A good bat house plan should include instructions for a narrow inner space, grooved or textured surface, and dark color. The bat house plan should also have tips on mounting the house at the right height and location for attracting bats.
Unlike birds, which nest in large, open cavities, bats prefer nesting in tight spaces. This is because most bats' natural nesting locations are hollow areas between a tree's bark and its trunk. Therefore, a good bat house plan should have an inner space no more than a few inches deep.
A grooved or textured surface on the bat house allows the bats to cling to the house easily. This not only lets the bats land on the house without trouble, it also makes their nesting process easier.
A good bat house plan should also specify painting the house a dark color. A dark-colored bat house absorbs a lot of heat during the day. Because bats prefer nesting locations with adequate warmth, a warm house attracts more bats.
Even a perfectly constructed bat house does not attract many bats if it is in an unsuitable area. A good bat house location includes ready access to water and protection from predators. Mounting the house in a sunny area at least 15 feet off the ground on a smooth pole both lets the house get warm during the day and prevents predators from easily accessing the house.