Originally Posted by magneticpersona
here is proof that this is not allowed:
rule 2-126(b)(ii) appendix B
FT4 to be used in spaces between a floor and a ceiling or ceiling and a roof,that may be used in as a plenum (that means current or possible future installation) in buildings of combustible or non-combustible construction. Its against building code too.
That's an unreasonable interpretation of that statement.
I would have thought a reasonable inspector would first look at the space to determine if it "may be used" as a plenum. If there are no return air ducts connected to the space, a reasonable person would conclude that it certainly can't used as a plenum, so it doesn't fall into the scope of a space that "may be used" as a plenum.
In any event, although Appendix B is a good guide, it isn't code. See the note under the heading.
Your inspectors would have a better argument if the National Building Code said that spaces that aren't plenums are subject to the same rules as plenums, but until I see that, if it isn't a plenum, it simply isn't a plenum.
Thankfully, such obscure interpretations are restricted to the island.