If you're wondering when it's time to replace your air conditioning filter, the answer is simple: when it looks dirty, dusty, or has locks of hair and dust. A clogged filter interferes with the normal air flow of the air conditioning system, and it also allows dirt to accumulate in the cooling coils, which impairs the system's ability to keep you cool. Replacing your HVAC air filter can increase efficiency and reduce energy consumption by up to 15 percent. In general, most air filter manufacturers and HVAC companies recommend changing the air filter every 90 days or 3 months.
This can change depending on the location of your home, if you have pets, and the age of your system and equipment. As an expert in HVAC systems, I recommend that if you have pets at home, you should consider changing the filter every 60 days or 2 months. For homes with several pets or people with allergies or respiratory conditions, I suggest changing the filter every 20 to 45 days. Vacation homes or empty houses that aren't used much usually wait to change the filters every 9 to 12 months.
The best way to know when to change your HVAC air filter is to check it monthly. Replace it if it looks dirty. In the meantime, be sure to watch for signs such as increased dust in your home, higher energy bills, and reduced airflow from your vents. The only way to be sure how often your air filter should be changed is to visually inspect the filter every month.
After a few months, you'll get an idea of how quickly it gets dirty. You'll need to re-evaluate if you have a new pet or if the outdoor air quality has been poor. Pleated filters are usually better than non-pleated ones, as they allow more surface area to accumulate dust, pet hair, and other debris that floats in the air. In smaller homes, the air conditioning system has to move less air, which may mean replacing air filters less frequently.
Using an air filter with a MERV rating higher than that recommended by the boiler or air conditioner manufacturer can actually impair its performance. You will no longer be able to filter the air properly, allowing dust and contaminants to enter the air conditioning system. The only type of filters that trap allergens and spores are HEPA, or high-energy particulate air filters. These air filters act as barriers to prevent contaminants from entering the air conditioning system or circulating through the air.
For people with chronic conditions such as allergies or asthma, clean filters can alleviate annoying symptoms. However, some air conditioning systems have filters inside the return air ducts spread over several rooms in the house. If you live alone, don't have pets, and the surrounding outdoor air is of good quality, then following the manufacturer's recommendations for changing filters will probably work well for you. The HVAC air filter helps keep indoor air clean by trapping particles of mold, pollen, and other contaminants that move through the system.
If you live in a big city, pollutants such as smoke, dust, and other debris will seep inside and clog the air filter at a much faster rate. Air filters are usually made of spun fiberglass (the same that forms the insulation of the attic) or of pleated paper framed with cardboard for greater stability and rigidity.