wasniewc wrote: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?