Most heating, ventilating, and air-conditioning (HVAC) systems rely on refrigerants to transport heat from one place to another. These refrigerants help move heat away from a warm room to make it cooler, or they help transport heat to a chilly room to make it warmer. A wide range of refrigerants are available with varying degrees of cost and performance. Some refrigerants transport heat well with low input energy; these are energy-efficient refrigerants. Others are less efficient at moving heat around, but they come with peripheral benefits such as being less toxic, less flammable, or less damaging to the environment. Some refrigerants are natural and easily sourced, while others are synthetic compounds which are costly to produce.
The American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) classifies refrigerants based on their toxicity and flammability. The International Code Council (ICC) regulates refrigerants based on ASHRAE’s classifications, and the Environmental Protection Agency (EPA) regulates refrigerants based on their impacts to the environment. These classifications and regulations help guide equipment manufacturers to standardize equipment around a select few refrigerants which become industry norms over time. Unfortunately, the legacy refrigerants that the industry has standardized around have relatively high global warming potential (GWP).
The EPA’s Technology Transitions Program was updated with a final ruling in late 2023 which prohibits the installation of new residential and light commercial air conditioning and heat pump systems using refrigerants with a GWP of 700 or more after January 1st, 2025.[1] These soon-to-be-prohibited refrigerants have long been the industry standard because they are cost-effective and energy-efficient. New non-toxic refrigerants, such as R-32 and R-454B, are available with GWP ratings below 700, but they are slightly flammable – a trait with implications for the architecture, engineering, and construction (AEC) industry that are anything but slight. The successful adoption of these new refrigerants will require ample transition time, the commercial availability of compatible HVAC equipment, and clear, robust code language describing means and methods of achieving safe and insurable installations.
Transition Time
A “good cause exemption” allowed the EPA to declare the final ruling in late 2023 without prior proposal or comment from the AEC industry.[2] With just over 14 months from issuance of the EPA’s final ruling to the initial effective date of January 1st, 2025, there was insufficient time to legally install completed HVAC designs which utilized legacy refrigerants. Large projects would require significant redesign efforts to incorporate new low-GWP refrigerants, and the cost and schedule impacts of redesign were destroying project viability. The AEC industry and affected parties petitioned the EPA to consider these cases where completed designs could not be installed before the planned effective date. In December of 2023, the EPA extended the planned effective date to January 1st, 2026 for systems imported before the original effective date, providing much-needed relief to property owners and design teams with projects underway.
Commercial Availability
Once the EPA’s final ruling was issued, HVAC equipment manufacturers began the process of adding compatible equipment to their product offerings. This multi-step process includes reviewing and selecting low-GWP refrigerants, designing new equipment, sourcing components, manufacturing equipment, testing equipment, and publishing resultant data. It can take multiple years to add new equipment to a product line using this standard process.
While equipment manufacturers were in the early stages of this process, HVAC design engineers were expected to be designing and applying new low-GWP solutions to projects which will have HVAC installations completed after the effective date. With the design and manufacture of new low-GWP equipment underway, the performance data of these systems is still not widely available to HVAC design engineers, limiting the feasibility of using low-GWP equipment as basis of design. Engineers who are responsible for sizing, selecting, and specifying HVAC equipment rely on the manufacturer’s published data to ensure that available equipment can meet or exceed project requirements; designs which are prematurely incorporating low-GWP refrigerants are exposed to increased risk.
Building Codes
Adopted building codes have not historically permitted the installation and operation of flammable refrigerants within buildings. The EPA’s final ruling prohibits the use of standard non-toxic and non-flammable refrigerants, so building codes were updated to describe methods for the safe and insurable installation of flammable refrigerants. Many of these updates were provided as interim updates in the 2021 ICC model codes, with final updates published for the 2024 ICC code cycle.
Updated code language contributes to increased occupant safety with respect to installing flammable refrigerant systems within buildings at the expense of decreased floor plate efficiency, increased project cost, and increased annual energy consumption.
1109.2.5 Refrigerant Pipe Shafts
“Refrigerant piping that penetrates two or more floor/ceiling assemblies shall be enclosed in a fire-resistant shaft enclosure. The fire-resistance-rated shaft enclosure shall comply with Section 713 of the International Building Code.”
