I use a red heat lamp but any incandescent that provides enough heat will do. The red color is supposed to be soothing to them. And I only heat one small area of the brooder. The rest cools off to ambient, whatever that is. Last fall, that was sometimes in the 40's or 50's Fahrenheit.
I...
I keep my brooder in the coop from day 1. The adults roost in that same coop and lay eggs in the coop. They have access all the time, but I do lock them in the coop at night. I use a red light as a heat source for the brooder and have not seen any problems with the adult chickens roosting at...