HVAC Testing, Adjusting & Balancing Services

Testing, adjusting, and balancing (TAB) is the engineering discipline that measures an HVAC system's actual airflow and water flow, adjusts every component to the design intent, and certifies the result in a documented report. dL Flow Tech is an independent, NEBB-certified TAB firm serving the Hudson Valley and the New York metro area since 1982. We verify that the system the engineer designed is the system that actually got built.

What is testing, adjusting, and balancing?

Testing, adjusting, and balancing is the final commissioning step that proves an HVAC system performs the way it was designed to. A certified technician measures airflow at every diffuser, water flow through every coil and pump, and pressures across the building, then physically adjusts dampers, valves, and drive settings until each reading matches the engineer's design quantities. The work closes with a signed report that becomes part of the permanent project record.

TAB is not maintenance and it is not a tune-up. It is independent verification. The mechanical contractor installs the system; the TAB firm proves it works. On most commercial projects that independence is a contractual requirement, because the owner and the design engineer need a third party — one who did not install the equipment — to confirm performance before the building is occupied.

The three phases, in order

Testing comes first. We take quantitative measurements throughout the system: supply, return, and exhaust airflow; coil water flow; static pressures; fan and pump performance; temperatures; and electrical readings on motors. Nothing is adjusted yet — testing establishes the system's as-found condition against the design.

Adjusting is the hands-on phase. We set fan speeds and sheave or VFD settings, position every balancing damper, and trim balancing valves so each branch, zone, and terminal delivers its design quantity. This is iterative: change one branch and the rest of the system shifts, so a balanced system is the product of many coordinated adjustments, not a single set-and-forget pass.

Balancing is the proof. We re-measure the adjusted system, confirm every reading falls within the allowable tolerance band (typically ±10% on air and water unless the spec is tighter), and document it. The deliverable is a NEBB-format report the engineer can stamp and the owner can keep.

Why HVAC testing and balancing matters

An HVAC system can be installed exactly to the drawings and still fail in the field. Duct leakage, fittings that don't match the plans, fans set at the factory default, and valves left wide open all push real-world airflow away from design. Without TAB, nobody knows by how much — they only find out when occupants complain or the energy bill arrives.

• Comfort. Hot and cold spots, rooms that never reach setpoint, and drafty lobbies are almost always airflow problems, not thermostat problems. Balancing moves the air to where the design put it.
• Energy cost. Fans and pumps oversupplying a building burn energy continuously. Trimming them to design is one of the cheapest efficiency measures available on a commercial system.
• Code and certification. Energy codes, LEED, and many local authorities require a balancing report before sign-off. Hospitals, labs, and other regulated spaces require documented pressure relationships that only TAB can certify.
• Indoor air quality. Outdoor-air rates and room pressurization are set during balancing. Get them wrong and you under-ventilate occupied spaces or let contaminated air migrate where it shouldn't.
• Equipment life. A motor running against the wrong system curve wears out early. Balancing protects the capital you just installed.

Our TAB services

The pages below cover each service in depth. Every one is performed to NEBB procedure and documented in a report you can hand to the engineer of record.

The dL Flow Tech TAB process

Every project runs the same disciplined sequence, because consistency is what makes a report defensible.

1. Drawings and spec review. Before anyone goes to site, we read the mechanical drawings, the controls sequence, and the TAB specification section. We build the report forms and identify the design quantities, required tolerances, and any pressure relationships the spec calls out.
2. Field readiness check. A system can't be balanced until it's ready — filters in, access doors on, controls in the correct mode. We confirm readiness up front so the crew isn't sent home, and we flag installation issues to the contractor early, while they're still cheap to fix.
3. Instrumented testing. We measure with calibrated instruments — flow hoods, micromanometers, pitot traverses, ultrasonic and direct-read flow meters, and Retrotec equipment for envelope and duct-tightness work. Every instrument carries a current calibration certificate.
4. Adjusting to design. We proportion the air and water side by side, set fan and pump drives, and trim terminals until the system holds tolerance under real operating conditions.
5. The certified report. You receive a complete NEBB-format report: instrument list and calibration dates, design-versus-actual readings for every point, deficiency notes, and a signed certification page.

