Think about potato houses, if you in centeral Maine there may still be some there. When guys build a new one the good farmers have them sprayed on the inside. This is usually the most expensive part of the whole thing. A good farmer will tell you they will heat themselves with some potatos in them, they need to vent out the moisture and some heat with it to keep it at 38F. I built my own home in 2009 100% myself, 3,200 square feet heated. Air tightness is the #1 priority, if you do that with spray foam, or some type of sheet good and pay attention to EVERY detail or posibility for an air leak as has been said you will be worlds ahead. Read about building science (we learned alot in the 70s and 80s when things started to tighten up, and what that does to the building envelope. Think vapor BARRIORS not retarders (hint metal is the only barrior, plastic or any petrolium is only a retarder). Don't let people tell "oh that place will be too tight" or "you need to let it breathe" with proper building science and correctly applied vapor and moisture control it will breathe in the correct way and wind will not affect your heat load. I'd use Roxul over fiberglass any day the 30% upcharge is well worth it, once you ues it, you will dispise any fiberglass insulation. Use blown in cellulose over the Roxul in the attic to fill in all the voids around trusses, and as ihookem said use heel trusses with 16" heels for good ventelation and leaving you plenty of space for that insulation, use some type of rafter-mate so when you blow in you will contain it to the attic and not let it fall to the soffit area.
Keep in mine that electrical penitrations are one of the biggest air leak areas, spray foam is your friend here. EVERY house I've worked in had had cold air coming in around all the outlets, I avoided this by breaking code and useing shallow boxes and having my wireing in the hidden airspace behind the drywall. For what it's worth think low temp heat emitter and then you can go with some type of solar (thick radiant slab works best as storage and emitter) then a small wood stove to make up the difference or a boiler and storage, but as Fred said it may never pay for itself. Solar orientation is key also, and the best windows you can afford, I have all triple glazed Paridigm out of Portland ME.
You can spend it now and save for a lifetime, or save now and spend for a lifetime. And a lifetime is a LOT of money.
TS