Top 5 Reasons You Have Poor Airflow – St. Louis Heating and Cooling

November 15, 2016

St. Louis homeowners sometimes complain of low airflow in their rooms. This could be the result of a number of issues.

St. Louis man inspecting vent

A trained HVAC professional can be called upon to determine the reason for poor airflow. Nevertheless, it is essential that St. Louis homeowners also have the proper knowledge about what causes poor airflow in their home. Consider the following reasons.

Dirty or excessively high efficiency furnace filters

Any dirt accumulating on the furnace filter over a period of time increases the thickness of the filter. Apart from causing a host of other issues, a dirty filter also restricts airflow causing inadequate or uneven distribution of air.

Another cause could be installing a filter with a high MERV rating. While filters with high MERV ratings are meant to purify air better, they can at times create resistance in airflow in an attempt to block small airborne particles. This resistance can pressurize the fan of the AC or the furnace and cause damage leading to poor airflow. Therefore, homeowners should check if their HVAC system is compatible with the high efficiency MERV filters.

Improper duct work

It is essential to design and install duct work properly, after careful consideration by a trained and experienced St. Louis HVAC technician. When designed and placed correctly, ducts are able to deliver the correct amount of air flow to a room, keeping it comfortable. Any blocks or cracks, too many bends and turns, or improper duct design can all lead to low airflow. (Also see: Signs Your Ductwork Needs to be Cleaned)


Any leaks caused by holes or cracks in the ductwork can lead to low airflow. Typically, an average duct system has about 30 to 35 percent of leakage. These spots, if left untreated, can reduce the quality of airflow and thereby decrease the efficiency of the HVAC system as well as the comfort levels in the room.

Not enough return vents

Ideally, an HVAC system is designed to produce a certain amount of air, distribute and circulate it throughout the house via the duct work and then return it via return vents for purification, so as to be circulated again. These HVAC systems are designed in a way that the vents return the same amount of air that is produced and circulated. When this return of air is not equal, or does not take place as designed, one experiences low airflow that is caused due to pressure created at the return vents.

Incorrect duct work size

If duct work is sized correctly, the air flows through the duct work and maintains a correct static pressure. In oversized duct work systems, this pressure is reduced and the flow of the air reduces as well.

St. Louis Heating and Cooling

Problems such as low airflow in an HVAC system can be solved by getting a trained and experienced St. Louis HVAC technician to check the HVAC system for airflow issues. Moreover, conducting regular maintenance checks and ensuring that all parts of the HVAC are in proper condition can reduce the probability of poor airflow issues and keep the HVAC system healthy. Call Scott-Lee Heating today at (314) 200-0788 to learn more!