Do you have a project involving split-system air conditioning in a multistory building? If so, you may find the regulatory landscape especially difficult to navigate right now.
As of January 2025, manufacturers are required to produce several refrigerant-based products—including split-system air-handling units, mini-splits, and dehumidifiers—using refrigerants with lower ozone depletion potential than legacy options. The most common replacements, R-32 and R-454B, fall under the relatively new A2L classification.
Why does this classification matter? A2L refrigerants are mildly flammable. While A2 refrigerants are flammable in general, the “L” signifies low burning velocity, which affects how they’re regulated.
The rollout of A2L refrigerants has prompted mixed reactions from code authorities and industry professionals. As R-410A supplies dwindle, A2L systems are often the only compliant option—but the path forward remains unclear.
What’s behind the confusion?
Several factors contribute to this uncertainty:
- Code cycles lag behind industry needs, with updates typically issued every three years.
- State legislatures must adopt codes, but they can’t act until the code councils publish updates.
- Local jurisdictions base adoptions on previous code versions, undergoing their own 2–3 year review and revision cycles.
- ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) is also revising Standard 15 to address these changes.
It’s common for Authorities Having Jurisdiction (AHJs) to be 3–6 years behind the most current codes.
A2L refrigerants weren’t meaningfully addressed until the 2024 ICC Code editions, which introduced stringent requirements—including fire-rated, ventilated shafts for piping running between floors, charge quantity limits, refrigerant monitoring, and strict construction and testing standards.
To help jurisdictions adapt, the International Code Council (ICC) provided formal guidance to amend earlier code versions (2012 through 2021) to align with the 2024 edition. Similarly, ASHRAE released ASHRAE 15-2024 to offer direction on handling A2L refrigerants.
However, in April 2025, the ICC acknowledged that some of these requirements—especially the shaft or “chase” construction—may have been overly conservative. It has since directed code authorities to look ahead to the draft 2027 code documents. These pending revisions propose more flexible chase requirements, provided refrigerant charge limits and testing standards are met.
ASHRAE 15-2024 likewise introduces relaxed requirements for limited-charge systems that are pressure-tested and otherwise compliant.
So how should you proceed?
Whether you’re an owner, contractor, engineer, or client, navigating this regulatory uncertainty is no small feat. Most jurisdictions have not yet adopted the 2024 ICC codes, much less reviewed the 2027 drafts or amendments suggested by ICC or ASHRAE. Even referencing ASHRAE 15-2024 may be problematic, as it isn’t incorporated into existing legal code frameworks.
Since these refrigerants are the only legal options moving forward, communication is key:
- Engage your local code authorities early to discuss the complexities of A2L implementation and seek guidance before design and construction begin.
- Advocate for clarity and change by contacting your local legislators, AHJs, and professional organizations. If enough voices speak up, there’s a chance the standards will evolve before 2027—or even 2030, given typical adoption lags.
Barton Associates continues to work through these issues with clients across many jurisdictions and will provide updates as the situation develops. For more information, feel free to reach out to Stephen Oskin, PE, LEED AP, Director of Engineering, at seo@ba-inc.com.