Building Codes 

Prior to the publication of the 2024 International Codes (I-Codes), which include the International Building Code (IBC), International Mechanical Code (IMC), International Fire Code (IFC), and International Residential Code (IRC), the use of A2L refrigerants for residential and light commercial comfort conditioning purposes was prohibited by the codes. The 2024 versions of the IBC, IMC, IFC, and IRC now allow the use of A2Ls for this purpose; however, these codes have not yet been widely adopted across the United States.  

As a result, local jurisdictions and building officials have had to develop alternative methods for addressing the use of A2L refrigerants and equipment. Over the past few years, efforts have been ongoing to have jurisdictions across the U.S. either adopt the 2024 I-Codes or amend current local codes to include provisions within the 2024 I-Codes addressing A2Ls.  

As can be imagined, cities and states are addressing this issue differently. That’s why it’s important for HVACR professionals to reach out to local building officials in the areas where they work, in order to understand the local code requirements that will be enforced related to systems that use A2Ls.  

Code Provisions 

At the present time, for jurisdictions that have chosen to adopt the 2024 I-Codes, there are multiple A2L-related code provisions impacting HVACR professionals. These include the following requirements: 

• Addition of risk of fire warning labels for A2L piping due to its flammability; 

• Additional requirements for building shafts containing A2L piping, including fire rating requirements, continuous ventilation requirements, and requirements for leak detection; 

• Requirements for refrigerant detectors that signal an alarm and activate the room’s ventilation system in machinery rooms containing A2L refrigerants; and  

• Limits to the amount of A2L refrigerant that can be used for air conditioning systems used for human comfort. 

Jurisdictions that have not adopted the 2024 I-Codes but have chosen to amend their existing building codes may incorporate some, or all, of these requirements as they deem fit for their locality. The result is a varying and ever-changing landscape across the U.S. of code requirements related to A2L refrigerants and equipment. Nearly all states and local jurisdictions have taken steps to allow the use of A2L refrigerants in residential and light commercial construction, but the changes have not come without some difficulties.  

Key Changes 

While the 2024 IMC — and the applicable ASHRAE and UL standards referenced within — address the use of A2L refrigerants, there were some necessary changes that did not make it into the 2024 IMC. For example, refrigerant lines for systems utilizing A2L refrigerants that penetrate two or more floor/ceiling assemblies must be located in a ventilated, fire-rated shaft. These requirements, which have been determined to be unnecessary by the ASHRAE 15 standards committee, have had a significant impact on multifamily construction. ASHRAE has since updated the ASHRAE 15 standard, and during the International Code Council’s 2027 code development cycle, the necessary changes were approved for the IMC, eliminating these requirements.  

The two key changes that will be incorporated into the 2027 IMC are as follows: 

• Section 1109.2.5 regulating refrigerant pipe shafts: Exception 2 has been modified such that piping in a direct refrigeration system using any refrigerant meeting the limitations of IMC Table 1103.1 are safe to install without a fire-rated shaft; and 

• Section 1109.3.2 regulating shaft ventilation: An allowance was added for residential systems to eliminate the ventilation of the shaft when the piping system is continuous, without fittings located in the shaft. 

Jurisdictions across the country have already begun adopting the approved 2027 IMC code language addressing these issues, and efforts are underway to get other jurisdictions to review these sections of code to determine the best method for addressing these issues in their area. While the HVACR industry may face some challenges, the evolving building landscape signals positive and beneficial change.