Couple of notes. I worked for many years in solar heating, both installation and design, including some passive, and many solariums (Northen California). Definitely do not insulate inside the foundation, there is no point. Good thermal mass, as another noted. Roof, insulate the north side, 8" - 12".
I viisted a home-made greenhouse in northern Massachusetts that met your needs. He was growing cirtrus. Don't recall the name, but Eric Toensmeier (sp?) took us there during a Permaculture event.
This man made his own trusses, brilliant. He made a form from stakes on the ground, in a quarter-cricle; then bent a 1x4 pine board and clamped it. Then he glued and screwed 2x6 blocks ( I would recommend 2x3 on the south, 2x8 or more on the north), then bent another 1x4 over those, glued and screwed. Instant curved truss.
Concrete floor and foundation, insulated. (Btw, as one option, insulation is as effective laid flat, just underdroud, out from the perimeter.)
He used a center beam, end to end, with the trusses from beam to foundation. On the south side he just stapled plastic inside and outside of the truss, instant double-glazing. On the north, he covered the outside with this plywood, then asphalt shingles. Inside on north I don't recall the finish, might have just been plastic, or thin ply again.
End walls were insultated.
Even though your structure is different, with your windows, the same technique could be used.
Good luck!
Christian Sweningsen
