Does a Merv 11 Filter Restrict Airflow?

Learn how using an air filter with too high Merv rating can restrict airflow and cause damage to your HVAC system.

Does a Merv 11 Filter Restrict Airflow?

When it comes to air filters, the MERV rating is an important factor to consider. A MERV rating is a measure of the filter's ability to capture particles, ranging from 0 to 16. The higher the MERV rating, the more particles the filter can capture. However, using an air filter with a MERV rating that is too high can be as bad as using one that is too low. This is because the thickness of the filter material may restrict airflow, leading to decreased comfort, increased energy use, and accelerated wear of HVAC components. In particular, using an air filter with too high a MERV rating can damage the compressor, heat exchanger and air conditioner coil.

Typically, a filter with a higher MERV rating will reduce airflow. However, there are many other factors at play, such as the size of the filter and the type of fan motor in your HVAC system. The short answer is that a Merv 11 filter can restrict airflow, but it's not really a problem except in extreme circumstances. Most modern HVAC systems have no problem working with higher MERV filters, so millions of homeowners rely on them. The main risk of high-efficiency air filters comes from the fact that they are not modified for long periods of time. If you're aware of changing filters regularly, you're unlikely to experience filter-related issues with your HVAC system.

A higher MERV rating means greater resistance, which means less airflow. When researching HVAC systems, airflow will increase a lot. This is because it is very important to the performance and longevity of your oven or your air handler. Airflow is also the key to a comfortable home. Researchers have found that airflow in high-MERV filters dropped by 7% and 11% in two HVAC systems compared to low-MERV filters. Similarly, medium MERV filters also showed decreased airflow relative to the low MERV filters, this time 3% and 8% lower in both systems. Using an oven filter with a higher MERV rating than your use case requires may have adverse effects.

The thickness of the filter material in a Merv 11 filter, for example, is greater than that of a MERV 8 filter. Therefore, in order for enough air to pass through the filter, a greater amount of energy is consumed. More use can lead to increased wear and tear, so be sure to maintain your oven regularly. However, MERV 11 filters are not considered too high for residential use. Anything higher than a MERV 11 is designed for commercial households or households with family members suffering from respiratory problems. The pressure drop lies in achieving the highest possible pleat per foot, and modern designs have far fewer airflow problems at higher MERV levels.

MERV 8 air filters are almost as affordable as less efficient products, making them good value for money. For example, Second Nature's Essential filter is about 450% more effective at capturing particles than a cheap low-efficiency fiberglass filter, but its airflow resistance is only 20% higher - a marginal difference. If someone has an allergy or respiratory problem, choose a Merv 11 air filter or even a merv 13 air filter. In fact, researchers have found that while high-MERV filters can create a pressure drop, the impact is not significant unless the filter is laden with dirt. While this assumption may have had some influence about a decade ago when these high-efficiency filters were new, modern varieties can increase airflow, save you money and keep your system cleaner. I have two identical sizes - I have two identical size MERV12 filter filters from 3M in my bank. Home Energy published an article by Dave Springer of Davis Energy Group at the time on the pressure drop and energy use of various MERV filters. So what can you do to be able to use a high MERV filter* and not suffer from a high pressure drop in the filter and consequent loss of air flow (PSC blower) or increased energy use (ECM blower)? In fact, it's quite simple - in my opinion air filters should be on the return air grilles rather than on the equipment. It is recommended to change filters in this category every two to four weeks which may be difficult for some to maintain.