I have used UCLA's HEED and various other models. The heat loss in this 1600 sf house  should be ~ 25k btu /hr at the design temp of 10 degrees F.  Of course, with about 50 tons of concrete in the house, the mean temp of ~ 30 degrees has more relevance. HEED estimates that the house will stay between 55 and 85 with no additional heating and cooling. I suspect it will come down to how well I can insulate those windows on cold nights. For the moment, I am aiming for R4 or R5 using bubble wrap radiant in shoji screen shutters.     
Passive solar is a crap shoot in south central Pa even though winters are moderate. Some Decembers Santa Claus makes more appearances than the sun.  I bought a wood stove boiler to stand in during gray stretches and to heat 300 gallons of water storage for DHW and on-demand radiant at some unknown interval. It should add a degree per hour to the slab at full blaze, or about 10 degrees/hour to water storage. A heat pump water heater will take over DHW in the summer and knock down the humidity in the house in the process.
My goal is $0 for heating and cooling, not counting chain saw gas, but I'll decide after the first winter if that's more wood than I want to handle.
Truth be told, firewood is quite attractive compared to my task at the moment.

 

Nice plan Todd...I like Wright too, except for his kitchens. Suggestions for your kitchen:

1. Both your refrigerator & oven open into a tight (no dimensions so not sure, but looks ~3') walkway; plan on min 3'6"  to max 4' walkway between island & wall base cabinets.
2. Try massing the double oven next to a pantry on the back wall on the opposite side near the wood stove
   
3. Better yet, consider a walk-in pantry, I gather that your site is not near the city
4. If possible design refrigerator access exclusive of island; thought about back wall on left, but it's next to the wood stove, better for the ovens.
   
5. Think about how you prepare meals, most stuff from the refrigerator either goes in the sink (washing veggies) or on the table (milk); the frozen stuff goes in the microwave. Make your kitchen user friendly.
6. I'd be inclined to put the big sink in the island and skip the little sink.

On another note, Wright added interest to his designs by varying floor and ceiling heights. I'm not a fan of steps or stairs, but varied ceiling heights and ceiling treatments will add interest and make your home more intimate.

Cheers, Sabaya

I put pantry/closets on each floor next to the chimney element because it is not clear at this point how much of the mechanicals I can shoehorn into this tight space. I'll have a better idea next week after my plumber drops the pump in the well and sets up temporary service.

Given my druthers, I'd set the refrigerator next to the woodstove. (No problem with an AAC wall between the two.) This was my kitchen in my last house, and it worked very well. With two sinks, separate work spaces on the counter and the island and 42 inches between them, two people could work in it with minimal conflict. Meanwhile, the fridge was handy for everyone else. The design you pan is second best. The fridge is still handy. The ovens are tucked away but only one or two people tend them, and then rarely.

While Wright's kitchens were cramped and poorly equipped by our standards, his Usonian designs broke new ground by bringing the work area into the living area. You still had worker bees on feast days but at least they weren't banished to a separate room.

For my money, the main sink should be an arm's length from the dishwasher and the cupboards. Everyone in my house loves to cook. No one volunteers to load or unload the dishwasher.

If you look at the graphics, you'll see two ceiling heights: 10'6" and 8'8". If you look really close, you'll see that the second floor "floats" inside the first, carried on beams on two sides rather than the first floor walls.