MERV stands for Minimum Efficiency Reporting Value, and the scale ranges from 1 to 20. The higher the MERV rating, the finer the filtration, meaning more and smaller particles are trapped by the filter. A MERV 11 filter can trap particles as small as 1.0 to 3.0 microns with a higher efficiency than a MERV 8 filter.
MERV 11 is generally not too high for most home HVAC systems and provides effective filtration, capturing smaller particles like pet dander, pollen, and mold spores. This level is beneficial for households with allergy sufferers or pets, as it improves indoor air quality.
The critical difference between MERV 11 and MERV 13 is that MERV 13 filters better trap fine particles. MERV 13 filters trap 50% of fine particles versus MERV 11 filters that trap 20%. In particular, MERV 13 filters can trap bacteria, viruses, smoke, and microscopic allergens.
MERV 11 should be ok - using a filter with too high a MERV rating with a system that isn't designed for it can cause issues due to increased static pressure.
For most homes, a MERV rating between 8 and 13 strikes the perfect balance between filtration, airflow, and cost. A MERV 11 filter, for instance, can last up to six months and offers excellent air cleaning without putting too much strain on your HVAC system.
In most cases, a MERV 11 air filter isn't too high for residential use. Generally speaking, anything under a MERV 13 air filter should provide very efficient air purification in a home without impacting airflow.
ASHRAE currently recommends using a minimum MERV 13 filter, which is at least 85% efficient at capturing particles in 1 µm to 3 µm size range. A MERV 14 filter is at least 90% efficient at capturing those same particles.
Generally, this is how long a filter lasts based on MERV ratings: MERV 1-4 furnace filters should be replaced once a month. MERV 5-8 filters need to be changed roughly every 3 months. MERV 9-11 filters require replacement every 6 months.
If not properly managed, high MERV filters can cause increased pressure drop, leading to overheating and potential damage to the heat exchanger and motor.
MERV 13 is the highest MERV value safe for residential furnaces; the higher ratings are used primarily in commercial units. If you are wondering what MERV to try, keep these recommendations in mind; ASHRAE recommends MERV 6 or higher. US Department of Energy recommends MERV 13.
1. HEPA Filters. High-efficiency particulate air (HEPA) filters are recommended by the U.S. Department of Health because they are able to remove at least 99.97% of airborne allergens and pollutants — including mold spores and dust that are as small as 0.3 microns.
MERV 11 and MERV 13 filters are specifically designed to trap and remove even the tiniest smoke particles from the air. These filters offer superior filtration capabilities and can help alleviate the negative effects of wildfire smoke on indoor air quality.
MERV 13 filters typically need to be changed every three to six months. However, the frequency with which you need to change your filter depends on a number of factors, including: The type / brand of filter you're using. The size of your HVAC system.
A filter's pressure drop directly corresponds to a filter's air flow rate. The higher the pressure drop the more restrictive the filter is to air flow. The lower the pressure drop the easier it is for air to flow through the filter.
Generally, for residential use, a MERV rating of 13 or higher is recommended to effectively capture common indoor particulates*.
In general, the best MERV rating for a home is somewhere between 8-10. These filters will capture a large portion of the airborne particles and improve indoor air quality without making your energy costs rise significantly.
Sometimes, a MERV 11 filter may be too restrictive, particularly for older or smaller HVAC systems not designed to handle the increased pressure drop. If you notice that airflow has diminished or your HVAC unit is cycling on and off more frequently, these could be signs that your filter is too restrictive.
The Purpose of Furnace Filters Is Clean Air
Blockages strain the system and result in premature breakdowns. Your furnace would also be redistributing pollutants into your breathing space. The result always involves poor indoor air quality and AC performance issues.
MERV 11 filters are more efficient than MERV 8 filters as they can capture smaller particles. They offer additional protection from pet dander, dust mites, auto-emissions, and lung-damaging dust. This is a good option for households with pets or those looking for even better air quality than the MERV 8 can provide.
For 1- to 2-inch filters, replace them every 1 to 3 months. For 3- to 4-inch filters, replace them every 6 to 9 months. For 5- to 6-inch filters, replace them every 9 to 12 months.
As a rule of thumb, our suggested MERV rating for furnace filters runs from 6 to 8 for a great balance between top furnace efficiency and home comfort. Choosing the best MERV rating for a furnace filter has a major impact on your indoor air quality, your HVAC system and, most important, your family's well-being.
What Does MERV Stand For? MERV stands for “minimum efficiency reporting value” and the MERV rating is a measure of how effectively a filter removes particles from the air that passes through it. The higher the MERV rating, the more particles the filter will catch.
All HEPA filters have a rating of a MERV 17 or higher. A HEPA filter with a MERV 17 rating will trap 99.97% of air particles that are 0.3-1.0 micron in size and an even better % of particles below 0.3 microns and above (HEPA filters are rated at their worst performance).