Insulating duct run in vented crawlspace
Thanks (I think) for confirming what I suspected. Since nothing was done right on this addition, its probably 40 years old or so, Iím guessing the rectangular duct is un-insulated. I just finished replacing all the insulation underneath since it was reversed and while I didnít find any mold on the wood, the insulation was discolored in many spots with black mold. The rectangular duct runs to the wall and then Tís into round ducts that run under the joists to the floor vents. I guessing the real solution is to replace the square duct with round, run it under the joists and then insulate the new and old ducts.
Thanks again for your comments,