gloves, doubled up for a large cleanup.
- Safety goggles, or just a full-face respirator so your eyes are covered too.
- A hair covering, because guano dust gets into everything.
Step-by-step cleanup
- Vacuum the guano with a HEPA vacuum. A regular shop vac just blows the fine dust right back out the exhaust. You want a vacuum rated for hazardous dust.
- Remove the contaminated insulation. If it has guano on it, urine staining, or a smell, it goes. Bag it in heavy-duty contractor bags and seal them before they leave the attic.
- Disinfect the surfaces. Mix about one part bleach to nine parts water, or use a disinfectant that is labeled for the fungus that causes histoplasmosis. Spray or mop it on. Do not pressure-wash, that just kicks the dust back into the air.
- Let everything dry completely.
- Seal the entry points before you put new insulation in. If even one gap is left, bats get back in and you start over.
- Install new insulation with a vapor barrier. Spray foam seals tighter than batt insulation and is less inviting to the next batch of bats.
When to hire a pro
Small, shallow guano piles can be handled yourself if you gear up properly. But call a biohazard or wildlife cleanup company if any of these apply:
- The guano is deep or spread across a large area.
- The colony was there for a long time.
- The wood is soaked or rotted from urine.
- You have a respiratory condition or a weak immune system.
- The attic is hard to access or unsafe.
Costs for professional remediation vary a lot by the size of the attic and how bad the contamination is, so get a couple of quotes before you commit.
Frequently Asked Questions
Yes, about one part bleach to nine parts water works against the fungus that causes histoplasmosis. Bleach can damage wood, so for big jobs I prefer a disinfectant that is specifically labeled for the fungus.
Years. Even old, dry guano from a colony that left a long time ago can still make you sick if you disturb it. That is why you never just sweep it.
Any insulation with visible guano, urine staining, or a smell should be replaced. If there is light contamination, you can sometimes get away with spot removal, but be honest with yourself about how far the dust spread.
No. Burying it just leaves a health problem waiting for the next time anyone works in the attic. Pull it out and be done with it.
