Choosing The Right MERV Rating: Get Your Numbers Straight

If you're like most Norfolk MA homeowners, you probably have no idea whether or not your HVAC equipment's air filter is properly cleaning the air in your home. To ensure that you are breathing quality air, here is a brief rundown on the MERV rating scale.

What's MERV? 

The Minimum Efficiency Reporting Value (MERV) is an industry standard that is used to measure air filter performance levels. Ratings are represented as a numerical value ranging from 1 to 20. An air filter's number tells you how well it captures and holds dust or dirt particles in a specific size range. For example, pollen and mold spores are 10 to 30 microns in particle size. Bacteria would be 2 to 3 microns in size, and tobacco smoke is 0.5 micron.

Which MERV rating is best?

In general, when it comes to MERV ratings, bigger is better. A higher number indicates a more efficient air filter. Let's take a look at a few guidelines to help you choose the right air filter for your HVAC system:

• 1 to 4 rating: The most inexpensive option, these fiberglass filters will only remove larger particles (over 10 microns in size) and will not do much to improve your home's air quality.
• 5 to 8 rating: These filters are of medium quality and can remove particles as low as 3.0 microns in size.
• 9 to 12 rating: A high-quality filter capable of removing particles down to 1.0 micron in size.
• 13 to 16 rating: In terms of standard filters, this is the highest quality MERV filter rating range. These filters will capture particles down to 0.3 microns.
• 17 to 20 rating: Deemed a HEPA (High Energy Particulate Air) filter when rated in this range, these types of filters will remove far more airborne particles than a typical MERV-rated filter, but they are generally only used in a dedicated air-cleaning system, not in HVAC equipment.

Another important factor to consider is airflow: As MERV rating climbs, a filter's ability to allow airflow through a furnace or A/C declines. Therefore, before installing any filter higher than a MERV 8, contact an HVAC expert for a professional assessment.

For more advice on choosing a filter with the right MERV rating and other matters related to home comfort, contact the professionals at Rodenhiser Plumbing, Heating & Air Conditioning. We have proudly served the Route 495/128 area of Norfolk MA since 1928.

Our goal is to help educate our customers about energy and home comfort issues (specific to HVAC systems).  For more information about air filters and other HVAC topics, download our free Home Comfort Solutions Guide.