Actually, Jimbo, I think getting slightly off the track is one of the primary benefits of a forum such as this, which is why they call it a "thread." It tends to weave around a bit and generates productive conversation in relation to the solution to a topic. After contemplating and reading the conversation, I think I see the point, though as we know, most likely, millions of homes have the dryers vented in this manner. Hot air does rise, but all air, hot or cold, has friction, whether forced or just lightly pushed as the case is in a dryer. I wonder out loud, if a larger diameter pipe could be used in the vertical exhaust? Many homes are designed so that the length would be the same to reach the outside, whether it is vertical or horizontal...? Any thoughts?