Introduction to Furnace Filters
Long before we began to look at air filters as a source for improving our indoor air, manufacturers of heating and cooling systems routinely incorporated air filters into the design of their air handling equipment to minimize the invasion of life-robbing air pollutants like dust, dirt, pollen and other airborne particulates.
Little consideration was given to the quality of the air that was passing through the system and into the living area. During this era in the evolution of air conditioning and heating systems, homes were not tightly constructed: Doors and windows were drafty.
But energy was cheap so there was little innovation in products that would better seal the indoors from outside elements. It was not until the 1970’s that more energy efficient construction came into the public’s view. Energy efficiency meant separating the occupants inside a building from outside elements. At that time, people began to look at their indoor air in a different light.
Too, problems began to surface from exposure to polluted indoor air. Marketers began to see the opportunities created by cleaning up the indoor air. This gave rise to an entire generation of air filters designed to clean the indoor air.
The following is intended to make you more aware of how your heating and air conditioning system actually works and to understand the vital role controlling the quality of your indoor air plays in the your overall health and the health of your furnace or air conditioning or HVAC system. Additionally, we have attempted to address our customer’s most frequently asked questions. We welcome your input and questions.
Below, you see the typical central heating and air conditioning system used in a home or small office. The system is a loop type of system meaning the air that passes thorough the HVAC system circulates in an endless loop for as long as the system is running. The loop begins when air comes into the system through the return ducts in the AC system.
The air passes through the ductwork and the HVAC systems filters. From there, the filtered air is passed through the main system where it is cooled or heated then back out through the ductwork and into the building.
As you can see from this illustration, there is little that can be done to improve the quality of the air that is being circulated through the system aside from replacing the air filters. The selection of your HVAC system’s air filters directly affects the quality of air being circulated throughout the system.
- 1 Introduction to Furnace Filters
- 1.1 What are the Different types of air filters currently in use in furnace filters, air conditioning systems and HVAC systems?
- 1.2 Where Are My Air Filters Located?
- 1.3 How Do I Know What Size Air Filter I Need?
- 1.4 When Should You Change Your Air Filters?
- 1.5 How Do I Properly Install a Pleated Air Filter?
- 1.6 Do Air Filters Kill germs, Reduce Dust and Eliminate Odors?
- 1.7 I Live in an Apartment/Condo: Can I Use other Air Filters?
- 1.8 How Can I Eliminate Dust?
- 1.9 What About Aluminum Washable Air Filters?
- 1.10 Will Air Filters Cause Air Flow Problems Through My HVAC System?
- 1.11 How Are Pleated Merv 12 Air Filters Better Than Fiberglass Air Filters?
- 1.12 Should I Put More Than One Air Filter in My HVAC System?
- 1.13 What Are Electrostatic Air Filters?
- 1.14 Do I Need An Air Purifier?
- 1.15 Why is air quality important?
- 1.16 Filter Size?
- 1.17 Share this:
What are the Different types of air filters currently in use in furnace filters, air conditioning systems and HVAC systems?
Air filters come in a variety of sizes and types. The primary distinction between one filter and another is the size of the filter (length, width and thickness) and the filter material or “media” that is used in the manufacture of the filter.
As you can see from the illustration above, the air in a furnace or air conditioning system first enters the home through the air return where it passes through the air filter(s) and into the air handler, over the cooling coils or heat exchanger part of the HVAC system (where the air is either cooled or heated) and out through the ductwork into the home.
The circulation throughout the HVAC system is accomplished through a powerful blower system (shown above). Because the air filter is the only device in the entire HVAC system capable of removing airborne impurities, it makes sense that frequent replacement of the air filter as well as careful consideration as to the type of air filter you use will directly impact the quality of your indoor air.
Conversely, ignoring the HVAC systems air filter means you are allowing the entry of polluted air into the entire system, driving down operating efficiency, filling up ductwork with all dust, pollen, dust mites, etc. and other airborne pollutants while exposing the building’s inhabitants to polluted air.
Though there are a wide variety of Air filters, they are generally termed as disposable air filters or reusable air filters,
Reusable Air Filters sound good, in concept. After all, replacement costs can add up over time. The problem is that reusable air filters do not do as efficient job as desired. To begin, reusable air filters are messy when removed from the HVAC system. Then there is the problem of finding a suitable area to clean the filters.
