The Bat House: a Green, Energy Efficient Insect Repellant

It's summer, and you know what that means.......an abundance of nature's flying vermin--mosquitos! 

Instead of buying a bug zapper, try building a GREEN, ENERGY EFFICIENT alternative: a bat house!

Bats are mother nature's insecticide, and a single brown bat can eat up to 1,000 mosquitos an hour! (http://www.eparks.org/wildlife_protection/wildlife_facts/bats/bat_house.asp). Additionally, bats are an essential part of a healthy ecosystem, and their populations have diminished in recent times due to deforestation and loss of habitat. Lastly, bats are just cool. 

Bat houses come in a myriad of shapes and sizes, but I decided to build the most simple version I could find. This is a Single Chamber bat house, and can hold up to 50 bats. This design was based off of the plans from eparks.org (link above), and I need to give credit to good friends of mine, the Warren clan for inspiring me to build one, and for tips and advice.

Step 1: Supplies and Materials

This is a fairly simple build, but you will need some hardware: 

The size of your bat house can vary, depending on the amount of wood you have available. Use these measurements as an approximation if your supplies are lacking. 

• 1/2'' or 3/4'' outdoor grade plywood (or whatever you have)
  • 26.5'' x 24'' -- the backboard
  • 16.5'' x 24''
  • 5'' x 24'' 
  • 1'' x 21.5'' (two)
  • 1'' x 22'' 
• 1'' screws
• exterior (water based!) staining or sealant 
• caulk
• black spray paint and tape (optional-for decaling)
• shingles, galvanized metal sheet, or left over wood for a roof (optional)
• saw
  • miter saw
  • table saw
  • hand saw (if don't have a miter saw or table saw)

Step 2: Step 1: Cut the Wood

1. Using a table saw, cut your 1/2'' or 3/4'' outdoor grade plywood: 

• 26.5'' x 24'' -- the backboard
• 16.5'' x 24''
• 5'' x 24''

Then cut the furring strips:

• 1'' x 21.5'' (two)
• 1'' x 22''

2. Then, saw grooves throughout the full length of  the backboard- this gives the bats something to grip, climb, and hang from in the bat house. The easiest way to do this is with a miter saw, but if you don't have one (I didn't) you can use a table saw- simply lower the saw height to about 1/4'' and saw lines across the board. If you don't have a table saw, you could do this with a handsaw or dremmel (warning- this is quite tedious). 

Step 3: Step 2: Paint/ Seal the Wood

Apply the wood sealant or stain to the interior of the backboard and outsides of all the pieces. 

Step 4: Step 3: Assemble the House

Attach the furring strips to the outer rim of the backboard with caulk. 

Then attach the front top and bottom piece on top with caulk. Leave a 1/2'' vent in between the top and bottom front piece. 

Then use screws to secure the pieces together. 

Step 5: Step 4: Put a Roof Over Their Little Heads

This is optional, but highly recommended. 

You can use shingles, galvanized metal, or left over wood to create a roof for the house. 

I simply used some left over pieces and cut the wood at a 45 degree angle for a roof. 

Step 6: Step 5: Tag It

This is also optional, and just as highly recommended. 

Make a paper stencil, cut it out, and trace it on some tape on the house. Cut out the stencil, and paint away.

Step 7: Step 6: Hang It

Using long nails or screws, mount the bat house. According to the National Wildlife Federation, the ideal location is about 10-15ft high, with a clear area below, free from branches, etc.

Also, NWF says bat houses mounted on poles or on the side of buildings are easier for bats to locate. 

Also, houses should ideally face southeast, to catch some sunlight during mornings to warm their little bat bodies up.

I mounted mine on tree, but may move it to a pole soon. It can take up to a year or so for bats to take refuge in your house. But once they do, you'll have these friendly, cuddly little minions to do your bidding. 

I hope you found this Instructable useful, and if you like it, please vote for me in the GREEN TECH Contest by clicking "vote" !

Comments

[mark_witha_k]

I love the simplicity of the project, I plan to use these plans this for my eagle scout project.

But how much plywood is there total? 1/4, 1/2, whole sheet?

[KingEdward]

After attending a lecture on local bats (micro-bats to be precise) by biologist & bat specialist Dr Lisa Cawthen at a local wildlife sanctuary (in southern Tasmania, where I live) I am making my first bat box. Dr Cawthen told us not to use any glues or paints because they are toxic to the bats.

[SaoD]

If you
want to choose the best sliding miter saw to cut the grooves. You can visit
website http://mitersawguides.com/ . I
think it will give you useful information.

[ouchmytoe]

I have two suggestions for cutting the grooves in step 2:

First, I think you ought to distinguish the saw you used by its whole
name: a sliding compound (power) miter saw; it's the "sliding"
part (which imitates a radial-arm
saw) that allows it to easily cut these grooves. (A full-size radial-arm saw
would be fantastic for this task, but they are getting pretty rare since the
advent of sliding compound miter saws). A basic rundown: a miter saw is
a hand saw used in a miter box. A power miter saw is a motorized saw
that incorporates the miter box into the saw's base, though nowadays, the word power is usually dropped. Nearly all
power miter saws are also compound miter saws, i.e., they have the
ability to slant the blade. However, and this is where many readers may be misled,
a lot of compound miter saws are NOT sliding compound miter saws. The
sliding version is often much more expensive than the basic version.

