What code officials actually flag, and how builders in Louisville, Lexington, and Indianapolis should plan their blower door sequence.

Why the 2024 IECC Air Leakage Numbers Are the Hard Constraint on Kentucky Schedules

The 2024 IECC air barrier and building tightness requirements tightened again on residential work. Whole-building air leakage rates dropped in most climate zones, and duct leakage to outside tightened independently. Kentucky and Indiana both adopt and enforce through state-specific pathways, and the rate your jurisdiction enforces determines the sequencing of insulation, drywall, and the final blower door test.

Builders who treat air sealing as a pre-drywall checkbox run into two predictable problems: drywall hides the worst leaks, and the final test fails with no remediation path. HECS schedules blower door testing in Louisville KY, Lexington KY, and Indianapolis IN projects after drywall but before finish flooring, so the worst leaks are still accessible from the attic side.

• Climate Zone 4 (Louisville, Lexington, Indianapolis, Cincinnati): target whole-building leakage in the mid-single digits per the published IECC residential table, verify the current edition adopted by your jurisdiction.
• Climate Zone 5 (Chicago, Cleveland, Columbus): tighter targets apply, and blower door sequencing becomes critical because HVAC commissioning windows are short.
• Duct leakage to outside: tested independently of the building envelope; sample thresholds typically run in the single-digit CFM per 100 sq ft range per the 2024 IECC residential duct leakage table.

A code official will accept either the prescriptive or performance path, but performance requires third-party verification and a tighter test schedule.

What HECS Actually Measures During an Air Leakage Test

A blower door test is a depressurization measurement with a calibrated fan assembly at the front door, a digital manometer reading interior-to-exterior pressure differential, and a single-point or multi-point test method. The result is CFM at 50 Pascals, commonly expressed as ACH50 after dividing by building volume.

What gets flagged in practice:

• Recessed lights in top-floor ceilings with no air-tight boxes.
• Attic hatches without continuous gaskets and compression latches.
• Plumbing penetrations through top plates that were foamed but not visually confirmed.
• Band joists sealed only with fiberglass, not spray foam or rigid foam.
• Garage-to-house common walls missing a continuous air barrier.
• HVAC returns in furred-out chases that bypass the air barrier entirely.

For FORTIFIED Home designation in Kentucky and the Gulf states, the roof and wall strengthening requirements overlap with, but do not replace, the air leakage requirements in the 2024 IECC. HECS finds that builders pursuing FORTIFIED and ENERGY STAR simultaneously save field time by sequencing the IBHS FORTIFIED Home Evaluator inspection alongside the ENERGY STAR v3.1 visual verification, since both review the same air barrier details.

Working with HECS

HECS handles blower door testing, duct leakage testing, and ENERGY STAR v3.1 verification for projects in Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. We staff IBHS FORTIFIED Home Evaluator inspections on the same trip when scope allows. For a scope call: (859) 983-7382 or hecsusa.com/contact/.

Kentucky vs. Indiana 2024 IECC Adoption: What Actually Applies

Kentucky's residential code pathway has historically tracked the IRC and the IECC, with the state Department of Housing, Buildings and Construction administering enforcement at the local level. Indiana adopted the 2020 IRC with state-specific amendments and has moved incrementally toward the 2024 IECC. Local jurisdictions retain amendment authority, and the result is uneven enforcement between adjacent counties.

HECS recommends confirming the current adopted edition with the local building department before sequencing tests. In our experience, the gap between the published 2024 IECC and the locally enforced edition is the single most common cause of failed final inspections on custom homes in this region.

Common Pitfalls on Kentucky and Indiana Air Sealing Projects

Field failures cluster around three categories.

First, the framing contractor and the insulation subcontractor both assume the other sealed the band joist. The result is no seal at all. HECS project data from Louisville KY and Lexington KY shows that band joist failures account for a disproportionate share of ACH50 overages in custom homes.

Second, HVAC returns and supply boots get installed before the air barrier inspection. Once drywall goes up, the gap at the boot-to-drywall interface becomes invisible. Builders who schedule the air barrier visual verification after mechanical rough-in but before drywall close-up catch this every time.

Third, the final blower door test gets scheduled before the home is genuinely "ready to test." All penetrations must be made, every wire, every pipe, but no finishes should block access. Range hoods, bathroom fans, and dryer vents should be installed and sealed because their absence creates reading instability.

For HVAC testing and balancing in Cincinnati OH projects, the balancing report and the duct leakage test run on consecutive days, and HECS coordinates both with the mechanical contractor.

Frequently Asked Questions

What ACH50 target should a Kentucky builder plan for in 2025-2026?

Plan for the rate published in the 2024 IECC residential table for Climate Zone 4, verified against your local jurisdiction's currently adopted edition. In our experience, builders who target mid-single digits pass without remediation in Louisville and Lexington. ENERGY STAR v3.1 and NGBS-2023 both require tighter thresholds than the IECC baseline, so verify the program target before sequencing.

Does NGBS-2023 require a blower door test on every certified home?

Yes. The NGBS-2023 Green Certified Verifier pathway requires third-party air leakage testing with results reported on the certification documentation. HECS provides both the test and the documentation upload for projects pursuing NGBS in Kentucky and Indiana.

Can a builder in Indiana use RESNET HERS scoring instead of the 2024 IECC prescriptive path?

Yes. The performance path through RESNET HERS scoring accepts compliance when the rated home meets or beats the reference home under ANSI/RESNET/ICC 301. HECS provides the blower door and duct leakage tests required for the HERS rating, and the rater assembles the compliance documentation for state submittal.

How to Engage HECS

HECS provides blower door testing, duct leakage testing, HVAC testing and balancing, and ENERGY STAR v3.1, NGBS-2023, and FORTIFIED Home 2025 verification for projects across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. Reach HECS at (859) 983-7382 or [email protected], or submit a scope through hecsusa.com/contact/. The full service list is at hecsusa.com/services/. For Kentucky projects, HECS also serves Louisville KY, Lexington KY, and Evansville IN directly. For Ohio and Tennessee work, ask about HECS's Cincinnati OH and Nashville TN scheduling windows.