MERV 8, 11 or 13? A plain-English furnace filter guide
Maintenance
By Ali
Your furnace filter protects your equipment and your lungs, but a filter that is too restrictive can do more harm than good.
What MERV means
MERV (Minimum Efficiency Reporting Value) measures how well a filter captures particles from 0.3 to 10 microns. Higher numbers catch smaller particles.
- MERV 8: catches dust, lint and pollen. Good basic protection.
- MERV 11: adds pet dander and fine dust. Best for most homes.
- MERV 13: captures smoke, bacteria and fine allergens. Ideal for allergies and wildfire season.
How often to change it
1-inch filters every 1–3 months, 4- and 5-inch media filters every 6–12 months. Change more often with pets, renovations or smoke events.
Will a MERV 13 hurt my system?
Not if your ductwork can handle it. In a 1-inch slot it can restrict airflow; a 4- or 5-inch media cabinet solves that. Ask your technician to measure static pressure at your next tune-up.