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Common HVAC System Installations

If you have recently moved, bought a new home, or simply decided to replace your indoor air filter, you may be wondering where the air filters are located in your house. Sometimes a simple task becomes a time-consuming chore. Below is a list of common places to look for your HVAC system(s), which may make finding your filter easier. There are several types of HVAC units, and each of these types may require the filter to be installed differently. In addition, some homes have multiple HVAC units. Therefore, you may have to search several locations.



First, inspect ceiling or wall returns. Some HVAC units place the air filter behind a return air grille, which is typically found on the wall or ceiling. This allows for easy access to change out your filter. Dirty, contaminated air enters the upstream side, passing through the filter and exiting the downstream side as clean, filtered air before reaching the blower motor.

Next, check basements, crawlspaces, attics, or garages for your HVAC air handler.


Vertical HVAC systems: Due to their orientation, vertical HVAC units are typically found in smaller basements or crawlspaces where room is limited. There are two types of vertical HVAC units—up-flow and down-flow.


Up-flow: The up-flow units are most common in homes today because of their natural direction of airflow. This energy-efficient style draws cool air from the bottom and forces heated air through the top. On up-flow units, the filter is most likely located at the bottom of the HVAC unit.

Down-flow: Due to their unnatural airflow direction, down-flow systems aren’t typically as energy efficient. This style draws cool air from the top and forces heated air out from the bottom. On down-flow units, the filter is most likely located at the top of the HVAC unit.

Horizontal HVAC systems: These units are most often found in attics, garages or large basements with the return duct connected to the side of the air handler. They draw cool air from one side and force heated air out of the other side. Typically, horizontal systems are suspended from the ceiling or placed on a platform. The filter will most likely be positioned vertically in a filter-housing slot on the side of the unit.

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