MERV Ratings Matter When You Go Shopping for Air Filter Replacements

Published on: March 26, 2014

When it comes time to shop for a new air filter for your furnace, air conditioner or heat pump system, a lot of homeowners just grab the first one they see with the correct dimensions. However, there’s a lot more that’s involved in choosing the right air filter for your forced-air heating and cooling system, and at the top of the list is the filter’s efficiency level. Learn about MERV ratings for air filters, and you can make your Southeast U.S. home healthier, your family more comfortable, and your HVAC equipment a lot more efficient.

What Is MERV?

The Minimum Efficiency Reporting Value (MERV) measures the ability of any air filter to capture airborne particulates. The rating system runs from 1-20, and the higher the number the smaller (and more) particles the filter will capture. For residential air filters, homeowners generally use filters with MERV ratings in the 1-12 range, though filters in the MERV 1-4 spectrum only capture the largest airborne particulates, and do little or nothing to clean your indoor air.

While some home HVAC systems do employ higher-efficiency filters with MERV numbers 13 and above, in most cases, they’ve had serious system modifications undertaken in order to accommodate the filter size and density. Basically, as the MERV numbers climb, while they do a better job of capturing airborne contaminants, in so doing, they also impede system airflow.

Who Needs MERV?

For most homeowners, an HVAC filter in the MERV 8-12 range will provide a desirable balance between maintaining good indoor air quality and maintaining proper system airflow. They will serve the basic purpose of keeping large dust particles, which can hamper system efficiency, out of components. They also remove a variety of airborne contaminants, including many of the mold spores, dust mites, bacteria, viruses, pet dander and other particles floating in your indoor air.

MERV Knows Best!

What can the right MERV filter do for you and your family? It can capture and remove from the air stream in your ducts an impressive list of particulates ranging the very largest down to the very tiniest, 0.3 microns:

  • Anthrax
  • Antiperspirant particles
  • Asbestos
  • Auto Emissions
  • Bacteria
  • Carbon black dust
  • Cement, coal, grain and insecticide dusts
  • Dust mites
  • Fiberglass insulation
  • Human dander and hair
  • Pet dander and hair
  • Lead, tea, coffee and talcum dust
  • Mold spores
  • Smoke from synthetic materials
  • Spider webs
  • Textile dust
  • Yeast cells

What MERV Ratings Should I Look For?

  • MERV 2 to 3 – If you buy your furnace filters from big-box or discount stores, you are not saving a penny. Rather, you are setting yourself up for some big expenses. Those flat spun fiberglass filters have a MERV rating of 1-4, so they hardly block anything. They are fine if no one suffers any allergies, asthma or lung sensitivity, or if you are renting a place for a month or so. Do not count on them to clean your air.
  • MERV 6 -8– A disposable pleated filter (not flat) made of polyester or cotton will remove a variety of small (though not the smallest) airborne particles including many allergens.
  • MERV 10 – A disposable electrostatic filter, using cotton or paper fibers, traps particles down to around three microns. Filters with MERV ratings of around 10 to 11 are affordable enough to replace a couple of times a year, but are several times costlier than the disposable pleated and flat filters.
  • MERV 14 to 16 – Equivalent to four or five disposable plain filters, a high-efficiency pleated filter is expensive but effectively block particles so your home’s air is hospital-quality safe. Particles even smaller than 0.3 microns can be blocked by these, so if someone’s respiratory system is compromised, this level of filtration may be needed. This filter requires a special housing and custom installation by an HVAC professional.

Proper MERV

Your furnace’s blower is designed to move the correct amount of air volume at the proper rate. You don’t want a high-efficiency air filter to mess up that balance by impeding airflow. Talk to your trusted HVAC technician about the highest-efficiency air filter your forced-air equipment can handle without straining the system.

For help finding a local contractor to assist you in selecting the ideal MERV rating for your Southeast U.S. home’s furnace and air filter, please contact us today.