Reading a TAB report

The testing, adjusting and balancing (TAB) report is often the most detailed record of how a building's HVAC systems actually performed at turnover. It lists the airflow at every diffuser, the water flow through every coil, and the speed, pressure and power of every fan and pump. Yet many TAB reports are filed away unread, and problems hidden in them surface only years later as comfort complaints or high energy bills.

Reading a TAB report is not difficult once you know how it is organized and what to look for. This guide explains the typical structure, the meaning of the key data and the red flags that should prompt questions before the report is accepted.

Typical report structure

Most reports follow a format set by the certifying body (AABC, NEBB or TABB) and the project specification. Common sections include:

1. Cover and certification page. Project name, TAB agency, date, and the signature and certification number of the responsible individual.
2. Table of contents and system index.
3. Summary and deficiency list. Items that could not be balanced to design, with explanations.
4. Instrument list. Each instrument used, with serial number and calibration date.
5. Equipment test sheets. Air handlers, rooftop units, exhaust fans, pumps, chillers, boilers and heat exchangers.
6. Terminal unit sheets. VAV boxes, fan coils, heat pumps and similar devices.
7. Outlet sheets. Airflow at each diffuser, grille and register.
8. Hydronic sheets. Flow at each balancing valve, coil or branch.
9. Traverse sheets. Pitot traverse data for main ducts.
10. Schematic drawings or marked-up floor plans showing outlet and device identification.

Reading the equipment sheets

Fan and air handling unit sheets

A fan sheet usually shows design and actual values side by side.

If a VFD is running at 100% and airflow is still below design, the fan has no reserve and the cause should be investigated. If airflow is met with the VFD at a low speed, the system may have been oversized, which is a useful finding for energy purposes.

Pump sheets

Pump sheets show design and measured flow and head, impeller diameter, speed, motor data and how flow was determined. Check whether flow was measured with a flow element or meter, or only estimated from the pump curve. Pump curve estimates are useful but less accurate.

Terminal unit sheets

For VAV boxes, look for:

• Design and measured maximum and minimum airflow.
• The BAS reading at each condition and any calibration factor applied.
• Inlet static pressure at maximum airflow.

A box whose measured maximum is well below design, with a fully open damper, signals an upstream problem: insufficient duct static pressure, leakage or an obstruction.

Reading the outlet and hydronic sheets

Outlet sheets list each diffuser or grille by identifier, size, design airflow, measured airflow and percentage of design. Hydronic sheets do the same for coils and balancing valves, often adding valve setting and measured differential pressure.

When reviewing these sheets:

• Check that every outlet on the drawings appears in the report.
• Look at the percentage of design column. Values should cluster within the specified tolerance.
• Note any outlets marked as unable to reach design and confirm they appear in the deficiency list.
• Compare the sum of outlet airflows with the measured fan or terminal total. Some difference is expected due to duct leakage and measurement uncertainty, but a large gap suggests either significant leakage or a measurement problem.

Red flags

Experienced reviewers look for patterns that suggest a report may not reflect reality.

• Every reading at exactly 100%. Real measurements vary. A page of perfect values deserves a field check.
• Identical numbers on similar outlets throughout a building.
• Missing instrument calibration data or calibration dates that expired before the testing.
• Dates that do not fit the construction schedule, such as readings recorded before ceilings were installed or equipment started.
• No deficiencies listed on a large, complex project. Almost every project has some.
• Outdoor air not measured or reported only as a calculated value.
• Motor amperage above nameplate without comment.
• Missing systems or areas compared with the drawings.

None of these proves the report is wrong, but each warrants a question.

Verifying the report

On most projects, the specification allows the engineer or commissioning agent to spot-check a sample of reported values, often around 10% of outlets and a selection of equipment, with the TAB technician present using the same instruments. If a set proportion of the checked readings fall outside tolerance, the specification may require rebalancing of the affected system and a revised report at the TAB agency's cost.

Spot-checks are most effective when the sample includes:

1. A mix of outlets near and far from the fan.
2. Critical spaces such as meeting rooms, server rooms, laboratories and health care rooms.
3. Outdoor air measurements on each air handler.
4. Items that the reviewer suspects from the red flags above.

See what testing, adjusting and balancing involves for how verification fits into the overall process.

Using the report after turnover

A TAB report remains valuable long after occupancy:

• As a baseline when investigating comfort complaints, using the procedures in hot and cold complaint troubleshooting.
• As a reference when filters, belts or motors are replaced, to confirm that fan performance has not changed.
• During renovations, to understand existing airflow before redesigning a space.
• In energy studies, where measured fan and pump data supports savings calculations.

The report should be included in the operations and maintenance documentation and kept in an accessible location, along with the marked balancing device positions.

Frequently asked questions

Should the owner receive the TAB report directly?

Yes. The owner should receive a copy of the final certified report, typically through the engineer as part of closeout. It forms part of the building record.

What if the report shows systems that could not be balanced?

Each deficiency should have a stated cause and a responsible party for correcting it. After correction, the affected system should be retested and the report revised.

Key takeaways

• TAB reports compare design and measured values for every fan, pump, terminal, outlet and coil.
• Check equipment static pressures, motor amperage and VFD speeds as well as airflow and water flow.
• Perfect numbers, missing calibration data and no deficiencies on a complex job are red flags.
• Spot-check a representative sample in the field before accepting the report.
• Keep the report as a long-term baseline for troubleshooting and renovations. Our air balancing team prepares and verifies TAB reports.