Air Balancing

stonesHVAC encompasses a broad range of separate but interconnected components and structures. When we talk about HVAC we could be talking about anything related to the heating, cooling and air ventilation of either a commercial or residential space. And the things related to these avenues such as insulation and indoor air quality. That’s a lot of ground to cover. One aspect of HVAC systems that perhaps isn’t discussed as often is air balancing, which is exactly why we’re going to take a look at this concept today.

Air balancing refers to the process of measuring and adjusting an HVAC system to provide the occupants with a more comfortable living space. Heating Austin homes is no simple task and doing so evenly and consistently throughout the season and throughout the home is even harder. That’s where air balancing comes in to play. Heating in Austin has become more than necessary, especially over the past week as we’ve finally felt the full power of the quickly approaching winter cold coming in. So read on to learn all about this process of air balancing, what it involves, and what it can do to improve your experience of Austin heating.

Harmony in the System

The overarching theme of the process of air balancing is harmony. It’s about making sure that all components of the HVAC (heating, ventilating, and air conditioning) system are working in harmony, at their optimum performance, providing total occupant comfort. It’s a process with the endgame of maximizing what you can get out of your HVAC system throughout all four seasons, day in and day out.

Air balancing is the single most important step that can be taken to assure your systems produce comfort and operate efficiently. It is often an overlooked step, which is a shame. Everyone has heard about energy efficiency ratings, SEER ratings, and most have a vague understanding of what different kinds of heaters and air conditioners are out there such as options for ductless heating and cooling, and maybe even what zoning is. But air balancing is the missing link that often goes ignored. One study found that less than 5% are operating above 90% of the equipment-rated capacity. Most operate in the 55% to 65% range before balancing or corrective measures are put in place. If your technicians aren't checking system airflow on every service call, you're doing your company and your customers a disservice. Air balancing is the missing link in getting residential HVAC systems to perform at or near their peak levels.

Luckily, there are companies out there that specialize in air balancing services. The first step is taking stock of the current balance of the system. There’s more than one way in which air balance can be tested and measured. In the next section, we’ll look at the two extreme ends of this spectrum.

Balance Measuring

The simplest form of air balance measuring that can be done is sometimes referred to as a comfort balance. It can be done by yourself without any tools or experience other than your own body and a careful assessment of your senses. It could be as simple as walking from room to room, holding a hand up to the ceiling to see if sufficient air is coming out of the registers, and asking yourself and the other household members if they notice any inconsistencies in comfort levels and temperatures throughout the different rooms and sections of the home.

The other end of the spectrum is getting your home carefully and meticulously tested for complete air balance. This involves a more scientific and structured process that can take on many forms. The whole process of certified testing is called the AABC Certified Air Balance. In some ways, the journey toward a certified air balance starts even before the testing stage. And it starts with engineering.

A mechanical engineer develops specifications and a set of mechanical drawings from a mix of occupant desires, local codes, ASHRAE standards, and many years of training. The correct ducting, airflow, registers, and unit performance are brought together with consideration for ventilation requirements and building exhaust needs. The most important part of the mechanical plans used by the certified balance company is the list of cfm requirements next to each supply, return, intake, exhaust and ventilation opening. Without this important information, a certified balance is not possible. To conduct an AABC Certified Air Balance, the building must first be totally sealed. Therefore this process would fall under the modular dealer's scope of work.

The first step may be to just determine what the specs of the system are and what the output should be. While few homes have mechanical plans or specifications to follow, you can reverse engineer the necessary information required to balance most systems. Some of this can actually be done on your own before you even make a call. First, find the equipment model numbers and go online to the manufacturer’s website to get the engineering information on that specific piece of air-moving equipment. Find the tonnage or heating output to determine the required system airflow. Divide the total system airflow so each room has its share. This can be done using Manual J or one of several estimating techniques, including online calculators designed for this purpose.

The next steps will have to involve a professional. They’ll need to find the fan total external static pressure rating, blower motor horsepower and other key information for the balance report. This data will be used to substantiate and cross-reference your field measurements.

Airflow can be measured in several ways. One of the simplest ways is to test total external static pressure, compare it to manufacturer's documents, then measure airflow at all the supply and return grilles and registers. Next, assess how much air is moving through the furnace or air handler and how much is being delivered to and returned from the living space.

From this test-in procedure, the deficiency level can be assessed and the appropriate recommendations can be made to the homeowner for repairs.


The next step in the air balancing process is taking those recommendations and putting them into action in the form of adjustments to the HVAC system. These recommendations may include duct sealing, adding return ducts and grilles, modifying or changing the filtration set-up, adjusting fan speeds, cleaning the evaporator, performing combustion analysis, and adjusting the refrigerant charge.

Adjustments toward creating better air balance can take on many different forms depending on the results of the testing and measuring and the specific needs of your system and house. It might involve the setting of balancing devices such as dampers and valves, adjusting fan speeds and pump impeller sizes, in addition to automatic control devices such as thermostats and pressure controllers to achieve maximum specified system performance and efficiency during normal operation. This is in addition to the more obvious things like fixing any leaks in ducts, changing dirty air filters, and adjusting furniture layouts to avoid air register obstruction. Air balancing requires a holistic approach to HVAC and that’s why there’s such a variety in the kinds of adjustments that will be made during the adjustment phase of the process.

Final Testing

The next step after measuring and adjusting is the test-out and creating the documentation of the results showing the measured improvements in performance. This is when the air balancing professional will perform the final balancing, setting and adjusting dampers, etc. to achieve the desired end result.

The air balance report provides space to record each of these measurements. These tests include total external static pressure, fan speed, temperature change through the equipment, and electrical measurements. Each of these readings is compared to the manufacturer specifications and adjusted for certain part-load conditions. Using equipment specifications and fan laws, each value can be weighed against airflow data to verify overall accuracy.

Exactly how detailed and thorough your air balance report is can vary. It’s a matter of how far down the rabbit hole you want to go so to speak. To a basic air balance report you can add equipment and system BTU measurement, system commissioning steps, static pressure and temperature profiles, live duct leakage, refrigerant and combustion adjustment, building pressure analysis and many other tests.

At the end of the process, an air balance professional will have done tests and made measurements throughout your system to identify any and all problems and inconsistencies in air balance, both output and input. They will have made a variety of adjustments to the system, from the main components to the ducts and the registers to the thermostats and dampers and valves. Then they will have done a final measurement and testing of the system to prove concretely what the changes have done as far as improvements to the overall operation of the system. This will leave you with a balanced heating and cooling system and more efficient and comfortable home.

Air Balancing and Heating Repair in Austin

The goal of any cooling and heating system is to provide the occupants of a household with as much comfort as possible. The secondary goal is to achieve the first goal while using as little energy as possible. Achieving this balance between comfort and efficiency is what air balancing is all about. It’s a process to aims to inspect and identify any areas throughout the HVAC system which can be adjusted and improved in order to create a perfect harmony between the numerous parts and components of said system.

In addition to this process, any good HVAC contractor will be able to quickly and easily diagnose and repair any problems you may have with your heater. Heater repair in Austin is one of the specialties of AC Express. We’re an Austin heater repair company that can provide same-day heater repair for all of those in the Austin area, from Buda and Kyle to Pflugerville and Round Rock. For a full list of our service areas check out the corresponding page on our website. And if you’re looking for top-notch heater repair in Austin, call today!