One-line dek: A working guide to what the federal rule, 2024 IECC, and ENERGY STAR MFNC actually require on multifamily projects in Louisville, Lexington, and the Ohio River Valley.
The DOE multifamily final rule, paired with the 2024 IECC and ENERGY STAR MFNC v1.3 (Rev05), has changed the documentation trail builders must produce. On HECS jobs across Kentucky and southern Indiana, the same five problems keep surfacing: missing third-party verification, blower-door sampling done to the wrong table, duct leakage tested at the wrong code cycle, ventilation rates calculated against an outdated ASHRAE 62.2 reference, and ENERGY STAR checklists completed without an NCI-certified air balancer on site.
Kentucky sits in IECC Climate Zone 4A for most counties — Louisville (Jefferson), Fayette, Boone, Kenton, Campbell, and the I-75 corridor. The northeastern tier — Boyd, Carter, Greenup, Lawrence, Elliott, Morgan, Rowan, Bath, Menifee, Montgomery, and Robertson counties — is CZ 5A. Under 2024 IECC Table R402.4.1.1, both zones fall under the same 3.0 ACH50 ceiling. The old 2018 mapping (CZ 4 = 5.0, CZ 5 = 3.0) is dead. Projects quoting the previous numbers are getting rejected at plan review.
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Call (859) 983-7382 Get a QuoteThree documents govern a typical multifamily project in HECS's footprint: 2024 IECC Residential, ENERGY STAR MFNC v1.3 (Rev05) National, and ASHRAE 62.2-2022. NGBS-2023 enters when the owner is pursuing green certification.
| Compliance Path | Air Leakage Limit | Duct Leakage | Sampling Allowed |
|---|---|---|---|
| 2024 IECC R402.4.1.2 | ≤ 3.0 ACH50 (CZ 4A/5A) | ≤ 4 CFM25/100 ft² (R402.4.2 / R403.3.5) | Yes — Table R405.4.2(1) |
| ENERGY STAR MFNC v1.3 (Rev05) | Per ASHRAE 90.1-2019 | ≤ 6 CFM25 rough-in / ≤ 8 post | RESNET sampling |
| NGBS-2023 §702.1.1 | Tier-dependent | §704.1, tested per ANSI/RESNET/ICC 850 | Verifier-defined |
ASHRAE 62.2-2022 §4.1 sets the whole-building ventilation rate at Q_total = 0.03·A_floor + 7.5·(N_br+1) cfm. §4.1.4, updated by the 2024 addendum, governs MERV filtration credit. §4.3 covers local exhaust — kitchen range hoods at ≥100 cfm intermittent or ≥25 cfm continuous, bathrooms at ≥50 cfm intermittent. §4.4 caps the infiltration credit at the lesser of 2 ACH50 or 0.04·A_floor / 7.6 cfm.
Blower-door sampling for multifamily is governed by 2024 IECC Table R405.4.2(1), which sets sample sizes by building height and unit count. ENERGY STAR MFNC routes through ANSI/RESNET/ICC 380. NGBS-2023 uses verifier-defined sampling. The three sampling protocols are not interchangeable. Builders who submit one rater's sampling and have another program reviewer reject it lose weeks.
HECS scopes every multifamily project against three reference documents before the test day is scheduled: the 2024 IECC Residential provisions adopted by the local jurisdiction, the ENERGY STAR MFNC v1.3 (Rev05) National Program Requirements, and — if certification is in play — NGBS-2023 Chapter 7 (resource efficiency) and §702.1.1 (third-party verification).
The field workflow follows the same sequence on every job. First, verify which sampling protocol applies — Table R405.4.2(1), ANSI/RESNET/ICC 380, or NGBS verifier-defined. Second, run blower-door per ASTM E779. Third, run duct leakage per ASTM E1554 or RESNET/ICC Standard 380. Fourth, calculate ASHRAE 62.2-2022 ventilation using conditioned floor area and bedroom count. Fifth, complete the HVAC Functional Testing Checklist for every participating unit. HECS holds NCI Commercial Air Balancer certification, which is the credential ENERGY STAR MFNC and most green programs require for the airflow portion.
HECS handles multifamily code-compliance verification — blower door, duct leakage, ASHRAE 62.2 ventilation calculations, and HVAC Functional Testing Checklists — for projects in Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. For a scope call: (859) 983-7382 or hecsusa.com/contact/.
Every HECS multifamily report includes: tested ACH50 per building (with sampling location rationale per Table R405.4.2(1) or ANSI/RESNET/ICC 380); total duct leakage to outside in CFM25 per 100 ft² of conditioned floor area per R402.4.2 / R403.3.5; ASHRAE 62.2-2022 §4.1 required versus delivered ventilation for each unit type; local exhaust verification per §4.3; HVAC Functional Testing Checklist sign-off; and — when applicable — NGBS-2023 verifier signature with credential reference per §702.1.1.1.
The deliverable is a single PDF with the test data, the equipment serial numbers, the certified test technician's NCI credential number, and a pass/fail flag against each code section. That PDF is what plan reviewers, ENERGY STAR providers, and green program verifiers all read first.
Three patterns repeat. Projects submit R402.4.1.2 blower-door results to an ENERGY STAR reviewer who expects ANSI/RESNET/ICC 380 sampling and rejects the package. Projects cite §4.4 infiltration credit without confirming the 2 ACH50 / 0.04·A_floor / 7.6 cfm cap. Projects test duct leakage at rough-in only and skip post-construction — ENERGY STAR MFNC v1.3 (Rev05) requires both thresholds: ≤ 6 CFM25/100 ft² rough-in and ≤ 8 CFM25/100 ft² post-construction.
Does the DOE multifamily rule replace 2024 IECC on a Kentucky project? No. The DOE final rule establishes a federal baseline; Kentucky's adopted 2024 IECC Residential provisions remain the binding enforcement document at plan review. HECS tests to the more stringent of the two on every job.
Can blower-door sampling cover every unit in a 40-unit Louisville apartment building? Sampling is allowed under 2024 IECC Table R405.4.2(1), ENERGY STAR MFNC v1.3 (Rev05) via ANSI/RESNET/ICC 380, and NGBS-2023 with verifier-defined protocols — but the protocols differ. The HECS report documents which protocol applies and why.
What credential does a third-party verifier need for NGBS-2023 in Kentucky? Per §702.1.1.1, the verifier must be an NGBS Green Certified Verifier, RESNET Certified HERS Rater, BPI Building Analyst, or equivalent as approved by Home Innovation Research Labs. HECS holds the RESNET HERS Rater credential and the NGBS Green Certified Verifier credential — both accepted under that section.
HECS scopes multifamily code-compliance verification — blower door, duct leakage, ASHRAE 62.2 ventilation, HVAC Functional Testing Checklists — for projects across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. The relevant service pages are hecsusa.com/services/, hecsusa.com/contact/, and the city-cluster pages for Louisville KY, Lexington KY, Cincinnati OH, and Indianapolis IN. Reach the team at (859) 983-7382 or [email protected] to schedule a scope call before the rough-in stage so the sampling protocol is locked in early.
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