@aart didn't you recently have a marked up photo showing ventilation on this type of shed?
I live in NE TN so doesn't get to cold. Had below freezing temps for 2 weeks this year.
I grew up in the Cumberland Gap area of East Tennessee. I can remember several times it got below 0 F for a spell. Some winters were not too bad but most winters it got downright chilly a few days. Has the climate really changed that much? Even the worst winters I remember weren't all that bad for chickens.
What I see is an all-metal building with no wooden studs to hang anything off of. No overhang, which might allow rain to blow in. I'd guess 8' high before the roof starts. It is already assembled. Does it have a ridge vent?
This is a fence and not sheet metal, but this shows how I attach a support. I take two pieces of wood and make a sandwich around the metal or fence, screwing them together. This stiffens it up tremendously plus gives me something to attach things to. This idea may come on handy for certain parts of this.
Not having an overhang makes it a bit more challenging. I'm not worried about water running off the roof but rainwater blowing in. You don't want costs to get out of hand either. For winter I'd want openings in three or four walls higher than the chicken's heads when they are on the roost. Maybe some type of louvered gable vent. These come in different sizes. Maybe you can find something on Craigslist or at one of those Habitat Restore shops to keep costs down. If you have a ridge vent you don't need a lot of gable vents but don't be shy about putting these in if you don't gave a ridge vent.
In summer conditions change a lot. Heat is more of a threat in summer than cold in winter for you. You need natural light in there. I'd want at least one window down at roost level. Two might be better. It would be nice if you could open it in summer and keep the worst of the rain out. You are not far enough north that it needs to be on the south side to let light in during the summer. I like my window on the north side where it is cooler. Again, see what kind of window you can find on Craigslist or at a habitat store instead of buying new if you can. Or build your own windows. Frame out an area and cover it with hardware cloth for predators, then angle a piece of Plexiglas to keep rain out. In winter cover that opening with the Plexiglas.
I'd also want an opening pretty close to ground level on the north side. Hot air rises if cooler air can replace it. If you cut out and frame an area on the north side and cover it with hardware cloth the air coming in from the shaded side will be cooler than the air from a sunny side. In winter, cover that to stop cold breezes.
If you put your nests right up against that metal I'd want then on the north side in the shade. You don't want your nests to turn into ovens so don't put them on the hot sides.
The idea in winter is not that you need to give them a warm place. The idea is that you give them a place they can keep themselves warm. That means out of strong breezes and low moisture levels. Good ventilation in winter allows the moist air from their breath, their poop, and any vapors from thawed water to escape. If it is up high any breezes will be over their heads. In summer a cooling breeze feels good to them.