Not all bat houses are created equal. Here's what certification actually means, which standards matter today, and how to make sure your bat house will attract — not harm — bats.
Why bat house certification exists
Walk through any garden center or scroll through Amazon and you'll find dozens of bat houses at every price point. The problem? Many of them are poorly designed — too small, poorly ventilated, built with materials that can injure bats, or constructed with gaps that create fatal drafts. A bat house that looks charming on your wall but doesn't meet bat needs is just outdoor décor.
That's why certification programs exist. They establish science-backed design standards that ensure a bat house actually functions as safe, effective habitat. Two organizations have led this effort: Bat Conservation International (BCI) and Merlin Tuttle's Bat Conservation (MTBC).
BCI certification: the original standard (1998–2020)
Bat Conservation International created the first bat house certification program in 1998. For over two decades, BCI set the benchmark for bat house design. Manufacturers submitted finished bat houses to BCI headquarters in Texas, where they were physically inspected against a rigorous set of 10 criteria. Only houses that met every single standard received the "Bat Approved" seal.
The BCI program was instrumental in raising quality across the industry. It gave buyers a reliable way to distinguish well-engineered bat houses from decorative junk, and it pushed manufacturers to take bat biology seriously in their designs.
However, BCI discontinued its certification program in late 2020. The program is no longer active, and BCI no longer evaluates or certifies bat houses from any manufacturer. Their published design guidelines remain an excellent reference, but the certification seal itself is historical — no new products can earn it.
This matters because you'll still see "BCI certified" language on many websites and product listings. In some cases, this refers to houses that were legitimately certified before the program ended. In other cases, it's simply outdated or misleading marketing. If a company claims current BCI certification on a product designed after 2020, that should raise questions.
MTBC certification: the active standard today
When BCI stepped back from certification, Merlin Tuttle's Bat Conservation (MTBC) stepped forward.
Dr. Merlin Tuttle is widely regarded as the world's foremost authority on bats. He founded BCI in 1982 and led it for three decades before establishing MTBC to continue his conservation and research work. His 2023 book The Bat House Guide represents the most current, research-backed guidance available on bat house design, construction, and placement.
MTBC certification means a bat house has been evaluated against the latest scientific understanding of what bats need — not standards from decades ago, but criteria informed by ongoing field research and occupancy data.
Big Bat Box (WildYard) products are certified by Merlin Tuttle's Bat Conservation. This is the most current, actively maintained certification available in the bat house industry today.
The 10 design criteria that define a quality bat house
Whether you're evaluating a certified bat house or building your own, these are the science-backed standards established through decades of research. Big Bat Box products meet or exceed every one.
1. Chamber height: minimum 20 inches (taller is better)
Taller chambers create a wider range of internal temperatures. Bats move up and down within the house to find their preferred temperature — a short chamber eliminates that option. Many cheap bat houses on the market are only 12–15 inches tall, which provides almost no thermal gradient.
Our three-chamber bat houses provide generous vertical roosting space that gives bats the thermal diversity they need through daily and seasonal temperature shifts.
2. Chamber width: minimum 14 inches
Wider chambers accommodate more bats and provide better temperature stability. Houses with roost chambers wider than 16 inches may need spacer blocks between partitions to prevent sagging. Rocket-style houses with 360-degree chambers are an exception to the width minimum.
3. Crevice spacing: ¾ to 1 inch between partitions
This is where many uncertified houses fail. The spacing between roosting partitions must be precisely ¾ to 1 inch apart. The optimal crevice size for most North American bats is ¾ inch. Crevices wider than 1 inch become attractive to wasps and other non-target animals rather than bats. Our houses are built to the ¾-inch bat-preferred spacing.
4. Landing area: 3 to 6 inches below the entrance
Bats need somewhere to land and grip before climbing into the roosting chambers. Either the backboard should extend 3–6 inches below the entrance, or partitions should be recessed so bats can land on the interior walls. Without an adequate landing zone, bats simply can't get in.
5. Textured interior surfaces
All interior surfaces and landing areas must provide footholds for bats to cling to. Acceptable methods include rough-sawn wood, mechanical grooves scored horizontally at ¼ to ½-inch intervals (approximately 1/16 inch deep), or durable plastic mesh securely stapled every two inches in all directions.
Important: Metal mesh, hardware cloth, and aluminum window screen must never be used — these materials can injure bats. Any plastic mesh must be taut with no sharp edges. Big Bat Box houses feature permanently scored grooves that will never sag, buckle, or trap bats.
6. No protruding hardware inside chambers
Screws, staples, nails, splinters, and mounting hardware must not extend into roosting chambers. All hardware and metal components should be exterior grade (coated, galvanized, or brass). Major assembly should use screws — nails, brads, or staples alone do not hold well over the lifespan of a bat house, which may need to endure years before achieving occupancy.
7. Proper ventilation
Half-inch-tall ventilation slots must be placed no more than one-third of the distance from the bottom of the house. Front vents should run the full width of the house. Side vents (optional) should be approximately six inches tall by one inch wide. Ventilation is especially critical in warmer climates like the southern United States, where internal temperatures can become lethal without adequate airflow.
8. Draft-free, durable construction
Bat houses must be tightly constructed with no unplanned gaps. All exterior joints should be caulked or glued during assembly to prevent drafts — bats will abandon a draughty house. The house must be built to last, since it may take anywhere from a few months to several years before bats discover and occupy it. A house that deteriorates before occupancy is a waste.
