Heating: Dirty Details of ‘High Efficiency’ Disposable Furnace Filters

August 11, 2015

Properly maintaining your heating and cooling systems is of course important to help extend the lifespan of your equipment and ensure safe operation. In addition, it is important to help save you money. Replacing your furnace filter regularly is a great way to let air flow freely through your HVAC equipment, and dirty, old, clogged filters can cause a lot of wasted energy and added operating expense.

We all agree that a good furnace filter is important. However, there is one type of filter in particular that you need to be wary of: higher end disposable furnace filters, marketed as ‘high efficiency, anti-allergen’ filters. While the denser, tighter-woven material in these products does make it harder for smaller particles and allergens to re-circulate throughout your home, these furnace filters have some potentially serious drawbacks.

Decreasing the Life of Your Blower Motor

One of the largest drawbacks to these expensive filters is that they make it harder for air to pass through your heating and cooling systems. When they are clean, the difference is negligible. However, as the tightly woven fibers filter the air, the gaps become even smaller and they make your blower work harder and consequently could decrease its useful life.

Furthermore, these types of filters become dirty much faster than regular filters. Though that may sound like a good thing at first—they are allowing less debris to circulate back into your home—it also means that you’ll need to change your filters more often – something many people forget to do. Once these filters become dirty and clogged, they make your blower work that much harder. Over the years, we’ve seen many cases of burned out blower motors caused by too much stress on a blower motor.

In fact, by significantly reducing the airflow thru your furnace, these expensive disposable filters can even cause failure of parts such as high-temperature safety switches or the heart of the furnace, the heat exchanger. Furnaces use high limit sensors to shut down the furnace in the event that the heat exchanger overheats. And what do you think the number one cause of these sensors going off is? Insufficient airflow across the heat exchanger.

Overuse of these switches can cause premature failure of this important safety device. In a worse case scenario, consistent, excessive overheating of a furnace’s heat exchanger can cause the metal in the exchanger to fail prematurely, resulting in cracks, holes, or the failure of a welded seam—a potentially unsafe and very expensive proposition!

Basically, unless very closely and consistently inspected, and replaced regularly throughout the heating and air conditioning seasons, these expensive ‘high efficiency’ disposable furnace filters are much more likely to create furnace service issues than a standard, reliable, 1” cardboard frame pleated filter. The discussion of how these more restrictive filters can negatively impact airflow through your home is yet another related issue.

Negative Effects on Air Conditioners

These filters can potentially be just as harmful for your central air conditioner. If a filter should restrict airflow through the furnace compartment too much, it can create a condition that causes the cooling system’s indoor evaporator coil—or ‘A-coil’—located in the ducting on the output side of the furnace, to ice-over, blocking all airflow through the furnace and to the house. The AC system would then need to be turned off for a period of time, allowing the evaporator coil to thaw out, often making a wet mess on the mechanical room floor while you you or your service company try to figure out what happened.

Unfortunately, a frozen evaporator coil can be caused by other factors as well. If it turns out to have been caused by a plugged furnace filter and you’re able to negotiate the issue without having us come out, it’s been a good day and more power to you! In worse case scenarios, we have seen heavily neglected, plugged furnace filters cause failure of the compressor, which is the heart and most expensive component in your AC system.

When is it Right to Use a ‘High Efficiency’ Disposable Filter?

Remember, these filters don’t increase the ability of your heating and cooling system to blow air throughout your household. They simply do a better job of catching dust, which is a good thing as long as the filter doesn’t create collateral issues along the way.

It would be a good idea to simply avoid these types of disposable filters if you own a central AC system, especially in multi-level homes; it’s just asking for trouble with little extra return on the risk. A ranch style home that employs an entirely separate cooling system (ductless AC, evaporative cooler, etc.) is often the type of home that is least likely to experience issues with these high-end disposable filters, but that is not an iron-clad rule of thumb because not all ranch style homes (and their families) are the same!

Finding Help

The safest thing to do when considering an upgrade of your existing furnace filter is to consult one of our technicians or estimators to learn more about the many options available. Take the time to determine what makes the most sense for you, your family, and your home. Sometimes, we can assist you fully over the phone, and in other cases it makes more sense for one of us come out and take a closer look. Today, your options of high quality furnace filters and central air purifiers are broader than ever and it’s well worth the time to educated yourself fully before making a decision!