Uninsulated Ducts in Unconditioned SpacesHeat transfer through duct walls can contribute significantly to energy losses. Conductive heat losses are typically at least as great as the energy losses due to air leakage. If the duct system runs through an attic or vented crawlspace and is not insulated, you can be sure that much energy is being wasted. If the ducts are in a basement, you will have to weigh the fact that insulating the ducts will cause the basement to get colder. If both the ducts and the basement walls are uninsulated, you should consider insulating the basement walls instead of the ducts.
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