Changing your furnace filter is the single easiest and most impactful maintenance task you can do as a homeowner. A clean filter improves airflow, reduces energy consumption, extends the life of your furnace, and keeps your indoor air clean. But how often should you actually change it?
General Guidelines by Filter Type
- 1-inch fibreglass filters: replace every 30 days
- 1-inch pleated filters: replace every 60 to 90 days
- 4-inch pleated filters: replace every 6 to 12 months
- HEPA filters: replace every 12 months (or per manufacturer instructions)
- Washable/reusable filters: clean monthly
Factors That Require More Frequent Changes
Several factors can shorten the interval between filter changes. If you have pets, their hair and dander clog filters faster — change every 30 to 60 days. Allergy or asthma sufferers benefit from more frequent changes. Homes undergoing renovation produce extra dust. And during peak heating or cooling season, when the system runs more, filters get dirty faster.
What Happens If You Do Not Change the Filter
A clogged filter restricts airflow, forcing your furnace to work harder and consume more energy. Over time, this strain can lead to overheating, cracked heat exchangers, frozen AC coils, and premature system failure. Many no-heat emergency calls in the GTA trace back to nothing more than a dirty filter.
How to Choose the Right Filter
Look for the MERV rating (Minimum Efficiency Reporting Value). For most homes, a MERV 8 to 11 filter provides good filtration without restricting airflow. Higher MERV ratings (13+) offer better filtration but may require a system capable of handling the increased air resistance.
Not sure which filter is right for your furnace? ZK Mechanical can recommend the ideal filter for your system and home conditions. We serve the entire Greater Toronto Area. Contact us for advice or to schedule a maintenance visit.