Gonna resurrect this one for a bit.
Would you consider a dryer vent in this situation a through penetration or a membrane penetration or something else? I had a discussion today with someone who felt that the dryer pipe did not qualify as a through penetration because it did not penetrate the floor and ceiling of the assembly where I believe the intent of the definition is that the pipe enters and exits the assembly.
Yes, Michael, I will attempt to resurrect this topic again, and I will stay on track.
First, I am in a jurisdiction that does not support the use of dryer wrap. I am in agreement with the direction you are going, but I get there differently. I have expressed my frustration with IBC Chapter 7 in several posts in this forum. This will be no different.
Note, the end of your original post referred to Exception 1 of 714.4.1.1 and Exception 1 of 714.4.1.2. These do not apply to this installation. "conduits, pipes, tubes or vents" are not ducts. "Vent" has a definition in the IMC.
Starting with 2015 IBC, 717.6 references ducts that penetrate the ceiling membrane of a roof/ceiling assembly. This really should apply to the ceiling membrane of a floor/ceiling assembly as well but that's not how this is written. I cannot think of any good reason that it shouldn't apply, especially as I move forward. Just another fix to Chapter 7.
717.6.2 states that ducts that penetrate the ceiling membrane of a floor/ceiling or roof/ceiling (they got the floor/ceiling in this one!) be protected with a shaft or a ceiling radiation damper. I choose damper.
717.6.2.1 states that ceiling radiation dampers are not required if one of two apply. I choose two. "Where exhaust duct penetrations are protected in accordance with Section 714.4.1.2, are located in the cavity of a wall and do not pass through another dwelling unit or tenant space." .......... no damper required.
714.4.1.2 directs you to 714.4.1.1.2 which allows for the double top plate penetration of this 4" exhaust duct (because it is within the cavity of a wall and the double top plate is a continuation of the ceiling membrane of the floor/ceiling or roof/ceiling assembly) to be protected by an
approved through-penetration firestop system.
Good luck finding one to match. Most systems are shown to penetrate the ceiling membrane
and the floor. I haven't been able to find one that only penetrated the ceiling membrane and had the duct turn 90 degrees. Years ago, we had a fire protection engineer provide us with one that we used (
approved). It was no different than many of the systems that we've seen and approved from the NRTL's except that it didn't penetrate the floor. The primary protection was simply annular space materials, no damper and no duct wrap required. Show me a NRTL system using a 4" duct that penetrates the ceiling and the floor, and I will most likely
approve it for this application.
There is much similarity in 717.6.1 Exception.