The filters in your home, though often taken to be of a set-and-forget nature, require periodic replacement to ensure that they serve its purpose. While many choose to simply hire a professional to replace their furnace filter, knowing your furnace filter needs and getting the job done yourself can reap countless benefits, both short and long term. However, if you are new to the world of furnace filters, there is a possibility that the concept of MERV ratings might throw you off, or make you feel overwhelmed. Not to worry, we’re here to help.
Furnace filters are arguably the most important component of an HVAC system. This is the part of your air filtration system that holds back much of the harmful contaminants present in the air and circulates purified, clean air around your home.
Purchasing a furnace filter can be somewhat tricky for someone who is doing it for the first time, due to something called the MERV rating system. Though confusing, MERV ratings can be your best friend when trying to figure out which furnace filter is best suited for your needs.
In this article, we address one of the most commonly asked questions about furnace filters—what’s the difference between a MERV 11 and a MERV 13 furnace filter? Read on to find out more about the MERV rating system and how to choose the perfect filter for your air filtration needs.
Understanding the MERV Rating System
You may have heard the words “MERV rating” being thrown around a lot with regard to furnace filters without having an idea of what it means. However, having a basic idea about this rating system is crucial in helping you determine what the right choice is for your HVAC system. Minimum Efficiency Reporting Value, popularly abbreviated as MERV, is a standardized rating system applied to air filters. This system includes a scale ranging from 1 to 20, wherein 1 indicates the lowest possible efficiency and 20 indicates the highest.
Designed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers in 1987, the MERV rating system was tailored specifically for central HVAC systems. The MERV rating of a furnace filter represents its ability to filter out air contaminants—a filter with a lower MERV rating would be able to trap fewer particles and contaminants in comparison to one with a higher rating. When trying to determine the right MERV rating for your air filter, however, it is vital to bear in mind that the MERV rating of a furnace filter denotes its minimum capacity.
While other rating systems such as Filter Performance Rating (FPR) and Micro-Particle Performance Rating (MPR) are also used for furnace filters, the MERV scale is the most commonly used as it is straightforward, simple to understand, and accurate.
MERV 11 vs. MERV 13—What’s the difference?
While it may seem that a MERV 11 filter is not all that different from one with a MERV 13 rating, that is absolutely not the case. These two ratings differ greatly when it comes to filtration capacity.
- The MERV 11 rating is one of the most popular choices when it comes to residential use. The MERV 13 is less popular and is the highest rating that is recommended for residential use. Anything above 13 is mainly used for commercial/industrial purposes.
- A MERV 11 rated furnace filter can trap the majority of harmful contaminants that are present in the air. This includes pollen, dust, lint, mold, dust mites, smoke, pet dander, and smog.
- A MERV 13 filter is capable of filtering out all particle impurities like dust, lint, pollen, mold, dust mites, pet dander, smog, and smoke. On top of this, it can also trap bacteria and viruses.
- MERV 11 furnace filters have a particle arrestance of a little over 90%. In comparison, MERV 13 HVAC filters have a particle arrestance of around 98%. Naturally, it is significantly more efficient.
- MERV 11 rated air filters are ideal for those who live in a moderately polluted area, have mild allergies, or own a pet.
- MERV 13 filters are best suited for homes that are situated in heavily polluted areas and for those who suffer from severe allergies or asthma, own multiple pets, or are concerned about bacterial or viral infections.
What MERV Rating Should I Use?
Ask yourself the following questions:
- Do I own a pet?
- Is my home located in an urban, moderately or high polluted area?
- Does anyone in my household suffer from mild allergies?
- Do members of my household suffer from asthma?
- Do I live with someone who has an immunocompromised system?
What MERV Rating Can My Furnace Handle?
The air handler or blower in every furnace can take a specific amount of pressure drop. Since filters with a high MERV rating offer high resistance to the airflow, their pressure drop is also greater. Most modern HVAC systems are capable of working with higher MERV ratings. However, if your furnace is older or sensitive to airflow, it may not be able to handle a filter with a higher rating.
Start by checking your furnace’s manufacturer guide, contacting the manufacturer, or asking a HVAC professional. It’s crucial that your furnace filter is of the right size and compatible with your furnace. Here’s PureFilter’s guide to the different furnace filter sizes.
Knowing the Difference
If you were wondering what’s the difference between a MERV 11 and a MERV 13 furnace filter, we hope this article answered your question. Switching from one of these ratings to the other makes a world of difference in terms of performance. Whichever MERV rating you end up choosing, it is imperative that you replace your filter periodically to keep your furnace in top shape for years to come.