Ducting Systems and Air Ventilation - Dryer ducting under deck?

Our house has a gas dryer in the full basement that vents out through the little window above. (I can't move the dryer because that's where the gas line & elec. outlet are.)

We plan to build a deck just above where the vent comes out of the window. (Yes, the window will get covered by the deck.)

Is it better to:
1) let the dryer vent itself under the deck, or
2) extend the dryer duct 5 feet to the right (requiring a 90 turn)?

Option 1 is what we have now -- works fine, but will soon be under a deck. I'm concerned about rotting the deck.

Under option 2, I'm concerned about:
A) lint build-up in the bend
B) the length of the duct
C) exposed ducting in the outdoors (northeast winter). I'm considering boxing the exterior sections of duct in plywood with some insulation. (All under the deck.)

Attached is a crude picture.

Oh, re-routing the duct on the inside would require the ducting to run along the ceiling of a finished room.



http://img522.imageshack.us/img522/8349/dscf0014qep.jpg

yes #1 is a bad idea. Rot plus CO. #2 would be best but I would like to see the duct ran inside and then out past the deck.

I vote for # 2, which is similar to my set up. Just be sure to use metal ducting and secure it so it does not pull apart (PITA crawling under the deck in a snow storm). My setup makes several 90's without problem. I do check and clean it about once a year.

Thanks. Any thoughts on condensation, freezing, or the duct's pitch?

Insulation outside?

The Airman has spoken. I would normally have nothing more to add.

However, you should look at the install manual (check mfg website) for venting specs and follow them.

Thanks guys.

So, what about the idea of boxing in the duct under the deck? Plywood box with rigid foam? Batt? Is that overkill?

Any recommendations on the pitch of the duct under the deck? I've read both to pitch upward (to allow steam to escape) and downward (to drain condensation)...

Always pitch the dryer vent downward. Steam will be pushed out by the exhaust, but you really don't want water collecting anywhere. I'd say it's even more important here since it looks like it will be quite difficult to get under the deck after it's in place.

I would seal the duct somehow in pressure-treated plywood. You'll want to keep condensation from forming on the exterior of the pipe in humid weather as it may cause the pipe to rust. It will also add another layer of protection from critters finding their way into the house.

I would run it in the room to the side of the house at the ceiling, ( as airman said), and exit through the rim joist. Anything outside will condense the moisture and trap lint, causing a possible fire. We are not allowed to run dryer ducts in concealed wall spaces, this would be the same thing in a box. Instead of a 90*, do two 45's*. Much better on flow restrictions and back pressure. Use foil tape, not screws, and tape every joint in the elbows (weak points), supporting it well.
Be safe, G