Residential compliance, leak testing, and certification changes affecting Kentucky installers.
The EPA's American Innovation and Manufacturing (AIM) Act ruling phases down higher-GWP refrigerants, and the residential HVAC market has effectively landed on two A2L replacements, R-454B for unitary split systems and R-32 for several mini-split product lines. A2L refrigerants are classified as mildly flammable, lower-toxicity, which changes how installers work on commissioning day and how third-party verifiers prove the system is leak-tight.
Kentucky contractors have reported pressure to install A2L condensing units before the field workforce has fully internalized the new leak-test threshold, the charge-weight documentation, and the combustion-air separation rules. Based on HECS project data, that gap is where failed commissioning trips and rejected ENERGY STAR Multifamily New Construction National Program Requirements v1.3 (Rev05) certifications tend to cluster.
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Call (859) 983-7382 Get a QuoteThe 2024 IECC, adopted through Kentucky's regulatory cycle and enforced in Louisville/Jefferson County on its current effective date, controls residential envelope and duct tightness independently of refrigerant type. Per 2024 IECC R402.4.1.2, the building must be tested per ASTM E779 or equivalent, with verified rate at or below the Table R402.4.1.1 maximum. For Kentucky's climate zones (CZ 4A across most counties and CZ 5A in the northeast), the binding ceiling is 3.0 ACH50, not 5.0.
Duct tightness is a separate test. 2024 IECC R403.3.5 requires verified total leakage to outside of 4 CFM25 per 100 ft² of conditioned floor area when ducts run outside the conditioned envelope. ASHRAE 62.2-2022 §4.1 governs mechanical ventilation rates, Q_total = 0.03·A_floor + 7.5·(N_br+1) cfm, and §4.3 sets local exhaust minimums (≥100 cfm intermittent kitchens, ≥50 cfm intermittent baths). A2L work touches none of these directly, but HECS routinely finds that a refrigerant-charge issue traces back to an airflow or duct-leakage miss that the installer missed.
HECS handles A2L transition verification, HVAC Testing & Balancing, and envelope certification for projects in Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. For a scope call: (859) 983-7382 or hecsusa.com/contact/.
HECS treats the A2L change as a three-part verification problem: refrigerant-side leak tightness, airflow-side performance, and code-side documentation. The refrigerant side is governed by AHRI and manufacturer leak-test procedures, not a section HECS can cite from the energy code, so we anchor on the airflow and envelope thresholds that the residential energy and ventilation codes do cite.
For a typical Louisville single-family project, HECS verifies the system against the 2024 IECC envelope, the ASHRAE 62.2-2022 ventilation rate, and the NGBS-2023 tier the builder is pursuing. A2L charge-weight reporting and combustion-air separation get cross-checked against the manufacturer installation manual, but the binding numbers come from the energy and ventilation codes.
A standard HECS residential A2L-era commissioning deliverable includes:
For NGBS projects, the HECS verifier holds the NGBS Green Certified Verifier credential, and the report is structured to satisfy the third-party verification requirement at NGBS-2023 §702.1.1. For multifamily work targeting ENERGY STAR, the blower door and duct leakage tests roll into the sampling protocol at ANSI/RESNET/ICC 301-2022 with sample sizes per building height and unit count.
| Standard | Section | Binding Threshold | HECS Use |
|---|---|---|---|
| 2024 IECC | R402.4.1.2 / Table R402.4.1.1 | 3.0 ACH50 (CZ 3-8) | Blower door pass |
| 2024 IECC | R403.3.5 | 4 CFM25 / 100 ft² | Duct tightness pass |
| ASHRAE 62.2-2022 | §4.1 | 0.03·A + 7.5·(N_br+1) cfm | Ventilation rate |
| ASHRAE 62.2-2022 | §4.3 | Kitchen 100 cfm / Bath 50 cfm | Local exhaust |
| NGBS-2023 | §702.1.1 | 3rd-party verification | Verifier signature |
Does A2L adoption change the blower door or duct leakage thresholds for Kentucky projects? No. The 2024 IECC envelope numbers are refrigerant-agnostic. For Louisville (CZ 4A), the binding ceiling is 3.0 ACH50 per 2024 IECC R402.4.1.2, and duct leakage to outside is 4 CFM25 per 100 ft² conditioned area per 2024 IECC R403.3.5. HECS verifies both regardless of refrigerant.
What does HECS actually check on the refrigerant side during an A2L commissioning? HECS confirms the installed charge weight against the manufacturer nameplate, records the leak-test pass/fail per the OEM installation manual, and verifies combustion-air separation distances. The energy code does not cite a numeric refrigerant leak threshold, so HECS reports the refrigerant-side data as a deliverable against the manufacturer's documented procedure rather than against an IECC section.
How does A2L affect a builder's path to ENERGY STAR or NGBS certification? It does not change the certification thresholds directly. ENERGY STAR MFNC functional testing and NGBS-2023 third-party verification still ride on the envelope, duct, and ventilation numbers from the 2024 IECC and ASHRAE 62.2-2022 §4.1. HECS structures the report so the same field visit satisfies both pathways.
HECS supports A2L-era residential HVAC commissioning, blower door and duct leakage testing, and NGBS / ENERGY STAR verification for projects across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. Builders, code officials, and developers should reach HECS at (859) 983-7382 or [email protected] to scope a project. Service-area pages cover Louisville KY, Lexington KY, Cincinnati OH, Indianapolis IN, Nashville TN, St. Louis MO, and Chicago IL. For a full list of available services and to schedule a site visit, go to hecsusa.com/services/ or submit a request at hecsusa.com/contact/.
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