Where you mount your bat house plays a major role in the internal temperature. Houses can be mounted on such structures as poles, sides of buildings and tall trees without obstructions. Houses placed on poles and structures tend to become occupied quicker than houses placed on trees. Bat houses should face south to southeast to take advantage of the morning sun. In northern states and Canada, bat houses need to receive at least 6 to 8 hours of direct sunlight. It is also advantageous to paint the house black to absorb plenty of heat (when baby bats are born, they need it very warm). Use non-toxic, latex paint to paint your bat house and only paint the outside. Your bat house should be mounted at least 15 feet above the ground, the higher the house the greater the chance of attracting bats. Bats return from migration and awaken from hibernation as early as March in most of the U.S., but stay active year-round in the extreme southern U.S. They will be abundant through out the summer and into late fall. Most houses used by bats are occupied in the first 1 to 6 months (during the first summer the bat house was erected). If bats do not roost in your house by the end of the second summer, move the house to another location.
Information provided by Organization for Bat Conservation.