The member who wrote this article lives in NC.
https://www.backyardchickens.com/articles/hot-climate-chicken-housing-and-care.77263/
In a hot climate, insulation can be helpful under the roof, depending on the design and materials of the roof, to resist the suns rays.
Insulating walls doesn't make much sense to me, because if there's enough ventilation to prevent a humid coop, the internal temperature should be about the same as external.
This can be different in a climate where hot days still have cold nights, where you may still be able to trap coolness from the ground and the building materials.
In a southern state, you won't be getting those cold nights, and more than anything the birds need more ventilation, even an open-air coop design or modification like taking off a wall and replacing with hardware cloth on a shady or well over-hanged side.
There's a problem when it comes to the way people are taught by movies and each other regarding chicken coops... the idea is that it's a box with a roof. That works ok up north... but those of us in the south run into a lot of problems, eventually you realize you're just cutting more holes in the box... so I'd like to push for the idea to be more like a tree. Shaded and covered but open and airy. Only with hardware cloth to protect them. A tree made of metal. Okay, I'll shush now.