[3] International Code Council (ICC); “2024 International Mechanical Code”; June 2023
Legacy building codes allowed refrigerant piping to penetrate multiple fire-rated floors if appropriately fire-caulked. The legacy “drill hole, insert tube, add intumescent caulk” installation process contributed to the popularity of split direct-expansion HVAC systems. With the advancement to low-GWP refrigerants, code language has been updated to require vertical refrigerant pipe pathways to be installed within 2-hour fire rated enclosures. A fire-rated shaft enclosure requires more material, space, and labor than legacy installations, and therefore increased project cost. The additional space required for fire-rated shafts also reduces rentable square footage and floor plate efficiency; these considerations must be incorporated into early feasibility studies as they can affect project viability.
1109.3.1 Protection Against Physical Damage
“In addition to the requirements of Section 305.5, aluminum, copper and steel tube used for Group A2, A3, B2 and B3 [flammable] refrigerants and located in concealed locations where tubing is installed in studs, joists, rafters or similar member spaces, and located less than 1-1/4 inches (32mm) from the nearest edge of the member, shall be continuously protected by shield plates. Protective steel shield plates shall cover the area of the tube plus the area extending not less than 2 inches (51 mm) beyond both sides of the tube.”
[4] International Code Council (ICC); “2024 International Mechanical Code”; June 2023.
Here, again, one can expect the installation of low-GWP systems to require more material, labor, and cost than the incumbent industry standard approach.
1109.3.2 Shaft Ventilation
“Refrigerant pipe shafts with systems using Group A2L or B2L [slightly flammable] refrigerant shall be naturally or mechanically ventilated. Refrigerant pipe shafts with one or more systems using any Group A2, A3, B2 or B3 [flammable] refrigerant shall be continuously mechanically ventilated and shall include a refrigerant detector. The shaft ventilation exhaust outlet shall comply with Section 501.3.1. Naturally ventilated shafts shall have a pipe, duct or conduit not less than 4 inches (102 mm) in diameter that connects to the lowest point of the shaft and extends to the outdoors. The pipe, duct, or conduit shall be level or pitched downward to the outdoors. Mechanically ventilated shafts shall have a minimum airflow velocity in accordance with Table 1109.3.2.3“
[3] International Code Council (ICC); “2024 International Mechanical Code”; June 2023
This section has the same implications regarding labor, material, and cost as those mentioned above. The extension of ventilated shafts to the outdoors raises the issue of energy lost as the system copes with the outside air temperature, and continuously mechanically ventilated shafts raise the issue of additional energy consumption to keep fans running. If modeled correctly, these additional energy expenditures could affect a project’s ability to achieve required energy performance credits for programs such as LEED, further affecting project viability.
The total energy cost of implementing low-GWP refrigerants is unclear. Shaft ventilation requirements and less energy-efficient refrigerants will increase energy use onsite. The manufacture of synthetic refrigerants and the increased use of vehicles and equipment in the construction process will increase energy use offsite. In the absence of low-GWP equipment performance data, HVAC design engineers are unable to develop a solid understanding of how environmentally superior the new low-GWP refrigerants are. The waters become murkier considering that prohibited legacy refrigerants can still be exported up to three years after the ban on their manufacture [5], mitigating the positive environmental impact of reduced GWP systems.
It is encouraging that the EPA considered stakeholders’ concerns and extended the initial effective date of the final ruling. The AEC industry and the EPA generally share a desire to move towards a sustainable future, and working together is the only sensible path forward. Engenium Group looks forward to continued collaboration with the ICC, the EPA, and other entities that help define how AEC systems affect the world in which we live.
- [1] EPA; Docket EA-HQ-OAR-2021-0643-0234 “Phasedown of Hydrofluorocarbons: Technology Transitions Program Residential and Light Commercial Air Conditioning and Heat Pump Subsector”; December 2023.
- [2] EPA 2023
- [3] International Code Council (ICC); “2024 International Mechanical Code”; June 2023
- [4] International Code Council (ICC); “2024 International Mechanical Code”; June 2023.
- [5] Bolen, Brittany, Samuel Boxerman, and Hannah Posen; Sidley Environmental Energy Brief; “U.S. EPA Bans Hydrofluorocarbons in Refrigeration, Air Conditioning, and Heating Products”; October 2023.
