dryer vent termination

[pitteach]

I am installing a stacked washer/dryer in a closet on the 2nd floor. I need some ideas for running the 4" vent. The closet does not sit on an exterior wall, but about 6 feet in. The ceiling is cathedral.

Ideally, I'd like to go out through the roof since it would be a straight 4 ft run.
My concerns are:
Lint on the roof (not a big deal to me)
Wind. Prevailing wind on this side of the house.
Condensation collecting and dripping down the pipe.
Ice formation on the roof during the snow months.
Other than this, its the perfect scenario.

Other options are:
Go through the floor between the joists about 6 ft to an exterior wall.
Problem is I may be adding on to the rear house where the vent will terminate and it may have to be moved later.
OR
Run multiple 90s through an attic space and terminate out an exterior wall about 20 feet away with minimal wind and totally out of sight. The distance and the # of 90s are within manufacturer specs, but it seems a little restrictive.

I guess I'm trying to talk myself out of going through the roof. Any experiences with roof venting?

 

[Jdoll42]

When my house was built (about a year ago), the contractor used rigid metal pipe up the wall cavity (2x6 cavity to accommodate the vent) straight up to a roof vent. The total length of the run is about 10-11'. The vent has a "flapper" in it with a rubber or neoprene seal to keep the weather out. I think the vent is actually designed to exhaust bathroom fans, but seems to work equally as well for a dryer. The only modification was to remove the screen on the outside that helps to keep the larger critters out; otherwise it just turns into another lint catcher. I have not had any problems with lint on the roof nor ice buildup nor condensation.

I could be wrong with this, but I think on a short run like that the heat from the dryer keeps the water vapor from condensing until it gets exhausted outside, at which point (even on the coldest days) it just dissipates into the air? Anyway, I don't know if this is the "right" way to do it, but it seems to be working quite well and I haven't seen any ill effects (yet?).

Here's a link to the vent they used: http://doitbest.com/Dryer+vents+and+hose-Broan-Nutone-model-636-doitbest-sku-261567.dib