Thread: "Duct Tape"

Is there a code reference as to when duct tape was not allowed for duct connections? I find flexible duct connections with duct/duck tape quite frequently. On a recent inspection, the HVAC guy chastized me for calling this out... Any help?

Thanks,

Chris

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Originally Posted by Chris Stichter

Is there a code reference as to when duct tape was not allowed for duct connections? I find flexible duct connections with duct/duck tape quite frequently. On a recent inspection, the HVAC guy chastized me for calling this out... Any help?

Thanks,

Chris

No duct tape. Just foil type duct tape. Regular duct tape is not going to hold up. The foil type duct tape becomes part of the foil outer duct covering. Of course it must be put on when the duct is clean. The HVAC guy got POd because he got bagged being stupid.

HVAC tech said it was ok when the home was built....2001.

Originally Posted by Chris Stichter

HVAC tech said it was ok when the home was built....2001.

Regular old grey sticky used for everything duct tape has never been alright on foil type ducts. Could it have been OK on older type duct work. I doubt it. I don't think it was ever OK on any duct work.

Thanks Ted,

Any code references?

Originally Posted by Chris Stichter

Thanks Ted,

Any code references?

Where I am I have a 2006 IRC and I do not believe there is anything in there.

It's legal in West Virgina, everybody else must have UL181 on the tape.

If it's 10 years old and the joints are tight and not leaking then so be it.

In California Jan 2001 is when the code change took affect.

Just wipe the outside with UL181 mastic, to comply and seal leaks.

Edit... just because it says UL181, means the tape meets the flame and smoketests.
When installed and the parts were coated in oil or heavy dust, no tape will stick.
It best to run the equipment and feel for leaks

Chris,

The 2003 IECC calls for Ul Listed tape and/or sealant for ducts. I do not know what the 2001 IECC called for.

Originally Posted by Craig Ervin

It's legal in West Virgina, everybody else must have UL181 on the tape.

To my knowledge, the only "duct tape" ever "approved for use" was listed to UL 181.

The old style non-foil/cloth-rubberized adhesive stuff was originally used in WWII in the service and was developed to be wrapped around ammo boxes and the like to keep them 'water tight' while in transit across water. Once the GIs got home and a/c systems started being used, which mean insulating the exterior of the metal duct, the GIs (who were now 'contractors' or 'workers') grabbed what they knew best and thought would work - Duck Tape now became duct tape. Never was "approved" though - not to my knowledge - it was just one of those things which "was done" and as codes and standards advances, materials and methods were evaluated and the materials which met the new standards became "approved", i.e., UL 181, and the old materials eventually stopped being used as everyone learned of the new standards ... but, come on a/c installer guy (not you Craig, the a/c installer guy), 20001? That stuff has not been approved for use since 15-20 years ago, maybe even further back than that.

UL 181 duct sealing:
may be tape or mastic

181-A is rated for ductboard
181-b is rated for flex duct

Many jurisdictions are getting away from foil tape and requiring 181-a/b-FX duct mastic exclusively along with 50lb test UV resistant Zipties on both the inner takeoff collar and the outer vapor barrier. The Calif. Ch. 24 site on this is excellent with professionally done instructional videos for free. I'll try to find the link or just Googlize it. You want less than 7% duct leakage are your target. Don't forget to inspect the furnace blower plenum where it connects to the combustion chamber. If there are any minor penetrations here, you can pull CO into the home and screw up your combustion, too (technical term).

Sealing return leaks protects against backdrafting, reveals your true External Static Pressure (so you can accurately assess the duct sizing and installation AND assess combustion analysis properly), get your true Delta T, prevent air stagnation in the far corners of the building, prevent entraining funky CAZ air into the home with possible pollutants, and better adjust the comfort in each room. Think of sealing returns for IAQ.

Sealing supply leaks gets more of the good stuff to where you want it to go. If dirt blows by the filter, it will clog the A coil, which will cause heat to backup into the HX thus prematurely wearing it out. With too much heat, you can get additional energy lost up the stack. Your blower will die an untimely death from coil asthma. With proper airflow through the supply, rooms can then be measured and balanced for comfort. Think Energy and Comfort with supply leak sealing. Once you seal ducts, your ESP will go up. Your Delta T may also rise if it is pulling warmer return air rather than cooler basement air. However, you want the true picture of your system prior to a tech tinkering or adjusting it. Since such sealing does affect performance, it should ALWAYS be followed by professional combustion analysis and adjustment as needed.

FYI, rubber cement tapes are no longer recognized by the IMC, ACCA, or ASHRAE for duct sealing and are expressly prohibited in most jurisdictions. Aside from the fact that they seal poorly, degrade over time and have a high flame spread rating, the acrylic adhesive breaks down in just a few yrs.( same problem with foil tapes) and they lose adhesion. That's another reason for mastic. Also, mastic flexes with metal expansion & contraction and tends to muffle sounds.

I've heard the "duck tape" GI story, too Jerry. Kept the ammo tight as a duck's exhaust system( think about it---it the duck's exhaust leaks, he would sink!)
Bob