I would proceed as follows:

1) I would make multiple sets of the drawings according to which Tim framed 
   the house. (This is easy for me to do.)
2) With these plans in hand, I would canvass insulation specialists: 
   a) at (possibly numerous) Home Depots,
   b) at (possibly numerous) Lowe's,
   c) at as many Nantucket insulation contractors as would talk to me,
   d) at (possibly numerous) insulation contractors on the mainland,
   to ascertain their interpretation of code requirements and of the
   techniques by which they would comply with these requirements.
3) Based on the information obtained from 2) above, I would make a written
   plan of exactly with what materials and with what techniques I proposed 
   to install the insulation.
4) I would submit this written plan to the Nantucket Building Commissioner
   requesting his prior approval, or his directives what I should do differently.
5) I would precisely follow his directions and then submit the completed 
   insulation installation to him for inspection.