They're still sleeping in a pile in the bedding. One or two have been testing the possibility of roosting on the edge of the now-open integration pen.
They will move up to the roosts when they're ready. As long as they're not in the nestboxes they can sleep where they want to. :)
I'm at the border of garden zone 7b and 8a and I find it reasonable to just bring the water in at night.
It's almost never significantly below freezing in the daytime and when it is I can just change out waterers.
Here's my article on coop ventilation, which is just as critical in the winter as in the summer:
https://www.backyardchickens.com/articles/repecka-illustrates-coop-ventilation.77659/
We don't need to keep them warm, we just keep them dry and out of the wind and they keep themselves warm.
It's been in the mid-to-low 20's overnight here in central NC and I have 6-week-old babies in an open-air coop without heat. They're fine and waiting for me to bring the water back out. :)...