" Some were against kraft facing in general. What's the final verdict? I trust buildingscience.com but I can't really find their opinion on it."----------- depends on location, as Joe said. If in Zone 1-4, no vapor retarder/barrier, except 4 coastal; http://www.buildingscience.com/docum...commendations/
IMO, use some PIC (foil-faced iso foamboard) behind the warm supply ducting, has a high heat factor of 200*F or something, google it. Ask local AHJ. I agree with Nailbags, no poly over kraft faced.
Clothes taking longer to dry?
Clean the dryer screen in HOT water if using fabric softener sheets.
They leave a residue that impedes air-flow, costing you money.
Clean the ducting in the last six months? 17,000 dryer fires annually!