Very often, highly toxic cleaners are required for adequate cleaning of reusable air filters. Once the chemical is used on the filter, it is absorbed into the filter and therefore a certain amount of the cleaner can be released back into the circulating air posing a potential health threat.
We do not endorse this type of filter and does not sell reusable filters.
Make-Your-Own Air Filters are designed to enable you to construct your own filter. Buyers for these types of media filters usually do so because their HVAC system does not accommodate standard sized air filters. The most common media for filtration is fiberglass.
The handling of fiberglass is difficult as fibers from fiberglass can break off in the skin causing discomfort. Further, fiberglass provides only marginal filter effectiveness. Too, the Make-Your-Own-Filters often have no frames to use in securing the media material.
As a consequence, the filters can often collapse necessitating a service call by an air conditioning professional. We do not endorse the use of this type of filters. Our many years of manufacturing expertise has enabled us to manufacture a custom filter at about the same price as off-the-shelf air filters from competitors.
The most significant difference is that the media material is much higher in quality and has a frame around the material and the media is attached to the frame with a support material insuring there are no collapsed filters.
Disposable Panel Air Filters are the most commonly used type of air filter in furnaces, air conditioning systems or HVAC systems. Panel air filters, being disposable, solve the problems associated with handling dirty filters while insuring ease of removal/replacement. Disposable panel air filters use a variety of media for filtration.
A “panel” air filter gets its name because the air filter is actually manufactured as a self-contained, one-piece “panel” that consists of the (a.) air filter media material (b.) any internal structure that supports the air filter media material such as metal fabric, wire or even cardboard, and (c.) the box or frame in which the air filter media material and the media support material is attached to and housed within. The box or frame of a Disposable Panel Air Filter is rigid.
The frame is normally constructed of cardboard, plastic or even metal and made to withstand the insertion of the filter into the HVAC system and keep its structural integrity while the HVAC system is operating. The frame is defined by the length, width and thickness of the box housing the filter media.
The most common type of air filters on the market are panel air filters that use fiberglass as the filter media. Fiberglass filters are very cheap and do an effective job at removing only the largest of airborne particulates. In addition to it’s limited ability to filter finer particulate, fiberglass is very brittle and can cause harm when handled.
Further, there is a potential for the fiberglass fibers to break off and enter passing air creating a serious health problem. We do not endorse the use of fiberglass filters, both because of their limited ability to filter the air, especially smaller particulate and the health implications.
Pleated Furnace Filters are much like Disposable Panel Air Filters in that the filter media is housed in a rigid panel but the difference is that the media material used to filter the air, as well as the way the material is mounted into the air filter box or frame is different.
The filter media used in pleated filters most often resembles fabric and has the capability of removing significantly smaller particulate from the air. Further, when the filter media is integrated into the filter, it is pleated to provide more surface area for filtration.
This pleating adds more than double the surface area of un-pleated filters. The net effect is that you end up with a filter that removes more of the particulate in the passing air AND has at least twice as much surface area. Combined, pleated air filters provide a significantly higher level of filtration.
Electrostatic Pleated Furnace Filters are a more highly evolved version of the pleated air filter. In addition to a higher quality media filter material and pleats for increased surface area for filtration, Electrostatic Pleated Air Filters are also electrostatic meaning that the filter media material is electrically charged so that the media material acts much like a magnet to draw more particulate into the media filter material for more efficient filtration.
Another benefit of electrostatic air filters is the material is that it does not permit the growth of bacteria, often a problem with other filters. Our MERV 12 filters are Electrostatic Pleated Air Filters in a wide variety of lengths and widths with thickness from 1” to 5”.
Now that I know the different types of filters, how can I tell one from another?
In an effort to aid the consumer in determining the difference between the quality of one filter compared to another, the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) developed a rating system called the MERV Rating?
MERV stands for Minimum Efficiency Reporting Value. ASHRAE assigns a MERV number intended to help people compare air filters that are for use in heating and air conditioning systems. The MERV air filter is a rating of the efficiency of the air filter, regardless of whether it is used as an air conditioner filter or furnace filter or a HVAC system that combines both heating and air conditioning into one HVAC system. MERV ratings rank air filter efficiency by assigning a number ranging from 1 to 16, with one being the lowest air filter efficiency and 16 the highest air filter efficiency when used in an HVAC system.
