Building Code committee backs emergency-rule updates to allow A2L refrigerants in split HVAC systems

On Oct. 10, 2025, the NDPE committee of the Washington State Building Code Council recommended that the full council establish an emergency basis to modify an existing emergency rule for the 2021 International Mechanical Code (IMC) to reflect recent clarifications in ASHRAE 15 about A2L refrigerants, and separately recommended staff pursue a pathway to add corresponding language to the 2024 IMC filing (CR 102).

The change seeks to align IMC Chapter 11 with ASHRAE 15 addenda that distinguish continuous refrigerant piping from other equipment and relax, in some cases, the requirement to enclose refrigerant piping for split systems — such as mini-split heat pumps and variable refrigerant flow (VRF) systems — in rated vented shafts. Eric Vandermee, proponent and consultant with Delta E Consulting, told the committee, "The mechanical code chapter 11 requires compliance with both the mechanical code and with ASHRAE 15, and ASHRAE 15 is a continuous maintenance standard." He said the recent addenda clarify when rated shafts are not required for continuous pipe and tube that has been pressure-tested per ASHRAE 15 and…