What It Means
MERV stands for Minimum Efficiency Reporting Value. It measures how well an air filter captures particles between 0.3 and 1010,000 stepsA popular daily step goal that began as the name of a 1960s Japanese pedometer; later studies find health benefits begin well below it. See more microns across, and the rating comes from a test written by ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers). A higher number means the filter traps more of the smaller particles in that range. EPA uses the rating to compare furnace and HVAC filtersHVAC filterThe removable filter in a furnace, central air conditioner or heat pump that traps dust from the air; ENERGY STAR says check it monthly and change it at least every 3 months. See more and suggests at least MERV 13 when a home system can handle it.
Try It: Slide Through the MERV Scale
Slide to a MERV number to see what EPA says about that part of the scale.
MERV 1 to 4 is where EPA places a typical 1-inch spun fiberglass furnace filter.
MERV 5 to 13 is medium efficiency, the range EPA gives for pleated filters, and reasonably good at small to large airborne particles.
From MERV 13 up, a filter must remove at least 50% of the smallest particles tested, 0.3 to 1 micron. EPA suggests at least this level if your system can take it.
MERV 14 to 16 is high efficiency, and EPA notes these filters look much like true HEPA filters. Check that your system's fan can push air through one.
EPA: MERV 13 suits most home systems as long as the filter gets changed often.
How It Sounds at Home
- "Get the MERV 13 ones this time."
- "What MERV does our furnace take?"
- "The cheap fiberglass filter is only a MERV 4."
The Breakdown
What the numbers mean, per EPA
| MERV | What it tells you |
|---|---|
| 1 to 4 | The range of a typical 1-inch spun fiberglass furnace filter |
| 5 to 13 | Medium efficiency, the range for pleated filters; reasonably good at small to large particles |
| 13 and up | Required to remove at least 50% of the smallest particles tested, 0.3 to 1 micron |
| 14 to 16 | High efficiency; these look much like true HEPA filters |
How to pick a filter by MERV
- Find the size and MERV of the filter in your system now, from the filter itself or the box it came in.
- Check your system's manual, or ask an HVAC technician, how high a MERV its fan and filter slot can take.
- Aim for MERV 13 if the system allows it, as EPA suggests for an upgrade.
- If 13 is too much for your system, choose the highest rating it can handle.
- Check the new filter every month, and change it when it's dirty and at least every 3 months, per ENERGY STAR.
Try it today. Look up the MERV and the size of the filter in your system and write both down where you'll find them at the store. If the number is 1 to 4, ask whether your system can take something higher next time.
Where It Comes From
The rating comes from ASHRAE Standard 52.2, a test method for air filters. Its test sorts particles into three size ranges, 0.3 to 1 micron, 1 to 3 microns and 3 to 10 microns, and a filter's measured efficiency across those ranges sets its MERV.
Good to Know
EPA cautions that a higher-efficiency filter adds resistance, so any upgrade has to suit your ducted system or it can hold back airflow. Its advice is to pick at least MERV 13 or the highest rating your system's fan and filter slot can accommodate. Whatever the number, a clogged filter slows airflow, so keep up the monthly checks ENERGY STAR recommends.
FAQ
What MERV rating should I use at home?
EPA suggests at least MERV 13 if your system's fan and filter slot can take it, or else the highest rating that fits. EPA adds that MERV 13 suits most home systems as long as the filter gets changed often.
Is a higher MERV always better?
A higher MERV traps more small particles, but it can also restrict airflow. EPA says to make sure any higher-efficiency filter suits your existing system so air still moves freely through it.
What does MERV 8 mean?
MERV 8 falls in the medium-efficiency range of 5 to 13, which EPA calls reasonably good at catching particles from small to large. EPA says filters rated MERV 13 and above must remove at least half of the smallest particles tested, which puts MERV 8 below that mark.
Do It in Buhata
Household Notes, Maintenance (Household X)
Save your filter's size and MERV in Household Notes in Buhata so whoever buys the next one gets the right match.
Open BuhataRelated Terms and Categories
- HVAC filter
The removable filter in a furnace, central air conditioner or heat pump that traps dust from the air; ENERGY STAR says check it monthly and change it at least every 3 months.
- HVAC tune-up
A service visit where a qualified contractor checks, cleans and adjusts a heating or cooling system; ENERGY STAR advises one for cooling each spring and heating each fall.
- Furnace maintenance
The routine care a furnace needs: a monthly filter check, a yearly professional cleaning and inspection before heating season, and a working carbon monoxide alarm.
- Seasonal home maintenance
Home upkeep sorted by time of year, so each job lands when the weather suits it and before the system it protects is needed most.
Sources
U.S. EPA, "What is a MERV rating?"; U.S. EPA, "Guide to Air Cleaners in the Home"; U.S. EPA, "What kind of filter should I use in my home HVAC system?"; ASHRAE, Addendum to ANSI/ASHRAE Standard 52.2; ENERGY STAR, "Maintenance Checklist"
- www.epa.gov/indoor-air-quality-iaq/what-merv-rating
- www.epa.gov/indoor-air-quality-iaq/guide-air-cleaners-home
- www.epa.gov/indoor-air-quality-iaq/what-kind-filter-should-i-use-my-home-hvac-system-help-protect-my-family
- www.ashrae.org/file%20library/technical%20resources/standards%20and%20guidelines/standards%20addenda/52_2_2007_supplement_final.pdf
- www.energystar.gov/saveathome/heating-cooling/maintenance-checklist
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