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I'm installing properly sealed round metal ducts in my unconditioned attic for heating and cooling. I've probably got 100' total of 6" duct to cover. I'm trying to achieve an R-8 insulation value, but the big box stores only sell R-6 Frost King wraps. Can I use un-faced insulation batts (that you use in the attic), and then wrap a foil layer around it? Any other suggestions?

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Why do you need R-8? Why must you buy from a big box store? – Tester101 Nov 6 '13 at 18:02
I have found it easier and cheaper to actually wrap the entire round duct in an insulated flex duct and just "specially" wrap the points where it branches off. – Matthew Nov 6 '13 at 18:53
@Tester101 R-8 seems to be recommended for energy efficiency in unconditioned spaces. Do you recommend otherwise? Big box isn't a requirement, just the place I looked first. – Jason Rikard Nov 6 '13 at 19:16
up vote 1 down vote accepted

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.

enter image description here

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

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