The EPA's AIM Act phase-down reshapes what residential HVAC crews carry, vent, and test on Kentucky job sites.
The EPA's American Innovation and Manufacturing (AIM) Act phase-down is forcing a residential refrigerant transition from R-410A to A2L refrigerants — primarily R-454B and R-32 — across U.S. split-system manufacturing. Equipment lines shipped after the cutoff date will arrive charged with mildly flammable A2Ls, and Kentucky contractors will handle them on virtually every new-construction and replacement job from 2026 forward.
A2Ls differ from R-410A in three ways that matter in the field. They carry a 2L flammability classification (ASHRAE 34), so refrigerant leak sensors, recovery equipment, and venting practice must adapt. They require different oils in many cases — R-454B typically pairs with POE, R-32 historically paired with mineral oil but POE is now standard. They operate at lower glide and different discharge temperatures, which shifts superheat targets and TXV behavior during commissioning.
For Louisville-area residential HVAC contractors, the practical impact shows up in three places: tools and recovery machines (they must be A2L-rated by January 2026), refrigerant charge procedures (a new R-454B system will not charge the same way as R-410A), and combustion/venting clearance if any portion of the equipment sits indoors (A2Ls require revised combustion appliance zone considerations per the International Residential Code (IRC) Chapter 24 and the equipment listing).
Need HECS for your project?
NCI-certified testing and certification across KY, IN, OH, TN, IL, MO.
Call (859) 983-7382 Get a QuoteThe IRC mechanical chapters now reference ASHRAE Standard 15 and 34 for refrigerant classification, and the 2024 IRC M1411 requires refrigerant detectors and mitigation equipment in certain occupancies when refrigerant charge exceeds threshold limits. The 2024 International Mechanical Code (IMC) Chapter 11 carries the parallel commercial requirements, but residential contractors feel this through equipment listings rather than direct code text.
The key reference for classification and safety classification is ASHRAE Standard 34-2022, which assigns the "2L" designation to R-454B and R-32. The 2024 IRC adopts Standard 34 by reference for designation letters, while ASHRAE Standard 15 governs system safety group classifications. The EPA SNAP Rule 20 and 21 listings (under the AIM Act) approved R-454B and R-32 for residential use and require A2L-rated equipment, leak detection per specific room-size thresholds, and revised installation clearances.
For Louisville (Jefferson County), Kentucky is in DOE Building America climate zone 4A for IECC purposes — meaning any blower door or duct leakage testing for code compliance falls under the 2024 IECC envelope requirements, not refrigerant code directly. The refrigerant rules apply to the equipment itself; the IECC applies to the building envelope the equipment serves.
HECS treats the A2L transition as a procedural change, not a refrigerant change. The verification work — blower door, duct leakage to outside, and airflow measurement — does not shift because the refrigerant shifted. What shifts is the equipment nameplate data on the rating plate and how commissioning forms get filled out.
| Test Type | Reference Standard | Kentucky/Indiana Threshold |
|---|---|---|
| Blower door | ASTM E779 / RESNET Std 380 | 2024 IECC Table R402.4.1.1: 3.0 ACH50 (CZ 3-8) |
| Duct leakage to outside | ASTM E1554 / RESNET Std 380 | 2024 IECC R403.3.5: ≤ 4 CFM25 per 100 ft² conditioned area |
| Room airflow | NCI Residential Air Balancer | Per ACCA Manual D / room-by-room load |
HECS recommends contractors keep the existing workflow for envelope testing but adjust the refrigerant-handling workflow: confirm recovery machines and recovery cylinders are A2L-rated, verify leak detectors are rated for the specific refrigerant shipped, and document the A2L charge weight on startup forms because the AHRI certificate will reflect different charge amounts than R-410A equipment.
HECS handles blower door, duct leakage, and residential HVAC airflow verification for builders across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. For an A2L-era commissioning scope call: (859) 983-7382 or hecsusa.com/contact/.
HECS field reports for Louisville-area residential projects include the building envelope metrics tied to IECC compliance, plus airflow verification tied to NCI Residential Air Balancer procedures. The refrigerant transition does not change those deliverables — but it changes the equipment being tested. R-454B split systems ship with different AHRI reference numbers, different factory charge weights, and different coil configurations that affect static pressure and external static resistance on the airside.
The deliverable a contractor receives is unchanged in format: ACH50 result, CFM25 to outside, room-by-room supply CFM versus ACCA Manual D design, and total system CFM per ton. What changes is the cross-reference against the new equipment's rated performance. HECS flags when measured airflow falls outside the AHRI-rated envelope for the specific model installed — which matters more with A2L equipment because manufacturers are still publishing revised performance data through 2026.
For projects seeking ENERGY STAR Multifamily New Construction or NGBS-2023 certification, the HVAC Functional Testing Checklist still applies regardless of refrigerant, and the duct leakage thresholds remain at the ENERGY STAR MFNC v1.3 (Rev05) levels — 6 CFM25 per 100 ft² rough-in and 8 CFM25 post-construction.
Does the A2L refrigerant transition change how HECS tests blower door or duct leakage on a Louisville new-construction home? No. The refrigerant in the indoor and outdoor units does not affect the air barrier or duct tightness. HECS still tests to the 2024 IECC R402.4.1.2 blower door requirements — 3.0 ACH50 for Jefferson County (CZ 4A) — and 2024 IECC R403.3.5 duct leakage thresholds at 4 CFM25 per 100 ft² of conditioned floor area. The same RESNET Standard 380 protocol and sampling rules apply.
What A2L-rated tools does a Kentucky HVAC contractor need by January 2026? Recovery machines, recovery cylinders, leak detectors, and vacuum pumps must carry A2L certification labels. HECS verifies that startup documentation reflects the listed refrigerant (R-454B or R-32), the correct charge weight per the AHRI certificate, and the appropriate oil type — but HECS does not sell or service refrigerant recovery equipment.
If a project is registering for ENERGY STAR or NGBS, does the A2L transition affect HECS's certification deliverable? No. The ENERGY STAR MFNC v1.3 (Rev05) and NGBS-2023 verification paths test envelope performance, duct leakage, and HVAC airflow regardless of refrigerant type. HECS reports remain the same deliverable.
HECS supports residential HVAC verification across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. Services relevant to the refrigerant transition include blower door testing, duct leakage to outside verification, residential HVAC airflow measurement under NCI Residential Air Balancer protocols, and ENERGY STAR / NGBS third-party verification where applicable. Reach HECS at (859) 983-7382 or [email protected], or request a scope through hecsusa.com/contact/. The full service menu is at hecsusa.com/services/. HECS also serves Louisville KY, Lexington KY, Cincinnati OH, Indianapolis IN, Nashville TN, Evansville IN, and St. Louis MO — see hecsusa.com/hvac-testing-and-balancing-cincinnati-oh/ for the regional service-area pages.
One short email per month with code updates, testing data, and what HECS is seeing in the field across KY / IN / OH / TN / IL / MO. Unsubscribe in one click.