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Interior Duct Coating

Mike Lamb

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It's the same process and material used for relining municipal sewer lines. It's a mix of latex, Kevlar and zinc. I think one brand name is Duct Armor. I've recommended it for specific buildings that would be difficult to retrofit new duct systems.

I think it's supposed to be 1/4" thick when applied inside Transite ducts. Should have the ducts scoped after application to check for complete coverage.

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I thought the sewer stuff was Insituform, a tube form based application using thermosetting epoxies. Treat the tube with goop, slide it into the old sewer, then pump steam or heat through the tube to cure the plastic.

The duct lining thing is a rubbery aerosolized glop that gets sprayed into the ducts with a system of high pressure fans. Particulate in the glop seals up the gaps and holes, and the remaining glop spreads out through the ducts. Duct Armor is spray glop AFAIK.

My buddy Bob did one the other day. Maybe it was Duct Armor. It worked great to correct a leaky attic duct installation. I'll get the name of the stuff.


It cost a couple grand per system, i.e., $4K for a two zone house.

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Increased air flow, from nonfunctional to surprisingly good, and stopping leaky ducts in the attic from turning the attic into a swamp. Worth every penny. This was part of a $54k roof and attic retrofit to repair the building science disaster some moron perpetrated back in '04.

Payback? I have no idea. We saved a house.

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What are we trying to accomplish with this material ? What would be the economic justification of several $K for this install ? Any guess on payback period ?

As Kurt said, vast air flow improvement and sealing leaky ducts could be the reason, or as Bill alluded, it is a coating used on asbestos lined ducts. I was told the clip for this was $7K. It's not something you would do for the heck of it.

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  • 2 weeks later...

Hi Mike,

This is John from Duct Armor of Chicago. We provide the Duct Armor services for Illinois. The picture you posted is a rubberized duct liner that is used for in-slab duct work. It is applied using a camera and a spray applicator. The product is latex based and has zinc in it, to control mold growth. It also has a bonding agent that allows it to adhere to existing duct work and to itself for layering. The application is used to repair many different types of underground air ducts including rusted galvanized ducts and plenums, cardboard ducts and pvc air ducts. It also can encapsulate transite/asbestos pipe. The product has passed many rigorous safety tests and comes with a 15 year warranty.

If you have any questions, would like a sample of the product, or would like more information about Duct Armor please call. I can be reached at 1-844-757-3828. Our website address is: ductarmor-crete-il.com .

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