My silkies are about 6 weeks old, and their feathers are coming in nicely. At what age should I move them outside to the shed I've set up as a coop? I live in Maryland, and it sometimes gets cold, but typically our lows are in the 30s. Also, since I'm moving them to a shed while it's still cold outside, are there any special requirements or equipment (i.e. heat lamps) I should set up?