You can install a bat house any time of the year. However the late summer to early spring seasons are the ideal time of the year to prepare for the returning bats that have been in hibernation.
Established bat house will have time to weather and be ready when bats come back in late spring to nest. Bats find the bat houses just like birds find bird houses, by sight. If a house is in the proper location, meets the bats’ requirements and is needed, bats will move in on their own. The majority of bats that use houses are females using the house as nurseries.
In Michigan the Little Brown Bat and the Big Brown Bat are the most likely to use Wild Birds Unlimited bat houses which meet the specifications determined by Bat Conservation International and the Organization for Bat Conservation.
The greatest bat house in the world will never contain a bat unless it is placed properly in the field. In Michigan it is best to avoid shady locations at all costs. Research also shows that they are more successful if they have at least 8 hours of sun. The morning sun is most important. Bat houses should face the south or southeast.
Bat boxes should be hung at least 15’ above the ground-- the higher, the better. Houses mounted 20’ away from trees they are inhabited twice as quickly as those in wooded areas. In northern areas the top third of the house can be painted brown or black with a latex water base paint to aid in warming the box. In southern parts of the country, the boxes can be painted latex water base white, if there is too much direct sun.