Particles in the indoor air that pass through the HVAC Systems air filter are measured in microns, which is 1/1000 of a millimeter. A human hair is about 100 microns wide. Regardless of the purpose, whether it is used as air conditioning filter or furnace filter or used in a combination HVAC system, our air filters capture airborne particles as small as 0.3 microns!
A MERV 12 rating represents the best balance between airborne particulate removal of dust, pollen, airborne pathogens, etc. and overall HVAC system efficiency. Air filters above MERV12 generally require larger, more expensive HVAC systems not normally intended for traditional home or smaller office heating and air conditioning systems. This is due to the “drag” imposed on the HVAC system.
Top-notch HVAC professionals who buy from us daily highly endorse the MERV12 rating as providing the highest efficiency of an air filter while not overtaxing the HVAC system. MERV12 requires 80% or better air filter efficiency on 1 – 3 micron particles and a greater than 90% air filter efficiency on 3 -10 micron airborne particles when tested in accordance with ASHRAE Test Standard 52.2 used in testing air filters and air filter efficiency. Our air filters measured 97.8% air filter efficiency in removing airborne particles 3-10 microns in size, 84.1% air filter efficiency in removing airborne 1-3 microns in size and 60% air filter efficiency for smaller particles.
Our air conditioner furnace filters do not allow the growth of mold or bacteria, keeping your home healthier. No harsh chemicals are necessary to make the air conditioner furnace filter “antibacterial”. Our air conditioner furnace filters use permanently charged electrostatic material that helps dust cling to the air conditioner furnace filter. The following shows efficiency of air filters by media.
Where Are My Air Filters Located?
Air conditioner furnace filters in most homes are generally located behind an air intake grate in your home’s walls, ceiling, basement or attic. These generally look like large vents, but the air flows into them, rather than out of them when the heating or cooling system is blowing air. They may also be located in or near the air conditioner or furnace. Many homes may have more than one, and they may be different sizes.
If you can’t find your air conditioner system filter here are some places to look:
- At the central air return register, grille located in a wall or ceiling if your system uses centralized air returns instead of individual room-air return ducts. There may be several central return points, depending on the design of your system. If there are more than two, chances are the filter was placed at the air handler instead of at these grilles. Unfortunately that means that the return ducts themselves become more soiled with dust and debris from the building.
- At the air handler look for a slot which has a removable cover. The slot may be just an inch or so wide if 1″ thick filters are used, or it could be several inches wide if a wide high-capacity pleated or similar filter was used. The return air plenum on an attic or basement air conditioner blower unit will usually be a large metal enclosure about the same dimensions in width and height as the air conditioner blower unit itself. Look for a filter slot right where the return plenum contacts the blower fan assembly.
- At a basement air handler we also look for an air filter at the return air plenum which is often next to the bottom of the air handler if the system is an “up-flow” unit (or vice versa for the less common case of return air entering at the top of the air handler and exiting at its bottom).
- Next to an electrostatic air cleaner: if your air conditioning air handler has an electrostatic air cleaner installed, look for the air filter, if there is one, next to the electrostatic air cleaner. In addition, the electrostatic air cleaner, which is a type of particle incinerating filter itself, needs to be removed and cleaned periodically. Check with your unit’s manufacturer for cleaning interval and procedures. Often the electrostatic unit can be cleaned inside a dishwasher. Often there is also a thin metal washable air filter installed along with the electrostatic air cleaner.
We recommend you check your HVAC system’s manual for additional information.
*Make sure you find all of the filters as some systems have multiple filters and even multiple types of filters installed, such as a fiberglass or pleated paper filter, a washable filter, and an electrostatic air cleaner. These last two are cleaned, not replaced, when they’re dirty.
Change your air filters every month when the air conditioning system is in operation but make sure the system is turned off when you actually replace the air filters.
(Air Filter Accessibility: Air filters which are hard to access are rarely changed as often as necessary. I frequently see HVAC systems designed by someone who obviously has never had to service them.
Placement of filters and air handler access doors in very hard-to-access locations such as at the far end of a minuscule attic behind a forest of trusses means that the system is very unlikely to receive the periodic inspection and maintenance it needs. I prefer to see A/C and heating filters placed at the building side of the air return register or grille, so as to protect the return duct from debris accumulation.)
How Do I Know What Size Air Filter I Need?
