The One Big Beautiful Bill Act rewrote §45L — here's what developers in Kentucky, North Carolina, and Alabama need to verify before claiming.

What OBBBA Actually Changed in §45L

The One Big Beautiful Bill Act (Public Law 119-21) was signed July 4, 2025 and materially restructured the §45L New Energy Efficient Home Credit for homes or apartments acquired after December 31, 2024. Under prior law, base credits ranged roughly from $2,000-$5,000 per unit depending on energy improvement, with bonuses for meeting prevailing-wage and apprenticeship requirements. The OBBBA version keeps the energy-savings tiers but tightens qualifying thresholds and restructures the prevailing-wage adders.

For multifamily developers, the practical shift is documentation. Each unit claiming the credit must now be certified under a DOE-approved program — typically ENERGY STAR Multifamily New Construction (MFNC) or the Zero Energy Ready Home (ZERH) program — and the certifying body must be a RESNET-accredited CEA. HECS holds RESNET Certified HERS Rater credentials, which is the prerequisite for performing the required on-site verifications.

The earlier credit regime expired for projects placed in service after the OBBBA transition window; the revised structure governs forward. Builders should expect IRS audit focus on the certification chain — the rater, the provider, and the program version must all reconcile on the Form 8908 attachment.

Verifying MFNC v3.1 and ZERH Compliance in the Field

The active ENERGY STAR MFNC program requirements (Rev05 in the v3.x series) define a thermal envelope checklist that drives most of HECS's field testing scope. The two thermal envelope measurements that consume field time are blower-door airtightness and duct leakage to outside. In our experience, the duct leakage pass rate is the more common failure point on Kentucky multifamily projects.

The 2024 International Energy Conservation Code (IECC) §R402.4.2 sets the underlying duct leakage target for code compliance, but ENERGY STAR and ZERH layer additional verification on top. HECS performs duct leakage testing per ACCA Manual D coordination with the HVAC design, and reports results in CFM25 per square foot of conditioned floor area — the metric both programs use for compliance.

ZERH adds an EPA FORTIFIED Roof requirement set on top of ENERGY STAR, which expands HECS's field checklist to include radon testing in EPA Zone 1 counties and mechanical ventilation rate verification per ASHRAE 62.2-2022. Southern Indiana and the Ohio River counties in Kentucky and Illinois sit in Zone 1, which means the radon measurement is not optional there.

Working with HECS

HECS handles FORTIFIED Roof evaluation certification for multifamily and single-family projects across Kentucky, North Carolina, Alabama, Georgia, West Virginia, Kansas, and Missouri. We staff the rater, run the field verification, and produce the certification package your CPA files with Form 8908. For a scope call: (859) 983-7382 or hecsusa.com/contact/.

Sampling, Rater-of-Record Rules, and Documentation Gaps

The MFNC and ZERH sampling protocols are not optional. A project sampling ratio is typically 1 in 7 units per building for blower-door and duct leakage, with the rater-of-record responsible for selecting which units are tested. Failed units trigger re-sampling and, in some cases, full-building retesting depending on the failure rate. Based on HECS project data, builders who skip the pre-construction design review typically see 20-30% field-time compression lost to remediation testing.

The documentation chain matters as much as the field result. Each certified unit needs:

• ENERGY STAR or ZERH checklist completed and signed
• Blower-door test report at final inspection
• Duct leakage test report at rough-in or final
• HVAC start-up per ACCA Manual S and Manual T commissioning
• Thermal imaging verification of insulation continuity
• RESNET rater-of-record signature linking the unit to the certification

When one of these is missing at audit, the credit is denied at the unit level — not the project level. That makes the rater-of-record relationship one of the most consequential subcontracts on a 45L project.

Comparison of Qualifying Certification Pathways

The ZERH path generally produces the strongest 45L documentation because it forces a single rater to verify all checklist items. The NGBS and EarthCraft paths add value when the project is also pursuing green financing or a state-level affordable housing scoring bonus.

Coordination with FORTIFIED Home and Other Stackable Programs

The FORTIFIED Home 2025 standard addresses roof, wall, and opening resistance to wind and hail — it is structurally orthogonal to 45L's energy scope, but HECS is an IBHS FORTIFIED Home Evaluator and clients increasingly bundle both verifications to stack insurance discounts with federal tax credits. For projects in high-wind zones in western Tennessee and southern Illinois, the combined deliverable reduces total third-party inspection visits.

The NCI Certified Air Balancer credential that HECS holds covers the commercial balancing side, while the HERS Rater credential covers residential 45L. A single project rarely needs both, but mixed-use developments with retail or office space below residential floors do.

Frequently Asked Questions

What documentation does HECS deliver for a 45L claim?

HECS produces a per-unit certification package including the ENERGY STAR or ZERH checklist, blower-door and duct leakage reports, HVAC commissioning record, and a RESNET rater-of-record sign-off. That package is what your CPA attaches to Form 8908 — missing elements are the most common reason credits are denied at IRS review.

Does OBBBA change the prevailing-wage requirement for §45L?

The OBBBA revision retains the prevailing-wage and apprenticeship adder structure but redefines the qualifying wage thresholds and the documentation required to claim the bonus tier. HECS does not provide prevailing-wage payroll certification, but we confirm the energy-side documentation that the bonus tier requires so the two audit trails do not contradict each other.

Can a builder use 2024 IECC compliance in place of an ENERGY STAR certification?

No. The 2024 IECC and ENERGY STAR MFNC v3.1 overlap on airtightness and duct leakage, but 45L requires certification under a DOE-approved program — IECC code compliance alone does not satisfy the credit. The two work together; neither substitutes for the other.

How to Engage HECS

HECS supports 45L certification, ENERGY STAR MFNC and ZERH verification, HVAC testing and balancing, blower-door and duct leakage testing, and FORTIFIED Home evaluation across Kentucky, North Carolina, Alabama, Georgia, West Virginia, Kansas, and Missouri. Project scopes typically begin with a 30-minute design review call where we flag the field-testing sequence, the sampling plan, and the rater-of-record assignment. Reach the HECS team at (859) 983-7382 or [email protected] to schedule, or submit a scope through hecsusa.com/contact/. HECS also serves Louisville KY, Lexington KY, Cincinnati OH, Indianapolis IN, Nashville TN, Evansville IN, and Columbus OH — and we travel for projects with unit counts that justify mobilization from Louisville. For a full service list, see hecsusa.com/services/.