Something I did with my Ecoglow that worked and may work for you when you go to transition them outdoors: I put the Ecoglow under a box, sort of a combined heating plate and huddle box, without the assembly of a mama heating pad. The box was only just barely tall enough to accommodate the Ecoglow at its highest and I left three of the sides intact so heat could only escape out one side. I cut out the bottom so they would be on the ground and not soggy cardboard. It was actually the box for my incubator, if that gives you the idea of its size. I put the chicks outside at two weeks with this in their brooder, a puppy play pen inside the coop that was 30x90 inches. They did well in there until I felt comfortable letting them have the run of the coop about 10 days later. This was before this super cold weather, but still December in the mountains of Virginia.
Another idea, and I’ve done this, too: if you decide it must be the basement, once they are weaned off heat (since there’s only one Ecoglow, same here, too) maybe you could split them up into separate brooders? This worked well for me when I had other chicks still coming in for the night but spending the day outside. Once they don’t need the heat inside, they can sleep in anything that can contain them.
Another idea, and I’ve done this, too: if you decide it must be the basement, once they are weaned off heat (since there’s only one Ecoglow, same here, too) maybe you could split them up into separate brooders? This worked well for me when I had other chicks still coming in for the night but spending the day outside. Once they don’t need the heat inside, they can sleep in anything that can contain them.

