Background

Under the AIM act, the EPA was directed to phase down HFC refrigerants in the U.S. based on their Global Warming Potential (GWP). HFC refrigerants are commonly used in air source heat pumps; HVAC systems that heat and cool buildings efficiently and without the use of fossil fuels. A common and highly scalable version of these air source heat pumps are mini/multi-split systems and VRV/VRF systems, which distribute heating and cooling directly throughout buildings using refrigerant. These systems currently use R-410a, a high pressure HFC refrigerant with a GWP of just over 2,000.

These HFC refrigerants are not harmful to the environment if they remain inside HVAC systems, but a certain percentage of leakage needs to be assumed and does occur due to field issues and incidents, weather events, improper repairs or improper end-of-life procedures. As a result, and to achieve local and global emissions reduction goals, it is important to transition to high pressure HFC refrigerants with lower GWP’s, and to do so safely, and without compromising our ability to electrify buildings efficiently and at scale.

Under the EPA’s final rule, most HVAC systems using R-410a refrigerant including mini/multi split air source heat pumps cannot be manufactured or imported into the U.S. beyond 1/1/2025. The installation of R-410a equipment purchased in 2024 will be allowed through the end of 2025. R-410a VRV/VRF systems have an extra year under the ruling and can be manufactured and imported until 1/1/2026. Beyond these dates, only equipment with refrigerants below a GWP of 700 will be allowed by the EPA.

The sub-700 GWP alternatives to R-410a will be refrigerants in a different flammability classification (as per ASHRAE Standard 34), called the A2L class. Of the 4 flammability classes, of which R-410a lives in the lowest flammability class (A1 – still flammable but non-flame propagating under specific conditions), A2Ls are in the second lowest class. The highest and most flammable class (A3) is home to refrigerants such as R-290 (Propane) and R-50 (Natural Gas). A2L refrigerants can be ignited under certain conditions but require a certain concentration and a continuous energy source. If they are ignited, their heat of combustion and burn velocities are far less than A3 refrigerants (see this AHRI factsheet for details). The slightly more flammable characteristic of A2Ls compared to A1s is what makes them retain less heat in the atmosphere should they be accidentally released, lowering their GWP.

New low GWP A2L refrigerants such as R-32 require updated code language to be applied and used in buildings, whether the refrigerant is distributed throughout the building by a split system or VRV, or contained in a packaged unit, or in a classified machine room. Systems that distribute refrigerants through buildings and with heat exchangers that condition the occupied space directly are referred to by ASHRAE as “direct systems”. Direct systems are very energy efficient, especially for cold climate heating, and can be applied and installed in new and existing buildings in a cost-effective way compared to alternative electrified HVAC solutions, making them a cornerstone of building decarbonization. 

The ASHRAE 15 and 34 standard committees have been analyzing and reviewing research around A2L refrigerants and their safety for over a decade. The ASHRAE 15 standard has evolved from having practically no allowance of A2Ls in direct systems, to having some allowances, to now having clear allowances with many clarified and improved sections. The latest standard also adds new safety requirements such as refrigerant detection and automatic safety shut off valves to better mitigate leaks and increase safety.

This latest published language on the safe and effective application of A2L refrigerants lives in the 2022 version of the ASHRAE 15 standard, however the use of this language is not explicitly allowed in all States and jurisdictions yet. Many States and jurisdictions are working on updating their code language, by either updating the model code cycle used or by allowing the use of ASHRAE language. Model code language does tend to lag ASHRAE language by the nature of their cycles, and as a result the 2021 model codes do not yet have the latest language. The 2024 model codes have adopted more of the latest ASHRAE language, however, it is expected that the 2027 cycle will be home to most updated language.

Please contact our Refrigerant Transition Support Team to learn about our knowledge of the codes and language in your State or jurisdiction!