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HVAC Definition Series – Merv Ratings

Merv Ratings Definition

In the world of HVAC, we have our own vocabulary that we use every day, but sometimes the words we use don’t translate to our customers. In this blog series, we will cover some of this terminology to help our customers understand what we mean and why these terms are important to their HVAC maintenance and installation. This week, we define the term MERV Rating and explain why it is important.


The letters in the acronym MERV stand for Minimum Efficiency Reporting Value, and a MERV Rating is the standard that rates the overall effectiveness of all air filters. The Merv Rating scale was designed in 1987 by the American Society of Heating, Refrigeration, and Air Conditioning, and the scale runs from the number 1 through 20.

What Does the Scale Mean?

The higher the rating on the MERV Rating scale equates to better filtration, meaning fewer dust particles and other airborne contaminants can pass through the filter. The scale was designed to represent both the worst and best case performance of a filter. The higher an air filter is rated, the more it can help improve your health, reduce utility costs and increase energy efficiency.

What Rating Should My Filters Have?

If your home has window A/C units, a MERV Rating between 1 and 4 will effectively filter pollen, dust mites, and particles like carpet fibers. A residence using a central HVAC system will typically require filters with a rating between 8 and 13. These filters will help to catch mold spores, dust mites and debris, pet dander and some viruses and bacterias.

Filters with MERV Ratings of 14 through 20 are usually used for hospitals and general surgery settings. It’s important to note, however, that filters with a professional grade MERV rating may actually filter the air in your home too well, and can cause your system to work much harder than it is meant to if installed residentially.

One of the key benefits of Middleton’s preventative maintenance appointments is that we do our best to ensure that your system is efficient, and your air filters are a part of that process. We will check to make sure your filters are clean and that you are using the correct one as a part of your annual maintenance contract.

To ask specific questions about the filters in your home, or to schedule your preventative maintenance with Middleton, visit us online or give us a call at 1-800-404-0371 to speak with a comfort specialist today.

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