Does a MERV 13 Filter Restrict Air Flow?

Any air filter with a rating higher than 13 can cause damage to your HVAC system, leading to costly repairs. A MERV rating of 13 to 16 is considered hospital-level air quality, so your home is unlikely to need more than that. According to the US Environmental Protection Agency, filters in the 7-13 range often have little difference from higher MERV ratings, but will allow your system to operate much more efficiently. 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. Second, there is a pressure drop across the filter which can reduce airflow. This can cause problems on the cooling side of your HVAC system, as the cold coil can eventually freeze and become an ice ball, restricting airflow completely.

High MERV filters offer superior filtration, trapping everything from construction dust and tobacco smoke to bacteria. However, they are not modified for long periods of time and can cause a high pressure drop in the filter and consequent loss of air flow or increased energy use. To avoid this problem, you should change your filter regularly. Low-efficiency filters are typically found within MERV 1-4 and high-efficiency filters are MERV 13 and later.

Air filters that are MERV 13 and above are recommended for those who prioritize air quality and may have to handle asthma, severe allergies and other similar circumstances. They are effective at removing large particles such as carpet fibers, airborne paint droplets and sanding dust, but cannot help with contaminants such as hairspray, mold spores or even flour that might have escaped from the mixer.

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