Actually, brooding in a coop or barn was common practice before people began treating chickens as pets. The indoor brooder has become so accepted that now folks feel guilty for doing something wrong when they consider brooding chicks outdoors when this practice is actually more beneficial in many ways than brooding in your house.
I brood in my covered, secure run, and the chicks become cold hardened early on, feathering faster, and weaned off heat sooner. When brooded with adult chickens watching their development, the chicks become full members of the flock from the start, and integration is a breeze.
I write about how I brood in my run here.
https://www.backyardchickens.com/ar...and-start-raising-your-chicks-outdoors.71995/