Hi I am looking to insulate circular metal air ducts in my basement because the air reaching some of the farther rooms (from furnace) on the second floor of my home is comparatively much cooler.

I was planning on wrapping r12 blanket pink fibreglass insulation I bought it in a 40ft roll.

However I am wondering if I can use this since it does not have the shiny reflective coating on the outside of the insulation that normal duct wrap insulation has. I do not know what that reflective coating is for or if it is even necessary.

In addition I have read that insulating the air ducts will actually trap heat into the insulation(remove from air) if not wrapped at a proper CLEARANCE, is this true or can I wrap the insulation right up against the metal ducts?

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    Any heat that insulation "traps" would have been lost anyway. By definition, it hinders thermal exchange. – Comintern Nov 15 '15 at 2:54

There are products specially made for wrapping the metal HVAC ducts. Its not recommended to use wall insulation (your 40-ft roll) with HVAC because it isn't designed to handle the temp changes.

Before you insulate the ducts they should be properly sealed with mastic or foil tape. This basically means cleaning the dirt/dust off of the duct before sealing.

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    You mentioned that the 40' roll the OP mentioned isn't designed to handle the temp changes. What will be the consequences if he/she uses it? – RockPaperLz- Mask it or Casket Dec 25 '15 at 10:20

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