Displaced furnace filter - Nonprofit Home InspectionsRoutinely changing the filter for your heating and cooling system is one of the best ways to keep your home comfortable and healthy. However, proper filter maintenance is also essential for efficient operation and longevity of your equipment.

Most people think that the filter in their forced air HVAC system is primarily there to keep indoor air clean from particulates and other air pollutants. Although it is true that filters do clean indoor air to a certain extent, the filter’s actual function has more to do with keeping the heating and cooling equipment clean and free of dust.

If a filter is not installed in a forced air system, or if the filter is displaced, the blower equipment, heat exchanger and coils can become dirty which could cause premature failure and inefficient operation. Forced air systems are designed with an inline filter primarily to keep important equipment components clean, but the filter has a dual function and helps to keep indoor air clean too.

Dirty air filter - Nonprofit Home InspectionsOther equipment issues can be caused if a filter is installed but not replaced routinely. A clogged dirty filter can inhibit proper airflow which can also contribute to premature equipment failure and efficiency issues. Additionally, a clogged air filter can lead to serious issues such as a cracked heat exchanger (in gas or oil furnaces) which could potentially allow toxic carbon monoxide into the home.

So how often should you change your air filter? Well there’s lots of variables, such as how busy is the home? Do you live on a dirt road? Are there environmental pollutants such as exhaust gasses or smoke form forest fires? How many people live in the house? What size is the filter? What is the MERV (efficiency rating) of the filter? Check out the linked video for a good description of how often you should change your air filter.

One thing is for certain, the bigger the surface area of the filter, the better. That’s why most HVAC professionals recommend 4 inch pleated filters. The more surface area your filter has, the less often you have to replace it, and the better the air flow through the system. Be careful of the efficiency rating of the filter. High efficiency filters (high MERV rating) will filter out more particulates, but can clog sooner and cause airflow issues.

You can usually find your filter in a housing next to the furnace, or behind a return register grille. You can ask your HVAC service technician where your filter is located, what size filter to install, and how often to replace it. Don’t forget to line up the airflow arrow on the filter properly. Adding a label next to the filter housing can help to remind you which way to install the filter.

Heat Pump Dirty Filter - Nonprofit Home InspectionsAlso, be sure to check washable filters for equipment much as mini split heat pumps. Failure to keep heat pump systems clean will lead to less efficient performance and reduced life expectancy.