Your air conditioner and furnace filters size is measured by the width x length x thickness in inches. For example, a pleated air filter that is 20x25x1 means 20 inches wide by 25 inches long by 1 inch thick. Most residential air conditioner furnace filters are 1” thick. The actual measurements of each air conditioner furnace filters are usually about half an inch less than the listed size. The actual size of our 20x25x1” air conditioner furnace filter is 19 ½ x 24 ½ x ¾”. This is normal. Most air conditioner furnace filters have the size printed on them, so you just have to find your existing air conditioner furnace filters. Sometimes homes have 2 or 3 different sizes of air conditioner furnace filters in various locations in your home. Again, consult your HVAC system’s operating manual for information. You can see which filter is the best by size for your system here.
Generally every 2 – 3 months, but you may want to change them more often. During periods where you are using your HVAC system continuously, we recommend changing monthly to maintain the best indoor air quality. The following chart should assist you:
|RECOMMENDED FILTER CHANGE INTERVALS|
“The most important maintenance task that will ensure the efficiency of your air conditioner is to routinely replace your air filters[…] air conditioner furnace filters may need more frequent attention if the air conditioner is in constant use, is subjected to dusty conditions, or you have fur-bearing pets in the house.” – United States Department of Energy
So make sure you have an Annual Furnace Maintenance plan in place!
How Do I Properly Install a Pleated Air Filter?
Look for the arrow showing airflow direction on the old air conditioner furnace filter and remember which way that it points. Make sure that you turn off your HVAC system to stop the airflow. Remove the old air conditioner furnace filter and discard it carefully so you don’t put the dust and other airborne contaminants back in the air. Write the date you install the air conditioner furnace filters on the place indicated on the side of the air filter frame. We strongly suggest you take the time to check your air filter from time to time to make sure it is not clogged. Remember, the pollutants you see on a dirty filter could be airborne particles you breathe – Change your air filters regularly and use our FREE Better Air Reminder Service to help you! Simply go to our Better Air Reminder Service page on this site to get started or place your order and you will be automatically enrolled.
Look for the arrow showing airflow direction, and install the new pleated air filter so the air flows in the direction of the arrows. Many air conditioner furnace filters are located at air return vents, where the air flows into the wall or ceiling. Note: On some custom size air conditioner furnace filters, the arrow may not be visible. If so, the air flows from the side without the metal mesh to the side with the metal mesh.
Do Air Filters Kill germs, Reduce Dust and Eliminate Odors?
Most air filters do not kill germs, however, the material many air filters are made out of does not permit the growth of bacteria or mold. As a result, it is not necessary to add any potentially irritating chemicals to the air filter to kill germs. Odors are most often a combination of gas and particulate. Air Filters do not remove the gases but can remove the particulate. Particulate produced from tobacco smoke or a burning fireplace as the airborne particulates are filtered through the MERV12 rated, high-efficiency air filter.
Most air conditioner furnace filters can reduce many common airborne allergens far more effectively than ordinary air filters: Up to 97.8% reduction for pollen and other major allergens and irritants flowing through the air filter.
Better filtration is important to improving indoor air quality that can lead to better health. Dust, pollen, mold spores, animal dander, lint, bacteria, and dust mites and dust mite feces are some of the airborne pollutants we inhale in our indoor air without proper filtration.
I Live in an Apartment/Condo: Can I Use other Air Filters?
Virtually all apartments provide air filters for their tenants. Normally, cost is the primary consideration given to air filters for HVAC systems. As a consequence, you are not likely going to get the best air filtration possible. We recommend you contact the Property Manager and explain your desire to obtain a higher-quality filter in your HVAC system. If they are unable or unwilling to supply the quality of air filter you desire, ask and obtain permission to supply your own before ordering our air filters. Once you receive approval, then place your order.
If you are in a condo, you actually own the HVAC system and it’s components, Anything you can do to extend the life of your HVAC system is in your best interests. If a maintenance person installs your air filters for you, we suggest you notify them of the location of your replacement air filters and make them accessible.
How Can I Eliminate Dust?
Dust is actually a combination of dirt, pollen, hair, dead skin, pet dander, dust mites, dust mite feces and a myriad of microbiological pollutants. Though there is no way to completely eliminate dust, you can control the dust with adequate filtering of the air through your HVAC filter. Choosing the right filter medium like our pleated electrostatic filter media enables maximum filtration without taxing your HVAC system. Our Merv12 air conditioner furnace filters remove up to 97.8% of pollen, pet dander, dust, mold spores, dust mites, tobacco smoke and other airborne particles, therefore helping to reduce the amount of dust while providing a more healthy indoor environment.
