our chicks are always outside in the coop, just in a seperate area with a heat lamp. Then at about 3 1/2 weeks old or until they have mostly all their feathers we put them in the whole coop (still away from the older hens) with a heat lamp hanging in a corner so they can go under it if they are cold or stay away if they are hot. Then, when they are about 6 1/2 weeks old we turn the light off. Our chicks right now are 3 OEGB bantams, 1 silkie, 1 mille fleur D'Uccle bantam, 9 black sexlink, and 6 golden sexlink. And they are very healthy and very talkative/lively.