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]