Did you know that most bats weigh less than a £1 coin? They usually have only one baby a year, which is called a pup, and they return to the same roost again and again. Most bats don’t like light which is what this blog is about. However, as well as being cute, they are also protected by wide ranging legislation.
Basically, it is a criminal offence to damage or disturb a bat roost or foraging route. If in doubt, ask an ecologist or your Local Authority Ecological Officer. Since bats don’t like much light, you need a well-designed scheme to ensure neither the roosts or foraging routes are affected. Good lighting design can help you get planning approval.
The general recommendation from the Bat Conservation Trust is that the bat flight paths and roosts should receive less than 0.5 lux. That’s about the same as the illumination from a full moon in a clear sky. Some Local Authorities might also specify 0.5 lux vertical at a height of, say, 2m above ground. Either way, it means the lighting should, in effect, cut off before it reaches the sensitive areas. You especially need to keep any illumination well away from the roosts.
Spill light from windows can also be a significant contribution. This is especially so for brightly lit interiors such as factories and warehouses. We can provide 3D models showing the amount of light from the windows.
Bats will often avoid crossing continuous lines of light such as a uniformly lit footpath or road. They can be “seen” as barriers and bats may avoid them. The solution is to use pools of light with dark areas in between but this may not be acceptable to us humans for reasons of safety or simply seeing where you are going. A related aspect is that bats often fly quite low and it’s best if your light sources are even lower to the ground.
Bats also prefer Warm light sources such as 3000K, 2700K or less. Budget LED lights are often much Cooler and bats and other wildlife will avoid them.
If you want to know more about bats a good place to start is the Bat Conservation Trust. They have lots of free documents you can download on a wide variety of bat topics. There is also an ILP/BCT guide on lighting for bats. We can design your lighting so it conforms to these guides.