Big Bat Box houses are constructed from premium cedar, a naturally weather-resistant wood, and are built to withstand years of exposure.
9. Appropriate finish
If painted, bat houses should use exterior-grade, water-based paint or stain only. The interior must never be painted. House color should be chosen based on your climate zone — darker colors (black or dark brown) for cooler northern climates to absorb heat, lighter colors (brown or cedar) for hotter southern climates to avoid overheating.
We offer our bat houses in black, brown, and natural cedar finishes specifically so you can match the right color to your region. Check our climate color guide →
10. Honest, accurate marketing
Certified bat houses may not make unsubstantiated claims. Statements like "no more mosquito problems" or guaranteed occupancy timelines are not permitted. Instruction materials must include adequate guidance on painting, sun exposure, mounting height, mounting sites, and recommended distances to water and obstacles.
We take this seriously. While bats are extraordinary pest controllers — a single bat can eat its body weight in insects nightly — we won't promise results we can't guarantee. What we can guarantee is that our houses are designed to give you the best possible chance of attracting and safely housing bats.
How Big Bat Box meets these standards
Every bat house in our collection is built against these criteria and carries active MTBC certification. Here's what that means in practice:
- Material: Premium Western Red Cedar — naturally rot-resistant, excellent thermal properties, chemical-free
- Chamber design: Multi-chamber construction (2 or 3 chambers depending on model) with ¾-inch bat-preferred crevice spacing
- Interior surfaces: Permanently scored grooves for secure bat grip — no mesh that can sag or trap bats
- Ventilation: Properly sized and positioned ventilation slots for climate-appropriate airflow
- Hardware: All exterior-grade, no protrusions into roosting chambers, screw-assembled for long-term durability
- Landing area: Extended backboard landing zone for safe bat entry
- Construction: Tight, caulked joints for draft-free roosting
We're also proud members of 1% for the Planet and trusted by national parks across the U.S. and Europe.
Browse our MTBC-certified bat houses →
What to watch out for when shopping for a bat house
Not every bat house on the market will actually attract bats. Here are red flags:
Too small. If the roosting chamber is under 20 inches tall or under 14 inches wide, bats are unlikely to use it. Many decorative bat houses fall into this category.
No ventilation. A sealed box becomes an oven in summer. Without proper vents positioned in the lower third, internal temperatures can become lethal.
Metal mesh or screen inside. This can injure bats. Look for scored wood grooves or properly installed plastic mesh instead.
Assembled with nails only. Nails loosen over time, creating gaps and structural failure. Quality bat houses are screw-assembled.
Vague or missing specifications. If a manufacturer doesn't list chamber dimensions, crevice spacing, and materials, there's usually a reason.
Outdated certification claims. "BCI certified" is meaningful only if the product was certified before 2020 when the program was active. Look for current MTBC certification as today's active standard.
Placement matters as much as design
Even the best-certified bat house will fail if placed incorrectly. Key guidelines:
- Height: Mount at least 12–15 feet above ground. Higher is generally better.
- Sun exposure: 6–8 hours of direct morning sun minimum. In hot climates (Texas, the Deep South), provide afternoon shade or use a lighter-colored house.
- Mounting surface: Buildings and poles are far more successful than trees. Trees provide predator access and too much shade.
- Water proximity: Within a quarter-mile of a pond, stream, lake, or river dramatically improves your chances.
- Timing: Install in late winter/early spring before bat migration season begins.
- Patience: Occupancy can take anywhere from a few weeks to a few years. Once bats establish a colony, they typically return year after year.
For detailed installation instructions specific to your climate and setup, visit our Installation Guide.
Frequently asked questions
Is BCI still certifying bat houses?
No. BCI discontinued their certification program in 2020. Their design guidelines remain a valuable reference, but no new certifications are being issued.
What is MTBC certification?
MTBC (Merlin Tuttle's Bat Conservation) is the currently active certification program for bat houses. Dr. Merlin Tuttle, the founder of BCI and the world's leading bat authority, runs this program based on the most current research.
Are Big Bat Box houses certified?
Yes. All Big Bat Box (WildYard) bat houses are certified by Merlin Tuttle's Bat Conservation and built to meet or exceed the original BCI 10-point design criteria.
Do certified houses guarantee bats will move in?
No bat house can guarantee occupancy — bats are wild animals with specific habitat needs. But certified houses built to proper standards and correctly placed give you the best possible chance. In areas with existing bat populations, occupancy within a few months is common.
What's the difference between a 2-chamber and 3-chamber bat house?
More chambers provide more roosting space and a wider range of internal temperatures. Three-chamber houses can accommodate larger colonies and offer better thermal stability. For best results, multi-chamber houses with taller chambers are recommended.
Ready to give bats a proper home?
Every bat house in our collection carries active MTBC certification, is built from premium cedar, and is designed to the highest standards of bat conservation science. Whether you're looking for natural pest control, supporting local ecosystems, or simply fascinated by these extraordinary animals, a properly certified bat house is where it starts.
Shop MTBC-Certified Bat Houses →
Big Bat Box is part of the WildYard family. We're certified by Merlin Tuttle's Bat Conservation, members of 1% for the Planet, and trusted by national parks across the U.S. and Europe.
