Insulating a double wall

[jwhite]

I am working on an old timber-framed building. The exterior walls are not plumb so it was decided to go with a double wall to get the inside plumb. We are kind of at a crossroads here, not really sure of how to insulate it. The two walls will be no more than 3 inches apart.
I have seen large quantities of reclaimed ISO and XPS foam insulation available recently at attractive prices. It could be ripped and foamed in place in the stud bays with 6 in. fiberglass inner wall or placed in sheets on the inside of the outer wall with fiberglass or cellulose outside.
We could insulate the inner and outer with 3 1/2 inch fiberglass and put the middle layer in horizontally.
I am concerned about the dew point as the house is located in the northern NY.
Any thougths or comment would be appreciated.

[mike maines]

Seems to me like a good candidate for dense-packed cellulose. Fitting in all those pieces of rigid foam would be very labor intensive.

What are you doing with the roof?