What Makes a Great Bat House?

If you really want to be successful in attracting bats to your bat house one of the most important aspects is the construction and design of the bat house itself.  These days there are plenty of options for a potential bat house customer looking for a new bat house. Unfortunately many of the bat houses on the market are severely deficient in materials quality or of very poor design others are poorly built or way too small to be practical.  After spending 20 years designing bat houses I thought it would be a good idea to list the most important aspects one should look for when picking out a bat house.  

 Size. 

Let’s start with size, as this alone immediately disqualifies many of the over the counter bat houses you might find at a big box store or filling your Amazon feed.     Here at bigbathouses.com we obviously love “big” bat houses and for good reason. Tiny shoe box bat houses just don’t work. Picture this, you’re a night time loving bat trying to sleep in the day but every hawk, crow or jay out there is looking for an easy meal… if you’re roosted in a small bat house it’s no problem for a hawk or other predator to just reach right in and snatch you out!   Plus if you like to roost alongside a few dozen of your buddies to conserve body heat its near impossible. Now I am not saying you need a super huge bat house… but please don’t buy the super small ones. It is cheap and more profitable to build them small, but not good for bats. Look for a bat house with roosting crevices at least 16” tall.  

Design. 

Many bat houses are poorly designed, often with no real features bats have shown a preference for.   More gimmicks than features! Look for roosting chambers which are spaced ¾” to 1” apart. For me this spacing barely allows me to extend my fingers up into the crevice.  It may seem like no bat could fit into such a tight crevice but we have found they really prefer these types of roosts. Beware of bat houses with internal shelves or large cavernous internal spaces, these are not necessarily preferred by bats and if used they tend to collect guano which will quickly promote decay of the bat house.   Also take a look closely at the roosting crevices, you want to see a roughened surface, ideally with actual small grooves for the bats to grip.  

Exterior. 

Stay away from unpainted bat houses or those treated with only light stain.  Not so much for the durability of the house but more so for the house to gather solar heating.  Bats are endothermic which is a fancy word for “warm blooded”. They like to be warm and due to their small body size that can be a challenge!  For most of north America, even Florida I prefer a medium-dark color. Dark browns or greens are my favorite.   

Mounting options. 

Beware of bat house purveyors who have bat houses mounted on trees!  If you see pictures of their bat houses on trees, rest assured they may sell bat houses or even build them but they know little about real world bat house use.  Bat houses do best mounted high on a pole or to the side of a large building like a barn. Look for a bat house with mounting options for a pole or flat surface…not a tree!   

Materials. 

First make sure ‘treated” lumber is not used on the interior of the house.  Treated lumber often contains chemicals which can be hazardous to bats in the long term.   And yes bats are long lived mammals for their size! Often reaching 35 years of age! Exterior grade plywood or siding is fine.  I try to avoid exotic woods or rare native lumber types for sustainability reasons. Most modern industrial wood products are resources sustainably (check out the Sustainable Forestry Initiative for more www.sfiprogram.org )  

Third party certification.

A great indication of whether a bat house is built properly is to look for approval by a respected conservation organization.  Bat Conservation International provides a list of “certified bat approved” bat house builders on their website. Check it out here-  www.batcon.org