Air Filters: Understanding Their Function and How to Choose the Right One

The air filter in your home’s furnace, air conditioner or heat pump is an important but often overlooked component of the HVAC system. Though they may seem like nothing more than large cardboard boxes full of fibers or pleated material, air filters actually affect several crucial areas of indoor comfort and HVAC equipment performance. Here’s a brief introduction to air filters and why these seemingly minor components are so critical to your home’s heating and cooling systems.

The Function of Air Filters

An air filter is usually made of a spun fiberglass material or from pleated paper or cloth enclosed in a cardboard frame. It’s basic function is to clean the air that circulates through your heating and cooling system. Filters trap and hold many types of particulates and contaminants that could affect your health and comfort, including:

• Dust and dirt
• Pollen
• Mold and mold spores
• Fibers and lint
• Metal, plaster or wood particles
• Hair and animal fur
• Bacteria and microorganisms

Filtration usually occurs when expended air is brought back into the HVAC equipment to be conditioned and distributed again. The air is forced through the filter, and the material removes particulates and other contaminants from the air.

MERV Ratings and Filter Efficiency

Not all air filters will clean your indoor air with the same level of efficiency. Higher-quality filters, while costing more, will be able to remove more contaminants from your indoor air.

Filter efficiency and performance is often indicated by the filters’ minimum efficiency reporting value, or MERV rating. Standard MERV values range from 1 to 16, with the number serving as an indicator of how well the filter will remove material from the air. Higher MERV numbers indicate better filtration.

• MERV 1-4: These are common standard filters that provide a basic level of filtration at low cost.
• MERV 6-8: These filters provide good filtration and are commonly used in residential settings. They’re often made of pleated cloth or paper to provide more surfaces for capturing particles.
• MERV 9-12: Mid-range filters like these are of relatively high quality and can capture very small particles of 1 micron or larger.
• MERV 13-16: These high-efficiency filters are the best standard filters available. They can remove very small particulates of 0.3 microns or larger.

Filters and filtration systems are also available with MERV ratings higher than 16. These types of filters are very effective, but they’re also thick and dense and can interfere with airflow inside your home’s HVAC equipment. High-MERV filters can reduce your heating and cooling effectiveness and could damage your HVAC system by restricting airflow. Make sure your heating or cooling equipment can handle the higher-MERV filters before installing one.

Separate air filtration and purification units can also be installed along with your HVAC system. These air cleaners also provide superior air cleaning using high-quality filters. Check with your local trusted HVAC service provider to see if an air purification systems is right for you.

Air Filter Maintenance

All of the air that heats or cools your home will eventually pass through the air filter in the HVAC system. For this reason, it’s extremely important that you keep clean filters in your heating or cooling equipment.

• Dirty, clogged air filters are a primary source of HVAC system malfunctions. In the more extreme cases, dirty filters can damage heating and cooling equipment.
• Dirty air filters can reduce the airflow inside the HVAC system, which can cause air-handling fans to work harder and wear out quicker.
• Dirty air filters can’t remove particulates and contaminants effectively, which allows these materials back into your indoor air.
• Dirty air filters can cause contaminants to accumulate in your HVAC system’s ductwork.
• Dirty air filters can cause HVAC equipment to work harder, increasing energy usage and unnecessarily driving up your monthly energy bills.

Air filters should be checked every month and changed when they get dirty. A visual inspection should show you whether the filters are dirty or clogged. Hold the filter up to a light source; if you can’t see the light through the filter, it should be changed.

Davis Air Conditioning has served home heating and cooling customers in the Texas communities of Houston, Galveston, Brazoria and Sugar Land since 1971. Contact us today for more information on the importance of air filters in your HVAC system and for help choosing the right filter for your needs.

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