Timing the certification pathway before the §45L energy efficient home credit lapses.

§45L Background and the 2026 Sunset Date

The §45L New Energy Efficient Home Credit, codified at IRC §45L, has anchored production-builder energy programs since its 2005 reauthorization. The current framework, established by the Inflation Reduction Act, allows a $2,500 credit per dwelling certified at 50% energy savings above the 2006 IECC reference, or $5,000 per unit at the 80% savings tier (Zero Energy Ready Home). The credit applies to homes or apartments acquired on or before December 31, 2025 and placed in service before January 1, 2026 for ENERGY STAR certifications; the deadline extends to June 30, 2026 for DOE Zero Energy Ready Home (ZERH) certifications per Energy.gov §45L guidance.

Because certification must be obtained before the unit closes, builders pursuing ZERH must complete HERS ratings, blower door tests, duct leakage tests, and thermal enclosure checklists well before June 30, 2026. HECS project data shows production builders typically need 6-10 weeks of lead time for the verification chain. Schedules that begin in April 2026 will not close.

Compliance Pathways: ENERGY STAR v3.2 vs DOE ZERH

Three certification tracks qualify a dwelling for §45L in the 2025-2026 window:

Each track requires an accredited HERS Rater to register the home with ENERGY STAR and RESNET, perform on-site verification, and submit the certification package. Per the RESNET Standards, the rater — not the builder — is responsible for the certification seal. Builders cannot self-certify.

Working with HECS: HECS handles HERS rating, blower door testing, duct leakage testing, and ENERGY STAR v3.2 multifamily certification for production builders in Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. Our NCI-certified and RESNET-certified team manages the full verification chain so your eligibility file is airtight before the cutoff. For a scope call: (859) 983-7382 or hecsusa.com/contact/.

Verification Fieldwork: What HECS Actually Measures

A §45L file requires field-verified performance data, not modeled estimates alone. HECS delivers the following per the RESNET Standards and ASHRAE 111:

• Blower door test to RESNET 380 — typically 3-5 ACH50 for ZERH compliance, depending on climate zone.
• Duct leakage to RESNET 380 — total leakage typically ≤ 4 CFM25 per 100 sq ft conditioned floor area for ZERH; handler rough-in tested where applicable.
• HVAC testing and balancing per ACCA Manual J/S/D/T — equipment sizing, duct design, and commissioning verified before certification.
• Thermal imaging of the building enclosure per RESNET grading criteria.

For multifamily projects, HECS follows ENERGY STAR Multifamily New Construction (MFNC) v3.1 pathway requirements including fire compartmentalization pressure tests and common-area ventilation measurements. The MFNC checklist is denser than the SFNH path, and raters must be ENERGY STAR Multifamily Reviewer certified — a credential HECS holds.

Common Pitfalls That Disqualify §45L Submissions

Based on HECS project data, four failure modes recur in builder submissions:

1. HERS Index filed after the placement-in-service date — the credit is lost for that unit.
2. Insulation grade III rather than grade I — RESNET requires grade I for the reference home; grade II or III reduces HERS performance.
3. Duct leakage measured at rough-in only — ZERH requires both rough-in and final tests.
4. Missing rater photos of every window and door — RESNET QA rejects files without the photo log.

A fifth pitfall, increasingly common in 2025 builds: HVAC equipment rated for the 2024 IECC but commissioned without a Manual J load calculation, which causes the RESNET reference home to assume oversized equipment and depresses the certified HERS Index below the threshold.

Frequently Asked Questions

Does §45L apply to multifamily projects, or only single-family homes?

IRC §45L covers both single-family and multifamily dwellings, but the certification pathway differs. Multifamily buildings with four or more units must follow ENERGY STAR MFNC v3.1 or NGBS Green Certified multifamily program requirements. HECS is an NGBS Green Certified Verifier and ENERGY STAR Multifamily Reviewer — we manage the verifier role so the developer does not need separate staff. Per 45L tax credit Louisville KY, our Kentucky multifamily clients routinely certify 50-200 unit projects.

Can a builder still claim §45L after June 30, 2026?

No. Per Energy.gov §45L guidance, ZERH certifications must be completed before the deadline; ENERGY STAR certifications must be obtained before the unit closes. After June 30, 2026, the credit expires unless Congress extends it. HECS has no visibility into future reauthorizations and treats the current sunset as final. Builders in HECS's region should assume no extension and prioritize their closing pipeline accordingly.

What is the difference between a HERS Index and an ASHRAE 90.1 compliance rating?

A HERS Index is a RESNET-defined scoring system where 100 represents the 2006 IECC reference home, and lower numbers indicate better performance. An ASHRAE 90.1 rating, by contrast, is a compliance pathway used in commercial and multifamily work where the building must meet ASHRAE 90.1-2019 or 90.1-2022 prescriptive or performance criteria. HECS delivers HERS ratings per RESNET Standards and can coordinate ASHRAE 90.1 performance verification with the project's design engineer.

How to Engage HECS

HECS provides blower door testing, duct leakage testing, HVAC testing and balancing, ENERGY STAR v3.2 and MFNC v3.1 certification, NGBS Green and EarthCraft verification, and full §45L file preparation for builders and developers. We serve Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri — including Louisville KY, Lexington KY, Cincinnati OH, Indianapolis IN, Nashville TN, St. Louis MO, Chicago IL, Evansville IN, and Columbus OH. Contact John Sabbak at (859) 983-7382 or [email protected] to scope a project, or submit a request at hecsusa.com/contact/. Full service descriptions are available at hecsusa.com/services/.