Yup, in Louisiana your big issue is making sure the structure is largely open-air in the summer so it doesn't get too hot (no hotter than the surrounding air, I mean).
For a lot of breeds, you wouldn't necessarily need to do anything in winter other than make sure they have a good sheltered (wind-blocked) area around the roost to prevent cold breezes. For large-combed or very sensitive breeds, I suppose you might want to give them a larger area like that, so you could cover the most major wall openings with something solid (plywood, well-attached tarp, stapled-on feedbags, translucent or clear plastic roofing panels, whatever you like). Leave some openings open, though, preferably high up and at the furthest end from the roost (not an issue for most chickens, only for the *very* most sensitive.... the 20s is really not cold for most chickens)
Good luck, have fun,
Pat