MERV Rating: What It Means and How to Choose
What is MERV?
When shopping for air filters the word MERV gets thrown around a lot but the average joe doesn't know what that means.
MERV stands for Minimum Efficiency Reporting Value. This system was created by the American Society of Heating Refrigeration and Air Conditioner Engineers (ASHRAE) to set a standard of quality for air filters. Essentially the higher the MERV Rating the more airborne particles are trapped. ASHRAE recommends that all systems use an air filter rated at MERV 6 or higher but the typical household filter is rated between MERV 8 - MERV 13.
Attached below is a diagram that shows the particles that Specific MERV ratings are able to filter out.
What Filter is Right For Me?
When shopping for air filters if you see a fiberglass filter that is a good indicator to STAY AWAY. Fiberglass air filters typically have a MERV rating between 1 and 4 which is not anywhere near ASHRAE's minimum recommendation. Using a filter with a low MERV rating not only can produce a lower quality of air but also cause damage to a HVAC System.
Pleated air filters are a much safer product since the pleats provide a greater surface area to catch airborne particles.
For the typical home owner a MERV 11 filter is recommended. These air filters are able to remove a large percentage of airborne particles including pet dander! MERV 11 is usually the sweet spot for having an efficient HVAC unit. Before you purchase an air filter it might be wise for you to contact the person in-charge of servicing your HVAC unit and get a recommendation from them.
Still Can't Decide? Let's take a closer look at each MERV Rating.
MERV 6
Filters out 35%-49% of particles between 3.0-10.0 Microns in size. Particles that fit in this category are pollen, dust mites, standing dust, spray paint dust, and carpet fibers.
MERV 8
Filters out 70%-85% of particles between 3.0-10.0 Microns in size. This includes everything listed in MERV 6 as well as mold spores and chemical mists.
MERV 11
Can handle 85% or more of any particle between 3.0-10.0 Microns in size as well as 65%-79% of particles sized between 1.0-3.0 Microns. This filters out the same particles as MERV 8 does as well as pet dander, auto emissions, lead dust, and humidifier dust.
MERV 13
Filters are able to remove 90% or more of particles larger than 1.0 Micron. Air filters with this rating are also able to trap particles that are sized 0.3 - 1.0 Microns with an efficiency of around 75%. Particles that fit in to this range are bacteria, tobacco smoke, and droplet nuclei.
Filter Types.
Air Filter Express offers filters from many trusted brands such as Accumulair, Dupont, and Arm and Hammer.
The traditional style of media which can be found in Accumulair's Emerald, Gold, Platinum, and Diamond series filters is pleated once per inch of media. The filter is then reinforced by an aluminum mesh to keep the hold the pleats and keep its shape.
A carbon impregnated media rated at a MERV 10 is offered under Accumulair's carbon series. The carbon is used to block unwanted and offensive odors. The build of this filter is exactly the same as the traditional styles with the only difference being the carbon based media.
Accumulair also offers a mini-pleated series of air filters. They are the Ruby (MERV 11) and Titanium (MERV 13). These filters use a self supporting media and are pleated once every 3/4 of an inch. The higher pleat count in these filters offers superior filtration with a greater surface area.