What can I use to adequately insulate round rigid metal ducts?
Owens Corning's 3" Type 75 SOFTR® Duct Wrap FRK, touts and installed R-value of 8.3.

If it's not in-stock at your local big box store, they should be able to order it for you.



I am in no way affiliated with Owens Corning, and do not recommend or endorse the use of any of their products or services.