I have been researching a building project myself. Much smaller scale. There is a lot of good information here. I would like to add a few items. Be cafeful if you use spray foam and fiberglass. This is called a hybrid system. Many of the spray foam companies will squirt 1 inch of spray foam on the back side of the sheathing, then tell you to put fiberglass batting over it. They say the foam is the vapor barrier and you can save money with fiberglass. This does not conform to the NYS Building Code. 2 inches of closed cell foam are required to meet the Bldg Code for a vapor barrier. Open cell foam requires nearly twice the tickness to create a vapor barrier. If you install a hybrid system, be sure a proper vapor barrier is installed. If not, you will create the perfect environment for mold. I had the attic in my house spray foamed. It is expensive. About $1/board foot (12"x12"X1"). But it is great if done correctly. Closed cell foam has an approximate R value of 7 per inch. The next piece of advice is to hire a qualified engineer or architect. Like mentioned before, they can calculate snow loads the correct way. As we all know this winter was tough in upstate and central NY. I still have 12"-24" of snow on the lawn. My information comes from my coworker who is the Building Codes Enforcement Official for our town. We share an office and have had many "lessons learned" conversations about residents either getting swindled or that had contractors that know everything because they have been in the business for "x" years. I have seen many "experienced" contractors have their world turned upside down after being educated by the CEO. Most contractors don't have a copy of the Code, or even know how to access it for free online. They rely on the CEO to find any issues during the construction inspections, especially if an architect or engineer did not do the design. Good luck with your project! Remember, you usually get what you pay for. One last item I just remembered. Before you do anything at all, go see your Zoning Enforcement Official to discuss your proposed project. I am the ZEO for our town. I've had numerous residents anxious to get the shovel in the ground, find out that they are in a NYSDEC wetland, Land Conservation District or FEMA designated floodplain. Better to find out these issues before you start to spend any money. Don't be my brother in law who built his 32x64 pole barn on top of a 60" water main. He had to move the pole barn. D'oh! He didn't know the number for 1-888-DIG-SAFE. He was also an "experienced" contractor. All you need is a few trucks with magnetic signs in NY. My apologies for the extended rant.