Air filters are a central, but often under-appreciated part of a central HVAC system. They don’t just filter out bits of pollen and dust that would otherwise circulate through the home and lower indoor air quality. They also provide a first line of defense against larger objects such as bits of loose insulation being pulled into the system where they could cause damage or present a fire risk. But if you don’t change your air filter regularly, it can turn against you. Clogged air filters are the number one cause of HVAC system failure.All the air handled by the HVAC system passes through the air filter at one point or another. As the filter catches more and more of the natural particulate pollution of your home – dust, mold and fungal spores, pet dander, fabric fibers, etc. – the fine mesh through which air passes becomes denser. This means that if you don’t change your air filter regularly, air can’t pass through as readily.
Effects of a Dirty Air Filter
The blower fan in the HVAC system has to work harder to push air. When it’s working harder, it’s drawing more energy, leading to higher bills. It’s also more likely to wear out from the strain.
The difficulty in moving air means that your living areas may not get all the air they need. This means poor home comfort for you, and the temperature sensors which regulate when the HVAC system turns on and off might not ever register the temperature needed to signal the system to power down. That’s another source of expense, which puts more strain on the fan motor.
Because the heated or cooled air can’t travel out of the furnace, heat pump, or air conditioner as easily, the system runs the risk of overheating or freezing up. You’ll be paying the same amount of energy or using the same amount of gas or oil, but there will be no commensurate change in indoor temperature.
The additional material on the air filter itself can provide a space for moisture to gather, encouraging the growth of mold or bacteria colonies. Not only do these form an even stronger barrier to circulating air, but if they colonize the wrong side of the filter, they can begin to introduce more pollutants and allergens into the indoor air. And if they get into the HVAC system and form colonies there, it could spell a lot of trouble for the entire system.
Because air doesn’t circulate as quickly, particulates can settle in ducts and on household surfaces when they’d usually be carried into the system and filtered. It’s a lot simpler to change your air filter than it is to schedule a duct cleaning, but dirty ducts can result in an ongoing drain to your system efficiency and a long-term source of pollutants in your air supply.
When to Change Your Air Filter
It’s best to change your air filter every month or two, especially if you have pets or live in a high-pollen area. Air filters are generally inexpensive, and changing your air filter is a simple task that doesn’t require a professional hand. In most cases, you should simply be able to slide the old filter out and slide a new one in.
Check your unit’s documentation to determine what size of filter you need, and what minimum efficiency reporting value (MERV) range the furnace should fall into. A high MERV filter with a very tight mesh may be too much for some units, resulting in a situation a lot like a clogged air filter, even just after you’ve changed it.