Everyone agrees that you should change your HVAC filter on a regular basis, but not everyone agrees on the type of filter you should use. Next time you go shopping for a furnace (or AC) filter, here are a few things to keep in mind. These tips can save you a bundle and perhaps even prevent you from inadvertently damaging your HVAC equipment.
I’ve learned the hard way that picking the right filter isn’t just about grabbing the cheapest one off the shelf. A little know-how can go a long way in keeping your system running smoothly and your wallet happy. For instance, understanding the balance between filtration efficiency and airflow is critical. According to studies from the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), improper filter selection can reduce HVAC system efficiency by up to 15%, leading to higher energy costs. I once installed a high-efficiency filter without checking my system’s specs, and my energy bill spiked because the system was working overtime. To avoid this, check your furnace or AC manual for recommended filter types, and if in doubt, consult a technician to ensure compatibility. This small step can prevent costly repairs and keep your system humming along efficiently.
The True Purpose of HVAC Filters
The primary purpose of a filter is to protect HVAC equipment, not to improve indoor air quality, as many homeowners have been led to believe. Many furnace manufacturers recommend that you use a low-cost fiberglass filter, but when I asked a representative of one major maker, his response was “no comment.”
Perhaps this was because high-efficiency filters that are too good may actually slow airflow across the heat exchanger, reducing the unit’s efficiency, raising your energy bills, and causing furnace damage due to overheating. Similarly, a high-efficiency filter can freeze the condensing coils on an AC unit. (A dirty filter can do the same thing.)
It’s surprising how many people think HVAC filters are all about cleaner air, but I’ve seen firsthand how that’s not the full story. The science backs this up: filters are designed to trap larger particles like dust and debris that can clog your system’s components. ASHRAE notes that filters with a MERV (Minimum Efficiency Reporting Value) rating of 1-4, like basic fiberglass ones, are often sufficient for equipment protection. Going for a MERV 13 or higher might sound great for air quality, but it can strain older systems not designed for such dense filters. My neighbor learned this the hard way when his AC unit froze up mid-summer due to a high-MERV filter. A practical tip? If you want better air quality, consider a separate air purifier for high-traffic areas rather than relying solely on your HVAC filter. It’s a smarter way to tackle allergens without risking your system.
Limits of Filters for Air Quality
Even more of a shocker is that furnace filters do relatively little to reduce the number of small particles you inhale. That’s because these particles tend to be in the air wherever there is human activity—and that’s not necessarily where your return registers and ductwork can capture them, according to research by the Canada Housing and Mortgage Corporation (CHMC).
In addition, furnaces (and central ACs) run only seasonally. Even during the heating and cooling seasons, furnaces run only part of the time. So it stands to reason they are not filtering the air when the fan is not running.
This was a real eye-opener for me when I first dug into it. I used to think my furnace filter was catching everything, but the CHMC research makes it clear that tiny particles from cooking, pets, or even just moving around don’t always make it to the filter. In fact, a 2020 study from the Environmental Protection Agency (EPA) found that HVAC systems only capture about 20-30% of fine particulate matter (PM2.5) in homes during typical operation. If you’re worried about air quality, running the fan continuously can help, but that bumps up your energy bill. I’ve found that opening windows on mild days and using a portable HEPA purifier in my living room makes a noticeable difference in air freshness without over-relying on the HVAC system. It’s a simple tweak that’s worked wonders in my home.
The Case for Washable Electrostatic Filters
Washable electrostatic filters are available in several standard sizes, as well as kits. Want to save money and stop wasting time trying to figure out conflicting furnace filter maker ratings systems? Make your next filter a permanent electrostatic filter (also known as a washable one). The kit I tried is available online and can be cut to fit most filter cabinets. Washable filters may be reused for 5 to 10 years and cost about $20 each. These filters should be rinsed once a month and prior to re-installation, they should be allowed to dry. Some permanent electrostatic filters include carbon filtration for odor removal.
Keep in mind that electrostatic filters are most effective when new and clean, so they should be washed frequently. Pre-made sizes are limited, but some manufacturers, such as WebProducts, will fabricate filters to your specs for about $35 each.
I switched to a washable electrostatic filter a couple of years ago, and it’s been a game-changer. Not only do I save about $50 a year compared to buying disposable filters every few months, but I also love that it’s a greener option. According to the EPA, Americans throw out millions of disposable HVAC filters annually, adding to landfill waste. Cleaning the filter is a breeze—just rinse it under water and let it dry overnight. One pro tip: set a monthly calendar reminder to wash it, because a dirty electrostatic filter can lose its edge fast. If your system has an odd-sized filter slot, don’t sweat it; custom options like those from WebProducts are a lifesaver. Just measure carefully to avoid gaps, as I learned after a slightly off-cut filter let some dust sneak through. This small investment upfront can save you money and hassle in the long run.