ASHRAE 62.2-2022 Compliance in Tight Kentucky Homes: Field Findings

What HECS documents during 2026 residential ventilation testing — and why code-minimum homes still fail.

The Problem: Tight Envelopes, Thin Ventilation Margins

Kentucky sits in 2024 IECC Climate Zones 4A and 5A — meaning code-maximum airtightness under 2024 IECC Table R402.4.1.1 is 3.0 ACH50 across nearly every county HECS tests. As envelope leakage drops, the dilution that once masked under-ventilation disappears. Builders who hit 2.5 ACH50 routinely assume mechanical ventilation will "just work." It rarely does without design intent.

Field data from HECS 2025–2026 residential projects shows three recurring failures when ASHRAE 62.2-2022 compliance is attempted but not verified:

• Supply-only fans wired but never airflow-tested.
• Bathroom exhaust fans installed at 30–40 cfm when ASHRAE 62.2-2022 §4.3 requires ≥50 cfm intermittent.
• Kitchen range hoods either non-ducted or ducted through unconditioned attic with no insulation on the duct itself — failing the duct-sealing requirement at 2024 IECC R403.3.5.

The standard's §4.1 whole-building equation — Q_total = 0.03·A_floor + 7.5·(N_br+1) cfm — is well-known. What is not well-understood is how aggressively this scales with bedroom count. A 2,400 ft², four-bedroom home needs roughly 112 cfm of mechanical ventilation. Builders who specified "a 100 cfm fan" are already under by the equation alone, before any real-world derate.

The Code and Standard Stack

ASHRAE 62.2-2022 (with Addendum a from February 2024) is the primary indoor-air-quality reference. Kentucky has not formally adopted 62.2 as code by reference, but it is invoked through:

• NGBS-2023 §903 — ventilation per ASHRAE 62.2-2022 is the cited reference for all certified tiers.
• ENERGY STAR MFNC v1.3 (Rev05) National Program Requirements (January 2025) — Indoor Air Quality section requires ASHRAE 62.2-2022 §4 compliance.
• 2024 IECC R402.4.1.2 — blower door testing verifies infiltration credit only when used to reduce mechanical ventilation under ASHRAE 62.2-2022 §4.4 (capped at the lesser of 2 ACH50 or 0.04·A_floor / 7.6 cfm).

The §4.1.4 filtration credit — updated by the February 2024 addendum — allows MERV-rated equipment to reduce required mechanical cfm by a defined percentage. HECS finds this credit is often claimed without the supporting filter being installed or the equipment being cycled. Documented airflow measurements close that loophole.

Working with HECS

HECS performs ASHRAE 62.2 compliance documentation for builders, raters, and code officials across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. Reports include measured cfm at every exhaust point, whole-building cfm versus the §4.1 equation, and corrected infiltration credit. For scope: (859) 983-7382 or hecsusa.com/contact/.

HECS Recommendation: Verify, Don't Assume

HECS approaches compliance as a measured dataset, not a checklist. The on-site test sequence is:

1. Blower door at 50 Pa. Used to verify Table R402.4.1.1 compliance and to populate the §4.4 infiltration credit — if the builder elects to use it.
2. Duct leakage to outside, per 2024 IECC R403.3.5, at both rough-in and post-construction if ducts serve unconditioned space.
3. Local exhaust airflow, captured with a calibrated hood at the grille or termination. HECS has measured kitchen hoods flowing 18 cfm at the grille against an 80 cfm rated fan — the run was 30 equivalent feet with two 90-degree elbows.
4. Supply ventilation cfm, measured at the outdoor inlet of the fresh-air duct, not at the equipment nameplate.
5. Run-time verification for cycling fans. A fan rated for 8-hour continuous service may be wired to a 20-minute bathroom timer — failing ASHRAE 62.2-2022 on operating hours.

What HECS Documents in the Report

Every HECS compliance packet includes raw measurements, derivations, and pass/fail against each cited section:

• Calculated Q_total using the §4.1 equation with project-specific conditioned floor area and bedroom count.
• Measured supply cfm, exhaust cfm, and net difference — the operative number for §4.1.
• Local exhaust readings annotated against §4.3 thresholds (kitchen ≥100 cfm intermittent or ≥25 cfm continuous; bath ≥50 cfm intermittent).
• For NGBS projects, the §903 reference and the verifier-of-record signature line.
• For ENERGY STAR multifamily, cross-reference to the HVAC Functional Testing Checklist sections completed on-site.

HECS findings from 2025–2026 include projects that passed blower door at 2.4 ACH50 but failed 62.2 because exhaust fans were undersized. Tightness alone is no proxy for ventilation compliance.

Frequently Asked Questions

Does meeting 2024 IECC R402.4.1.1 (3.0 ACH50 in CZ 4A/5A) satisfy ASHRAE 62.2-2022?

No. 2024 IECC R402.4.1.1 is an airtightness requirement, not a ventilation requirement. ASHRAE 62.2-2022 §4.1 mandates a separate mechanical whole-building ventilation rate calculated from conditioned floor area and bedroom count. Tightness does not waive this — though under §4.4 an infiltration credit (capped at the lesser of 2 ACH50 or 0.04·A_floor / 7.6 cfm) can offset part of it.

What does HECS measure on-site to verify local exhaust?

HECS uses a calibrated flow hood at the grille or termination, capturing actual cfm against ASHRAE 62.2-2022 §4.3 thresholds. Kitchens need ≥100 cfm intermittent or ≥25 cfm continuous; bathrooms need ≥50 cfm intermittent. Nameplate ratings are not used — HECS has measured grille-side flow at 30–50% of rated nameplate on field installations.

How does the §4.1.4 filtration credit interact with mechanical ventilation rates?

The February 2024 addendum to ASHRAE 62.2-2022 allows a defined reduction in required mechanical cfm when MERV-rated filtration is installed at the HVAC equipment. HECS documents the installed filter MERV value and verifies the equipment is operating on a schedule that actually pulls air through it — credit cannot be claimed for