Exterior Duct Insulation Code Question.

[wasniewc]

Code Reference
IMC 2012
IBC 2012
Code Edition
2012
Code Section
IMC Section 604, IBC 2603
Questions
Roofing, Siding, Wall insulation, even many interiors per the IBC allow a CLASS A Flame and Smoke Developed index of 25/450.
My question is, is there a flame and smoke developed index that applies strictly to outdoor hvac ductwork. In the IMC 2012 there is a section relating to duct insulation, however i feel it applies to indoor duct as the flame and smoke index are 25/50 which is a plenum rating.
If i have an outdoor ductwork system that is covered with insulation, not lined, and then a cladding as a weather barrier is applied. what are the flame and smoke developed index requirements for this insulation application / design? And also what are the flame and smoke developed index requirements of the outdoor weather barrier "cladding". I feel like it should follow everything else that is on the roof / siding / roof insulation / etc. and the Class A should be fine flame spread <25, smoke <450. I just cant seem to find a section that related to outdoor products specifically and why the Class A wouldn't qualify as it is outdoor with everything else that is Class A. Any help is much appreciated. Thank you.

[Jerry Peck - Codeman]

Because the ducts are not in a plenum, I would address it this way:
- 2012 IMC (underlining is mine)(My comments are in italics)
- - Section 602
- - - Plenums
- - - - (Jerry's comment: Because the ducts are not in a plenum as described, Section 602, Plenums, is not applicable.)
- - Section 603
- - - Duct Construction and Installation
- - - 603.1 An air distribution system shall be designed and installed to supply the required distribution of air. The installation of an air distribution system shall not affect the fire protection requirements specified in the International Building Code. Ducts shall be constructed, braced, reinforced and installed to provide structural strength and durability.
- - - (Jerry's comment: This section directs you to the International Building Code to "not affect the fire protection requirements specified in" ... because the ducts described are not in a plenum and smoke/flame will not be affecting air in a plenum ... you need to go elsewhere - other than plenums - in this case to 603.1, to address fire protection.)
.
- - - 603.15 Mechanical protection.
- - - - Ducts installed in locations where they are exposed to mechanical damage by vehicles or from other causes shall be protected by approved barriers.
- - - - (Jerry's comment: Regardless of the cause, or potential cause, of mechanical damage, the ducts require protection from that damage or potential damage.)
- - - 603.16 Weather protection
- - - - All ducts including linings, coverings and vibration isolation connections installed on the exterior of the building shall be protected against the elements.
- - - - (Jerry's comment: Exterior ducts would require weather protection, that weather protection would also need to meet 603.1.)

- - Section 604
- - - Insulation
- - - 604.1 General
- - - - Duct insulation shall conform to the requirements of Sections 604.2 through 604.13 and the International Energy Conservation code.
- - - - (Jerry's comment: The insulation would need to meet the R-values of the energy code for the area.)

The above sections would be applicable, while Section 602 Plenums would not be applicable (because the ducts on not in a plenum).

[wasniewc]

Thanks Jerry, very well written.


What about the applicability of section 604.3, this seems to point back to all NON-Plenum duct even outdoor duct coverings having a plenum rating on the insulation of 25/50?

[Jerry Peck - Codeman]

What about the applicability of section 604.3, this seems to point back to all NON-Plenum duct even outdoor duct coverings having a plenum rating on the insulation of 25/50?

My apologies for not having gone through my thinking about that:

- Section 604
- - Insulation
- - 604.1 General
- - - Duct insulation shall conform to the requirements of Sections 604.2 through 604.13 and the International Energy Conservation code.
- - - (Jerry's comment: The insulation would need to meet the R-values of the energy code for the area.)
- - 604.3 Coverings and linings.
- - - Coverings and linings, including adhesives where used, shall have a flame spread index not more than 25 and a smoke-developed index not more than 50, when tested in accordance with ASTM E 84 or UL 723, using the specimen preparation and mounting procedures of ASTM # 2231. Duct coverings and linings shall not flame, glow, smolder or smoke when tested in accordance with ASTM C 411 at the temperature to which they are exposed in service. The test temperature shall not fall below 250°F (121°C). Coverings and linings shall be listed and labeled.

I started near the end of 604.3 Coverings and linings:
- "Coverings and linings shall be listed and labeled."

My presumption was that the "duct" and its "covering" was "listed and labeled", and, as such, the covering would meet those stated requirements.

I then went back to: (underlining is mine)
- 603.16 Weather protection
- - All ducts including linings, coverings and vibration isolation connections installed on the exterior of the building shall be protected against the elements.

Which is where I made the additional presumption that you were asking about the 'outer most exposed protection which encases the duct' ... the 'listed and labeled' "covering" of the duct ... where that 'outer most exposed protection' would be whatever is on the outside of the 'covered' duct protecting it from the weather and that was what the question was about.

My thinking is that two things need to be, are being, addressed:
- a) The duct itself in which the lining is exposed to the air in the duct and the covering which is exposed to the environmental air outside the duct but inside the building.
- b) The protection of the duct, both from mechanical damage (which could be balusters or other protective barriers or a sufficiently strong enough covering to resist mechanical damage) and from weather damage (which could be many things, even metal, all of which would be expected to not contribute to any required fire resistance limitations applicable on the outside of the building.

I think the key lies in the wording (bold is mine): duct lining, duct covering, mechanical protection, weather protection ... and that one should not intermingle the use of the word "covering" with "protection" and vice-versa - albeit "protection" could be a 'covering' in one sense of the word, but it would not necessarily be "the" 'duct covering'.

After all, what is "protected" (the duct) by the "protection" (whatever that may be) is not what is exposed to the fire, or what is producing smoke - that would be the final outer "protection".

Or I may have misunderstood the question?