What is a HVAC Filter and How Does it Work?

The HVAC filters used in your home's heating and cooling system have an important job to do - they filter dust, pollen, pet dander and other small particles from the air you and your family breathe. These particles are trapped in the filter to prevent them from being recirculated throughout the house. In its most basic function, an air filter removes impurities such as dust, pet dander, or even bacteria from the air that flows through the system. Not only does this improve the air quality inside your home, but it also protects your HVAC system from potential damage. When air is introduced into the HVAC system, it is first heated or cooled and then pushed through the ducts that lead it to every room in the house.

The HVAC filter cleans the air just before it enters through the blower and circulates through the ducts. As air is forced through the filter, the material, usually cloth or pleated paper, traps any contaminants that are in the air. The primary purpose of a filter is to protect HVAC equipment, not improve indoor air quality, as many homeowners have been led to believe. Many oven manufacturers recommend using an inexpensive fiberglass filter, but when I asked a representative of a major manufacturer, their answer was “no comment”. Most HVAC units are forced air systems; they literally force air through a filter into the rest of the house to cool or heat internal rooms.

All of the air that heats or cools your home will eventually pass through the HVAC system's air filter. Although they may look like nothing more than large cardboard boxes filled with fibers or pleated material, air filters affect several crucial areas of interior comfort and performance of HVAC equipment. A fiberglass HVAC filter may be right for you if you don't have pets, allergies, or chronic respiratory conditions. Some HVAC systems are not strong enough to push air through more restrictive filters that block smaller particles, that is, those with a higher MERV or CADR rating, which can reduce airflow and cause your home to heat and cool less efficiently. If you want to buy a higher MERV filter than recommended by the manufacturer, you risk burning the blower and heat exchanger of your HVAC unit. Finally, you'll need to consider the dimensions of the vents and spaces your HVAC system is servicing, which will determine the size and thickness of the filter you'll need.

The minimum value of efficiency reports, or MERV, is the standard way to rate the efficiency and performance of HVAC filters. Proper maintenance of air filters, whether replacing them or washing them regularly, is crucial not only to providing clean air in your home, but also to keeping your HVAC system working properly. It's also important to note that HVAC filters with higher MERV ratings can interfere with airflow. These types of filters are very effective, but they are also thick and dense and can interfere with the flow of air inside your home's HVAC equipment. Your home's boiler, air conditioner, or heat pump air filter is an important but often overlooked component of the HVAC system. If you take great care of your HVAC unit but know that it will eventually fail - like all HVAC units do - consider investing in a home warranty to protect it. In this post, we discuss four different types of HVAC air filters: fiberglass filters; pleated filters; high-efficiency particulate arrestance (HEPA) filters; and electrostatic filters.

We also explain how each type works and how they can help improve indoor air quality.

Shana Gojcaj
Shana Gojcaj

Avid web nerd. Subtly charming social media specialist. Amateur zombie guru. Evil web trailblazer. Proud twitter practitioner.