Sounds like that guy basically did a mini coop within a coop...a fully enclosed huddle box with doors.
Most fabric stores sell a thick, transparent vinyl "cloth" that you could staple up over the wire sections (like you said, leaving up to a foot or so along the top) come winter time. You'd have to screw battans along the edges to make sure wind didn't pull it loose. That would be your simplest route to winterizing. Well, tarps would probably be simplist, but the clear vinyl would allow the sun in, would keep blowing snow out, and would make the coop a much nicer place to visit when tending the flock in winter time, plus it's much easier on the eyes than tarps. And you may STILL want to do the huddle box (but I'd forgo the light in a small space like that), but not so fancy a one. Whatever you go with, you want them be out of icy drafts come winter time. If your chickens are anything like mine their first winter will be their hardest; my girls handled winter much better the 2nd year.
Most fabric stores sell a thick, transparent vinyl "cloth" that you could staple up over the wire sections (like you said, leaving up to a foot or so along the top) come winter time. You'd have to screw battans along the edges to make sure wind didn't pull it loose. That would be your simplest route to winterizing. Well, tarps would probably be simplist, but the clear vinyl would allow the sun in, would keep blowing snow out, and would make the coop a much nicer place to visit when tending the flock in winter time, plus it's much easier on the eyes than tarps. And you may STILL want to do the huddle box (but I'd forgo the light in a small space like that), but not so fancy a one. Whatever you go with, you want them be out of icy drafts come winter time. If your chickens are anything like mine their first winter will be their hardest; my girls handled winter much better the 2nd year.