Significant changes to the 2021 International Mechanical Code
The 2021 Significant Changes guides are available for the International Building, Residential, Fire, Energy Conservation, Plumbing, Mechanical and Fuel Gas Codes. This valuable series can help any code user save time by zeroing in on the most critical changes in the 2021 International Codes. The Code Council’s technical experts provide summaries, analysis and graphics for these changes making them clear and easy to understand.
2021 International Mechanical Code
A modification to Section 602.2.1.8 (Pipe and Duct Insulation Within Plenums) states that the revision addresses the practice of using pipe insulation materials to protect piping that does not meet the required fire performance requirements.
It is common for plastic piping to be installed in plenum spaces, such as above-ceiling return air plenums. Section 602.2.1 requires that materials installed within plenums be noncombustible or have 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 E84 or UL 723. Some plastic piping materials cannot meet the requirements of Section 602.2.1; therefore, if they are installed within a plenum, they must be protected by some material that does meet the fire performance requirements and that is listed for that application. Section 602.2.1 allows combustible piping to be “fully enclosed within materials listed and labeled for installation within a plenum and listed for the application.” The revised code text states that if pipe insulation is used as the enclosing material, the entire assembly of the pipe, the insulation and any coverings and adhesives must be tested as a composite assembly. Although there are insulation materials available that meet the fire performance requirements themselves, it is an unknown how the entire assembly will perform unless the entire assembly is tested. Without being tested as a composite assembly, it is possible that the protected piping could break down and degrade when exposed to heat, despite being protected by a pipe insulation material.
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