HVAC guys are running a vertical duct (supply and return) from my basement to my 2nd floor attic. It will run adjacent to an exterior wall and will eventually be enclosed in a drywalled-in vertical soffit. My question is in regards to the insulation in the exterior wall cavity: Would the metal of the ducts touching the kraft-faced insulation be enough to provide the fire protection that kraft-faced insulation needs?
Or should I go with unfaced insulation and just use 6 mil poly as my vapor barrier? Or maybe a combination of unfaced insulation and a foil faced foam board?