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MERV Ratings: Explained Once and for All 

If you have an air condition/heating system, you’ve probably bought a filter or two for it and on those filters, there was a MERV rating that you may or may not have understood. In fact, there may be a lot of things about air filtration that wasn’t immediately obvious to you. No worries. This article is going to fill you in on what you need to know about HVAC, MERV, and AC systems, and while you may not end up being an expert, it should give you enough info to at least be a responsible owner. 


To begin with, let’s get the term HVAC out of the way. HVAC means “heating, ventilation, and air conditioning” and HVAC systems make indoor environments more comfortable by controlling temperature and improving air quality. In order to do that, air filters must be compatible with HVAC systems so that they collect particles you don’t want to breathe in, but don’t overload your system.

Importance of MERV and the Different Levels

Higher MERV equals higher levels of protection, but also a greater strain on airflow. When an air filter is too restrictive or dirty, the airflow is affected, causing malfunctions or a rise in costs. Higher MERV rated filters are only used for extremely high maintenance and sanitized buildings, not homes. The setting of a filter determines the MERV rating required for air and furnace filters to function properly.

So, What Are MERV Ratings?

MERV is another acronym you may have heard bandied about. MERV stands for Minimum Efficiency Reporting Value. It’s basically a grading system that evaluates how good a filter is at blocking out smaller and smaller particles. The higher the MERV rating, the more effective a filter is in blocking out different types of particles. So, when you read the MERV chart below, it’s important to understand that the higher the rating means that everything in that rating and above it is blocked from going through the filter. If you get a filter with a MERV rating of eight, for instance, it will also block spray paint dust, hairspray, duties mites, and pollen. But here’s the catch: The higher the rating, the harder your HVAC unit has to work to push air through because there’s more blockage. The trick is finding the sweet spot for your home or business. 


MERV Rating Chart


MERV Rating Pro Tips

We came up with a quick and dirty cheat sheet for when you’re ordering your filters.You may even enjoy it as some light reading at your own convenience!

MERV Ratings 1-6

Filters with a MERV rating between 1 and 4 come in both the washable or disposable varieties. They offer the least filtration but are much less expensive than filters with higher MERV ratings. Because of this, they aren’t really a very good choice for human most living situations. 


Filters with a MERV ratings 5 and 6 can be either cartridge or pleated filters. Pleated filters work by trapping particles in their many folds. The more folds, or pleats, the higher the level of filtration. They are often made with a cotton-polyester blend. These filters are disposable. We recommend MERV 6 for frugal renters who do not want to spend too much for good air filtration.

MERV Ratings 8-13

In this category, you’ll find most of the ratings that are recommended for households. Here are some other rules of thumb for choosing the right rating:

  • MERV 8 is a good place to start. If no one in your house currently has any breathing issues, such as allergies or even more serious issues, then MERV 8 should be suitable.
  • MERV 5-9 are recommended for the home for those without respiratory issues. 
  • MERV 11 is good for homes of people with pets and mild allergies, as well as those who have asthma.
  • MERV 13 is good if your home has smokers in it, if you’re in a city with smog, or if you have a wood-burning fireplace in your home.

MERV Ratings 14-20

The two types of filters used at MERV 14-16 are bag filters and box filters. Bag filters, also known as baghouse filters or fabric filters, are capable of collecting particulates and gas released from industrial and commercial processes from the air. Places that use these types of filters include steel mills, chemical production, power plants, pharmaceutical, and food manufacturing facilities. In hospitals, they are used in surgery operating rooms. You can use these in your house or workplace, but be aware that your AC bill may start to climb.


Filters with a MERV rating of 17 or higher are typically found in orthopedic surgery rooms, pharmaceutical manufacturing facilities, and clean rooms. They are used when absolute and impeccable cleanliness is vital.


Nice as it may be to breathe 20-rating filtered air, the odds of finding one of these that will fit your home AC unit and at an affordable price are pretty slim. Drop down a few notches for clean air at an affordable price.


Why You Shouldn’t Max Out Your Filter

We know what some of you are thinking: “I must go out and lay my hands on a MERV 20 filter to protect me and mine from every possible contingency!” But there are a few reasons that we don’t recommend using a filter with a rating higher than 8. 


  • Most HVAC systems aren’t designed to operate with higher-rated filters. They put an unnecessary strain on the motor and you will have to replace or repair it. 
  • Labs and other facilities that use higher-rated filters take an abundance of other precautions to eliminate particles. If you live in a normal home, you walk through doors, open windows, and wear the same clothes inside and outside. While it’s possible to have a very hygienic household, you’re not going to achieve lab conditions just by changing an air filter — and it’s unnecessary. 
  • Higher-rated filters are more expensive. And aside from them costing more, they need to be replaced more often as they fill up with nearly every pathogen and become clogged. 


Make the smart move and replace your filter with something from the household range (8-13). 


Perils of High MERV Ratings in Hot Weather

Air filters work by trapping particles in them, but as they trap smaller and smaller particles, they also make it more difficult for air to pass through. That means that as your air conditioning unit is trying to heat or cool your home or commercial property, it’s going to have a harder time depending on the type of filter that you are using. As we’ve previously mentioned, when you have a filter with a higher MERV rating, it’s harder to blow air through the system. Let’s say it’s summer and you put a filter in your air conditioning system with a very high MERV rating. Your house would be warmer because your air conditioner would be working harder to push cold air through the filter and cool your home. Meanwhile, all that trapped air is freezing up and can eventually damage your HVAC system. When this occurs in a furnace, the furnace can overheat.


Well, How Often Do I Change My Filter?

You might be thinking that the best course of action is to change your filter as often as possible, but like so many of life’s other tasks — changing your oil, getting a haircut, visiting the dentist, etc. — doing it too often is inconvenient, expensive, unnecessary. Some people may be able to change theirs every 6 to 12 months, whereas others have to change theirs every month. Things that you should consider when deciding the frequency of your filter changes include:


  • The number of people living in your home
  • Whether or not you have pets and how many
  • How often you cook in your kitchen
  • Whether or not someone smokes in your house


The more of these factors that come into play and the higher the number of occurrences, the more often you should change your filter. A surefire way to determine how often you should change your filter is to check it once a week. If it starts looking gray and covered with dust, it’s time to replace. Once you figure out your rhythm, Filter King can hook you up with regular deliveries.


Why Choose Filter King?

At Filter King, we believe that homeowners and property owners should be able to work with a supplier that makes remembering to maintain their HVAC units and changing their filters a whole lot easier. We also want the people that we serve to protect their air-conditioning systems so that they save money on repairs later on. 

 

We understand that good health is at the forefront of everyone’s minds right now, and we are ready to answer your questions about what type of air filter is best for your air-conditioning system and for your family‘s health. Be sure to let us know if you have any pets or any health concerns so we can advise you on the best filter brands for your needs. Call us or take our online air filter survey.