We have a new deck that attaches to the house and extends 18' outward.
To eliminate the moist exhaust from discharging under the deck we used
4" galvanized stove pipe coming from the inside of the ledge board on
the house all the way through the outside of the deck structure. We
fit a flapping louver on the outside flush with the deck fascia board.

While this seems to work just fine, it seems our drying time has
increased somewhat. Most likely this is due to the extended distance
the air must be "pushed" to exhaust to the outside. Prior to
installing this I checked the dryer manufacturer's site to calculate
the maximum length of the exhaust and our total was well within the
max.

So, my question is this: Has anyone every installed an auxilliary
exhaust fan on the outer end of a dryer vent before? Does anyone know
of a cylindrical fan that might fit into a 4" pipe? What would be
ideal is a section of exhaust pipe containg a fan that could be retro
fit on the end of this setup.

Anyone have any suggestions? Thanks for any ideas.

Bob