Change your home air filter regularly to extend HVAC system life, reduce energy bills, and improve indoor air quality.

Air conditionerWhen was the last time you changed out the air filter in your home? Are you thinking, “Wait. What air filter?” Don’t worry! You’re not alone.

Clean air filters save energy and money. Routinely changing or cleaning the filters from your home’s heating and air conditioning system helps the units run more efficiently and enjoy a longer lifespan. But what’s the actual purpose of these filters? How do you know if they’re working? When should you change them? What should you do if they look clean when it’s time to replace them?

“I would estimate that in three-quarters of the homes I inspect, the air filter is dirty with build-up and well beyond its useful life,” says Texas-based home inspector, Micah Stephens, of SafeShield Inspections, LLC. “If you know where your air filter is located and how often to change it out, it takes less than five minutes to replace it. Ultimately, it will make a difference in energy efficiency, system lifespan, and air quality in the home.”

Here is a look into the basics of what air filters do, the types of air filters, and how often they should be changed depending on your unique household situation.

What do air filters do?

To change the temperature in your home, your heating and air-conditioning system sucks in air from a room. The air travels over coils to heat or chill it. The tempered air is then blown through ducts to the other rooms in your home.

man changing out a home air filterThe air filter is positioned at the point where air is pulled into the system. As the air is sucked in, the filter traps air-born particles and keeps them from blocking the blower and building up on the coils. Consequently, clogged coils can’t heat or cool the air passing over them. They could damage the system. The air filter helps your heating and cooling system do its job, keeps it running efficiently and protects it so it will last longer.

Heather Kolich writes in an article for How Stuff Works, “Filters also help to keep dust from building up in your ducts, or being blown into other rooms of your house. In recent years, this air cleaning function has become more important to homeowners, and manufacturers have designed filters that use your heating and air system to remove microscopic particles like dust, pollen, pet dander, bacteria, plant and mold spores, and even smoke from the air in your home.”

Are all air filters the same, or are there different types of filters? Is there a rating system?

Pleated air filterAir filters are rated based on their MERV (minimum efficiency reporting value) number. The MERV value ranges from 1 to 20. Air filters are tested six times by organizations and manufacturers to determine their MERV rating. Filters that capture large dust particles rate a MERV score of 1 to 4. The higher the rating, the smaller the particles that are captured. Filters with a MERV 8 to 12 rating are most often recommended for residential use. Accordingly, MERV 13 to 16 rated filters are commonly used for commercial or industrial HVAC systems.

In addition to the MERV rating system for air filters, the filters can be made with different materials and in a variety of styles.

Five of the most common types of filters include:
  • Flat Panel Fiberglass Filters: Most commonly used in residential air returns. MERV rating of 4. Monthly replacement. Low maintenance. Disposable.
  • Pleated Filters: Most popular air filter type. Can be used with any type HVAC system. MERV rating 5-13. Disposable.
  • Media Filters: Used in many newer homes. MERV rating 10-13. Bulkier than flat panel or pleated filters. Only for use with designated models of air cleaners. 6-12 month lifespan.
  • HEPA Filters: Commercial/industrial and medical facility use. Fiberglass. Highest MERV rating. Must be replaced often.
  • Washable/Reusable Filters: Newer air filter type. Gaining popularity. Green option. Permanent; must be washed every 2-3 months. Lasts about 5 years.

Media air filter

Media Filter

Air returns are typically built in standard sizes, but they are not all the same size. You will need to measure your filter before purchasing your replacement. Replacing a filter with a smaller size filter is not recommended because unfiltered air will flow around the filter and cause dust, allergens, and debris to collect on the coil. On the other hand, a filter that is too large will not fit or do its job properly either.

How often should air filters be changed out?

