What Is The Most Common Cause Of Poor Air Flow In a Duct System?

ByMarc Silberberg


If you’re like me you might be sitting at a desk wearing a sweatshirt trying to fend off the cold fall chill, the harbinger for the upcoming cold winter season. But if my thermostat is set to 70° why is the heat not kicking in to warm the parts of our home that we occupy throughout the day and night? 

There can be a variety of reasons for poor heating during the fall and winter months that correlates to weak cooling during the summer months. But today we are going to be addressing the issues of poor air flow in your home’s duct work and the solutions that can solve the issues without breaking the bank. 

Make Sure Your HVAC Is Working Properly

Prior to troubleshooting if your home has a poor airflow in the ducts it’s vital to establish that your HVAC system is working properly.  Go to an area closer to the blower where you’re certain that the heating and cooling are working properly and check the register and return vents. In our case we are checking to make sure that the heating system is operating well and feel for a healthy burst of warm air from the floor registers. At the same time you want to be sure that the intake is functioning efficiently. Take a tissue or piece of toilet paper and place over the grill by the return on the wall or ceiling. It should be able to stick to the grill due to the suction from the system. The cold air that is pulled into your system is reheated and pushed back into the conditioned areas. Assuming that the equipment for your heating system is working well we can now begin to address the issue of poor air flow in your duct system.

How To Get More Air Flow From Upstairs Vents 

There are some homes that are privileged to have a devoted system for each floor while others simply have just one system which distributes conditioned air throughout the home. It is most likely that a home that is having issues with poor air flow in the upstairs has just one system. The system in my home is 3.5 tons that should condition 1,800 to 2,100 square feet. The problem is that my home is 2,400 square feet and can really use another system but we went with the more economical system. Having multiple systems would have been costly and the duct work would have to be redone. Below are some hacks on how one can improve the airflow on the second floor of a single family home.

Hack # 1 – Closed Vents: It goes without saying that you should make sure that all your registers are in the open position. Even if you have a little tissue taped to the ceiling vent you want to be certain that the vent is open all the way. It happened many times to me that the vent was closed or not open all the way. It could be a guest that was cold during the summer months who shut the vent to prevent the air conditioning from blowing on them so regardless you must check to see that there is air flowing through the vent.

Since you most likely have already checked that all vents are open it’s now time to get a bit savvy to balance out the air flowing upstairs. Often there can be one room that is warmer than the others. Try to close the vent there (without jeopardizing the room temperature) and see if you get more warm air being pushed into the rooms where the air flow is poor. This might be a quick fix that can help balance out the air to be properly distributed throughout the upstairs. 

Hack # 2 – Replace Dirty Air Filters: It goes without saying that dirty air filters can disrupt the air flow of your heating and cooling system. Just to be certain that your air filter is clean, change them religiously once a month. With the accumulation of dust and debris that gets caught in the air filter, the air flow from the blower is reduced which can impact how the warm air gets distributed upstairs. You don’t need to spend money on the expensive air filters, the generic brand will suffice to allow your heating system to work efficiently. 

Hack # 3 – Smart Sensors For Thermostat: If your home is like mine and has just one HVAC system for the entire house, the thermostat is most likely on the first floor. The original contractor placed it there because the first floor is occupied the most. The problem with that is that there is no signal to tell the heating system to turn on if it is cold upstairs when it is warm downstairs. Fortunately today we have a smart thermostat that can connect to the internet and with smart sensors it can pick up the temperature on multiple spots throughout the house. Therefore the thermostat can pick up temperatures upstairs to continue pumping heat to areas of the home which are cooler than others. In our home, we use the Ecobee3 Lite SmartThermostat which connects to two SmartSensors. One is placed in the master bedroom and the other is placed in the kids bedroom. When the degrees drop in the night time in those rooms the heat will continue to pump. 

Hack # 4 – Clean Dirty Air Ducts: Over the course of time dust will begin to accumulate inside the ductwork. Once there is a thin lining of dust, other particles will accumulate creating the environment for impeding the airflow within the duct. No it won’t be visual to the eye but you will need to call a professional duct cleaner to clear those blockages. True, there is a filter to prevent dust and dirt from getting into your system’s duct work but there are other ways those unwanted elements can get in such as through the registers and vents. It’s recommended to have your air ducts cleaned once every four years but it really depends on how dusty your home is. One of the signals that your air ducts need to be cleaned is when you begin to see a film of dust around vents. 

Other Common Causes For Poor Flow In Ducts

Another common cause for poor air flow in home duct work is due to the age of the home. Even if you purchased an existing home and the previous owner said that they just installed a new HVAC system a couple of years ago, the duct work is most likely to be the same as when the home was built. Over the course of time the conditions of the ducts begin to deteriorate which hampers the air flow. Cracked corners begin to peel and perforations begin to start leaking air. All this can impact how efficiently the air is spread throughout the home. Think of the furnace which creates the heat as the heart and the duct work as the arteries. Faulty arteries can be a big problem and be devastating for one’s health. It is quite the same for the HVAC ductwork that should distribute the air evenly throughout the home. 

It is also quite common for a home’s ductwork to run through the attic. If there is ever any work done in the attic such as searching for a leak or installing spotlights in the rooms, workers can accidentally misplace a piece of wood or building material and leave it on top of a duct disrupting the air flow. Peek into the attic and make sure that there is nothing sitting on the flex ducts restricting air flow. Laborers try to be careful not to step on the ducts in the attic but in a cramped space it is sometimes unavoidable. As in my case, when the contractor was renovating a walk in closet they removed an air vent and forgot to put it back. It took some time for me to realize that there was a vent blowing into an empty attic that was affecting air temperature in the master bedroom. Always check the attic for blockages that can negatively impact the airflow in your home’s ductwork.

Final Words

 Homeowners can only speculate as to what is causing poor air flow in your home heating and cooling system. If you are uncertain as to what is the cause of the poor air flow save yourself the headache and call a specialist who will evaluate what is wrong with your system and why the heating or cooling is not getting distributed properly throughout the home. If you do sense a lack of proper air flow in your upstairs try some of the hacks mentioned above or call a local HVAC specialist to diagnose the issues. All we can do is try to see if the economical issue works by fixing the poor air flow issue. Sometimes we just have to humble ourselves and pick up the phone to call a trusted professional.  

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