An In-Depth Look at Furnace Filter Maintenance

January 5, 2021

Save Home Heat - January 2021 Blog Post 1While comprehensive annual furnace maintenance is usually taken care of by an experienced, professional HVAC service technician, there is one important aspect of ongoing furnace upkeep during the season that many homeowners take care of themselves: replacing (or cleaning) the furnace filter. Ensuring that the furnace filter is properly maintained throughout the year affords numerous, clear benefits for you, your wallet, your home, and your furnace. Selecting the right filter for your needs is important, too. Let’s take a closer look at year-round furnace filter maintenance and related factors that our team feels all homeowners who have forced air heating (and AC) systems should keep in mind.

Why is a Clean Filter Important?

You may know that your furnace has an air filter, and you might already know what can happen if you don’t replace it (or clean it, if you have a permanent filter) frequently enough. Dust and other airborne particulates will eventually clog the filter, impeding its ability to properly filter your air. Dust will be discharged back into the ducting system and your breathing air, as well around the furnace fan and motor. Airflow will become restricted, comfort levels will drop, and heating bills will go up. A dirty filter will force your furnace to work harder, increasing the chance of equipment failure.

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Lennox Filter graphicLooking at this from the other side of the coin, a clean, effective furnace filter provides many benefits. A clean filter will do the best job of providing cleaner, healthier air, reducing airborne and surface dust. Depending on the type of filter, it can help reduce a variety of other indoor air pollutants. A clean furnace filter will allow for optimal airflow to the ducting and throughout your home, assuring the lowest operating costs and best heat delivery possible to all rooms. It also helps extend the lifespan of your furnace by minimizing the thermal stress placed on your furnace’s heat exchanger. A cracked heat exchanger is one of the most common reasons why a furnace needs to be replaced. Your furnace fan and blower motor also benefit, along with other components such as high limit switches, fan controls, igniters, and ignition controls, among others.

Key benefits of a properly maintained, good quality furnace filter:
  • Cleaner, healthier air
  • Lowest operating costs
  • Optimal airflow
  • Greatest comfort levels
  • Helps extend furnace lifespan
  • Helps reduce breakdowns
  • Protection for indoor cooling coil (if system has central AC)
Special Note for Homes with Central AC

Year-round filter maintenance is doubly important for homes that have central air conditioning. Your filter is crucial in protecting the indoor evaporator coil (aka. A-coil, or cooling coil) that’s typically located in the output ducting adjacent to the furnace. An A-coil can be thought of as similar to a triangular shaped car radiator, with lots of aluminum fins that are a magnet for airborne dust. If an evaporator coil gets heavily loaded or plugged with dust this can have a number of negative effects, including reduced airflow and comfort levels; higher utility bills to cool your home; increased stress on the system causing increased likelihood of parts failures; imbalance of refrigerant pressures, potentially causing a ‘freeze-up’ (think block of ice) of the cooling coil, which will shut the system down and often generate a service call. A properly installed, good quality, properly maintained furnace filter will provide proper protection for the cooling coil and keep your heating and AC system running smoothly, reliably, and efficiently.

When Is It Time to Replace The Filter?

One of the most common questions we hear from our furnace customers is, “When should I replace the filter?” The answer depends on many different factors, foremost among these how often the furnace is operated, how many people live there, cleaning habits, lifestyles of the occupants – are there smokers, a studio, or workshop? – allergy issues, and potential pollutants from outdoor air. Equally important, are there pets, and do they shed a lot? In addition, what type of furnace filter do you have? High performance 5” thick media filters, for example, don’t require replacement as frequently as standard 1” filters.

Dirty Furnace Filter - Save Home HeatAn accepted practice for determining if a standard 1” thick air filter in a forced air system needs to be replaced is based on comparing (with the system turned off!) a new, identical filter with the existing one, holding both up to a bright light to see if the existing one lets much less light through. A bit imprecise, of course, but when in doubt, replace the filter. A monthly check during times that the furnace blower is being used regularly (heating and AC season) may be overkill in some cases, but it’s a good way to start out.

In the Denver-Boulder area, you can trust our home comfort team at Save Home Heat Company to help you determine the right filter maintenance schedule for your home’s furnace. One good way to get started is to consult with your service technician when we come out to perform annual maintenance on your central heating and AC systems. Once we’re more familiar with you, your home, and your system, we’ll be able to offer expert advice on determining how often the furnace filter should be replaced – or cleaned, if your furnace has a permanent filter. As suggested above, in many cases we recommend initially checking the filter each month that the heating or cooling system is being operated. This cleaning check is typically performed by the homeowner, but not always. After a full year, having gained more information, we can discuss and advise you further on how to proceed in your unique situation.

