Part 2: Understanding the New A2L Refrigerants Code Requirements

by David Spiegel II

The following analysis highlights the portions of the International Mechanical Codes (IMC) pertinent to designing for the new A2L refrigerants.

Refresher: How did we get here?

To be in compliance with the Environmental Protection Agency (EPA) new refrigerant regulations, HVAC equipment manufacturers needed to find an alternative refrigerant with lower Global Warming Potential (GWP). The most common refrigerants used to meet this demand are R-32 and R-454B, which ASHRAE classifies as an A2L refrigerant. These A2L refrigerants are slightly more flammable than the older A1 refrigerants but still have a lower toxicity level than the B series refrigerants. Due to these refrigerants’ slightly higher flammability characteristics, the building and mechanical codes have required some revisions to ensure safe installation.

What does the code say, and what is the implication?

The 2021 and 2024 editions of the International Mechanical Codes (IMC) have added verbiage into Chapter 11 (Refrigeration) to address the use of these refrigerants and maintain the safety of the occupants.

Section 1109 of the IMC outlines the requirements for refrigerant piping installations. One major code revision starting in the 2021 IMC is section 1109.2.5 (see below), requires that the newer A2L refrigerants be routed in a fire-resistance-rated shaft enclosure whenever the refrigerant piping penetrates two or more floor/ceiling assemblies.

This requirement can substantially increase the construction cost of typical multifamily renovation projects. This is particularly prevalent for affordable housing and low-income housing tax credit (LIHTC) developers performing renovations. Several potential challenges here need to be considered: increased construction cost, procurementissues, and construction schedule (the ability to turn units and whether a rehab is tenant-in-place).

Section 1109.2.5 Refrigerant Pipe Shafts (2021 IMC)

Refrigerant piping penetrating two or more floor/ceiling assemblies shall be enclosed in a fire-resistance-rated shaft enclosure. The fire-resistance-rated shaft enclosure shall comply with Section 713 of the International Building Code.

Exceptions:

1. Systems using R-718 refrigerant (water).

2. Piping in a direct system using Group A1 refrigerant where the refrigerant quantity does not exceed the limits of Table 1103.1 for the smallest occupied space through which the piping passes.

3. Piping located on the exterior of the building where vented to the outdoors.

Code discrepancy.

There is a discrepancy in the code; however, further attention is required. That discrepancy is that Section 1109.2.5, exception 2 in the IMC, is inconsistent with

ASHRAE 15 – 2022, section 9.12.1.5.1 (b). This section allows for all refrigerant groups to be installed without a fire-resistance-rated shaft where refrigerant quantity does not exceed the limits of Table 1103.1 for the smallest occupied space through which the piping passes. As a result, the International Code Council (ICC) has reviewed this inconsistency and approved the removal of the A1 refrigerant restriction starting in the 2027 IMC.

Next steps.

It is critical to plan for the new A2L refrigerants at the outset of a project. At the same time, it is encouraged to contact the AHJ code official to review the existing code discrepancy between AHSRAE 15-2022 and the forthcoming 2027 IMC shaft requirements.

HDJ, Inc., is a leading national design firm providing architectural and engineering expertise to support the affordable housing industry throughout the United States. HDJ’s diverse portfolio includes successful outcomes with adaptive reuse renovation, acquisition rehab, new construction, historic preservation, and RAD. Contact HDJ to learn more about how we can support your design needs with these new systems.