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HVAC 101: What is a MERV rating and why does it matter?

HVAC 101: The MERV Rating. Middleton Heat and Air

With the advancement of modern technology, systems we all have in our homes can still seem foreign and confusing. Take the HVAC system, for example. There’s filters, ratings, fans, registers, maintenance, and thermostats, but do you know how all these factors work together to provide you and your family with clean air? With our new series, HVAC 101, we at Middleton Heat and Air hope to clear up some of the confusion and help you make informed decisions about your home. In today’s edition, we’ll be discussing the MERV rating!

What is a MERV rating?

MERV stands for Minimum Efficiency Reporting Value, and is a way to quickly understand the quality and effectiveness of any given air filter. This industry standard rating system, developed by the ASHRAE, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, allows you to quickly compare filters of all different styles and brands easily.

The MERV rating system consists of numbers 1-20, with 1 being of the lowest quality and 20 being the highest. The quality is determined by how well the filter stops pollutant particles from passing through, and what size these particles are.

What filter rating do I need?

For example, a HEPA grade air filter, or the highest grade filter you can purchase, has a MERV rating of 17-20, but are actually too good at doing their jobs for traditional residential hvac systems. They block such small air particles that they impede too much airflow, and would make it impossible for your standard hvac system to function properly.

The cheapest air filters, like the standard “blue” filters you can find for a dollar or less a piece, generally have a MERV rating of 1-4, meaning they remove less than 10% of the pollutants in your home’s air! These filters will help protect your hvac system, but will do little to nothing to improve the actual quality of your home’s breathing air.


When it comes time to replace the filters in your home, remember; MERV matters! Aim for a rating of anywhere from 10-16 to have the best quality air within your budget. According to the United States Environmental Protection Agency, Indoor air pollution ranks among the top 5 environmental health risks. With MERV ratings, you don’t even have to take extra time to make a better decision about your health. Just take a second to check the MERV number and breath easier!

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