the idea behind the spray foam is pretty much what you said, it just makes for a better build and better insulation. since we are doing a total rebuild, any future plans are already being planned for like a solar setup; places are being setup and reframed for future upgrades, all of which are planned. the only upgrade I don't have now is the solar, everything else will be installed as soon as possible(already piled in kitchen lol)
the plan is this; right now its a flatbed truck with the walls, floor, and roof all in their single respective pieces in the yard, rotten wood being replaced. as soon as its done, the floor, walls, and roof go one and then the metal panels. from there, I do plumbing(only sinks and shower, using compost toilet), and electrical. I have a wave 8 heater so no ventilation needed, and a domestic cool freeze fridge so no venting there either.
I'm already looking at plumbing and electric options, but am unsure of what brand insulation to use. I probably will use a professional, I've heard the foam is around 600-700$, the mask & suit another 150$, and the pro would do it for a total of 900$ including cleanup. if thats the case, I will go with the pro as soon as everything else is done.
thank you so much!