Sounds like the older "envelope house" idea. (google "double envelope house") The ones I have inspected had a crawl space open to the frame walls and attic. The walls were double with about 12 inches of space between the interior and exterior wall. In my opinion they are a fire trap.
They "always" (at least the 2 I have seen) have homemade passive solar crap that leaks, hence the "miniature biosphere" between the walls.