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A Comprehensive Guide to Air Filters:


Choosing, Measuring & Replacing Your Filters



What Do Air Filters Do?

Air filters are an essential part to your home’s forced air system. Most home have at least two filters that stand guard over your home’s air. Their job? Removing bacteria and harmful particles that may be pumped through the air.
Virtually all of the air in your home passes through these filters, typically at a rate of two times per hour. People living in homes with updated air filters tend to be healthier and avoid health problems that may arise from unclean air. A quality filter captures the harmful bacteria typically found in sneezes, coughs, viruses and molds, as well as pollutants like dust and car fumes.
Clean filters also keep your HVAC system running efficiently all throughout the year. They can even greatly reduce the cost of your monthly energy bills! About half of your monthly energy bill can be traced back to your HVAC system, and keeping clean air filters is the single best way to ensure they are always working to the best of their ability. Clogged filters can make your HVAC system work extra hard, which greatly raises the cost of your monthly energy bill. If you have no filters at all, the coils will clog and your HVAC system will be in even worse condition.

How Often Should I Change a Filter?

Most air system experts advise users to change out their filters at least every 3 months, but changing them every 1 to 2 months may be recommended depending on the air quality around you. Filters should be changed more frequently especially if you have a particularly busy lifestyle, you or someone in your family is prone to allergies, or if you have pets in your home.


How Do I Change a Filter?

Air filters are extremely easy to replace and can be found inside the return vents in your home. These vents are usually located in the ceiling, wall, or in the actual HVAC system itself. Most regularly sized homes contain two or three return vents, or alternately, two 5-inch filters that go within the HVAC system itself. Return vents are typically more accessible than HVAC systems, which makes replacement a much easier and faster process.

How Do I Size a Filter?

Many people who are looking to change out their old filters struggle with deciding which size to buy. The easiest way to find the size of a furnace or air filter is to look for the size that is printed on the filter currently in use. The sizes on the filters are typically located on the outside edges and are written in nominal dimensions. Nominal dimensions are the rounded actual dimensions of the filter and they can give you more leeway in fitting them into the vent itself. Can’t find the nominal dimensions on the filter? No problem: simply measure the filter’s width, depth, and length yourself using a tape measure or ruler. After recording the size, round each dimension up to the nearest inch (i.e. 14.67” = 15”). The rounded up measurements will now serve as your nominal dimensions. Don’t worry about your filter being too large, almost all filters are undercut slightly.

How Do I Choose a Filter?

After removing your used air filter and recording its size you are ready to purchase a new one. This is where many home and apartment owners encounter trouble, as it can be difficult to decide which features to look for in a filter and choose on that fits your budget.
Here are two things to consider:
  • Which type of filter best suits you
  • Which MERV (Minimum Efficiency Reporting Value) works best for your lifestyle
There are a four different types of air filters you can choose from. It’s also important to note that each type of air filter has different capabilities and therefore, identifying which of the four best suits you and your home environment is crucial. Below is a list of the three different filters and their benefits:


1. Fiberglass Filters: These filters are the most cost-efficient of the four, which also makes them the most popular choice. These are throwaway filters that feature a multi-layered fiberglass composition and are reinforced with a metal grating that supports the media to prevent disintegration and failure.

2. Polyester and Pleated Filters: These filters are very similar to fiberglass filters, but are noted to have a higher resistance to airflow and a superior dust-stopping ability. These filters are especially useful if you or someone in your family is prone to allergies or you have more than one pet.

3. Washable Filters: These filters are extremely convenient for people who don’t wish to regularly purchase new filters. However, these products are not as common nor are they as popular as the other models because they rely on the build-up of dust along the cloth to improve the efficiency of the filter. Industrial processes involving high volumes of coarse dust are typical applications for washable filters.

4. High Efficiency Particulate Arrestance (HEPA) Filters: These filters are the most resistant of the three and consequentially tend to be the most expensive. The price doesn’t go without merit, however, seeing as HEPA’s are able to filter air at a very fine scale. HEPA filters meet a variety of The US Department of Energy’s building codes and requirements and are typically used in high trafficked venues like offices, retailers, or public entertainment spots.

After deciding which filter type best suits your individual needs, consider which Minimum Efficiency Reporting Value (MERV) you are most comfortable with. In its broadest definition, MERV simply refers to a measurement scale designed in 1987 by the American Society of Heating, Refrigeration and Air Conditioning Engineers to rate the effectiveness of air filters. Not only is this scale extremely helpful in determining which filters successfully produce cleaner air, but it also allows for improved health, reduced cost on monthly bills and energy efficiency in heating, ventilations, and air conditioning in HVAC design. Below is a handy chart that explains which ratings remove what from the air and will help you decide which filter to choose:


Now that you have gained all the information you need to buy an air filter, you can begin on the installation process. Before replacing the filter completely, be sure to carefully clean the filter frame and surrounding areas with a cloth or small vacuum. Installation of the filter could not be easier; simply place in your new filter by observing the direction of arrows printed on the filter and the air filter frame. After completing this, you can close the vent and enjoy fresh, breathable air for up to 3 months before replacing the filter once again. Feel free to contact us online or through phone at 855-568-9300 to speak to one of our air filter experts!