Significant changes to the 2018 International Residential Code

The 2018 Significant Changes guides are available for the International Building, Residential, Fire, 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 2018 International Codes (I-Codes). The Code Council’s technical experts provide summaries, analysis and graphics for these changes making them clear and easy to understand.

2018 International Residential Code

A clarification to Section N1102.2.5 (Mass Walls) states that the mass wall provisions have been itemized in a numbered list to bring accuracy and clarity to the technical requirements.

The IRC provides prescriptive requirements for the construction of mass walls for conserving energy. Mass walls are built of dense materials, typically concrete, concrete masonry units and brick. Alternative materials used for mass walls include solid logs, adobe and rammed earth. Frame walls and mass walls perform very differently and require different amounts of insulation. Mass walls store heat and require less insulation than frame walls. When part of the building thermal envelope, the minimum insulation R-values in Table N1102.1.2 are applicable. The amount of insulation depends on the location of the insulation on the mass wall. If more than 50% of the insulation is on the interior (conditioned) side, it impairs the efficiency of the mass wall and significantly more insulation is required. A pointer to the mass wall provisions in Section N1102.2.5 has been added to the mass wall footnote in Table N1102.1.2. The provisions for mass walls in Section N1102.2.5 have been revised and itemized in a numbered list.

To be considered a mass wall component of the thermal envelope, the wall must meet one of two items in the list. These changes are primarily editorial and intend to identify mass walls used in the building thermal envelope in an objective, measurable way. Once determined to be a mass wall in accordance with this section, the designer and builder can apply the advantages of reduced R-values in Table N1102.1.2.

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