Here is another picture showing the insulation and how it connects to the grate that I showed in one of the original pictures. I don’t see any rot or anything like that but it’s also never had heat running in it before, which I assume would make things worse. The fact it leads straight to where the insulation with no gap or anything feels all kinds of wrong… Would something like baffles be helpful? I could potentially push them behind the insulation to open a gap between the roof deck and insulation.