A heating and cooling vent

What Is a MERV Rating & Why Is It Important?

If you’ve ever tried to buy your own air filter, you may very well have been confused by the process. Do you know what size air filter you should buy? What material? What thickness? These are just a few of the measurements you’ll need to keep in mind when making your choice. However, while the size may be straightforward and easy to replicate, there’s one metric that most people don’t usually understand completely: MERV rating.

What Is a MERV Rating?

MERV stands for Minimum Efficiency Reporting Value, and is a value used to compare how much or how little air a filter allows to pass through it compared to others of the same dimensions. Lower numbers generally allow more air to pass through, but at the cost of worse filtering performance. The opposite is also true: higher numbers tend to filter out more debris from the air, but at the expense of airflow.

Now, you might be thinking that a larger number means better performance and therefore you should always look for the highest number you can find. This is far from true. The truth is your HVAC system is designed to work with a filter of particular dimensions and particular capacity. A filter that strains too much puts too much resistance between your return register and your blower fan. That means your fan will struggle to pull enough air through in order to operate properly, and your entire HVAC system will suffer as a result. Not only will you see increased energy bills from lengthened cycle times, but critical components will fail prematurely due to lack of adequate airflow to make them work as they’re supposed to.

Likewise, high-MERV air filters tend to fill up quickly, which means they need to be changed frequently. Sure, you’re supposed to change your air filter every two to three months, but how would you feel if you discovered that your air filter was jammed up and needed replaced every three weeks to a month? It might start to feel tedious after a while. And it’ll really feel annoying when you see just how expensive some of the highest-MERV filters can get.

There’s a reason why these filters are almost exclusively designed for highly-specialized uses, including cleanrooms at laboratories, operating rooms in hospitals, and so much more—the HVAC systems in these applications are designed to work with this type of filter, and therefore make use of it appropriately. For the average home, however, you simply do not need that level of filtration to enjoy a high quality of life and great indoor air.

What MERV Should I Buy?

How do you know what MERV rating to choose for your heating and cooling system? The easiest answer is to simply look through your HVAC system’s owner’s manual and see what the manufacturer recommends for normal operation. You trust the owner’s manual in your car for information like what type of brake fluid to buy or what kind of oil to use for your engine, so why not turn to the manufacturer’s recommendations for your air filter as well?

Now, as with your car, you don’t always need to stick with manufacturer-recommended specifications. If you know what you’re doing and you need to make a change, you can do so and still enjoy a reliable and efficient air conditioner. For example, if you find you suffer from low-quality indoor air, or you struggle from seasonal allergies or respiratory problems, increasing your MERV value slightly could benefit your quality of life by straining more and more particulate matter out of the air. Conversely, those who find their system is struggling because of their air filter, but they aren’t particularly struggling from indoor air quality issues could maybe afford to drop their MERV value just a touch. However, we never recommend exceeding the manufacturer-specified limit without first consulting a professional heating and cooling expert.

To learn more about what air filter is right for you and your home, call Performance Air Conditioning, Electrical & Plumbing at (727) 877-1294 to request an inspection today.