The air filter in an HVAC system plays a critical role in the health and wellbeing of you and your family. They promote clean and healthy air in your home by trapping allergens, dust, dander, pollen, viruses, and other pathogens.
When shopping for an air filter, you'll probably notice that they have different MERV ratings. But how do the ratings differ, and which one should you get?
This article discusses MERV ratings and which is best for your home, so continue reading to learn more!
What MERV Rating Is Best?
The best MERV rating varies based on your HVAC system. Our recommendation is to get the highest MERV rating compatible with your furnace, AC unit, or heat pump.
For example, MERV ratings between 5 and 8 are usually typical for homes. So, if your system works with up to a MERV-8 filter, get a MERV-8 (even though MERV 5 would work too).
Never use a MERV filter that is rated higher than your HVAC system. To elaborate, if the HVAC system is compatible with up to a MERV-8 filter, don't use a MERV-9 through 12 filter.
Info: An over-rated filter will limit airflow and stress your HVAC system. This could lead to inadequate heating and cooling in your home and damage the HVAC unit.
MERV-9 to MERV-12 is suitable for some residential HVAC units and commercial buildings.MERV-13 to MERV-16 filters offer superior filtration, but usually, only hospitals (or homes of residents with severe allergies) use them.
What Does MERV Rating Mean?
The MERV (Minimum Efficiency Reporting Value) rating on an air filter is a critical factor to keep in mind. This rating shows the overall efficiency of an air filter. The higher the rating, the more effective the filter is at catching particles of various sizes.
For example, a hospital setting requires exceptional filtration, so higher MERV ratings are needed. On the other hand, most homes don't need superior filtration, so a lower MERV rating is sufficient.
MERV ratings range from extremely low (1) to exceptionally high (20). The rating indicates the size of particles the filter can effectively remove from circulating airflow.
The higher ratings usually feature denser filtration material, which translates to additional force necessary to push air through the filter. Due to the dense composition, extremely powerful HVAC fans (blowers) are necessary to move air through the filters with high MERV ratings.
MERV Air Filter Guidelines
MERV ratings start at one and reach as high as 20. Each rating bracket is suitable for use in varying scenarios. The table below matches each bracket with its description, suitable application, and composition.
MERV-1 to MERV-4Capable of blocking carpet fibers and lint, unable to block much else
Filters down to particles 10 microns in size
MERV-5 to MERV-8Capable of blocking common dust, pollen, and some mold spores
Filters particles from 3 to 10 microns in size
MERV-9 to MERV-12Capable of blocking most mold spores, fine dust, smog, and pet dander
Filters down to particles 1 to 3 microns in size
MERV-13 to MERV-16Capable of blocking bacteria, smoke, viruses, and other microscopic particles
Filters particles down to 0.3 to 1 micron in size
MERV-17 to MERV-20Capable of blocking everything listed in every category, as well as viruses, sea salt, carbon dust, combustion smoke, microscopic allergens, radon
Filters down to particles less than 0.3 microns in size
What is The Best MERV Rating For My Home?
According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the best MERV rating for most residential homes is MERV-13. However, in some cases, this high rating may not be suitable.
Some systems cannot handle the reduced airflow, so an air filter rated between MERV-8 and MERV-10 will be sufficient. These filters can catch the majority of airborne particles, helping to improve your indoor air quality (IAQ). Since MERV-8 doesn't heavily restrict airflow, you shouldn't have any issues.
You could buy an air filter with a lower rating, such as a MERV-5 filter. These filters are typical residential filters. However, although airflow is optimized, the size of the pores in the filter allows more particles to pass through.
If you have allergies, asthma, or other health conditions that poor air quality may affect, a MERV-5 filter wouldn't be the best option for you (unless you want a runny nose).
Note: If anyone in your household has mild to severe allergies, you may want to consider a higher-rated air filter. An air filter between MERV-9 and MERV-12 is usually sufficient for mild allergies.
For severe allergies, you may need between MERV-13 to MERV-16 (or a HEPA filter), assuming your HVAC system can handle it.
Ultimately, the ideal MERV rating for your home depends on the local pollen count, the severity of your family's allergies (if any), and what your HVAC system can handle.
What Happens if I Choose The Wrong MERV Air Filter?
Whether it's too high or too low of a MERV rating, choosing the wrong air filter can have adverse effects on you and your family, your HVAC unit, or both.
If you purchase an air filter with too low of a MERV rating, smaller pollen, allergens, and other particles won't be filtered. This will allow them to freely circulate around your home, which may trigger allergies if you're sensitive to these particles.
People with health issues, compromised immune systems, etc., may have problems with poor indoor air quality.
On the other hand, if you purchase an air filter with too high of a rating, your HVAC system may be unable to handle it. If the mesh of the filter is too fine, your HVAC system may not be able to circulate air through it.
Info: High MERV-rated filters are exceptionally dense and require powerful HVAC fans for operation. If the system isn't equipped to handle a thick filter, you will have various issues.
When the system's airflow is restricted, your energy costs will skyrocket as the system works overtime in an attempt to force the air through the filter. In addition, the overworked system may become damaged, leaving you with unwanted repair costs.
Check the manufacturer's specifications if you're unsure what rating your system can handle. Look in your HVAC unit's instruction manual, its service panel, or Google the model number online to determine what MERV rating it can handle.
