Which foil tape to use with flex duct?

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Old 10-10-06, 06:21 PM
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Which foil tape to use with flex duct?

I'm told the inspector here is a real stickler, and failed a buddy of mine for using the wrong tape with his duct. So, I've been using Nashua 324 (w/ the UL-181 listing printed all over it) to seal all the duct to the metal fittings, no question there.

But what tape should I use to seal the insulation? Nashua 324 is stiff and hard to put on- Nashua 322 (w/ no listings outside the fire spread rating) is going on a LOT easier and seems to seal better. It appears to be specifically designed to seal foil insulation like on flex duct, but as there is no UL listing and IRC appears to be silent on the issue of HOW exactly to seal the vapor barrier of foil insulation, just that a certain mil foil must be used. Does code care?
 

Last edited by grover; 10-10-06 at 07:09 PM.
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Old 10-10-06, 06:51 PM
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Wink

Code is code We use tie bands on the inside liner to the metal pipe then a tie band on the outside of the flex insulation. Then have to seal the flex to the duct with mastic duct sealant

ED
 
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Old 10-10-06, 07:05 PM
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? IRC M1601.3.1 requires 181B-FX be used for joints of flex duct systems- I don't see where mastic is even allowed with flex per code. The manufacturer's instructions (standard ada pamphlet) listed a number of methods, though- one being tie-wraps and mastic, another being 181B-FX tape, but each appeared to be OK by itself and not required in any combination. Am I misreading the code?

I put tie-wraps on overtop of the tape for extra reinforcement as it wasn't disallowed, but ran out of the UL-181 listed tie-wraps and used a handy-bundler for about 1/3 of them, as it seemed like just extra reinforcement and not required.

Wouldn't tie-wrapping the insulation ruin the insulative properties?

Maybe I'll be able to get in touch with one of the mechanical inspectors tomorrow and find out exactly what he's looking for, but those damn guys are slippery!
 

Last edited by grover; 10-10-06 at 07:16 PM.
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Old 10-11-06, 06:14 AM
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OK, I just talked to my AHJ and he verifies 181B-FX/A-P tape for all connections of duct liner to the fittings. Now, looking over manufacturer specs this morning ADC (and IRC) requires 181B-FX be used to secure the flex duct, but the duct wrap manufacturer only requires the tape match the duct. The AHJ first said I had to use listed tape to seal the insulation, but then later said the insulation didn't have to be sealed at all? I think I'll just use the 181 tape to be safe, it's only $10 and I certainly don't want to have to go back!

He also said I can cut off pieces of scrap flex duct vice buying duct wrap, so that's cool and will probably save me $30
 
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Old 10-19-06, 12:52 PM
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I passed mechanical rough-in inspection, woohoo!! Was really worried about this one Plumbing inspector came back-to-back, too, just as the mechanical inspector was pulling out, and I passed that too

Now it's just to finish the insulation and get the combination framing/insulation inspection done, and we can start drywalling!
 
 

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