You might be inclined to walk into the nearest hardware store and purchase the first air filter you find. Unfortunately, this is not the best idea as some air filters are more effective and efficient than others. When looking for the best home air filter, you may find recommendations for both MERV and HEPA air filters. What is the difference between the two? And which filter is best for your home? In order to answer these questions, it’s important to understand the purpose, strengths and weaknesses of both.
What Are MERV Filters?
First and foremost, it’s important to understand that MERV is actually a rating system. There are actually several MERV filters, or really, air filters with a MERV rating. Developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), MERV is an acronym meaning minimum efficiency reporting value. The purpose of the MERV rating system is to measure and compare air filters’ ability to capture particles between 0.3 and 10 micrometers in size. The MERV scale ranges from 1 to 20, the latter being the highest. The following chart lists some of the air pollutants air filters can capture based on the MERV rating.
| MERV Rating | Abilities |
|---|---|
| MERV 1–4 | – Pollen – Dust and Dust Mites – Textile Fibers |
| MERV 5–8 | – Mold Spores – Furniture Polish |
| MERV 9–12 | – Exhaust Fumes – Lead Dust |
| MERV 13–16 | – Bacteria – Tobacco Smoke – Respiratory Droplets |
| MERV 17+ | – Viruses – Microscopic Allergens |
While any air filter is better than no air filter, you’ll find that air filters in the range of MERV 11–13 are just right for most residential spaces. Lower-rated filters require more frequent replacement and cannot capture as many air pollutants as high-efficiency filters. Furthermore, air filters with a MERV 11 or MERV 13 rating are generally beneficial for asthma and allergy sufferers as well as homes with pets.
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HEPA filters are extremely efficient and effective. Also an acronym, HEPA stands for high-efficiency particulate air. They can capture 99.7% of air pollutants as small as 0.3 micrometers, which explains why they are favored in operating rooms, clean rooms and the like. It’s also why they have such a good rap.
Unfortunately, air filters that are this powerful tend to reduce airflow in the average home HVAC system. A residential HVAC system is forced to work harder to push air through a HEPA filter. More often than not, HEPA filters require costly system retrofits and additional fans to filter the air, making compatibility difficult. That lack of compatibility results in increased energy costs, the strain on the system and worse indoor air quality. More often than not, a HEPA filter is not a viable whole-home HVAC filter option.
Do HEPA Filters Have a MERV Rating?
HEPA filters are not MERV-rated because they exceed the ASHRAE Standard rating system. Informally, however, if HEPA filters were to receive a MERV rating, they would rate roughly at MERV 17 or higher.
MERV 17+ filters are also favored by operating rooms, clean rooms and indoor spaces that require significant air filtration. Again, this upper MERV rating level and HEPA filters are too much for homes and residential spaces. Air filters below MERV 16 are favored for residential use as well as commercial buildings.
MERV vs. HEPA for Homeowners
As indoor air quality experts, we strongly recommend investing in air filters with a MERV rating of 11 or 13 for your home! As aforementioned, air filters in this rating range efficiently capture a wide variety of air pollutants without restricting airflow. This is the perfect combination for homeowners.
