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What You Need To Know About MERV Ratings

By All-Temp Heating & Cooling

Date Published: February 18, 2022

When it’s time to buy a new air filter, do you ever wonder why there are so many options to choose from? Or why some are affordable and others are more pricey? The main difference between the filters is the MERV rating, but what exactly does that mean? 

What is MERV?

MERV stands for Minimum Efficiency Reporting Values. The rating was developed from a test method by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). The filter sizes range between 0.3 and 10 microns (µm). Essentially, the higher the MERV rating, the smaller the filter pores. The pore size increases or decreases the ability to catch smaller particles.

Why are MERV ratings important?

MERV ratings are important because they measure the effectiveness of air filters. The rating helps you choose the right air filter for your space. Understanding the rating allows you to maximize your air quality, while allowing your HVAC system to function properly.

High MERV vs. Low MERV

While it might seem like everyone should install a high MERV filter in their home, there are also things to consider when installing a filter. We recommend everyone should evaluate the differences between high and low MERV for their given space, situation, and HVAC system.


High MERV filters protect from smaller particles like pet dander. Higher MERV is great for people with allergies or asthma due to the increased air quality. So, what’s the catch?

High MERV ratings can harm your HVAC system. The airflow resistance is greater in higher MERV due to the smaller pores. The system has to work harder to produce a certain amount of air in your space. If the system isn’t designed for it, further problems may arise for your unit and require maintenance. Problems can include a general struggle for your system and higher utility costs. 


The primary function for a low MERV filter is to keep the HVAC system clean. Lower ratings tend to capture airborne particulates such as dust mites and pollen and typically provide good filtration. This filter can keep your system more efficient, as long as you replace your filters regularly.

In short, your air flow depends on your HVAC system. To determine what MERV rating is best for you and your system, give us a call at (540) 712-8902. Let’s properly install the right MERV rating for your unit before allergy season is upon us here in Virginia!