How often you change out your home air filters depend on a number of factors, including:
  • Type of filter
  • Overall indoor air quality
  • Number of pets in the home
  • Number of people in the home
  • Amount of exterior air pollution and/or construction around the home
Pets can affect indoor air qualityHere are some very generic averages that might help you know how often you should change the air filter at home (assuming a basic fiberglass or pleated filter):
  • Vacation home (i.e. home not used regularly) and no pets or allergies: every 6-12 months
  • “Average” suburban home without pets: every 90 days
  • Add a dog or cat: every 60 days
  • For a home within the city or near a construction zone: 45-60 days
  • Add more than one pet or anyone that has allergies: 20-45 days

Where are my air filters located?

Your air filter is most likely located right next to your furnace or air conditioning system air handler. The air handler is the large box containing the fan and fan motor. The air filter is typically located at the point where the return duct enters the air handler. Look for a 1″ wide hinged or removable cover. The air filter will be inside.

Increasingly, air handlers are being installed in attics. This sometimes limited space will require installation of the air filter in the return. The filter is accessed by removing the grate covering the return duct. You may find more than one return in your house with an air filter installed in each return.

Some larger houses have more than one HVAC system. Subsequently, each system will typically have at least one air filter. Therefore, your house may have air filters located at the air handler AND in the returns. You should check each possible location to make sure you have located all of your air filters.

What if the “old” filter looks clean when I start to replace it?

When it’s time to change your filter — anywhere from 20 days to 6 months after you installed a fresh one — it should look dirty. If your filter looks clean after it’s been in place for the recommended time, How Stuff Works recommends you check the following areas:

  1. Does the filter fit properly into the holder? If the filter is loose or too small for the space, the air can circulate around it instead of going through it. Measure the filter space and purchase a filter that fits snugly.
  2. Is the filter installed upside down? There is a correct air-flow direction for most air filters. Look for arrows on the filter frame, and install the filter so that the arrows point toward the fan.
  3. Is the filter you’re using right for the job you want it to do? If you’re using a low-end filter, it’s not going to catch much dust. Upgrade to a filter with a higher MERV rating to increase the air cleaning efficiency.
  4. Check your rate of air exchange. According to Williams, if your system is functioning properly, it should run for about 15 minutes per cycle, with a cycle rate of not more than three in an hour. If it runs shorter cycles, it isn’t creating the desired rate of air exchange. Call a professional and get your system checked.

If your home is well sealed, you have no pets, no dust-prone furnishings like carpet and fabric-covered furniture, and you dust and vacuum every day, your air filters will have fewer air-born particles to collect. Also, the system only filters the air when it’s running. If you install a new filter, but don’t turn on the heat or air conditioning until a month or two later, the filter should still be relatively clean since the system hasn’t been forcing air through it.

What are the benefits of regularly replacing the air filter?

Healthy family outsideDuring the times of year when your HVAC system is getting the most use, it is just good practice to regularly swap out a dirty air filter for a new, clean one. Why?

  • Extend the life of your HVAC system.
  • Help you maintain healthy air quality within your home.
  • Help keep your energy costs down.
  • Keep your HVAC system clean, minimizing the need for unexpected repairs.


Annual Home Maintenance Schedule and Inspection

In addition to changing your filter every month, it’s important stay on a regular home maintenance schedule for all areas of your home.

Even the most vigilant homeowner can, from time to time, miss small problems or forget about performing some routine home repairs and seasonal maintenance. That’s why an Annual Home Maintenance Inspection will keep you aware of your home’s condition and help you prevent it from suffering serious, long-term, and expensive damage from minor issues that should be addressed now.

Just as you regularly maintain your vehicle, consider getting an Annual Home Maintenance Inspection as part of the cost of upkeep for your most valuable investment…your home.

Your future deserves the attention of a professional. If you have questions or would like more information on a Home Maintenance Inspection, please contact Micah Stephens with SafeShield Inspections, LLC at (832) 953-6992 or email Micah@SafeShieldInspections.comCLICK HERE for a free quote.

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Alli Stephens is a marketing and communications professional who works to ensure the highest level of service for clients. Alli believes that a wise customer is an informed customer, and she knows that a home inspection provides clients with important details about the current condition of a home.