 It's almost like wet insulation, if that explains it any better. But if you've got it going up through the roof, the contractor should have put a bird shield on it at the top. And that's another problem because the bird shield has a little wire, and it goes up through there, and a little wire catches. And if you use that dryer very much at all, if you've got a household with you and your wife and a couple of kids, that thing's going to have to be a major clean job every other month.