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What is MERV?
MERV is a good way to help judge the effectiveness of an air filter. As you might have expected MERV is an acronym for Minimum Efficiency Reporting Value which was developed by the American Society of Heating, Refrigeration and Air Conditioner Engineers, ASHRAE. The MERV value represents a performance indicator for an air filter from the beginning to the end of the filters life. The highest MERV value available is 16 and the lowest is 1, in this case the higher the value the more efficient the filter will be in trapping airborne particles.
One factor to consider is air flow through the system. Leaving a dirty air filter in place may result in low air flow and possibly cause the system to malfunction. In some cases, using an air filter that is too restrictive for your system may cause low air flow problems as well. MERV 13 is the highest MERV value safe for residential furnaces; the higher ratings are used primarily in commercial units.
If you are wondering what MERV to try, keep these recommendations in mind;
  • ASHRAE recommends MERV 6 or higher
  • US Department of Energy recommends MERV 13
  • Leadership in Energy and Environmental Design, LEED recommends a minimum of MERV 8
Keep the air flow issue in mind and change you air filters regularly according to the manufacturer’s recommendation. When you’re purchasing a furnace filter for your home, you want to be sure that you are buying a filter that will keep the air in your home clean. While all of our filters will provide you with the filtering efficiency needed to improve the air quality of your home, you may require a filter that has a higher MERV rating. Cases in which this is likely are those when you or someone in your home suffers from allergies, respiratory problems, or other similar incidences. Then again, you may just want to get the best filter for your family so that your indoor air quality is the best it can possibly be.
On the MERV scale, dirt particles are graded from 0.3 microns to 10 microns. A micron is 1 millionth of a millimeter, and just to give you an idea of just how small that is, you can look at the size of a single human hair. The average strand of human hair is about 100 microns thick, so imagine just how small 0.3 microns of dirt is.
Residential filters commonly have MERV ratings of 1-13. The higher the MERV rating, the more efficient the filter is, and the more particles it can filter.
  • A MERV rating of 6 means the filter is 35% to 50% minimum efficient at capturing particles, sized 3.0-10.0 microns.
  • A MERV rating of 7 means the filter is 50% to 70% minimum efficient at capturing particles, sized 3.0-10 microns.
  • A MERV rating of 8 means the filter is 70% minimum efficient at capturing particles, sized 3.0-10.0 microns.
  • A MERV rating of 11 means the filter is 85% minimum efficient at capturing particles, sized 3.0-10.0 microns.
  • A MERV rating of 13 means the filter is 90% to 98% minimum efficient at capturing particles, sized 3.0-10.0 microns.
How big is a Micron?

Below is a chart that will show you the efficiency of each MERV rating and help determine which MERV rating is right for you (Click on the chart to open it for a better view)