Symptoms of Not Enough Return Air

Return air ducts are an essential part of your HVAC system, and if you aren’t getting enough return air, your system won’t work correctly, and your air quality will suffer. Luckily, there are some tell-tale signs that you’re not getting enough return air that you can quickly identify.  

Symptoms of your HVAC system not getting enough return air include varying temperatures in different rooms, a lack of airflow, warm air from the air conditioner, cold air from the furnace, and varying air pressures. 

This article will discuss all the different symptoms you should look out for to determine if you’re not getting enough return air. To learn more, please read on! 

1. Some Rooms Are Hot, and Others Are Cold

If you walk around your home and notice that some rooms are significantly hotter or colder than others, your HVAC unit probably isn’t getting enough return air. You can double-check this by checking the temperature of rooms from various distances from the central unit. 

If the rooms closer to your HVAC unit are colder than the rooms that are further away when you’re running your air conditioning—this is a sign that the unit isn’t getting enough return air to pump back out to the rooms further away.

Similarly, when you’re running your heating, and the room closer to the furnace is significantly hotter than the rooms further away, you’re not getting enough return air. 

If the temperature difference is significant, you’ll probably be able to tell just from walking around from room to room. To verify what you’re feeling, though, you may want to use a thermometer. 

I like this ThermoPro Digital Indoor Thermometer from Amazon.com because it is highly accurate, plus or minus one degree Fahrenheit. I also like that it measures humidity with an accuracy of plus or minus 2%. Finally, I appreciate that the thermometer automatically refreshes every ten seconds to keep up with any temperature changes.    

ThermoPro Digital Indoor Thermometer
$6.55
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12/03/2022 08:04 am GMT

2. Not a Lot of Air Is Coming Through the Supply Vents

You can’t feel the air circulating through a return vent because it pumps air out of the room and to the HVAC unit. However, if you notice that there isn’t a lot of air coming through the supply vents, this may be because the system isn’t getting enough return air.  

Checking for this symptom is easy. All you need to do is place a hand in front of your vent and see if you can feel any air coming through the flue. If the amount of air coming through seems weak, or if it seems different than usual, this might indicate that you’re having return air problems

You may also notice a lack of air flowing through your vents—one vent might be more affected than others. There are many reasons why your airflow might be suffering. I recommend reading my article on increasing airflow in ductwork for more information.   

3. The Air Conditioner Is Blowing Warm Air

The whole system will suffer if your ducts don’t have sufficient airflow from the return air. As a result, your HVAC unit won’t be able to condition adequately. This issue occurs because it does not have the right amount of air to send back through the house through the supply ducts if it doesn’t first get enough air from the return ducts.  

This issue means that, during hot summer months, the supply air into your HVAC system will be warmer because it won’t be conditioned air coming in from the return ducts. Then, your air conditioner will start blowing out warm air instead of cold air. 

There are other reasons why an air conditioner might start blowing warm air, so if you notice this symptom, don’t automatically assume you’re not getting enough return air. If your AC unit starts blowing warm air after a power outage, I recommend reading my article on what to check in this situation. 

4. The Furnace Is Blowing Cool Air

For the same reasons that insufficient return air usually causes an air conditioner to start blowing out warm air, the problem will cause a furnace to begin blowing out cold air. 

If the initial air supply is cold because it isn’t coming from the return air duct, then the furnace won’t be able to heat it properly before sending it back into the house. 

If you’re experiencing other furnaces problems, you may be due for a reset. For more information, check out my article on troubleshooting and resetting a furnace. 

Read: Why Furnace Blowing Cold Air? – Troubleshooting Guide

5. Different Rooms Have Different Air Pressures

If your HVAC unit isn’t getting enough return air, the rooms in your house will likely have different air pressures because rooms closer to the central HVAC unit will always get more return air than the rooms further away. 

If you have positive air pressure in a room, you’ll probably notice doors opening by themselves, and inward-swinging doors will become challenging for you to open. If a room has negative air pressure, you might see that outward-opening doors start to open by themselves.  

It’s unlikely that the air pressure difference will get so extreme that you can feel it physically, but it is possible! Your ears might start to hurt in different rooms of your house because of the air pressure. 

Having imbalanced air pressure throughout your house is a problem, not only because doors swinging open without warning is creepy! 

Pressure differences can cause the following issues: 

  • Increased heating and cooling costs 
  • Discomfort in the home because the air isn’t a comfortable temperature 
  • Humid air gets into holes in your walls, where it can deposit moisture and cause mold 
  • Strange whistling noises 
  • Extremely drafty rooms 
  • Some rooms are too hot, whereas others are too cold
  • Nose bleeds 
  • Chapped lips 

You can use a barometer to check the air pressure in your home. I like the Aowutus Store Outdoor Barometer from Amazon.com because it accurately measures humidity, air pressure, and temperature. It’s also lightweight and easy to carry, and its small size means that storage won’t be too much of a hassle. 

Aowutus Store Outdoor Barometer
$32.99
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12/03/2022 08:19 am GMT

There are many reasons why you need more return air. If you notice any of the above symptoms, the cause could be a lack of return air because of the following issues: 

  • Your return air vents are blocked. If a piece of furniture or a pile of clothing obstructs the return air vent, it won’t be able to pull in air from the room and take it to the HVAC system. 
  • Your filters are clogged. Clogged filters make airflow much more challenging, which leads to the above symptoms. To avoid this issue, you should replace your air filter at least once a month. Not only will this ensure you get enough return air, but it will also significantly improve your air quality. Check out my article on the importance of air quality for more information.     
  • Your ducts are leaking. If your return air ducts have leaks, less air will make it to the HVAC unit. Check for holes and cracks in your ductwork and apply seals where necessary.  
  • Your return ducts aren’t big enough. The size of your return air ducts is essential. If the vents aren’t large enough, they won’t be able to take in enough air to keep up with the supply vents. This issue is more prevalent if you live in an older home with fewer return vents.