Furnace Filters and Indoor Air Quality

A very important home maintenance task for homeowners with forced air heating systems is to change the furnace filter at regular intervals. The filter should be changed regularly during the heating season and for homes with whole house air-conditioning this should be done throughout the year.

The furnace filter is located between the air intake and the furnace motor. The original and most important purpose of the filter is to protect your furnace motor and internal components from airborne particles that could cause damage and reduce operating efficiency. Changing your furnace filter frequently will protect your furnace and improve its efficiency resulting in savings in both maintenance costs and energy use.

Today there are many different types of filters on the market along with marketing campaigns that try to convince you that you can use your furnace filter not only to protect your furnace but to improve the quality of your indoor air. Many of these claims can be very misleading.

My recommendation when it comes to furnace filters and maintenance is “buy cheap, change often”. According to a study done by the Canada Mortgage and Housing Corporation (CMHC), using furnace filters as a way to improve your indoor air quality is not only expensive but makes only a moderate difference in the quality of your indoor air when compared to other changes you can make in your home. CMHC Study

Furnace filter recommendations

1. Don’t use your furnace filter as a way to clean your indoor air.

2. Buy an inexpensive filter and change it every month throughout the heating season or year round if you have whole house air conditioning.

3. If you choose to buy a more expensive filter check it each month to monitor it’s cleanliness to assure the airflow to the furnace is not being restricted potentially causing damage.

Recommendations to improve indoor air quality (from CMHC study)

1. Remove your shoes when entering your home

2. Keep major dust generators (smoking, pets, etc.) out of the house

3. Reduce dust collecting surfaces (open shelves, carpets, upholstered furniture, etc.)

4. Frequent vacuuming with an efficient vacuum cleaner

5. Reduce the entry of particle-laden outdoor air by closing windows