What NEBB certification means for your project

dL Flow Tech is certified by the National Environmental Balancing Bureau (NEBB), the standard credential for the TAB trade in North America. NEBB certification requires a certified professional on staff, calibrated instrumentation on a documented schedule, and adherence to published NEBB procedural standards, all subject to recertification.

For an owner or engineer, hiring a NEBB-certified firm means three things: the procedures follow a recognized national standard; the instruments are demonstrably calibrated; and the report carries a conformance certification that satisfies most specifications calling for "balancing by a certified TAB agency." Our broader quality stack also includes affiliations across TABB, SMACNA, ASHRAE, BPI, and additional regional trade associations.

Industries we serve

TAB requirements get stricter as the stakes rise, and our portfolio is built on the demanding end of the market. In healthcare, our work includes projects such as the chiller-plant and air-balancing scope at Northwell Health's Northern Westchester Hospital and the Center for Discovery's Specialty Children's Hospital. In research and laboratory environments — including Pepsi's R&D facility in Valhalla — fume-hood face velocity and room pressurization have to be measured and certified. We also serve senior living (Broadview), schools and universities, data centers, and commercial kitchens and restaurants.

Service area

dL Flow Tech is based in Fishkill, New York and serves the corridor from New York City north through the Hudson Valley to Albany — Dutchess, Westchester, Orange, Putnam, Rockland, and Ulster counties, the five boroughs, and the Capital Region. Being a Hudson Valley firm, we're close enough to most of our market to handle the site revisits that real balancing requires.

When do you need a TAB contractor?

• A new HVAC system is being commissioned and the spec requires a balancing report before occupancy.
• A renovation or tenant fit-out changes airflow or hydronic loads and the existing balance no longer holds.
• You're chasing comfort complaints — hot/cold rooms, pressure issues, doors that won't close — that maintenance hasn't solved.
• A project needs LEED, energy-code, or local authority sign-off that calls for documented balancing.
• A hospital, lab, or cleanroom needs certified pressure relationships or ventilation rates for accreditation or compliance.
• An owner wants an independent, third-party report rather than the installing contractor's own numbers.

Frequently asked questions

What is the difference between TAB and HVAC commissioning?

TAB measures and adjusts the physical airflow and water flow and certifies the readings. Commissioning is the broader process that verifies the whole system — controls, sequences, and integrated performance — meets the owner's project requirements. TAB is one input to commissioning. On many projects we provide both; see our commissioning services.

How long does balancing a building take?

It depends on system size and complexity, not square footage alone. A single rooftop unit serving an open office can be a day; a hospital wing with dozens of terminals and certified pressure relationships can run weeks across several visits. We give a realistic schedule with the quote, after reviewing the drawings.

Do I have to use a NEBB-certified firm?

If your specification names a certified TAB agency — most commercial specs do — then yes, the firm must hold that certification for the report to be accepted. Even when it isn't required, a certified firm's report is far more likely to be accepted by the engineer of record without rework.

What does a TAB report include?

A complete NEBB-format report lists every instrument used and its calibration date, the design quantity and actual measured reading for each test point, any deficiencies found, and a signed certification page. It's a standalone document the design engineer can review and stamp.

Can you balance an existing building that was never properly commissioned?

Yes. Re-balancing an older or never-balanced building is a large part of our work. We test the as-found condition, identify why it's drifted from design, and bring it back into tolerance — often recovering energy and resolving long-standing comfort complaints.

What does HVAC testing and balancing cost?

Cost is driven by the number of test points, system type, and required tolerances, so it's quoted per project rather than by a flat rate. Send the mechanical drawings and TAB spec and we'll return a fixed-scope proposal.