Double wrapping bathroom exhaust fan ducts in attic to increase R value

I have 2 baths that that I am planning to vent via 6 inch metal ducting and flexible ducting.  I am planning to vent with an in line Fantech 200+… I have 2 baths that that I am planning to vent via 6 inch metal ducting and flexible ducting.  I am planning to vent with an in line Fantech 200+…Read MoreGreenBuildingAdvisor