Jumping the Box?

[Bloody Idgit]

I recently had the 2nd floor of my cape style house removed and a new one built so that we could add a bedroom and have 8 foot ceilings. We initially hired a contractor to do all the framing, the sheathing, the roofing and wrap the house so that we could proceed with the rest. After the demo of the second floor the contractor told us that if he tried to build on top of the existing 2nd floor plywood subfloor he would risk damaging the plaster ceiling of the first floor so he asked us if we had an objection to his "jumping the box". This essentially meant installing new floor joists, such that the bottom of the new joists was a couple of inches above the top of the old joists (- ow the distance between the first floor ceiling and the second floor subfloor was was more like 18". The problem, which I did not notice until the builder was done and I was insulation, was that the soffits vented into the space between the old and new subloors which. This allows exterior air to enter throught the soffits and circulate between the floors, throughout the whole footprind of the house. I did the best I could to block off all of the air flow by stuffing insulation. This was not so simple as the sheetrock had already been insalled and it mean navigating through very tight spaces - good thing I am not clostrophobic. I am know of another area I have to hit - hopefully I can reach it by removing the soffit outside and doing the stuffing, because the access from inside is minimal.

After discoveging the problem I notified the builder and said that I thought the soffit should have been structurally boxed out and isolated from the space between the old and new floor, but he contended that it was the responsibility of the inslulator. I am curious to hear what people on this thread think.