Choosing an air filter for your HVAC system may seem simple, but for many homeowners, it can become confusing. Once you start shopping, you are quickly hit with a variety of options such as MERV ratings, allergy claims, even marketing claims that offer “hospital-grade,” all at a wide range of pricing. If you do deeper research online you are likely to find conflicting advice.
It is easy to assume that the highest-rated, or more expensive, filter must automatically be the best choice. But in reality, this is not always true. The best filter is typically the one that provides the best indoor air quality along with proper airflow for your HVAC system. A filter that will work great in one home may actually create problems in another.
What Is a MERV Rating?
MERV is an acronym that stands for “Minimum Efficiency Reporting Value.” It is the system used in the HVAC industry to rate the effectiveness of an air filter in capturing a variety of airborne particles. The higher the MERV rating, the smaller the particles the filter can trap.
That may sound simple enough, but the level of filtration is only part of the equation. Your HVAC system also needs to be able to move enough air to heat and cool all of the livable areas of your home properly. When a filter is too restrictive, the airflow can suffer, which often puts extra strain on the system.
This is where many homeowners can be misled. Higher-rated filters are often marketed as being better, but that does not necessarily mean they are the right fit for your home.
Understanding Common MERV Ratings
MERV 1–4
These are very basic filters which are designed mainly to capture large particles like lint and dust. They are designed more to protect HVAC equipment rather than to improve the quality of indoor air. Most homeowners today will want something more effective than this range.
MERV 5–8
With many homes, the MERV 8 filters are a practical middle ground. They will capture the common particles like dust, pollen, mold, and pet dander while still allowing a strong airflow through the system. This range often works well for most households that do not have any major allergy concerns. It improves the quality of air without making the HVAC system work any harder than is necessary.
MERV 9–12
This range is popular for homeowners where there are pets, allergies, or higher than normal dust levels. The MERV 11 filters often provide a strong balance between an improved level of filtration and a healthy airflow. Many newer residential systems are able to easily handle this filtration range. Homeowners who use these filters often notice less buildup of dust and cleaner indoor air without noticing any significant airflow problems.
MERV 13 and Higher
MERV 13 filters are excellent for capturing very small airborne particles, eliminating smoke particles and even some bacteria-sized contaminants. During the pandemic, these filters became very popular. However, do not assume that this level of filtration is right for your home. Higher-rated filters are significantly denser, which causes a greater restriction in airflow. In some systems, that added strain can lead to weak airflow, frozen coils, reduced efficiency, or extra wear on the blower motor. Ask your HVAC technician which is right for your home, as higher is not always better.
Why Airflow Matters
Your HVAC system depends heavily on moving a sufficient amount of air through the equipment at all times. When the airflow becomes restricted, the system has to work harder to maintain a comfortable temperature level.
This is even more important in Arizona, especially during long stretches of extreme heat. When the outdoor temperatures are above 100 degrees, air conditioners are already working hard. An overly restrictive HVAC filter can make the cooling performance worse, making it less comfortable inside, and increases the stress on the system.
Why Would My HVAC Technician Recommend a Basic Filter?
Some homeowners are surprised when their HVAC technician actually recommends a lower-rated or basic air filter. In many cases, the reasoning simply comes down to airflow. This is especially common with older systems where the equipment and ductwork were not designed to handle the newer, highly restrictive filters. A lower-MERV-rated filter will often help the system move air more efficiently, reduce strain on the equipment, and improve overall performance. That doesn’t mean the higher-rated filters are bad, it simply means that it is the best filter for your specific system and needs of the home.
The Marketing Confusion
One reason shopping for air filters can be so confusing is the marketing language used. Companies need to sell products, so they use strategic language that often includes phrases like “Maximum Allergen Protection” or “Hospital Grade” to make the higher-rated, and more expensive, filters sound like they must be better. What those labels often avoid mentioning the tradeoff in airflow. A filter can technically capture more particles effectively while still being the wrong fit for your HVAC system.
It is also important to remember that the filter is only one part of indoor air quality. Factors such as duct leakage, dirty coils, poor insulation, and dust entering from attic spaces can also impact the quality of air inside your home. A better filter may help, but it is not a bulletproof solution by itself.
The Bottom Line
So, when it comes to HVAC filters, remember that higher MERV ratings are not automatically better. The right filter improves indoor air quality while still allowing your HVAC system to move air properly. If you are unsure what your system can safely handle, a quick conversation with an HVAC professional can help you avoid airflow problems while still improving the air inside your home. Give us a call, we love to talk about air flow!
Key Takeaways
- MERV ratings measure the effectiveness of the filter with capturing airborne particles.
- Higher-rated filters can restrict airflow in some HVAC systems, which is especially important with older systems.
- MERV 8 and MERV 11 filters are often the ideal filtration level for many homes.
- Airflow throughout all living spaces in your home is just as important as the filtration quality.
- Indoor air quality depends on more than just the air filter alone and is impacted by ducts, coils, insulation, and attic air leakage.
Learn More About Home Air Filters:
How to Choose an Air Filter For Your HVAC
How Often Should You Change Your AC Filter an Honest Answer
Reasons Why My A/C is Blowing Warm Air
3 Ways Dust And Dirt Affect Your HVAC System
How to Control Your Asthma With Your A/C