MERV or Minimum Efficiency Reporting Value is a scale to measure the efficiency of the HVAC unit. Developed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) to check and report the effectiveness of air filters. Their measurement process is more accurate and detailed than other ratings.
The measurement scale provides a numerical value with 1 as lowest and 20 as highest efficiency. MERV calculates how effectively an air filter can restrict pollutants, dust, and other minute particles from entering the home.
Clean and pure air is vital for indoor equipment because polluted air can lead to health concerns for you and your family.
If you plan to buy an HVAC product and check filter effectiveness, the MERV method is the best currently. Let’s understand this in detail.
MERV Ratings For Air Filter and Efficiency
MERV ratings for the air filter should be according to the manufacturer’s recommendation. You can also ask the technician about a suitable air filter for the home. Only a higher MERV rating does not guarantee a comprehensive comfort level. On the contrary, it can impair performance.
Some high MERV-rated filters come with minor pores that restrict airflow. If the filter is used with an HVAC unit not equipped to manage this resistance, the product will perform below expectations. With low efficiency, there will be more pressure on the machine and affect the indoor atmosphere.
MERV and Air Quality
ASHRAE published a research paper that claims the air filter provides several health benefits. There is a direct relation between contaminants and pollutants in the outside air and illnesses indoor. Air filters throw away pollutants and ensure a healthy atmosphere inside.
Key points of the research paper:
- The right air filter can be ‘modestly effective’ for different allergies and symptoms of asthma
- The air filter also lowers disease transmission inside the home consistently by restricting pollutants outside
- Better particle filtration means lesser exposure to the minute particles below 2.5 µm in diameter
- Using the MERV rating chart to understand the filters and its applications.
Contaminant Size Intervals
To get the right HVAC product and suitable MERV-rated air filter, you should know the area that you want to use. Refer below to four average contaminant size intervals for MERV rating consideration.
|Pollutant Size||Categories Pollutant|
|0.3-1.0 μm||Smoke, dust, oil smell, bacteria, sneeze droplets|
|1.0-3.0 μm||Car emissions, bigger dust particles (lead), Legionella|
|3.0-10.0 μm||Cat/dog dander, Mold spored, mite debris, Hair spray, fabric protector,|
|10.0+ μm||Pollen, sanding dust, cockroach debris, textile fibers|
MERV Ratings and Specific Pollutant Size
We have mentioned the most overall ratings for your reference below.
|MERV Ratings||Pollutant Size and Efficiency|
|MERV 1-4||Less than 20% for 3.0-10 μm particles|
|MERV 6||49.9% for 3.0-10.0 μm particles|
|MERV 8||84.9% for 3.0-10.0 μm particles|
|MERV 10||85% for 3.0-10.0 μm particles, or greater/50% – 64.9% for 1.0-3.0 μm particles|
|MERV 12||90% for 3.0-10.0 μm particles, or greater/80% – 89.9% for 1.0-3.0 μm particles|
|MERV 14||90% for 1.0-3.0 μm particles, or greater/75% – 84% for 0.3-1.0 μm particles|
|MERV 16||75% for 0.3-1.0 μm particles, or greater|
The MERV scale gives ratings on the scale of 1 to 20. We have mentioned prominent ratings up to 16, where a higher number means more efficient filtering minute particles. Air filters above 16 ratings are categorized as High-Efficiency Particulate Arresting (HEPA).
MERV Ratings Test Procedure
MERV air filter efficiency rating method is known as ASHRAE Standard 52.2. The procedure tests particles size, and Standard 52.2 facilitates a protocol for testing.
The MERV test starts with a clean filter and contains six cycles. A predetermined quantity of dust particles is released into the airflow during each test cycle.
The dust particles are kept in three size groups;
- E1: Range 1 to 4 contains particles 0.30 to 1 micron in size
- E2: Range 5 to 8 includes particles 1 to 3 microns in size
- E3: Range 9 to 12 with particles 3 to 10 microns of size
In each cycle amount of dust particles retained and missed calculated. The procedure is repeated six times. The worst keeper of particles among E1, E2, and E3 during each of the six cycles is considered for the MERV ratings. MERV stands for Minimum Efficiency Rating Value, and so poorest performer is measured for MERV ratings.
We hope our analysis of the MERV ratings chart and procedure will clear your doubts about checking the air filter’s efficiency. Refer to the passage, read the product specifications, follow the manufacturer’s guidelines about the required MERV rating for your home, and make the final decision about an HVAC product for the convenience round of the year.
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