Do Higher MERV Filters Restrict Airflow?

When it comes to improving indoor air quality (IAQ), higher MERV ratings are often used in residential HVAC systems. But do they restrict airflow? Learn more about how higher MERV ratings affect airflow.

Do Higher MERV Filters Restrict Airflow?

When it comes to air quality, higher MERV ratings are the most effective. But, they can also cause damage to your HVAC system. This is because a higher MERV rating means more resistance, which in turn reduces airflow. When researching HVAC systems, you'll find that airflow is increased significantly.

Generally, a filter with a higher MERV rating will reduce airflow. However, there are other factors that come into play such as the size of the filter and the type of fan motor in your HVAC system. In most cases, it won't be an issue, but in extreme circumstances, it can be a problem. Most modern HVAC systems have no problem working with higher MERV filters, so many homeowners rely on them.

The main risk of high-efficiency air filters is that they are not changed regularly. If you're aware of when to change your filter, you won't experience any issues with your HVAC system. Using an air filter with a MERV rating that is too high is just as bad as using one that is too low. Air filters with higher MERV ratings may filter more particles, but the thickness of the filter material can restrict airflow.

This can lead to decreased comfort, increased energy use, and accelerated wear of HVAC components. In particular, using an air filter with a too high MERV rating can damage the compressor, heat exchanger, and air conditioner coil. When installing an air filter with a high MERV rating, two things happen. First, the air becomes cleaner which can help improve the longevity of your HVAC system.

The more particles are trapped, the less they stick to the inside of the vent and the better the air flow. Research shows that overall, HVAC systems with high MERV* filters have a higher pressure drop across the filter. This part is common to the three previous studies. The AC coil inside or near your furnace or air handler gets very cold as it draws heat out of the space and pumps it out. A normal flow of warm air over the coil will prevent its surface from falling below 32F. Low airflow allows coil to freeze cool.

Then the moisture in the air freezes and the coil is covered with ice. At this point, your air conditioning system won't be able to do its job properly. The goal of using a MERV 12 or higher filter is to improve indoor air quality (IAQ) for everyone, especially those with allergies, asthma, COPD etc. If you're not able to use a high MERV (12+) filter for your oven or air conditioner and would like to research air purifiers, here are two suggestions: I'm using a MerVi cape and I have a layer of Merv 1900 3M Filtrete on my mask (I made the mask as a cover so I could remove the filter to wash it). Air filters with a one-to-four MERV are effective at removing large particles such as carpet fibers, airborne paint droplets and sanding dust but they cannot help with contaminants such as hairspray, mold spores or even flour that might have escaped from the mixer. If you own pets then you'll need a MERV 10 to control their dander which tends to have smaller particles than other contaminants discussed above.

The Awair Element indoor air quality monitor is one of the best tools to monitor how good or bad your IAQ really is and whether or not your filters keep PM2.5 levels low enough. Fortunately I have a 3D printer and I have printed a mask with a MERV 13 filter. Filters and masks can be disinfected in a low-temperature oven following very specific guidelines. Alcohol disinfects very well if it is strong enough and if it is left to dry only on the surface or soaked in the filter cloth. They also have an external housing for a MERV 14 filter which I wish I had installed too. One thing to keep in mind is that you may need to change a Merv 11 air filter more often than a MERV 8 air filter. Meanwhile, air filters with a MERV rating of 14 or higher are designed for commercial HVAC systems that can handle coarsest filter material.

A metal coil is an excellent ozone filter so almost all residential HVAC systems are effective ozone filters. I don't think a filter needs to fit perfectly; the odds of a particle pointing at the crack and escaping the filter every time it is in a recirculation system defy the laws of Brownian motion. The higher the MERV rating of a filter, the less dust particles and other contaminants can pass through it.