What About Aluminum Washable Air Filters?
Though we touched on the subject at the beginning of the FAQ’s, you will find this is no longer a popular option as the handling of messy, used filters combined with the cleaning process turns off most people. Reusable filters must be cleaned and maintained as much as 2-3 times more frequently than disposable pleated air filters. Pay special attention to the removal of all moisture before reinserting the reusable air filter back into the HVAC system. Presence of moisture can produce mold and attract bacteria.
Will Air Filters Cause Air Flow Problems Through My HVAC System?
Our Merv 12 filters have a low air flow resistance for residential and commercial heating and cooling systems. Air flow is generally measured as a difference in air pressure on each side of the filter, measured by an instrument that uses water in a measured column to show air pressure. The higher the pressure difference, the more the water in the instrument moves. Its movement is measured in inches. The more inches of water moved, the more the pressure difference. This is called air flow resistance.
The more efficient an air filter is, the more it tends to resist air flow. However, MERV 12 air conditioner furnace filters provide only a few fractions of an inch more resistance than ordinary air conditioner furnace filters that are much less efficient at removing particles from the air. Our MERV 12 – 1″ air conditioner furnace filters have a low resistance of only 0.26″ at 300 feet per minute of airflow, which works fine with virtually all systems.
How Are Pleated Merv 12 Air Filters Better Than Fiberglass Air Filters?
Fiberglass air conditioner furnace filters are designed only to capture large particles and to protect your heating and air conditioning system; they do nothing to remove smaller particles like many allergens. These types of air conditioner furnace filters also have either no Merv rating assigned to them or in some instances, have a MERV rating of from 1 to 4. Our MERV anti-allergenic furnace filters not only protect your HVAC system from dust, and other airborne particles, These MERV 12 furnace filters remove up to 97.8% of the pollen, pet dander, dust mites, mold spores, tobacco smoke and other airborne particles in the indoor air. Since the average person spends 2-3 times more time indoors than outdoors, it is the healthier choice.
Should I Put More Than One Air Filter in My HVAC System?
You should not use more than one filter in any one place in the HVAC system due the air flow restriction it imposes on the HVAC system. Consult your service manual regarding specifications for your particular furnace or air conditioning system.
What Are Electrostatic Air Filters?
All of our MERV 12 air filters using a filter media that contains a permanent electrostatic charge causing dust to cling to the air conditioner furnace filter using the same principle as static electricity. As a consequence, our air filters are far more effective and efficient than traditional pleated filters. We do not endorse or sell the permanent metal electrostatic filters.
Do I Need An Air Purifier?
As effective as our air filters are in controlling airborne particulates throughout the home, it is simply impossible to rid your indoor air of all the potentially harmful particulate that could be present in your indoor air. As a result, we strongly suggest the addition to various areas of your home where odors or allergens are most likely to accumulate. For example, small portable air purifiers placed in strategic areas like laundry rooms, pet rooms, bathrooms are all excellent places to locate an air purifier. Air Purifiers help neutralize odors and provide additional filtration.
Why is air quality important?
According to the American Lung Association, in 1999, 85% of Americans did not realize the air in their homes might be a health hazard. However, more people are becoming increasingly aware of the importance of the quality of air that we breathe indoors. We take for granted the cleanliness of our indoor air. The average person spends 90% of their time indoors, may it be at a store, bank, school, etc. therefore making it vital to our health that we are informed on improving our indoor air quality.
Asthma, allergies, and other respiratory problems are affecting millions of people, and are on the rise. It is no wonder that researchers are studying the effects of indoor air quality on these ailments. In a 1996 survey, it showed that in 58% of homes at least one humidity-related or respiratory problem was present in the form of allergies, asthma, persistent coughs, and/or nasal congestion.
In 36% of the homes, at least one household member suffered from at least one respiratory ailment.
The increased awareness for a better indoor air quality has prompted changes in building codes, and development of products to maximize a healthier indoor air quality. Removing and/or containing the harmful particles and odors protect the home and provide a higher quality air for the entire family. Taking control of the quality of health environment in which you live and work in is the first step in improving your life. Finally, you can “breathe pure”, it is definitely worth every breath.
Filter Size: The size of a filter is listed by it’s length, height and thickness. For example, a common filter size would be listed as 20x20x1. 20 inches wide by 20 inches high and 1 inch thick.