When it comes to air filters, the deeper the better. That's the short answer. But why is that? A 4-inch filter will last longer and provide better air quality for your home than a 1-inch filter, according to virtually any HVAC professional. Thicker filters, known as media filters, are generally 4 to 5 inches thick compared to the ubiquitous 1 inch filters that you can buy at grocery stores.
Most air filters are 1 inch thick, but some systems can accommodate filters 2 to 5 inches thick. In tests, it was found that the thicker the filter, the better it works and the longer the replacement intervals. This means it's better for you and your heating, ventilation and air conditioning (HVAC) system. To understand why deeper air filters are better, we need to review some basic aspects of physics.
Flow and runtime go together; when you increase one, you decrease the other. 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. For example, a 4-inch filter will reduce airflow less than a 1-inch filter with a higher MERV rating.
This is because a 4-inch filter has more surface area to trap particles. As noted, most major brand ovens and air handlers come with 1-inch filter slots. But what about all the systems out there that aren't capable of withstanding the increased resistance of a more efficient filter? The answer is simple: recommend filters that are more efficient but have a low resistance and provide good airflow. To do this, look for filters with a low filtration volume and a high MERV rating.
For example, a 1-inch MERV 13 filter does the job of improving air quality through better air filtration without the expense of modifying your equipment. However, there are ways to mess up the job; for example, buying an incorrectly sized filter or placing it upside down can block airflow rather than cleaning it. Check your filter every 1-2 months during heavy use and change it when necessary to avoid efficiency and mechanical problems. And while media filters produce more airflow (less pressure drop) and clog less easily, be careful with the MERV rating; a HEPA filter is excessive since its efficiency is 99.98% compared to high MERV filters that have efficiencies greater than 90%. I recommend changing air filters every 1 to 2 months to maintain peak performance and energy efficiency levels. To sum up, deeper air filters are better because they have more surface area to trap particles and reduce airflow less than a 1-inch filter with a higher MERV rating.
They also last longer and provide better air quality for your home. Be sure to check your filter every 1-2 months during heavy use and change it when necessary.
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