Air Balancing


United Trades Exclusive
Air Balancing

By Dale Yelnich

When an HVAC system has been installed, updated or new components have been added, the final step to make it all flow together, is called air balancing. You can think of air balancing just like tuning up a car engine. Sure, the engine runs, but by making a few adjustments, turning a screw here or changing a setting there, a well tuned car engine becomes more effective, runs smoother and is more efficient when using fuel. These exact same performance fundamentals apply when air balancing an HVAC system. It is literally, airflow in perfect harmony.

Air balancing has been an integral part of forced air applications since the get-go. Even the first primitive types of HVAC had to have some type of air balancing involved, which is one of the reasons that closeable registers were created. In its simplest form, using a register to either increase or inhibit airflow is a way to balance the air coming into a room or a space. It is not the best solution, but in the early days of HVAC, it was all that was available.

On the face of it, most people, whether in a residential or a commercial situation, don’t much care whether the air coming from the registers is balanced or not. As long as the room they are in is comfortable, either in a home or an office, they’ll be happy. But while the human being in all of this may be fine, the HVAC system suffers for it. Imbalanced airflow can lead to uncomfortable hot and cold spots, a harder working fan and a higher energy bill than what it should be. All of these reasons are why air balancing is such an important part in every HVAC setup.

There are two types of air balancing techniques that are employed to fully tune up an HVAC system. One is called comfort balancing, and one is called an AABC (Associated Air Balance Council) Certified Air Balance. The methods and technologies employed between these two types are like night and day.

A comfort balance will work for most residential applications. Essentially, when the HVAC unit is running, each room is checked to see if it is comfortable to reside in. In most instances, there isn’t any fancy equipment here, perhaps a thermometer to determine if the room temperature is equal to the set temperature on the household thermostat. In many cases, the airflow into any given room is the determining factor on comfort. Dampers can be opened or closed, furniture can be moved around a room to allow unimpeded airflow, and even adjusting the registers themselves can be done to keep air from blowing directly on someone or some thing.

A person can who is certified for comfort balancing, from the NCI or National Comfort Institute, will go one step further and electronically check the diagnostics of your system. They may also employ an airflow capture hood to determine the air volume coming out of each of your registers. This type of precision air balancing is done primarily for residential applications, and it is the most effective air balancing treatment for your home.

An AABC certified air balance is a different animal entirely, and in most cases, they are limited to commercial, industrial or office applications. The basics for an AABC air balance service are composed of several things, one of which is having installed HVAC products that are capable of being balanced in the first place. The system should be a complete unit matched from the factory or a service technician, and not some cobbled together unit, with used, faulty or mismatched components. If your HVAC equipment is not reputable, it may not qualify for certified balancing.

Ideally, a mechanical engineer is needed to determine the CFM specifications needed for each room or space, and lastly, an HVAC contractor should be on-site during the certification procedure to take care of any problem if something goes amiss. If there is no HVAC contractor available and a problem occurs, the entire air balancing process will be shut down until the issue has been resolved.

Air balance certification begins by having the entire building sealed or closed, having opposed air dampers installed behind the face of each intake and exhaust opening, changing all of the filters and opening the ductwork dampers all the way.

With the system running, the ductwork dampers are slowly closed to meet the CFM requirements that have been determined by the mechanical engineer. This can be a hit and miss procedure, because as each damper is moved, it effects the airflow through the other dampers. Adjusting the dampers must be done several times each until the damper system is balanced. But it doesn’t stop there. Things like exhaust fans, air intakes and even registers must be factored into this overall balance scenario to achieve the correct performance requisites.

Once the entire system is balanced, the technician locks everything into place to ensure that the settings won’t change, and the system is now good to go. Perfectly balanced and perfectly in tune, but only at that exact moment. The fact is that no HVAC system will ever remain perfectly balanced, and you may now be wondering, how could that be?

In every commercial HVAC installation, the rooms that the unit serves will be used by people. People can interfere with a balanced system by blocking registers or turning them off, by doing office, cubicle or space renovation, and even something like desk fans blowing air around may upset the balance. These interactions can certainly be limited by using non-adjustable registers, checking to see that vents and grills are not blocked, and that if any redesign or remodeling is undertaken, making sure that extra walls or furniture don’t impede the airflow in any way. But realistically, unless a room is bare, a perfectly balanced system may never be achieved.

But just remember, under any circumstances, an HVAC system is going to keep doing its job keeping living spaces, offices or commercial areas as comfortable as possible. Small variations at registers, using desk fans or even blocking the airflow at one place or another, may affect the system at a specific place, but the overall system balance will still be largely uncompromised. By having an HVAC system air balanced, you will know that it is running at its peak efficiency and effectiveness, while maintaining the airflow in perfect harmony, for any residential or commercial HVAC application.

Leave a Reply