Which filter should you buy, what does MERV mean, and how often should it be changed? A plain-language guide.
The furnace filter is the cheapest part of your heating system and one of the most important. It protects the blower and heat exchanger from dust, and it cleans the air moving through your home. Choosing the right one and changing it on time makes a real difference.
What MERV means
MERV stands for Minimum Efficiency Reporting Value. It rates how well a filter captures particles, on a scale where a higher number catches smaller particles. Most residential filters fall somewhere between MERV 6 and MERV 13.
- Lower ratings catch larger dust and lint and let air through easily.
- Mid-range ratings (around MERV 8 to 11) are a good balance for most homes, catching finer dust, pollen and pet dander.
- Higher ratings capture very fine particles, but they also restrict more airflow. Check your furnace manual before using one.
Higher isn't always better
A very dense filter in a system that wasn't designed for it can make the blower work harder and reduce airflow to your rooms. If you want better filtration, ask a professional what your furnace can handle.
How often to change it
A common guideline is every one to three months. Check it monthly during heating season. Change it sooner if:
- you have pets,
- someone in the home has allergies,
- there has been renovation or construction work, or
- the filter looks grey or clogged when you hold it up to the light.
Install it the right way
Filters have an arrow printed on the frame. It should point toward the furnace, in the direction the air flows. Make sure the filter fits snugly with no gaps around the edges.
A good filter keeps a clean system clean. If your furnace or ducts are already dirty, a filter can't fix that. Call 403-651-5895 to book a cleaning.
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