Second, I believe a circular saw (sometimes called a Skil®
saw or framing saw) is a better choice than a table saw (which would require
constantly adjusting the fence) and MUCH better choice than a hand saw. Better
still, a circular saw will work for panels that are too wide for a sliding
compound power miter saw. Simply place the measured and marked panel on the
floor, a table, or sawhorses; clamp it down (or have a friend hold it); set the
cut depth on the saw; and cut away! You could clamp a board across the panel as
a guide for the saw if you have trouble cutting straight. A small router with a
dado or dovetail cutter/bit could be used in the same way. I suspect that many
readers who don't have access to the larger saws you mention could locate a
small circular saw or router.

[pete.hohensee]

It's not a repellant.

[glynis.sylvester]

How do you encourage them to come hangout?

[sconner1]

Good Idea. We have an area of standing water near out home. This woild be good to help fight mosquitos.
I know bats can get into some tight spaces, but do you think 1/2 to 3/4" is wide enough for them to nest?
I've seen other designs that look like there is about 1-1/2" to 2-1/2" inside.

[Dickerson888]

I discussed it a few years ago with a biologist and it (the opening size) can depend on the type of bats that are common to the area.

If I remember correctly for instance in the Memphis, TN area Mexican Free Tail and Small Brown Bats are common and he suggested 1/2 to 3/4 inch openings were best.

I designed a few years ago a multi-layered bat house that incorporated different size openings to give the best advantage for occupancy.

[slylee]

Well according to batcon.org, the space should be 1''. You don't want it too wide because they get cold easily, and you don't want heat to escape.

[Dickerson888]

Like some of the other said stay away from treated wood since it off gases. Some consideration may need to be given to the area of the country it's to be mounted. If's a real cold climate a darker color may be needed just as a hot area may need a lighter color.

You can go with a latex house paint but leave the interior plain. Check with your local extension agent or someone in the area familiar with bats to determine if a color is needed.

I suggest if possible let the wood age naturally. Bats often nest in dead trees or areas under the flaps of bark.

The grooves are great and it has a good size and landing area. The depth is important since the bats need to be able to stay away from predators.

I would suggest adding another layer on the interior. It should be open below the roof allowing the bats to move across the top of the divider. This gives them the ability to move from front to back depending on the temperature. They don't need much space between the layers since they like tight places.

The open area at the top below the roof is also beneficial for raising young.

This location has some good information. http://www.maberrybat.com/index.php?module=Pagesetter&func=viewpub&tid=5&pid=2

[slylee]

I haven't seen nor heard from any biologist I talked to of any proof about the harm of using synthetic wood. You don't want to add another opening below the roof because it would let heat out. This is the same reason why you should place the bat house in the sun. They get cold easily.

[Dickerson888]

Synthetic wood might be OK as long as it doesn't off gas as it ages or heats up.

I'm referring to an open area below the existing roof.

The box is slightly thicker with center dividers or additional panels. The panels would not go all the way to the top allowing an open area below the existing roof. This allows an area just below the roof on the interior where the bats can raise young.

This also allows the bats to move across the top of the panels front to back or back to front depending on the temperature.

[mikolynn]

AAAAAHHHH!!!!! STOP AND CORRECT IT! you do a BIG ERROR! If you build it with this kind of plywood or other synthetic wood, you kill the baby bats...
When the baby bats are there, is a great temperature inside the house and with this heat, the synthetic glues and polymers used to build up this "wood" generate gas who kill the bats. They are really sensitives to synthetic materials... The best what you can do with this house, is to burn it up, and build new one with natural, untreated wood. The unique material what you can use as a wood conservative is some vegetable (NOT MINERAL) oil. And also the same for the paint and sealants!

[slylee]

So I've been researching online and talking with local biologists at our University, and I found no evidence that plywood or treated wood is bad to use in a bat house. Furthermore, bats take up residence in attics and awnings all the time, and those places not only have synthetic wood, but also fireproofing materials. So I think it is perfectly ok to use plywood and synthetic wood to built a bat house. I also know of many people who built their bathhouses with plywood and each summer they have 50+bats living in each house.

[MonCal]

FYI Burning treated wood is an extremely bad idea. I don't know about the accuracy of your statement on bat health but this one is fairly common knowledge.

[mikolynn]

;) thats right, maybe the best is to build up another think, maybe a toy parking? a puppets theather? a magic mistery box?

[slylee]

Could you provide links or references for this? I'm not a bat expert, but I didn't read anything about this in any of the conservation websites for bat houses.

[mikolynn]

I know it from time along and read it somewhere arround... Loking for something I found this manual for how to build up nest-houses is in spanish, and they say the same, http://www.xoriguer.org/ftpxoriguer/volcam_2007/Manual_cajas_nido_VOLCAM_2007.pdf But only talk about the "preferences" of the bats with the wood or paints... Before, when I read about it I read something about the steams generated inside the house...
I continue loking for it. And If I find, I will inform... ;)

[GrumpyOldGoat]

IF you seal the interior, use a WATER BASED sealant only. The residual fumes will keep the bats away until the fumes are completely gone.

There is no real need for interior sealing.

Exterior sealant should also be water-based, same reason.

I built 3 two years ago, one I did not seal, the other 2 I sprayed.

Still waiting on bats to move into the 2 I sealed.

Good Instructable and good design. Thanks for a couple of good tips!

[slylee]

Thanks for the reminder. Did any bats move into your houses?