Balancing Act: Solving Airflow Issues in HVAC Systems
Today's homeowner is more concerned with energy efficiency than ever before. A National Association of Home Builders September 2016 survey found that energy-saving appliances were at or near the top of the must-have feature list for 80 percent of new home buyers. In January, the association released the results of another study that revealed homebuyers across all income brackets are increasingly choosing homes with energy-saving elements, as well as other amenities, and will sacrifice square footage to get them.
These same buyers surely want to maximize the efficiency of all the electrical and mechanical systems in their homes, and that includes their HVAC systems. Efficiency, however, is not only a cost-savings issue. It's a comfort issue as well, and one only has to be on the receiving end of frustrated customer telephone calls a few times to realize just how prized a properly functioning climate control system can be.
Issues with New Systems
It's not just older systems that can exhibit substandard performance levels. According to the National Comfort Institute, 50 percent of new systems have efficiency and comfort issues right out of the box. The Energy Star program uses that same figure, also citing that incorrect installs reduce new system functionality by up to 30 percent.
Combine those systems with those that have suffered at the hands of well-meaning DIYers—home insulation projects that damage ductwork, decorative elements blocking thermostats or returns—and one can begin to see the need for qualified technicians who can set things right. One word about qualifications: No HVAC contractor should test and balance before being properly trained to do so.
Symptoms of Airflow Problems
From my time as a contractor, I’ve heard several common homeowner complaints about ducted systems indicate that the issue could require testing for balanced airflow.
- Lack of consistent temperatures
The homeowner notices significant temperature variations from room to room, sometimes even within the same room. This is one of the most common complaints around "unbalanced" systems.
- Inconsistent airflow from register to register
Despite all registers being 100 percent open, the homeowner reports that there is a difference in the strength of airflow from one register to another.
The homeowner has noticed higher humidity in one or two rooms—indicating lack of airflow—and increased dust or "flotsam and jetsam" in another, a sign of too much airflow.
Testing for Airflow Problems
Contractors should take the following steps to test a system for balanced airflow, according to a Contracting Business article by Rob Falke, president of the NCI. This process can also be used to test new systems as well.
- Gather information about the equipment, and, using Manual J or other estimating tools, determine the required airflow for each room, as well as relevant pressure, horsepower and other benchmarks.
- Make sure you have the proper tools on hand. This includes air testing equipment like balometers and manometers, as well as basic power tools like a drill or cordless saw to fix any structural problems you may find. Have your standard hand tools at the ready as well.
- Draw a rough sketch of the system and number the registers and return grilles in the planned order of testing.
- Inspect the entire system and rectify obvious issues like disconnected ducts, closed dampers and dirty air filters.
- Start the system into full operation, set to either heating or cooling.
- Drill test ports for static pressure and temperature tests before and after air moving equipment and a port five feet after the cooling coil to get a temperature reading.
- Measure airflow from the registers and return the grilles according to the rough sketch from Step 2, using a commercial balancing hood. Add the register airflow figures together and the return grille airflow figures.
- Adjust the fan to obtain the correct cubic feet per minute in the information from Step 1.
- Test the register, return the grilles and compare the results to the information gathered in Step 1, making a note of those that have 110 percent of the prescribed airflow. Close those until the correct airflow is achieved. Repeat with return grilles.
- Retest to verify and record the successful damper settings.
- Continue testing and measuring items that appear on an NCI or other industry standard air balance report, including metrics like total external static pressure, fan speed and temperature changes.
Solving Airflow Issues
It could be that the adjustments made during testing don't resolve the airflow issues. Leaks or damaged ductwork can be the cause of irregular airflow through the system, so a repair or renovation of the ductwork could be in order. If the ductwork that was originally installed with the system can’t handle the airflow, then a total replacement might be in order.
Airflow testing is a great starting point for contractors as it allows them to obtain a clearer picture of the entire system. Additional investigation may be needed.
Kim Slowey is a freelance writer based in Florida. She has a degree in journalism but spent over 25 years in the construction industry and is still a Florida certified general contractor. Kim currently covers commercial and residential construction and real estate for publications such as Construction Dive and Forbes. Kim also writes about energy, HVAC and tools topics for The Home Depot.
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