How do you get rid of flies that like to hang out on the side of my house in the sun?
If you are looking for an ecological solution, then bear in mind that many types of lizard (and chameleons) feed off flies. Since they also like to hang out on sunny walls, you may have a meeting of minds here. This is why such animals are usually welcome in homes in sunny places such as Valencia, Spain (called "dracs").

Just remember that cats also like to eat lizards, so this will only work in a feline-free area.