I live in the Northeast and recently purchased a 1940s-era ranch house with metal ductwork running in an uninsulated crawlspace under the house. I want to insulate the ducts before winter approaches. Question: since the ducts are used for heating and cooling, can I wrap them with faced fiberglass insulation? Or will condensation form under the insulation during the air conditioning months and create mold or destroy the effectiveness of the insulation? How do I deal with that condensation issue? Any suggestions greatly appreciated. Thank you!