As you’re looking to replace your HVAC or furnace filter, you may have come across the terms “HEPA” and “MERV” among your range of options. It’s common for most homeowners to get the filter with the highest number possible for their system, as it’s assumed that it will mean better protection against the airborne bacteria, viruses and other foreign elements. However, higher rated HEPA filters may not be compatible in all homes, but this isn’t really a problem. You just need to get the right kind of filter that suits your needs and preferences.
There are several factors to consider when getting the right kind of filter, such as the number of occupants in your home, their health conditions, and how often the HVAC system is used. To understand more about air filters, here’s what our IAQ and HVAC maintenance experts at Cardinal Heating & Air have to say.
How Air Filters Work
A typical air filter consists of many interwoven fibers layered in random directions. When particles pass through the filter, they’re subjected to specific filtration mechanics. These are as follows:
Inertial Impaction – This is a filtration mechanic that occurs when a particle encounters a filter fiber due to the inertia of the particle. A typical example would be a large dust particle that can’t change its direction of flow due to its inertia as it impacts the air filter fiber and ends up getting attached to it.
Interception – This occurs when a particle follows a gas streamline that comes in contact with the surface of a fiber. An example of this would be a dust particle that follows the air flow that happens to come in contact with the surface of a fiber.
MERV is an acronym for Minimum Efficiency Reporting Value. This was first developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) in 1987, and is used to evaluate the efficiency of an air filter as it captures particles that are sized between 0.3 to 50 microns.
The MERV rating scale is 1 to 16, which explains the indicated numbers you’d see when looking for a replacement air filter. But there are several HVAC and thermostat companies that offer filters with a MERV rating between one and 20, along with descriptions of how effectively they’ll remove certain particles and allergens from the air. Filters that have a MERV rating between 1 to 4 MERV are considered low grade while a medium grade filter has a 5 to 12 MERV rating. Filters within this range can easily filter dust, pet dander, hair, dust mites, mold and pollen.
A high-efficiency filter is rated between 13 to 16 MERV and can remove 75% or greater airborne particles. In fact, a MERV 16 filter will be able to capture around 95% of particles ranging between 0.3 to 1.0 microns in size. The filter in this group can target biological growth, chemical fumes, volatile organic compounds and even smoke. MERV values may also vary from one brand to the other.
High Efficiency Particulate Air (HEPA) filters are sometimes recommended by HVAC maintenance contractors depending on the compatibility of the system and the type of environment it’s used in. They’re actually the only types of mechanical air filters that are tested and certified to meet a specific efficiency at a specific particle size. All HEPA filters have a minimum efficiency of 99.97% at 0.3 microns. If you’re wondering how small that is, the average strand of hair is about 45 microns.
To give you a better idea, let’s say that 10,000 0.3 micron-sized particles are blown into a HEPA air filter. In this case, only 3 particles are allowed to pass through. This means HEPA filters are at least 50% more effective than MERV filters, which only capture around 95% of particles from 0.3 to 1.0 microns. As such, HEPA filters can be described as a high quality MERV filter and ranked between 17 to 20 MERV. This surpasses the highest MERV filter rating, which is only 16!
Keep in mind that HEPA filters usually require an additional fan system to filter the air. To know whether your HVAC system is compatible, it should be inspected by a certified air conditioning and heating service technician. If a fan is needed, then it should be installed professionally. Otherwise, your HVAC system won’t operate efficiently and it will be forced to generate more power to move air through the filter. This puts additional strain which can affect other components of your system, as well as increase your monthly energy bills.
What’s the Best Rating for Your Home Environment?
Because of the high particle removal efficiency, HEPA filters are regularly used in environments such as nursery homes and educational institutions, as well as medical and healthcare applications like anterooms, isolation wards and surgery rooms. It’s possible to have a HEPA filter installed in your home’s HVAC system, but it’s not really necessary to go for the highest MERV rating.
HVAC and thermostat technicians would typically recommend a filter with a five to eight MERV rating if you or any member of your family doesn’t have any allergies or other respiratory problems. This is because it’s more than enough to keep the dust and pet dander off for several cycles. But if you’re still concerned about having better air quality, then you can choose filters with a MERV rating of nine and above.
Filters that are rated 13 to 16 are usually recommended for commercial structures, but they’re also ideal for people who have asthma, weak immune systems, or chronic diseases. So, when you’re replacing your air filter, it helps to consult with your trusted HVAC technician so you’ll know which type of filter is compatible with your system. Having a well-balanced ventilation system is important to keep your indoor air quality clean and safe to breathe.
If you’re looking for a trusted air conditioning and heating service expert, be sure to call Cardinal Heating & Air. With our services, you can be confident that your HVAC installation will be done professionally and efficiently. To get started, you can reach us at (425) 827-9997 or by filling out our convenient online contact form. Call us today!