Right now plan looks like 25 layers to start out. Maybe 10 Cornish x too. Not sure to start all at once or break down in smaller groups. What sq ft box would I need for a brooder. And if done out in the garage or barn what would be the lowest temps safe. Right now our temps are running in teens to 40's on some days. Mostly around 20-25 though. Would a heat lamp do in these temps? Or should i wit a month or so.