We recently moved our dryer into the garage stacked on top of a washer. The easiest way to vent it was straight up about 6' into the attic, then a right turn in the attic 12' out the back of the house.
I had an appliance repair guy out to help with some propane connection issues and he said we shouldn't ever vent a dryer 'up' as it makes it a lot more likely to accumulate lint.
While I have no reason to doubt him, this also isn't something I had heard before. Coming from MN where most every house has the dryer in the basement and vents up, it seems perfectly normal to me.
In addition, prior to moving the dryer, it vented 'down' through our crawlspace and that was still caked with lint when I went to clean it out.
The question: Is it true that venting a dryer up causes more lint buildup and, if so, to what extent is it a greater problem than just venting horizontally or down?
I'm fine cleaning the vent once or twice a year and if that's what I'd have to clean any vent, regardless of direction it goes, I don't know that I want to spend the effort to re-route it underneath the house (which wouldn't be all that easy).