Insulating Heat Ducts?

[jon_taylor1981]

Not sure if this is where to post my questions. I am building 3 bulk heads around heating ducts, I have app 60 sq feet of pink fiberglass insulation left over from build a wall. As long as every space is properly taped on the duct work, could I use the pink insulation in the bulk heads? They are not exterior walls. Thanks

[timjimbob]

heat ok, but do not do that for ac ducts