MERV Air Filter FAQ
Here at Essential Home & Garden, we get tons of questions about MERV ratings on air filters. Here are the most common ones we get asked.
What is the recommended MERV rating for furnace filters?
There is no single MERV rating that is right for all furnaces. The best answer is- it depends on your furnace. Use the highest-rated MERV filter your furnace can handle for the best filtration and cleanest indoor air.
Generally speaking, a furnace filter rated between MERV-6 and MERV-8 is usually sufficient for furnaces. These filters offer an adequate balance between comfort and efficiency. The pores in the filter are large enough to allow ample airflow but small enough to trap many particles flowing through.
Of course, if someone in your home struggles with allergies, you may want to use a higher-rated filter. Again, ensure your furnace can handle the higher rating. Check the manufacturer's specifications if you're not sure what filter rating range it can take. Alternatively, ask a local HVAC professional for advice.
Is MERV 13 Too High For Residential?
No, MERV-13 air filters aren't too high for residential use. However, it's essential to note that not all HVAC systems can handle a high MERV rating due to restricted airflow.
MERV-13 air filters are the highest-rated option for most home uses. If you choose a filter with a rating higher than 13, airflow can be restricted to the point where it can cause adverse side effects.
The filter may even limit airflow to the point where it causes damage to your HVAC system, leading to added expenses in repairs.
Note: It's best to choose an air filter with an appropriate rating for your specific HVAC equipment. Avoid selecting a filter higher than MERV-13 for home use, as you may end up with unwanted repair expenses and higher energy bills.
MERV-13 filters bacteria, viruses, microscopic allergens, and tobacco smoke. Since they are capable of filtering out the particles that lower-rated air filters cannot, they're generally a good choice for people with one or more of the following:
- Asthma
- Bad allergies
- A newborn baby
- Chronic bronchitis
- Chronic obstructive pulmonary disease (COPD)
- Lung disease
- Emphysema
- A weakened immune system
- Required to use an inhaler, oxygen tank, or ventilation machine
- An individual in the household that smokes
Is MERV 8 Good Enough?
A MERV-8 air filter is suitable for many scenarios and is a popular pick for many individuals in a residential setting. These filters have 90% efficiency for particles between 3 and 10 micrometers in size.
The pore size in the filter enables it to trap the majority of indoor particles that may negatively affect those with asthma and allergies. In addition, these filters are relatively inexpensive and easy to service.
Depending on the manufacturer, MERV-8 filters may last anywhere from three to six months, sometimes up to a year in residential use. But, it mostly depends on how "dirty" the air is in your home. For example, burning candles often, smoking indoors, or having lots of pets can clog your filter faster.
Still, the characteristics of MERV-8 air filters make them a common choice, given their well-rounded performance.
But if you have severe allergies or health issues that may worsen without highly filtered air, a MERV-8 air filter may not be the best choice for you. With that said, a MERV-8 air filter is sufficient for the average residential home.
Can I Clean a MERV Filter?
While you can clean washable MERV air filters without an issue, it's not recommended for disposable air filters. It may seem like a sensible solution to a dirty air filter, but most air filters don't hold up well for washing.
The filter materials don't do well when soaked with water. In addition to rips and tears that may occur, washing the filter substantially increases the chance of mold or bacteria growth on the filter itself.
The mold spores and bacteria particles may be released into household air when you reinsert the filter, causing various health issues. Mold inhalation can cause varying symptoms, ranging from mild to severe.
Note: Vacuuming the air filter is another go-to cleaning option for many people. While it is a healthier alternative to washing the filter, it's possible to damage it. Even minor rips in the material can allow particles to slip through, allowing them to circulate in household air.
On top of that, a vacuumed filter may release dust and other toxins into your home via the ductwork when you reinstall it. So, if the air filter isn't labeled as a washable filter, avoid trying to clean it. Instead, replace it routinely.
The necessary replacement frequency for the air filters in your home hinges on several things:
- Amount of time you run the system
- Type of flooring
- Outdoor air pollen
- People smoking in your home
- Lighting candles
- Cooking
- Pets
Usually, 1" air filters require replacement every two to three months, while larger box-style filters 4" thick can last up to a full year.
The story looks a little different if you have a washable air filter. As the name implies, these air filters can be safely washed. Generally, washable air filters require cleaning around once per month. And keeping them clean is a good way to reduce your AC energy costs.
Failing to wash the air filter regularly allows the accumulation of dirt and other particles, restricting the airflow.
To prolong the filter's lifespan and maintain ample airflow, wash the filter routinely. The process is simple:
- Safely remove the filter from the unit.
- Next, rinse it in a sink or tub of water.
- Use a soft-bristled brush and mild washing detergent to remove sticky or stubborn particles.
After the filter is clean, shake the excess water out and allow it to drain fully. Once the filter is free of excess water, reinstall the filter into the system (and make sure you put the filter back in the right way).
Final Filter Thoughts
Choosing the right MERV filter for your home is imperative. While each MERV rating has its place, not all ratings are suitable for every home. If you're unsure which option is best suited for you or what MERV rating your HVAC system can effectively handle, check its manual or reach out to an HVAC technician.
You don't want to choose too high of a rating for your unit, or you could damage the HVAC system. On the other hand, you don't want too low of a rating that will allow more particulates to pass through. Picking the right MERV filter is a fine balance between what's best for you and what's best for your system.
