Understanding the MERV Rating on an Air Filter
If you’ve ever shopped for a new HVAC filter, you have probably noticed that each one has a rating. Known as a MERV (Minimum Efficiency Reporting Value) rating, this value indicates how efficient the filter is at filtering out different sized particles from the air. Still, it is important to look more closely at this rating system in order to understand what the specific rating numbers mean.
How Does the MERV Rating System Work?
The MERV system rates the efficiency of an air filter on a scale from 1 to 20, with 20 being the highest and 1 being the lowest. In order to determine a specific filter’s rating, the system takes into account how effectively it filters out particles of different sizes. The system looks at three specific categories: particles between .3 and 1 microns in size, particles between 1 and 3 microns, and particles between 3 and 10 microns.
Low-efficiency filters range from MERV 1 to MERV 6. Typically, these lower MERV filters are the type you might find in a window AC unit. Nonetheless, you can often find MERV 4 to 6 filters designed for central heating and cooling systems as well. At these lowest levels, the filters mostly are only capable of trapping larger particles like pollen, mites, dust, and fabric particles. However, MERV 4 to 6 filters may also be able to trap some slightly smaller particles like mold spores and pet dander, albeit not as efficiently as higher-rated filters.
Medium-efficiency filters range from MERV 7 to 12, and these provide a much higher level of filtration for both residential and some commercial applications. In addition to the larger particles, these higher-rated filters can also trap smaller particles like hairspray, flour, and auto emission particulates.
High-efficiency filters range from MERV 13 to 16 and provide the highest level of filtration outside of using an actual HEPA filter. This type of filter can efficiently trap bacteria, smoke, and most other common pollutants. However, these filters also tend to restrict airflow much more than lower-rated filters, which is why they are mostly only suited for specific applications such as hospitals or doctor’s offices. In fact, these higher-rated filters are usually too restrictive in terms of airflow to be used in residential systems and even in most commercial applications. Not only that, but they also tend to be prohibitively expensive as well.
HEPA filters are those that have a MERV rating above 17. Although they do have a number of very specific commercial uses, HEPA filters are most commonly found in hospital operating rooms.
Choosing the Right Filter for Your Needs
Finding the right filter for your specific needs means paying attention to the MERV rating and the type of filter. Most lower-rated filters tend to be made out of aluminum mesh or fiberglass whereas higher-rated filters are usually made from synthetic materials. MERV 1 to 4 filters usually contain a single sheet of non-pleated material while most MERV 6 and above filters are almost always pleated. Pleated filters offer better performance and efficiency as the pleats provide more surface area and, thus, increase the amount of space available to filter and trap particles. Most filters MERV 8 and above are also what is known as electrostatically charged filters. This type of filter uses an electric charge to help attract more particles out of the air and provide better filtration.
For most residential uses, a MERV 6 to 10 filter is a good choice. However, if you live in an excessively dusty area or suffer from allergies or other respiratory problems, you may want to upgrade to a MERV 10 or 12 filter. Nonetheless, it is important to speak with a professional HVAC technician to make sure your system can handle the higher-efficiency filter. Generally speaking, these same medium-efficiency filters are also a good choice for the vast majority of commercial applications as they provide a good balance between performance and price.
HVAC Advice and Service You Can Trust
If you’re struggling to determine which air filter is best for your home or business, the team at Vastola Heating & Cooling is standing by to help. Not only can we recommend the right filter for your needs, but we also offer a full range of heating and cooling services to customers in Orchard Park and the surrounding area. We also specialize in backup generators, heat pumps, snowmelt systems, indoor air quality, and much more. To learn more about MERV ratings or for any other information, contact Vastola Heating & Cooling today.