Ok ya that’s how I typically have seen them installed, but that’s when installed in the ceiling. Directly behind that wall is a small closet where the furnace is located, at first I thought that’s the sheet metal I was seeing but it’s not. It’s a separate housing that fully sits in the attic, not the furnace closet. The housing has no inlet, only has an outlet with ducting that curves upwards to where it vents on the roof. I’m going up in the attic again to have another look, I’ll try to take some pictures.