Thanks for the info. I don't have a basement nor a garage and nowhere cool to keep him. The solarium is it. The chickens in the coop don't roost. They sleep on a nesting box that is just off the ground, all piled together. There is a shelf they could roost on, but they aren't interested in doing so. I'm afraid to put him in with them after dark. They are quite observant of my every move, even after dark. I think they might peck him to death, still, especially the big huge StepMama and the two other Roos.
A Dog Crate might work. Where would I buy one? It would be worth a try, I feel.
He has the full run of the solarium and it has high shelves he uses as a roost. I don't think it's terribly hot in there because he roosts at the end where the heater is, and if it were too hot, I think he'd move down to the end that has less heat. I do turn off the heat during the day, as long as it isn't freezing the plants. Today it said it was 46 F in there. That is the coolest I have seen it.
When he was tiny and I first put him in the solarium and he was only a day old, the temp registered only 82 in the middle of the night (when it dawned on me I should get up and check on him to see what the temperature was in there when it is cooler outside than during the daytime). It should have been 90-95 F at that stage of his life, with no snuggle-mates, but he survived this bad boo-boo, and I don't know how long he was in temps that cold, but luckily there were no drafts. This was late September. Another time we went away and I asked the neighbor to check in on him, and he didn't, and when we got home (I had put him in what I thought would be a less hot location than in the solarium that day), the thermometer said it was 112 degrees F! Poor little chick. It's a wonder he didn't cook to death. He was still tiny. But he got through that heat stress, too.
You don't suppose I could just move the little outdoors Bantie or one of the hens his same age into the solarium with him until the spring warm-up, do you?
I suppose another option would be to let my plants in the solarium all die over the next 2 weeks (he has eaten up so many of them, anyway), and just let him live in there. It would get pretty chilly, minus the drafts, helping him to acclimate to colder weather in a gradual sort of way? But he really seems to enjoy jumping in the pots and chewing on them, so it might be depressing to him if they all died.
A very sticky problem, indeed.