Can you open up more ventilation?
Add shade? A cheap picnic pavillion or even a tarp strung on a clothesline would probably help more than mylar bubblewrap. :)
:frow from Moore County in the Sandhills.
Having the right breeds helps. As a general rule, big single combs and clean legs -- though Brahmas are weirdly heat-tolerant up to a point.
I found that my Silver-Laced Wyandotte doesn't take heat as well as the Australorps. I've ordered more, this...
Welcome to BYC. Where, in general, are you? Climate matters.
Here's my article on Hot Climate chicken-keeping: https://www.backyardchickens.com/articles/hot-climate-chicken-housing-and-care.77263/
VENTILATION is #1 -- lots and lots and lots of airflow in both coop and run. The usual guideline...