The smell hit me halfway up the stairs. That's how it started.
Our house dates back to at least the mid-1800s, possibly earlier. Wide-plank floors, hand-hewn beams, walls that have absorbed more Vermont winters than I can count. I love every square foot of it. As it turns out, so did the bats.
Over the years we'd noticed them at dusk, flickering near the roofline. We went into the attic, looked for gaps, sealed what we could find. We thought we were managing it. We weren't.
What we didn't know was that bats weren't only in the attic. They had worked their way into wall cavities and hidden spaces along the roofline, places no casual inspection would ever reveal. They were quiet. Invisible. Completely unbothered by our occasional attic visits.
Then summer arrived, and the heat changed everything.
Halfway up the staircase, the smell hit us. Not overwhelming, but unmistakable once you knew what it was. Musty, sharp, wrong. The first floor was fine. The attic seemed fine. It was that in-between zone, warm and sealed off, that told the real story.
Between the neighbors we had talked to and the research we had done, my husband said he could do the work. He knew what he was getting into. Or thought he did. What he actually found stopped us both cold. Years of guano buried in eaves, tucked along rooflines, hidden in cavities we never would have thought to check. It had been building for a long time.
That experience changed how I talk about homes, and why Secret Life of your home is the first post in this year long series.
Why You Often Don't Know Until You Really Know
Bats are remarkably good at staying hidden. They don't need much space. A half-inch gap along a soffit or a loose piece of flashing is enough. They move in quietly, they stay quiet, and the evidence they leave behind tends to accumulate in places homeowners never look.
The signs are subtle, and often seasonal. An odor that appears in warm weather but seems to vanish when it cools down. A faint fluttering or scratching near the eaves, usually around dusk. Small dark stains along rooflines or upper exterior walls. Droppings showing up in unexpected spots like a windowsill, a garage ledge, or a porch corner. By the time any of these become noticeable, the situation isn't new. You're seeing the surface of something that's been quietly developing for seasons, sometimes years.
This Isn't a DIY Fix
Worth saying directly: bats are protected wildlife in Vermont and most other states. You cannot legally trap or kill them, and removal must be handled by a licensed wildlife professional during a specific seasonal window, outside of summer pupping season when young bats are present and cannot yet fly.
Attempting to seal entry points yourself, or using deterrents without a proper exclusion plan, almost always makes things worse. Bats scatter deeper into wall cavities or find new ways inside. The right approach is professional exclusion, with one-way exits installed at entry points so bats can leave but not return, followed by permanent sealing once the colony has vacated. It's methodical, it takes time, and it works.
The Real Concern: What They Leave Behind
Bats themselves are not aggressive. The issue is accumulation. Guano breaks down insulation, compromises wood, generates persistent ammonia-like odor, and can harbor a fungal spore called Histoplasma. When it collects in hidden spaces over multiple seasons, the remediation required is substantial, and the cost reflects that.
Catching it early, before it has years to build up, makes an enormous difference. Not just financially, but in terms of how disruptive the process is.
Homes Most at Risk
Any home can have this problem, but some are more vulnerable than others: older construction where decades of settling have opened small gaps in rooflines and siding, slate or wood shake roofs which have natural micro-spaces along edges and valleys, ridge vents or soffits that haven't been screened or inspected in years, locations near trees, wetlands, or open water, and chimneys without caps or with caps that have shifted and no longer seal properly. If your home checks more than one of these boxes, it's worth adding a wildlife entry assessment to your next professional attic inspection.
What Staying Ahead of It Looks Like
Once a year, walk the exterior of your home and take a slow look at the roofline, flashing, soffits, vents, and chimney cap. You're not looking for anything dramatic, just gaps, staining, or anything that seems out of place. Every few years, have a professional inspect the attic with wildlife activity on the checklist, not just structural concerns. Think of it the way you think about your furnace or your gutters. Not glamorous, not urgent, until it suddenly is.
The Bigger Lesson
Old homes tell stories. The ones you can see, the wide boards, the wavy glass, the hand-cut joinery, are the easy ones to love. It's the stories happening out of sight that require a little more intention.
I'm grateful for what our attic taught us, even if the lesson was expensive. It made me a better advocate for the buyers and sellers I work with, because I know firsthand how invisible these problems stay until they're not. The goal of this series is simple: the more you understand about what's happening inside your home, the better equipped you are to protect it.
Love the bones. But know the bones.
Ready to Talk Vermont Real Estate?
After 20 years helping Vermont buyers and sellers navigate everything from what to watch for to when to walk away, I've learned that the right information at the right time makes all the difference. Whether you're thinking about buying, getting ready to sell, or just want an honest conversation before making a move - let's talk.
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Email: nancy@asknancywarren.com
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The information in this post is based on 20 years of personal experience in Vermont real estate and is intended for educational purposes only. It should not be considered legal, environmental, or professional inspection advice. Always consult a licensed inspector, contractor, or relevant professional for guidance specific to your property and situation.