Winterizing Your Home: Furnace Filters


As we batten down the hatches for another blustery winter, it's easy to feel overwhelmed with big tasks. Luckily, we're here to show you one very important, but very simple way to get your home prepared for the cold season. You've already checked your smoke detectors and carbon monoxide detectors, and started sealing up all of the gaps and cracks around your doors and windows, but when was the last time you changed that old furnace filter?


 That dirty, clogged filter on the left should be replaced with the clean filter on the right.

Furnace filters should be changed at least once every three months.

However, there are environmental factors that could require more frequent changes. If you have pets, smokers, or ongoing construction in your home, it may be a good idea to change your filter every month. According to 3M Filtrete, if you use any filter for longer than the recommended lifetime, it may begin to restrict airflow or cause your heating/cooling system to malfunction. That means you'll find yourself turning the thermostat up when you don't really need to because your filter has become too clogged.


The furnace filter is generally located between the blower and the return duct.

Be sure to note the direction of the air flow in your particular furnace, and match the small arrows on the cardboard filter frame to the direction of the air flow. If you need help locating your furnace filter or determining the air flow direction, check out this simple tutorial from, or contact a licensed HVAC professional.


Your furnace needs a certain size filter.

Furnace filters come in a range of shapes and sizes, so it's important that you know the filter size your specific furnace needs. If your current filter does not have the size marked on the cardboard edge, you can measure the filter itself (short edge x long edge x depth). If you're still unsure, put the old filter in a clear trash bag and bring it to the store with you - we'll measure it on the spot.

Quality counts.

There are economy furnace filters available that are significantly less expensive than their competitors, but we strongly recommend that you avoid them. These filters are made of fiberglass, and were originally designed to protect your heating or cooling system from large dust particles. They were not intended to maintain or improve your indoor air quality, and generally do not filter out smoke, allergens, or pet odors. Filters that have an electrostatic charge remove 49% of sub-micron particles in the air, compared to only 2% removed by fiberglass filters, or 6% removed by washable filters.

Filtrete primarily uses a Filter Performance Rating (FPR) based on the ability of the filter to capture particles from 0.3 to 1.0 microns. These sub-micron particles are most likely to be inhaled, where they can cause problems in the lungs, especially for those with asthma or allergies. Their rating of filters range from 300 to 1600. The higher this FPR number is, more particles it can filter out of the air.

Still have questions? Visit your local Valu to speak to our knowledgeable Associates about winterizing your home.