Selecting the right HVAC filter
Updated: Jul 7
A filter might seem like a relatively insignificant part of a furnace or air conditioning system, yet good airflow is vital. If your filter is clean, your system works efficiently. If not, you are probably going to encounter problems.
Although most people believe that a HVAC filter is meant to clean the air coming into their home, this is not its main purpose. While the filter does improve the quality of the air inside your home by removing impurities, the main purpose of a filter is to protect the furnace itself. The filter protects the heat exchangers, motors, and other HVAC components from dirt and dust coming in through the return duct. Never run your furnace or HVAC system without the proper filter. The result will be poor performance, higher utility bills, and breakdowns.
Air filters come in many different sizes. It is important that you select a replacement filter that fits your unit’s filter cabinet correctly. The easiest way to determine the correct size is to measure your current filter. You will probably need to remove it to measure it. Make sure you note the direction of the airflow arrow on the filter's frame before removing it. Having the correct height, width and thickness are all important. Once you have determined the correct filter size, you may find it helpful to write the dimensions on the front of the air handler for future reference.
Above all, one of the most important factors to consider when choosing a furnace filter is the filter’s MERV rating (minimum efficiency reporting value). A MERV rating indicates the overall effectiveness of a filter to capture particles between 0.3 and 10 microns in size while the air is flowing through your heating or cooling system. The higher the number the more effective it is at removing particles from the air. The scale ranges from low-efficiency fiberglass filters with MERV ratings between 1 and 4 to high-efficiency HEPA filters with MERV ratings ranging from 16 to 20.
Selecting a filter with the highest MERV rating is not necessarily the best option. In fact, as the MERV rating goes up, air flow goes down—forcing your HVAC system to work harder to push air through it. Before purchasing a new filter, check your equipment manual to determine the highest-rated MERV filter that is recommended for your system. Be sure to buy a filter with a MERV rating below your system’s maximum.
Selecting the right MERV rating for your air filter is a balancing act between your HVAC system’s capabilities and the indoor air quality you want to achieve. We recommend using air filters with a MERV rating of around 6 to 8. A MERV rating in this range is a good compromise between air quality and airflow. They are also available at most stores for reasonable prices, so you don’t need to worry about breaking the bank.
When it comes to filters, there are several types to choose from, each with its own positives and negatives. This includes a new smart filter. But, how do you know what kind of filter is best for your home? Is a smart filter really worth it?
Fiberglass filters are the cheapest option. While they will provide maximum airflow, they will not trap smaller airborne allergens and particles. The MERV rating of a disposable fiberglass filter will generally be between 1 and 4.
Pleated filters are probably the most popular type of HVAC filter. They are both affordable and effective. These filters are made from paper and polyester. Their MERV value will generally be between 6 and 12. Pleated filters are more efficient and last longer than fiberglass/synthetic filters. They eliminate more pollutants from your air without significantly hindering airflow within your system.
Washable filters are available in flat paneled and pleated forms. Depending on the brand, they may last a few years. Still, they may require a specific washing procedure, which could include separating the filter into layers and washing them separately. Users must also make sure a washable filter is completely dry before reinstalling it to prevent mold and mildew growth. For many, using disposable filters is the better option.
Disposable electrostatic: Made of self-charging electrostatic paper fibers or cotton, disposable electrostatic filters are good at attracting and trapping small particles. While they cost a bit more than pleated or fiberglass filters, they are affordable in standard sizes.
Permanent electrostatic: Permanent electrostatic filters work similar to their disposable counterparts. The main difference is that you can remove and wash the filter for five to ten years. Because the filter needs time to dry well after washing it, many homeowners purchase two and alternate between them.
HEPA (High-Efficiency Particulate Air) filters provide excellent air filtration. However, due to their density, which allows them to trap even the smallest particles, they significantly restrict airflow. Most residential furnaces don't produce enough pressure to pull air through them. If that's the case, all you're doing is blocking up your system and actually getting no filtration at all. This can greatly increase your energy use and therefore your monthly energy bill. HEPA filters are most suitable for commercial buildings or hospital settings where the HVAC units are strong enough to bring air through the filter.
Smart filters are the newest and most advanced option on the market. They use exclusive 3M technology. With the use of a companion app, these Wi-Fi filters send reminders to your phone about when you should replace your filter, where to buy a replacement, the life stage of your filter based on time, airflow, and usage, information about outdoor air quality, tips for improving your indoor air quality, and information about filter types and what size filter your system requires. The app allows you to input your geographic location, allergies, respiratory conditions, pets, etc., in order to provide the most personalized information possible.
Are smart filters worth it? A smart filter isn’t absolutely necessary for everyone. However, for those who often forget to replace their filter on a regular basis, it might be a good option. Based on the personalized information you enter into the app, your smart filter will let you know when it needs to be changed. In addition to notifying you when your filter should be replaced, the app will also allow you to order a new filter and to easily pair the new filter’s Bluetooth sensor with the app. However, if you are already diligent about keeping tabs on your air filter and changing it often, the price for the smart filter technology may not be worth it.
When it comes to taking care of your HVAC system, changing the air filter regularly is the number one thing you can do. Just with normal system use the filter gets clogged and the airflow gets restricted. Next thing you know you’re dealing with poor performance and strain on the whole system.
A disposable furnace filter should be replaced at least every three months. Depending upon the filter itself, and the air inside and outside of your home, it may need to be replaced more frequently. Changing your filter regularly will help keep your HVAC system functioning properly. It will also help your indoor air quality be the best it can be and keep your energy bill low.
The first question we ask when a customer calls us with a furnace or air conditioning problem is “When did you last change your filter”.