Mechanical air filters are the most common type of home air filters used in residential HVAC systems.
These filters use synthetic fibers to trap small particles, debris, and dust, among other things — preventing those things from circulating in the air and getting into our lungs.
The effectiveness of a mechanical air filter is measured in MERV ratings (Minimum Efficiency Reporting Value). Generally speaking, the cheaper the filter is, the lower the MERV number is. In other words, you get what you pay for. Air filters with lower MERV ratings need to be replaced more frequently.
What you need to know
Mechanical air filters remove dust by capturing it on the filter medium, the material that makes up the filter element. A mechanical air filter is any type of dry media filter. All of the throwaway air filters used in HVAC systems and Air Handlers are mechanical air filters. Any man made or natural fiber filter is a mechanical air filter. This includes HEPA air filters as well.
Fiberglass air filters are very thin and they have a simple flat panel surface for trapping particles from the air. They were originally developed to protect your heating and air conditioning equipment, not to improve your indoor air quality. They can often be purchased for less than $1 apiece. Unfortunately, they remove less than 10% of the air pollutants from your home. They have a MERV rating between 1 and 4.
Pleated air filters remove up to 45% of the air pollutants from your home. The number of pleats per foot impact their overall efficiency. Click Here for Pricing. They have a MERV rating of 10 to 13.
The filter with more pleats per foot across the face will allow you to have better airflow throughout your home. The more air that flows through your house, the more often it is passed and re-circulated through the filter. The end result is cleaner air because of the higher frequency of air passes through the filter. For example, if you could find a way to install a hospital grade operating room filter in your home unit, it wouldn’t do you much good because your fan and motor doesn’t have enough power to push enough air through it. A good quality filter with a high MERV 11 rating can actually leave you with dirtier air than using a cheap 1 dollar filter if the MERV 11 filter doesn’t have enough pleats per foot. Less pleats per foot is a cheap and dirty way for filter sellers to trick buyers into thinking they are getting a better deal. Insist on MERV 11 filters that have a minimum of 18 pleats per foot!
High-efficiency air filters are the most practical air filters for most residential HVAC systems, removing up to 85% of the air pollutants from your home. They have a MERV rating between 14 and 16.
These filters can trap very small particles of dust, pollen, mold, and other irritants. Some of these filters work much like the air and oil filters in your car. They are made using pleated filter paper. Other filters are made with fine synthetic polyester fibers. Higher efficiency air filters can sometimes be coated with chemicals that can kill tiny microbes such as bacteria and mold. There are several advantages to using these higher efficiency air filters. Not only will your heating and cooling equipment perform better, your operating costs may well be lower. The air you breathe will be cleaner, as will your furniture and drapes. That $60 service call could have bought 10 filters that may have lasted through five cooling seasons!
True HEPA (or High Efficiency Particulate Air) filters provide the best filtration for your home by removing up to 98% of air pollutants from your home. They have a MERV rating between 17 and 20. However, they can only be used in a whole house filtration system or a standalone air purifier.
Unfortunately, HEPA filters restrict too much air to be used as a traditional furnace filter. A HEPA filter is extremely efficient, but a significant amount of air pressure is needed to force air through a HEPA filter. A typical HVAC system will not be equipped to provide enough air pressure to use a HEPA filter (which basically means that no air would blow out of your registers). In order to use a HEPA filter for whole house filtration, you need to install a separate HEPA filtration system. A system like this will pull some of the air out of the regular air flow through your furnace, and then boost the air and pass it through a HEPA filter. The extremely filtered air is then returned back into the normal air flow.