[mef526]

I am upgrading an existing furnace with galvanized 6" and 8" ducts. I'm sealing and insulating the existing ducts instead of replacing them.
Is it OK to use flexible duct 1" larger and pull it over the galvanized ducts instead of wrapping them or using duct sleeves?

Looks like the job will go quicker and flex duct is cheap compared to duct sleeves

 

[greg24k]

I am upgrading an existing furnace with galvanized 6" and 8" ducts. I'm sealing and insulating the existing ducts instead of replacing them.
Is it OK to use flexible duct 1" larger and pull it over the galvanized ducts instead of wrapping them or using duct sleeves?

Looks like the job will go quicker and flex duct is cheap compared to duct sleeves

Where you from and what is your trade?

 

[the rock]

I don't understand what you are trying to accomplish.Is your ductwork inside a cold zone such as a crawl space or attic?If this is not the case why are you trying to insulate them?What IS your trade anyway?Nick