Just added to job instructions: insulate ducting in attic.They should be fine if you start with the uncrimped end of the pipe at the fan. Best to insulate the pipe that is in the attic if you are in a cold in winter area. Other wise you will get a condensation buildup.
I considered insulated HVAC ducting, but opted for the traditional finger-slicing stuff, to reduce friction loss. Too anal?
My gable vent (the endpoint of my exhaust) is close to twenty feet off the ground. I wonder if I need the carbon filter? It is nearly as high as my plumbing vents. Honestly, I don't know what to expect. I've always been a consumer (only).