bathroom fan vent pipe insulation

[JonKvaalen]

What is the best kind of insulated vent pipe to go go vertically from the fan, through a cold attic and out the roof.

 

[Jadnashua]

You want it to be insulated, and be smooth on the inside so that it doesn't offer both resistance to flow of the air, or trap any condensation. The faster you can get it expelled without cooling off enough to get below the dew point, the better. You could use a metal duct, then install insulation, but if you choose a flexible plastic duct, make sure it is smooth inside.