Well, remember you will need ventilation in wintertime too (draft-free does not mean airtight
- it just means 'don't point a cold wind right at the chickens' bodies')
And if your wall space will be limited (it might help me understand this if you could post a sketch of your plans?) then it seems even more important to have openable windows. Honest, openable windows are not that difficult.
Of course the simplest thing is to use pre-made windows (from a Habitat for Humanity store, building materials recycling store, garage sales, craigslist, freecycle, acquaintances remodeling house, etc).
But if you can't or don't wanna, it is still really pretty simple to make a wood-framed plexiglas window that hinges at the top so that it tilts out to open. If summer heat is an issue you can make it so it's completely removeable for the months of July and August
Also, where in New England are you? I am wondering whether you are overestimating the need for extreme insulation and underestimating the chickens' own heat-production and tolerance for colder temperatures. Again, a sketch of your coop plans might be helpful.
I really don't think that a translucent roof or skylight is likely to be your best bet in a cold climate. (Also it is likely to give you problems during sunny winter days of getting the coop TOO hot, which requires that you open even MORE ventilation to avoid overstressing the chickens...)
Good luck,
Pat