Since when?The IRC is intended to be an all encompassing bible for SFRs. Everything that one needs to build SFRs is in that book. The IRC covers ductwork/return air chases ("plenum") and DWV piping. The IRC does have not a prohibition of PVC piping in a plenum. Cherry picking regulations from other I-Codes to apply to an SFR is standing on shaky ground.
You missed the point of the code path that I outlinedThe IRC does have not a prohibition of PVC piping in a plenum. Cherry picking regulations from other I-Codes to apply to an SFR is standing on shaky ground.
Well, fortunately for me, WA state does not adopt the plumbing sections of the IRC, but adopts the UPC for both residential and commercial.You have missed my point. Here's a simple example: The IPC requires a 3 inch drain when the fixture drain from an ACW combines with another drain. The IRC does not have that requirement. Should you apply the IPC requirement to the IRC building? No, because the IRC has everything you need to know about drainage piping for ACW standpipes and branch drain sizing. On the other hand, if someone installs a urinal in an IRC building, what do you do because the IRC doesn't cover urinals. That's when you go to the IPC for guidance on urinals.
There will always be questions as to how far you go in enforcing the requirements of another code (over the IRC) and does the IRC "sufficiently address" the general subject matter such that those who are developing the code, didn't see fit to make the IRC anymore complex and ultimately, more expensive to build homes. "Cherry picking" requirements out of other codes for construction of an IRC building could be viewed as arbitrary, depending on the situation. If it comes down to deposition time, what code section are you going to cite in the IRC that says that the arrangement is prohibited? This is why I used the "shaky ground" point. How are you going to look in front of a lawyer or in court when you try to support your grounds for making the installer do something that is not in the IRC.
R104.11 Alternative Materials, Design and Methods of Construction and Equipment
...Compliance with the specific performance-based provisions of the International Codes shall be an alternative to the specific requirements of this code. ...
You have missed my point. Here's a simple example: The IPC requires a 3 inch drain when the fixture drain from an ACW combines with another drain. The IRC does not have that requirement. Should you apply the IPC requirement to the IRC building? No, because the IRC has everything you need to know about drainage piping for ACW standpipes and branch drain sizing. On the other hand, if someone installs a urinal in an IRC building, what do you do because the IRC doesn't cover urinals. That's when you go to the IPC for guidance on urinals.
There will always be questions as to how far you go in enforcing the requirements of another code (over the IRC) and does the IRC "sufficiently address" the general subject matter such that those who are developing the code, didn't see fit to make the IRC anymore complex and ultimately, more expensive to build homes. "Cherry picking" requirements out of other codes for construction of an IRC building could be viewed as arbitrary, depending on the situation. If it comes down to deposition time, what code section are you going to cite in the IRC that says that the arrangement is prohibited? This is why I used the "shaky ground" point. How are you going to look in front of a lawyer or in court when you try to support your grounds for making the installer do something that is not in the IRC.
Even if you DO apply the IMC, PVC in plenums in SFR is still allowed^I assume this is a SFR and since the IRC is silent on this I will use the IPC and IMC.
2012 IPC
307.6 Piping materials exposed within plenums.
All piping materials exposed within plenums shall comply with the provisions of the International Mechanical Code.
602.2.1 Materials within plenums.
Except as required by sections 602.2.1.1 through 602.2.1.5, materials within plenums shall be noncombustible or shall be listed and labeled as having a flame spread index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E 84 or UL 723.
Exceptions:
1. Rigid and flexible ducts and connectors shall conform to Section 603.
2. Duct coverings, linings, tape and connectors shall conform to Sections 603 and 604.
3. This section shall not apply to materials exposed within plenums in one- and two-family dwellings.