Winters in north central Iowa are ridiculously windy and frigid, too. My coops are not insulated, and while I worry all winter long, my chickens are usually fine. With proper ventilation, chickens are surprisingly adept at managing the cold.
Having said that, this past winter was a rough one. I lost one hen during a -20-something night when four chickens piled into a single nest box and she, a Bantam on the bottom of the pile, smothered. That coop isn't insulated, but has lightweight paneling attached to the framed walls for easier clean up.
On a happier note, congrats on your basement brooder babies! And, welcome to BYC, where a lot of experienced, generous folks will be happy to offer guidance whenever needed!