Also northern NH, north of the notches, though not by much. Insulation shouldn't be needed. I agree with more ventilation, up high above the chickens' heads when they roost, so that it can vent the rising warm ammonia-laden air while not blowing directly on their bodies. Having that on two sides is ideal. However, you'll have to think about how to protect that from blowing snow, maybe constructing some sort of awning.
That shed looks like it has a floor? Or is it just open to the ground? If a floor, I like deep bedding in the winter. (You'll find the difference between deep bedding vs deep litter addressed elsewhere on this board, I think in an article; at least as used here, litter is assumed to be on a moist surface where it composts in place, bedding is dry and does not compost.) I use shredded cardboard & paper in my coop but add some horse stall pellets under the roosts. I don't have poop boards; since my winter coop is in a corner of my barn, I go in with the manure fork a couple times a week and scoop what's built up under the roosts, but don't worry about getting it all and let the rest mix in with the bedding. (That's the idea of deep bedding.) When spring comes it gets a complete clean-out, and the bedding with whatever manure is in it goes right onto the vegetable garden.
