I have some chicks that are about 6 weeks right now, youngest might be closer to five. Right now I've got them inside in a rabbit hutch which is good for small chicks but there's eleven of them and it's getting awful crowded – this is the first time I've had this many. Right now I've been putting them out in the morning and bringing them in to sleep, which is working fine, but I'm wondering what's a good time to start keeping them out overnight?
It's been getting down to about 50 here, but it's forecast to go as low as 45 next week. I do have a heat lamp which I've been putting out there, and when it gets into the evening, they like to hang out under it. There is a breeze that comes in which they have some shelter from but there isn't a perfectly enclosed area right now, the closest is an elevated (repurposed) rabbit hutch which they don't seem to like going up into much. That might change if I reposition the heating lamp, but I think right now they can't get into it easily.
Anyway, my main question is how big/feathered they need to be for these temperatures WITH artificial heating access. They're mostly feathered but a lot of them still have a bit of chick down around the neck and the feathers not quite all the way developed.