Your bat house building plans should take into account the design in general, how big to build it, where to hang it, and several other considerations that I'll get into below.
Why consider bat house building plans in the first place? With all the paranoid hype surrounding the bat population it's a wonder they're not extinct! Bats have been the target of myths and rumors for hundreds of years. Now scientists, through some long term and expensive research, are confirming what most farmers have known all along. Bats are not only good for the ecosystem, they're necessary. Some crops and plants wouldn't get pollenated without bats. They also eat crop destroying insects such as cutworms and grasshoppers. Bat droppings are also a much sought after fertilizer among some farmers because it's extremely rich in nutrients.
Bats in North America are insectivores. That means they eat insects by the bunches. Some bats also include certain fruits in their diets but that's not why you want to build bat hotels. The insect control is the main reason. Each bat can eat their own weight in insects every night.
Government officials have been trying educate the public about the benefits of having a healthy bat population for a long time. Bats, contrary to popular belief are clean communal mammels. They can be a major factor in keeping insect borne diseases in check. Some community officials have been proactive by strategically placing bat houses in their community to help with insect control.
Bat Houses in General - Most man made bat houses are used by females as a summertime maternal roost. Keeping this in mind makes it easier to understand why bats have to have certain things available before your house and location are attractive to them.
The way your bat house building plans are constructed and where you mount it makes a big difference as to whether your house will be used or not. It must stay dry and warm to protect the young or they won't move in at all. Do your research first before deciding on a design.
The next consideration is the size of the house. If you make it too large to begin with the bats will have a hard time keeping it warm and may avoid it altogether. Start out with a small one to two chamber unit. If the colony grows large enough to where you can see them roosting from the outside then its time to add another house. Always add a house beside the original one and leave the first one alone. If you must remove the original house then take it down in the middle of winter when the bats are hibernating somewhere else.
Make sure the bat house building plans you choose has a rough landing pad and a rough surface to help the bats climb into their roost. A good way to accomplish this is with heavy hardware cloth or window screening made of nylon. Don't use metal. I also put hardware cloth on the inside chamber walls for them to hang from.
When you're project is done you should hang it 10' to 15' high on a building if possible. Most researchers agree that bat houses on buildings seem to attract bats faster than if it's attached to a pole or a tree. If possible, locate it as close to water as you can because that's where most of the insect food source is.
Still not sure if you want bats around? Well, they're there anyway possibly roosting in your attic. Myself, well I'd rather provide them with a house to live in. And another point that just came to mind...what did you think the last time you were bitten by a mosquito? Did you think about all the mosquito borne diseases or did you think...Where's all the bats when you really need one! Use a good set of bat house building plans that take into consideration what bats need and you'll be pestered much less from the flying insects that can drive you indoors.