Air filters are an essential component of HVAC systems. Their primary purpose is to limit the dust that gets into the air handler and furnace. Nonetheless, an HVAC air filter can also help overcome or at least minimize indoor air quality issues, depending on how efficient it is.
What Do MERV Ratings Indicate?
MERV (Minimum Efficiency Reporting Value) is the most common scale to rate HVAC air filters. This rating tells you the efficiency of an air filter — how well it works to filter out different types of allergens and contaminants. The lowest rating is MERV 1, and the highest is MERV 15. The scale technically goes up to MERV 20. However, MERV 16 to 20 filters are the same as HEPA filters, which are only used in specific circumstances like some whole-home air purification systems.
To determine an air filter’s MERV rating, it must first be tested in a lab to determine the percentage of particles it traps and the percentage that can pass through it. The rating is then determined based on how many particles of varying sizes the filter removes from the air flowing through it. Filters at the lowest end of the scale only trap approximately 20%-40% of the largest particles around 8 to 10 microns in size. Particles of this size include dust and certain types of pollen. The vast majority of the other smaller allergens and contaminants pass right through the filter. That’s why the lowest MERV filters are primarily designed for use in equipment like window AC units.
Filters designed for residential HVAC systems typically start at MERV 5-6 and go up to MERV 12-13. You can find some up to MERV 15 to 16. These are known as media filters and range from 3 to 6 inches thick, whereas standard filters are only 1 inch thick. If you want to switch from a standard filter to a media filter, you may need to redo part of your supply ductwork to fit the thicker filter. The advantage of using a media filter is that it contains far more pleated filter material, meaning a much greater surface area makes the filter more efficient. You also need to check with a professional to see if the fan motor on your HVAC unit is strong enough to pull air through the restricted space. The increased surface area of a pleated filter means that it doesn’t clog up as quickly. A standard filter usually clogs up after only two to three months, whereas a media filter can last for six months or sometimes up to a year.
Types of Standard Air Filters
There are several different types of standard 1-inch air filters you can use in your home’s HVAC system. The most common type is disposable pleated filters. These filters are made from cotton or polyester fabric folded to create pleats, which increase the filter’s surface area and allow it to work more effectively. You can also find washable pleated filters that work just as well. Cost and convenience are the only fundamental differences between disposable and washable pleated filters.
Washable filters cost more but will save you money in the long run. A high-quality washable filter should last at least five years. That means you’ll end up paying quite a bit less than you would if you were to buy four to eight disposable filters every year. You’ll have to take the time to wash and clean it thoroughly every two to three months. Once the filter is clean, you must wait for it to completely dry before putting it back in place to ensure mold and mildew don’t start growing.
The cheapest option is to use fiberglass flat-panel filters. The drawback is that these filters are usually no higher than MERV 5. While they’re somewhat effective at preventing dust from getting sucked into your HVAC system, they have zero effect on most other allergens. You’ll also still end up with much more dust inside your HVAC system than with even the lowest-rated pleated filter.
Another option is to use an electrostatic filter. This type of filter uses static electricity to attract and trap certain particles like dust. Electrostatic filters are washable, meaning you can save money using the same filter for at least a few years. Another advantage is that they don’t restrict airflow as much as some pleated filters do. That means you usually won’t have to worry about the filter interfering with how effectively your HVAC system heats and cools. You often must wash an electrostatic filter monthly since it can clog up quickly. The downside is that electrostatic filters are usually only rated at MERV 5 or 6. Another issue is that an electrostatic filter is generally only effective at removing dust, pollen and other allergens. Smaller contaminants and germs will continue circulating in your house if you have an electrostatic filter.
How to Know Which MERV Rating Is Best
When trying to decide which type of filter and which MERV rating is best, you need to consider your specific priorities. Are you primarily focused on filtering out dust to protect your HVAC system and don’t want to spend too much on filters? If so, an electrostatic filter or a MERV 6-8 pleated filter will probably be your best choice.
Does someone in your household suffer from allergies or asthma? Are you concerned about harmful pollutants and contaminants in your house? If you answered yes to either of these two questions, you’re better off choosing at least a MERV 10 pleated filter if not a MERV 12 filter. These filters will significantly reduce the amount of allergens and pollutants spread around your house when your HVAC runs, helping improve your indoor air quality.
The only concern with MERV 12 filters is that they are relatively restrictive, meaning they reduce how much air gets drawn into the HVAC system. As a result, the filter can make the system heat and cool less effectively and cause an increase in the amount of energy it uses. Restricted airflow also leads to more wear and tear and will often at least slightly shorten the system’s lifespan. That’s why you may be better off choosing an electronic air cleaner that is separate from your HVAC system. This may be an add-on to your whole-home unit or a standalone air purifier for each room. Either of these options will make an even more significant improvement in your HVAC system without restricting airflow and hampering the system’s performance.
Southern Pride Service is proud to be one of the leading HVAC and indoor air quality services in White Plains and the surrounding areas in Southern Maryland. We’ve been in business for over 30 years and have the knowledge and skills to meet your needs. If you want to improve your indoor air quality or need assistance with your AC or heating, call us to schedule an appointment for AC maintenance.