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Is Your Furnace Filter Snug and Sized Right?

It’s equally important to make sure that the filter is installed so that no air can bypass it on its way back into the furnace. Air that bypasses the filter, and any dust it’s carrying, will get right back into your breathing air, not to mention into the innards of your furnace. Our service techs at Save Home Heat always make sure that the filter is the correct size to cover the entire return-air cutout in the side of the furnace, and that the filter track is setup properly – so that ALL of the air that circulates back into your furnace is filtered, not just some of it. The filter must fit snugly, but not so tight that is can’t be replaced without damaging it. We also make sure that the filter access door, typically made of sheet metal and located in the ducting right next to the furnace, is labeled, easy to spot, and user-friendly, so this important, regular task can be performed without stress.

Air Filters Available

Choosing a Filter

In addition to determining the appropriate filter replacement schedule for your home and furnace, selecting the right filter for your needs is important. There are plenty of options when it comes to picking a furnace filter, including a variety of 1” thick disposable filters, and high performance options such as media filters, electronic air cleaners, and more. When considering an upgrade, you should consider the level of performance you want from your filter, as well as factors such as routine maintenance requirements, and upfront and annual costs. Take the time learn about what makes sense to consider for your home, and ask lots of questions before you make a purchasing decision.

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MERV Ratings

When selecting a furnace filter, you’ll likely encounter ‘MERV’ ratings, short for Minimum Efficiency Reporting Values, for different filters that you’re comparing. Simply put, these ratings let you know how effective the product is at filtering a common range of particle sizes in the air; specifically, particles between .3 and 10 microns in size. The higher the MERV rating, the better job the filter will do catching dust and other airborne particles in that range. For example, a MERV6 filter is effective capturing dust, lint, and pollen, whereas a MERV8 filter will capture these particles, along with mold and dust mites. As the number goes up, so does effectiveness and the ability to filter a wider range of indoor air pollutants. MERV11 filters can also capture smoke, pet dander, and other undesirable airborne particles. MERV16 filters do all of the above, and add some common bacteria and viruses to the list.

Merv-16 filter - Save Home HeatIt’s important to note that choosing the highest MERV-rated filter isn’t always the best option. In homes where the ducting system is less than ideal, we sometimes conclude that the additional friction and resistance to airflow that the highest rated filters add may be undesirable for achieving optimal comfort and efficiency. For instance, there are cases where a MERV11 filter might be a better fit than a MERV16. So the choice of which filter to go with isn’t always clear cut until you consider all factors. This underscores the importance of obtaining professional advice and recommendations for the furnace filter that makes the most sense for your home and needs.

High Performance Media Filters: A Great Combination Of Benefits

Whenever we feel that it makes sense, our comfort team recommends upgrading to a high performance, high efficiency media furnace filter, which are also referred to as media air cleaners. These products do not use electricity or create any ozone, and feature an easily replaceable filter cartridge. Currently, our team installs a variety of media filters rated between MERV11 and MERV16, one of which also incorporates activated charcoal for assistance in odor control. In addition to greatly improved air filtration, these high efficiency filters also provide the benefit of needing replacement much less often than 1” filters. In many cases replacement is needed only once or twice a year, even with central AC.

The Ultimate IAQ Machine

It’s a given that most of our homes along the Colorado Front Range get a bit dry and dusty indoors during the heating season. It’s the nature of our regional climate. There’s no question that the right choice of furnace filter, professionally installed and properly maintained, will help improve your indoor air quality and as a result, help protect your health. Two other products that can assist further in improving your IAQ, working in concert with your furnace filter, are central humidifiers and central air purifiers. Kill a wide range of airborne and surface bacteria, germs, and viruses. Reduce static shock and dry sinuses, and protect valuable wood products. Please ask our team for more information on ways you can turn your furnace into the ultimate indoor air quality machine!

Denver-Boulder’s Furnace Filter Experts

Save Home Heat Company has been serving the Denver-Boulder metropolitan area with quality home comfort services for over forty years. We have extensive expertise helping our customers select proven furnace filters and IAQ products that best match their unique needs. Whether it’s a simple question about when to replace your filter, a desire to schedule annual maintenance and learn more, or to obtain a free, low-pressure quote for a new air cleaner installation, you can count on our team for friendly, professional advice and recommendations that always have your best interests in mind.

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