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The Indoor Climate & Energy Management Specialists

Testing and Balancing (TAB) systems

What is Air Balance?

The relationship of air inside a building is the differential pressure. Since air acts like a fluid, it will flow from the positive area to the negative area or from a higher pressure to lower pressure. Regulating air balance, whether it’s comparing inside to outside or comparing one zone to another is extremely important. Indoor air quality (IAQ), occupant comfort, system efficiency, and correct air flow are greatly affected and enhanced by proper air balance.

Air Movement and Relative Pressures Drawing

When is the proper time to balance?

You may need to consider having your systems balanced when one or more of the following problems exist:

  • The space configuration has changed since the last air balance
  • Personnel must continuously readjust control settings
  • Indoor air quality (IAQ) is a concern (ASHRAE Guideline Compliance)
  • Odors are present inside the building or hot and cold spots exist
  • The building is drafty or stuffy
  • Doors stay open or slam-closed
  • Excessive dirt or dust is present
  • Flies and other bugs are a nuisance and always present
  • Excessive complaints from your environmental safety department

Why is Air Balance Important?

One of two situations arise if makeup air is mismanaged. The building will become too positive or too negative. When a building is too positive or has too much outside air, it can use excessive energy to condition this air.

The second and more common result of mismanaging or ignoring make-up air is an unwanted negative building. A negative building will draw air in from anywhere it can. This air might come from undesirable sources such as trash bins, grease traps, truck docks, open doors, windows, cracks, etc. Every bit of unfiltered air or unconditioned air will affect an HVAC system’s ability to maintain the desired environment. In modern HVAC systems, provisions are made for equipment to recirculate conditioned air, exhaust air, and to bring in make-up (outside) air. The balance, which is struck between the volume of exhaust and make-up air, is called air balance. If the amount of air brought into the building is equal to the amount exhausted, the building is said to be “neutral.” In a situation where more air is brought in than is being exhausted, the building is said to be “positive.” Conversely, a building which brings in less air than it exhausts is said to be “negative”.

Considering the costs associated with a nonproductive workplace, it is to the owner’s advantage to have a TAB team make sure these problems are addressed. As we move closer to achieving sustainability objectives, testing, adjusting, and balance will become a core competency that every building owner will demand from his/her facility management personnel or mechanical service and maintenance provider.

Air Balance Drawing

The following check list gives the Facility Manager an opportunity to know what an air balance team will need in order to do their job.

  • Obtain as-built drawings
  • Perform physical survey to compare actual conditions to as-built drawings
  • Measure cubic feet per minute (CFM) of air being supplied to each diffuser
  • Measure discharge/return air volume and temperatures at unit
  • Measure revolutions per minute of blowers
  • Measure voltage and current draw of motors
  • Check condition of all cooling and heating coils, dampers, and equipment
  • Identify unusual noises within the system
  • Verify control system operating properly
  • Check responses of any computerized energy management systems
  • Calculate Air changes per hour (ACH) within the space and compare to ASHRAE standards

What is Water Balance?

Waterside systems also take a meticulous analysis of water flow hrough hydronic heating and cooling systems. Customers with water balance needs will find water-side balancing to be as detailed and important as the air distribution process.

The equipment and reports of the “certified” TAB firm allow the Facility Manager to feel comfortable that all instrumentation utilized for measurements is calibrated accurately and that personnel performing the work are trained and continuously educated. These latter two items are a fundamental criteria for achieving and remaining certified by NEBB.

The Enterprise Corporation is a TOTAL solution.

TAB (testing, adjusting, balancing) is now recognized as a critical aspect toward the HVAC Building Retro-commissioning Process. More and more, qualified firms are being recognized and called upon to fine tune complex systems and solve a variety of environmental problems. Many companies look to different service professionals for different needs. But how can you reach a complete solution when each of your vendors fail to understand what the other is doing?

The Enterprise Corporation can offer you


Mechanical systems, building controls, and air/water balance.

PROPERLY TESTED, ADJUSTED AND BALANCED HVAC SYSTEMS CAN SAVE YOU MONEY… A LOT of money – at least five percent off your energy bill – and in some cases even more! And the older your system, the more money you can save. The certified professionals at Enterprise can help you get your HVAC systems operating at peak performance and keep them there. And at peak performance, you’ll be using less energy, so you’ll be saving more money.