I have just completed an add-a-level on a New Jersey cape cod home and am at the point where I need to decide how to treat the insulation issue up there. I might add that there is a furnace up there in the attic with lots of ductwork which the installer wrapped. The south facing roof will be completely covered with solar panels. The existing insulation on the first floor is admittedly not the best, but short of ripping out all the walls there wasn't much I could do that I was aware of. The 2nd floor living space and attic are ready to go, with one room having a trey ceiling (10 ft., not cathedral). I am considering closed cell for the walls, but unsure of what to do beyond that. Is spraying the roof deck with foam going to increase the possibility of a major problem down the road if a leak should develop? There will be 54 holes drilled for the solar mounting system, and even though the installer assures me they won't leak....well....of course they will say that! Will foam on the walls make a difference upstairs even if the lower level is not great? Will making the upper level and attic air tight come back to bite me in the butt because there will be air infiltration on the lower level? Soo many things to consider, I'm a bit overwhelmed and undereducated on this. Any experience with a similar situation? Or maybe point me to a link that might address solar and attic insulation? Thanks in advance.