Practical code-compliance guidance for builders, engineers, and code officials in the Ohio Valley.

Why HVAC Testing & Balancing Breaks Down Without a Standard

Most commercial HVAC systems ship from the factory 10-25% off design airflow. Duct joints loosen during rigging, VAV box linkages drift, fan sheaves wear in. Without a written acceptance standard, the GC and the mechanical subcontractor argue about whose tolerance is "close enough." That argument almost always lands on the owner's lap at commissioning.

ASHRAE 111, Practices for Measurement, Testing, Adjusting, and Balancing of Building HVAC Systems, exists to end that argument. It defines what gets measured, which instruments are acceptable, and what reading passes as "in tolerance." When a project specifies TAB "per ASHRAE 111," the owner gets a defensible report instead of a receipt.

The field data problem is consistent: in our experience, supply terminals on commercial systems with VAV terminals commonly run 12-15% below design CFM before balancing, well past the acceptable band, because nobody verified fan performance against design.

What ASHRAE 111 Actually Requires

ASHRAE 111 establishes the test procedures, instrumentation classes, and reporting formats for HVAC TAB work. The standard is invoked by reference in project specifications (typically CSI Division 23 05 93), and it is the procedural backbone behind NCI Commercial Air Balancer certification, the credential HECS holds rather than NEBB or AABC.

Key procedural categories the standard covers:

• Instrument calibration, required accuracy, calibration records, and instrument-class ratings for flow hoods, manometers, and temperature instrumentation.
• Air-side measurement, supply, return, exhaust, and outdoor air CFM at terminal devices and central equipment.
• Hydronic measurement, flow at coils, chillers, boilers, and balance valves using calibrated balancing valves or ultrasonic flow metering.
• Reporting, a TAB report that lists design versus measured values, instrument data, and any deviations.

ASHRAE 111 itself does not set the CFM tolerance band; project specifications set it. Typical commercial specs cite ±10% of design CFM at supply diffusers, though HECS finds that band tight on systems with VAV terminals where measurement uncertainty can run 5-7% by the hood itself.

The standard does, however, govern how you prove compliance. A reading taken with an uncalibrated flow hood, or a fan curve adjusted without a traverse per AMCA standards referenced in HVAC literature, does not meet ASHRAE 111, regardless of the CFM number on the field sheet.

For code-compliance driven projects in Kentucky, Indiana, and Ohio, the credential often follows the spec. HECS's NCI Commercial Air Balancer certification covers commercial TAB procedures, hood and duct leakage, and the fan-law calculations that show up when system curves shift mid-balance.

The HECS Approach to TAB on Code-Bound Projects

HECS runs TAB as a three-pass operation on commercial projects, not a single visit. The first pass measures baseline airflow and hydronic flow after the mechanical contractor declares substantial completion. The second pass trims dampers, valves, and VAV box controllers after the controls contractor has commissioned the sequence. The third pass is the witness, final readings in front of the owner or commissioning authority.

Instrumentation matters more than most GCs expect. HECS uses capture hoods calibrated to manufacturer schedule, plus duct traverse per AMCA Figure 5.2 for any reading that affects a code-compliance threshold, outdoor air CFM at the DOAS unit, for instance. Single-point hood readings at modulating boxes can read low; a traverse is the legal record.

Working with HECS

HECS handles commercial HVAC testing and balancing for projects across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. For a scope call on a current project: (859) 983-7382 or hecsusa.com/contact/.

What the HECS TAB Report Contains, and What It Verifies

The HECS deliverable is a bound TAB report, not a spreadsheet. It includes:

• Project design data (design CFM, GPM, static pressure, RPM).
• Instrument list with calibration certificates and last-calibration dates.
• Field readings for every supply, return, exhaust, and outdoor air terminal.
• Hydronic readings at every coil and balance valve.
• Fan performance data: measured CFM, static pressure, RPM, and brake horsepower.
• Final settings of all dampers, valves, and VAV controllers.
• Deficiency log with before-and-after readings on items that failed the first pass.

The report meets ASHRAE 111 reporting requirements and aligns with 2024 IECC R403.3.5 duct leakage thresholds (4 CFM25 per 100 ft² of conditioned floor area) where ducts run outside the envelope. On multifamily projects, HECS also verifies against ENERGY STAR MFNC v1.3 (Rev05) duct leakage sampling: 6 CFM25 rough-in, 8 CFM25 post-construction.

For NGBS-2023 certified work, the report supports the verifier's NGBS §702.1.1 third-party verification at all tiers, Bronze through Emerald. The TAB log becomes the audit record.

When HECS Reads Design vs. Field Differently

Two patterns show up on nearly every commercial job HECS balances:

1. Outdoor air CFM low at the AHU but "passing" at the diffuser level. DOAS or mixed-air plenums often pull less return-side OA than design because duct leakage under negative pressure skews the traverse. HECS flags this in the report and re-reads at the unit, not the terminal.
2. VAV box controllers re-trim themselves after balance. The controls contractor's sequence ramps boxes back to design minimums and overrides HECS's setpoint. The TAB report documents the final reading taken after controls are locked.

Both patterns are predictable, and both belong in the report.

Frequently Asked Questions

Does ASHRAE 111 set the CFM tolerance band, or does the spec?

The spec sets the band. ASHRAE 111 sets the procedure and reporting requirements. Most commercial specs cite ±10% of design CFM at supply diffusers, but tighter bands (often ±5%) appear on healthcare and laboratory work.

How does ASHRAE 111 interact with 2024 IECC and ENERGY STAR on multifamily?

ASHRAE 111 governs the TAB procedure on commercial-grade equipment. 2024 IECC governs residential duct leakage to ≤4 CFM25 per 100 ft². ENERGY STAR MFNC v1.3 Rev05 uses 6 CFM25 rough-in and 8 CFM25 post-construction sampling on multi-family. HECS reports against whichever threshold the project is held to.

Is NCI certification equivalent to NEBB or AABC?

It is a different credential from a different certifying body. NCI certification emphasizes airflow measurement accuracy and field diagnostics. Specifiers should match the spec language to the credential the firm actually holds, HECS is NCI-certified, not NEBB or AABC.

How to Engage HECS

HECS delivers commercial HVAC testing and balancing across Kentucky, Indiana, Ohio, Tennessee, Illinois, and Missouri. The full service list is at hecsusa.com/services/, with project scoping handled through hecsusa.com/contact/. For TAB on current projects in Louisville KY, Lexington KY, Cincinnati OH, Indianapolis IN, or Nashville TN, call (859) 983-7382 or email [email protected]. Reports are issued as bound PDF deliverables with instrument certs and field logs, and are accepted by code officials, commissioning authorities, and NGBS-2023 verifiers.