Car exhaust, smokestacks, and smog are likely some of the first things you picture when you hear the words “air pollution.” However, what if we told you you’re way more likely to experience pollution within the walls of your own home?

According to the EPA, concentrations of indoor pollutants can be 2-5 times higher than they are outdoors. Since we spend an average of 90% of our time inside, this can be terrible for our health!

That’s where your filter comes in. Your furnace filter MERV rating tells you how well your system will capture airborne particles that pass through your home.

Unfortunately, the number scrawled on the side of the filter frame isn’t always easy to understand. How do you know which rating is best for your air quality? Do you need a HEPA filter, too?

We’ve got you covered. Here’s what you should know about choosing the right furnace filter for your home.

Basics of MERV Ratings

When you buy a filter, you’ll see the MERV rating printed as a number on the side. If you can’t find the rating, your filter likely has the lowest-quality MERV rating.

MERV stands for “Minimum Efficiency Reporting Value.” Designed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) back in the 80s, the rating system evaluates how well an air filter performs.

You’ll find MERV filters with ratings that run from 1-20. Each numerical rating lists a minimum amount of particles that the filter must be able to capture.

Lower-rated filters capture fewer particles. Higher-rated filters capture more. Because of this, you might consider choosing your filter a no-brainer: why not pick a filter with the highest possible rating?

Not so fast!

The more particles a filter can capture, the more reduced your airflow becomes. With the highest-rated MERV filters, your system may struggle to circulate air. This can put a serious strain on your furnace.

In other words, finding the right filter is always about balancing particle capture against efficiency.

Furnace Filter MERV Rating Guide

Every home is different, and you might prefer a higher or lower MERV rating based on your household makeup. This quick guide can help you navigate the rating system:

1-5 MERV Rating

For most households, we don’t recommend choosing a furnace filter with a MERV rating below 5.

These lower ratings don’t block particles smaller than lint, sanding dust, and carpet fibers. In other words, they allow the bulk of other airborne contaminants to circulate in your home.

6-8 MERV Rating

In general, we recommend that most homeowners start with a MERV rating of 6-8.

These filters will block out common pollutants like dust, pollen, dust mites, and even certain kinds of mold spores. For the average residential home, this option is a great balance between indoor air quality, comfort, and furnace efficiency.

9-13 MERV Rating

If anyone in your household has respiratory conditions, a better filter may be ideal.

Choosing a furnace filter with a MERV rating of 9-13 can help reduce common allergy symptoms. It will also trap fine dust, pet dander, smog, and smaller mold spores at the cost of slightly lower furnace efficiency.

14+ MERV Rating

We don’t recommend choosing a MERV filter above 13 for most Porterville homes. At these high levels, these filters become overkill.

Higher MERV filters are common in commercial buildings and hospitals. This is because they block airborne threats like smoke, bacteria, and even viruses like COVID-19. They’re great for industrial equipment, but they’re not ideal for your home furnace!

If you feel you need a higher-rated filter, speak to a reputable HVAC company about options and alternatives.

Additional Factors to Consider

Keep in mind that not all systems are capable of handling higher-rated MERV filters.

If you have an aging furnace, a filter of 13 or higher could cause serious damage over time. You may even overwork the system to the point of a breakdown.

Always check your owner’s manual, which should list the maximum recommended MERV rating. If needed, talk to a heating service professional about upgrading your system or finding a MERV rating that will work for an older unit.

In addition, maintaining a clean air HVAC filter is even more important with moderate to high MERV ratings, no matter the age of your filter. As a higher-rated MERV filter collects more contaminants faster, the buildup of debris can strain your system.

To make airflow easier, check and change your filter at least once every 90 days, depending on your household makeup. Periodic cleaning of your system helps as well.

What About HEPA Filters?

To add to the complexity of choosing an air filter, there’s another design standard you can opt into: HEPA filters.

HEPA stands for “high-efficiency particulate air.” These filters always have a MERV rating of 17 or higher.

In addition, HEPA filters can remove up to 99.97% of all airborne particles larger than 0.3 microns. If you’re concerned about your indoor air quality or anyone in your home has severe respiratory conditions, these filters are hard to beat.

It may be possible to find and buy a commercial-grade HEPA filter for your furnace, but you’ll run into the same problems we’ve mentioned above. Because these filters are so good at catching contaminants, they also create high air resistance. This can be tough on your furnace.

For that reason, we recommend choosing a separate air purifier or vacuum cleaner with a HEPA filter. These systems trap airborne particles without reducing your system’s energy efficiency.

Get More Out of Your Furnace Filter

Your filter is a crucial part of your furnace, shielding your system from debris while improving your air quality. That’s why it’s so important to find the right furnace filter MERV rating! Use the tips above to find a filter that balances your system’s and household’s needs, allowing you to enjoy cleaner air and a longer-lasting furnace.

If you’re struggling to choose or replace a furnace filter for your home, Comfort Now is here to help. Our team serves homes throughout the Hanford, Visalia, Portersville, and beyond.

Boost your indoor air quality and preserve your home’s comfort with a free system evaluation! Contact us to learn more.