Bat houses work best in a location within 1,000 ft. of water. Insect populations will be higher around water. The houses should be oriented toward the east or southeast so they warm up quickly in the morning. Hang them in an unobstructed spot 12' to 15' above the ground, but not too close to your living quarters because bat guano will accumulate underneath. Bat guano has a strongly sweet and powerful aroma. Bat guano is very high in nitrogen and great for your garden soil.
Image from Wikimedia
An excellent publication on bat houses is The Bat House Builders Handbook by Merlin Tuttle and Donna L. Hensley. It is available via Amazon and is also distributed by the University of Texas Press, P.O. Box 7819, Austin, Texas 78713-7819. Bat World in Mineral Wells also provides plans in exchange for a small donation and sells state-of-the-art bat houses.
Bat Houses for integrated Pest Management
Benefits for Bats and Organic Farmers: Phase I
Organic Farming Research Foundation