I have six 12 week old chicks in an open style coop/run (our first chickens.) They've been outside for about 3 weeks (in our living room before that) We live in the Phoenix area so in the long run we are more worried about heat than cold, but while they are young I don't know what low temps they can handle. We built a 4x2x2 plywood box for them to use while they are young and put a 100 watt red heat lamp at the top. We turn the lamp on in the evening and off in the morning. The box is open to the ground (shavings) and enclosed on four sides and top except for a door. The low temps will be 35 to 40 over the next week. Are they going to roast? At what low temp should I turn the lamp on? At what temp/age can I remove the box? Thanks for any help you can give. Here's a picture... (This is before my sister took a few of the chickens) A roost will be added this weekend and the nest boxes will be added soon also.