I live in the Pacific Northwest, in a moderate climate. My house is about 10 years old, and can be described as a nicer starter home...not a slapped-up shack, but not a high end custom build either. It's a 2-story, with the laundry up. My clothes dryer is electric.
Recently the dryer has been taking longer, and longer to run...even after vacuuming the inside of the dryer etc. So, up to the attic.
When the house was built, the dryer was vented into the wall, then straight up to the roof, through unheated attic truss space. While it does have rigid metal tube and is wrapped with insulation, the tube does NOT go to a dryer vent roof cap. Rather, the tube stops just below a roof vent located about a foot off the ridgeline. Needless to say, the bug screen on the roof vent got all jammed with lint, and there is lint all over the trusses etc. I've cleaned everything out the best I can, and have now waited out the worst of the winter. I had to tear out some of the bug screen, which puts lint on the roof, and has the potential for a real buggy mess going forward.
So, I want to re-rout my dryer vent. The nearest exterior wall is a bit less than 15 feet away, so I'll still need to go into the attic space. I'm thinking of doing a 90 degree bend a few feet above the insulation in the attic, then run it to an exterior wall, where I'll put a standard dryer vent cap with a flap. I'll use rigid metal tube and insulate it.
My big question is - should I run the tubing dead level, sloped up slightly towards the exterior, or sloped slightly down towards the exterior? I know that I need to be concerned about leaving a dip in the pipe where condensate could accumulate, but am not sure how to compensate for it.
Anything else that I should know? Something that I'm not thinking about?