If you take a trip to any big box hardware store, you will find a wide selection of air filters for your HVAC system. As you can imagine, the most popular models make claims that they can filter more than the competition, and it can be hard to make a decision. The best air filters have a Minimum Efficiency Reporting Value (MERV) rating of 10 or higher. The air filter packaging will tell you what the filter can remove, and many people just go with an air filter that has the highest MERV rating they can afford. In most cases, this is a bad decision, and there are other factors to consider. In this article, we will take a closer look at HVAC air filters to help you make a more informed decision. 

The Role of a Basic HVAC Air Filter

Before we begin, let’s examine the role of the air filter in your HVAC system. Many people believe that the air filter is designed to remove airborne contaminants to improve their indoor air quality (IAQ). This is only partially correct. Although a basic air filter removes contaminants, this is to protect the HVAC system. Removing airborne particulates will improve the IAQ a little, but it will not be as effective as a filter with a higher MERV rating or a dedicated air purification system.  Without an air filter in place, the HVAC equipment would be exposed to a large volume of dirt, dust, pet dander, and other airborne contaminants. This can cause a buildup of dirt on the HVAC system components, which can lower efficiency and lead to equipment failures. In extreme cases, very dirty HVAC components can even lead to a system failure and an earlier than expected replacement. So, you need a basic air filter to protect your HVAC system, and it doesn’t need to have a high MERV rating.

Using a High MERV Rating Air Filter to Improve IAQ

Studies have shown that many of us are living in homes that have a poor level of IAQ when compared to outdoors. There are a number of causes, and the increasing popularity of energy efficient homes that are virtually airtight hasn’t helped. Many homes contain a large number of contaminants. Some of them are airborne, and removing them from the air should be a priority. If you’ve noticed that people in your home tend to get sick easily and suffer from allergic reactions, you probably have poor IAQ. The first people to notice these issues are people that have asthma, allergies, and those with pre-existing respiratory diseases. If you want to improve your IAQ, it’s important to let some fresh air into your home regularly, and using an air filter with a higher MERV rating will help. Sadly, there is a catch that may affect your decision.

Air Filters with High MERV Ratings Create New Problems

The reason why an air filter with a higher MERV rating can remove more airborne particulates is down to its construction. This type of air filter is made of denser materials, and it may be pleated to increase the surface area. This means that the air filter can capture smaller particulates in greater concentrations. This sounds great in theory, but this can also impede the airflow because the air cannot pass easily through an air filter with a high MERV rating. Your HVAC system relies on a steady supply of air to distribute the treated air throughout your home and work efficiently. When the airflow is impeded, it can cause equipment failures and even reduce the lifespan of your HVAC system. The system will struggle to push the air through the filter, and this will cause the equipment to overwork which drives up your energy bill.

What is the Solution?

This may seem like an insurmountable challenge, but in reality, the solution is quite simple. It’s essential to get the correct air filter to match the square feet per ton of your HVAC system. This will ensure that your system gets the airflow that it needs, and the high MERV rated air filter can remove a greater variety of particulates. This is not a task for an amateur; you need to contact your local HVAC specialist and get them to check out your system. They will need to take some accurate measurements, and some adjustments may be needed to accommodate an air filter with a higher MERV rating. Let’s take a look at a detailed example:

Perhaps you have an HVAC system with a 3-ton capacity that keeps your home comfortable throughout the year. You change the air filters regularly, and you typically use a unit with a MERV rating of 8 to protect your system. But, you want to improve your IAQ, and you’ve noticed an air filter with a MERV rating of 16 that can remove far more particulates from the air. This seems like a great deal; you buy the air filter and look forward to easier breathing with better IAQ. But, this is where the problems begin because instead of getting a 3-ton capacity, the system can only manage 2.5-tons. Although the air may be cleaner, you’re getting less of it, and the HVAC system is being overworked as it attempts to compensate.

As you can see, it makes good sense to speak with an HVAC specialist before you choose a new type of air filter with a higher MERV rating. If you’ve tried out a new air filter and you like the way that it improves your IAQ, it may be possible to accommodate it safely. The HVAC specialist can use a formula to determine if adequate airflow is present in your system. It may be possible to add another return plenum with a filter to increase the airflow and negate the negative effects of the high MERV rated air filter. Another solution could be to make the existing plenum larger and fit a larger high rated MERV air filter. The exact solution chosen can vary depending on the type of HVAC system you have and other factors.

If you want to install a high MERV rated air filter in your system, contact your local heating and cooling specialist today.