how old to go outside

[camaro10]

This is my first time raising chicks. My 15 BR's ( all survived ) are about 3 weeks old. I live in Maine. How old do they have to be to put them out in the coop at night and do I need a lamp in the coop for warmth? They are growing like crazy everytime at look at them.

 

[SundownWaterfowl]

I move mine outside at around 3 weeks. They get a heat lamp at night, and during the day only if its cold, windy, or raining. I use a wire brooder and cover it all up at night.