Comments on: MERV Rating? What is that?

By: Christina Miller

Christina Miller — Fri, 13 Nov 2009 16:29:52 +0000

Something to note is that the percentages can be misleading. The reason the MERV system was adopted was because people were being mislead by the percentages. In the past someone could advertise a filter and say it is 75% effective but that does not tell you much. Is it 75% effective at trapping large particles, such as large carpet fibers, or 75% effective at trapping smaller particles, such as bacteria. Always be sure to look for the MERV rating when buying your filters!

By: christinamiller

christinamiller — Fri, 13 Nov 2009 14:16:07 +0000

Higher rated MERV ratings do have higher resistance to airflow. Usually a standard filter can be replaced with one with a higher MERV rating up to MERV 10 without affecting airlow. HOWEVER in all systems airflow characteristics are a function of the duct design and duct installation and would need to be evaluated on a case by case basis. The total airflow can be calculated my measuring the systems static pressure. A trained technician would be able to do this when the filter is upgraded.

By: Marc Kleinmann

Marc Kleinmann — Thu, 12 Nov 2009 18:30:42 +0000

In an existing system, can I just replace my current filters with a higher rated filter without restricting airflow at all? I would imagine that a MERV1 naturally allows for more airflow than a MERV16 – even when they're new & clean.

By: lindsaymarino

lindsaymarino — Thu, 12 Nov 2009 15:37:20 +0000

I knew there was varied levels of quality but I had no idea there was a rating system. I was looking on Lowe's website because you reminded me to change my filter and found some great information.

-pleated filters are more efficient than fiberglass layers
-a MERV rating of 6 is 35-50% efficient vs. a rating of 11 is 85-95% efficient
-reusable filters are available and can be cleaned with water (more green)
-natural material filters can be special ordered