So, there's the cost of the 2x4 curtain wall, plus the fiberglass in the stud cavities (if one chooses), the sheathing, the membrane, the rigid foam ($3,50 / sq ft for 6") the furring, . . .

Just curious, how does that compare with a sq ft cost for an installed SIP?

I like it 'cause I can get my hands on it and don't have to contract it out. Plus, I don't need cranes, specialty tools, and a crew of workers to get it on.