Well, after taking a closer look at my hood liner (mine's removed) I found a small spot chewed away by a mouse (don't ask) Anyway, I noticed the aluminum foil material inside, so it does act as a heat insulator as well. My bad.
I guess if I had one of those SRT "toaster ovens" under my hood, maybe I would be a little concerned. Or I'd open up my hood scoop to let the cool air in and not worry about it.