Big browns are difficult to get in bat houses and hard to hold in the bat houses.
Usually when the internal temp of a bat house exceeds 95 F , big browns abandon the house.
I have had some success holding them in 6 baffle -7 chamber bat houses.
This summer I am going to make several bat houses using 2" x 10" and 2" x 12" lumber to build some 3 chamber bat houses.
Size will be 2 ft. wide and 3 ft long.
I will cover the 2" material with 1/2" plywood to make the bat houses tight.
The 2" materail covered with the 1/2" ply should help keep internal temp of the bat house from exceeding 95 degrees. These houses will be placed in Wis.
Will paint both houses dark brown.
The roof and 6" of the front of one of the houses will use 1/4" steel on the outside of the bat house.
The steel should act as a heat well to keep bat house temps higher after the sun goes down.
I will weigh the house with the steel on it and let you know what it weighs.
Several different building contractors give me lumber and boards to experiment with. They used to chuckle about my bat house building but now several of them are are quite interested in bats and bat houses.
Being thicker and having a greater thermal mass in this case heat absorption, this design sounds like a potential winner Kent. I too have seen the Big Brown's preference for cooler temps with bachelor colonies and solitary males. I have frequently seen big brown bats roost in shutters on the east or southeast side of a house but rarely on the south/southwest side which is probably intolerable for them heatwise. Of course this is adjusted seasonly as well. I believe the quoted BCI temp of 95 is pretty accurate. My next rocket design will be simply made of all wide pine boards with a loadable rock/stone core the entire interior core length which will hopefully attract and not deter either big or little brown bats. Looking forward to your results with your design...
