Field impact on Kentucky HVAC testing, commissioning, and certification work.
The 2025 EPA ruling under the American Innovation and Manufacturing (AIM) Act phases down HFC refrigerants, and most residential split systems sold in the U.S. after January 1, 2026 must charge with A2L refrigerants — R-454B or R-32, depending on manufacturer. Louisville-area contractors are now handling equipment that is mildly flammable (ASHRAE 34 classification: A2L), carries new leak-detection requirements, and ships with factory-installed refrigerant sensors on many indoor units. The mechanical installation looks familiar, but the commissioning, leak-check, and documentation work has changed.
What builders and contractors get wrong most often: assuming the refrigerant transition is purely a chemistry issue handled by the installer. It is not. A2L adoption intersects with combustion air clearances, ventilation per ASHRAE 62.2-2022, condensate management, and the blower door / duct leakage testing that determines code compliance under 2024 IECC. Louisville (Jefferson County) sits in Climate Zone 4A, so the binding air-leakage limit is 3.0 ACH50 per Table R402.4.1.1 — not 5.0. Project teams that delay coordination between the mechanical sub and the third-party tester typically pay for it in retests.
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Call (859) 983-7382 Get a QuoteThe A2L transition is governed by multiple overlapping documents. ASHRAE 15 (Safety Standard for Refrigeration Systems) and ASHRAE 34 (Designation and Safety Classification of Refrigerants) define the A2L class and the room-volume and sensor requirements. The product safety standard is UL 60335-2-40 ( Household and Similar Electrical Appliances — Safety — Part 2-40: Heat Pumps, Air Conditioners and Dehumidifiers), which manufacturers cite to comply with the 2025 EPA rule.
On the Kentucky side, the 2024 IECC drives envelope and duct testing. The relevant sections are R402.4.1.2 (blower door testing per ASTM E779) and R402.4.2 / R403.3.5 (duct tightness to ≤ 4 CFM25 per 100 ft² conditioned floor area, tested per RESNET/ICC Standard 380). Ventilation follows ASHRAE 62.2-2022 §4.1: Q_total = 0.03·A_floor + 7.5·(N_br+1) cfm, with MERV filtration credit per §4.1.4 and local exhaust per §4.3. For ENERGY STAR MFNC v1.3 (Rev05) projects, the HVAC Functional Testing Checklist (v1.1/1.2/1.3) is required for every participating unit; townhomes are exempt from Sections 2 and 3.
| Standard | Section / Table | Threshold relevant to A2L field work |
|---|---|---|
| 2024 IECC | R402.4.1.2 + Table R402.4.1.1 | ≤ 3.0 ACH50 in CZ 4A/5A |
| 2024 IECC | R403.3.5 | Duct leakage to outside ≤ 4 CFM25 per 100 ft² |
| ASHRAE 62.2-2022 | §4.1 | Whole-building ventilation formula |
| ENERGY STAR MFNC v1.3 (Rev05) | HVAC Functional Testing Checklist v1.1/1.2/1.3 | Required for each participating unit |
| IRC §45L | Public Law 119-21 | Acquisition deadline 2026-06-30 |
A second citation the field often misses: IRC §45L. The One Big Beautiful Bill (Public Law 119-21, signed July 4, 2025) accelerated the energy-efficient home credit expiration. Homes acquired after 2026-06-30 do not qualify. A2L equipment pairs cleanly with §45L documentation, but only if the certification package is closed before the closing date.
HECS treats the A2L transition as a single integrated commissioning event rather than three separate trades. The sequence on a typical Louisville custom-home or multifamily project runs: pre-drywall blower door and duct leakage (rough-in) → A2L equipment set and leak-check by the mechanical contractor → final blower door + duct leakage to outside → ASHRAE 62.2-2022 ventilation verification → NCI residential air balancing → report package.
Two specific practices keep projects from blowing up. First, the rough-in duct leakage target. On ENERGY STAR MFNC v1.3 (Rev05) projects, total duct leakage at rough-in should land at or below 6 CFM25 per 100 ft² conditioned floor area; post-construction, ≤ 8 CFM25 per 100 ft². The 2024 IECC §R403.3.5 envelope of 4 CFM25 per 100 ft² is tighter. HECS recommends the tighter envelope for A2L projects because it gives margin against sensor-driven refrigerant shutdown events triggered by envelope-driven depressurization in mech rooms. Second, the ventilation credit under ASHRAE 62.2-2022 §4.1.4: a MERV-rated filter can reduce required mechanical ventilation, but the credit must be documented in the final report.
Working with HECS
HECS handles residential HVAC testing and balancing, blower door testing, duct leakage testing, and the full certification stack (ENERGY STAR, NGBS Green, FORTIFIED Home, 45L) for projects in Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. A2L projects are scoped case-by-case because the leak-check, sensor commissioning, and envelope documentation sequence varies by manufacturer. For a scope call: (859) 983-7382 or hecsusa.com/contact/.
The HECS report package for an A2L project contains specific deliverables that code officials and energy raters actually read:
The most common pitfall HECS finds on A2L projects: mech-room refrigerant sensor wiring was not commissioned before the final blower door test. The pressurization event triggers the sensor, the equipment locks out, and the test sequence stalls. Coordinating the sensor commissioning with the envelope test prevents the rework.
Does the 2025 EPA A2L mandate change the blower door test procedure under 2024 IECC R402.4.1.2?
No. The refrigerant transition changes the equipment and the leak-check, but the blower door test still runs per ASTM E779 to the threshold in Table R402.4.1.1 — 3.0 ACH50 for CZ 4A and 5A, which covers all HECS Kentucky and Indiana projects.
Can A2L equipment still qualify a project for the IRC §45L tax credit?
Yes, if the home is acquired on or before 2026-06-30 per Public Law 119-21. HECS ties the A2L commissioning documentation, blower door, duct leakage, and ENERGY STAR or NGBS verification into a single §45L package for the builder.
Is the ASHRAE 62.2-2022 whole-building ventilation formula different for A2L homes?
No. The Q_total = 0.03·A_floor + 7.5·(N_br+1) cfm equation in §4.1 is unchanged. What changes is that HECS coordinates the local exhaust per §4.3 and the §4.1.4 filtration credit on the same site visit as the A2L refrigerant leak-check, so the ventilation documentation is consistent with the equipment actually installed.
HECS supports A2L residential HVAC projects across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri, with field coverage in Louisville KY, Lexington KY, Cincinnati OH, Indianapolis IN, and Nashville TN. Pre-drywall rough-in, final envelope testing, NCI residential air balancing, ASHRAE 62.2-2022 ventilation verification, and the ENERGY STAR / NGBS / FORTIFIED Home / 45L certifications are all scoped and scheduled together. Reach (859) 983-7382 or [email protected] to start a scope call. Service details are at hecsusa.com/services/, and the project intake form is at hecsusa.com/contact/.
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