I live in central Minnesota i,m new to all this. 1st year. I have 25 plymouth rocks and 25 goldlinks. At 2 weeks old I wanted them out of the house. they were in a 4x8 brooder. took the brooder to the uninsulated coop which is 13x13 . Theirs a door on the brooder I left it opened so they could run around the coop. I had one 200 w red heat light 2 1/2 feet above the brooder on 24 hours a days. if they got cold they went in there. after 3 days I opened the door to the 24x13 run they'd be out there for hours at 45-50 temps . If they are cold they will find the heat. TODAY they are 5 weeks old I,m unplugging the heat light tonight. Personally with the experience I,ve had the last 5 weeks I think the heat thing is way over rated !! Have it available to them and they will go to it if they need it !!
p.s on all nights when they were only 3 weeks old i,d go check on them at night it would be in the 30's half the chick were always running around eating drinking playing outside the brooder where the heat is.