MERV stands for Minimum Efficiency Reporting Value. It rates how well an HVAC filter captures airborne particles, on a scale from 1 to 16 for standard filters. Higher numbers capture smaller particles.
What the Ranges Mean
- MERV 1–4: basic fiberglass filters that protect the equipment from large dust and lint.
- MERV 5–8: pleated filters that also catch mold spores and finer dust.
- MERV 9–12: better capture of fine dust and some smoke particles.
- MERV 13–16: high-efficiency filtration for fine particles such as smoke and bacteria-sized particles.
Higher Is Not Always Better
A denser filter restricts airflow. If your blower and ducts were not designed for it, a high-MERV filter can reduce airflow, which lowers comfort and strains the system. Thicker media filters, 4 to 5 inches deep, offer high MERV ratings with less restriction than a thin filter of the same rating.
Choosing the Right Filter
Most homes do well with a mid-range pleated filter changed on schedule. Homes dealing with wildfire smoke or allergies benefit from MERV 13 or higher in a system set up for it. We installed IQAir MERV 16 filtration in Kensington and Berkeley homes. See whole-house air filtration.
Frequently Asked Questions
What MERV rating should I use at home?
A mid-range pleated filter suits most homes. Choose MERV 13 or higher for smoke or allergies, in a system that can carry the airflow.
How often should I change my filter?
Follow the change interval for your filter type. Thin filters need changing more often than deep media filters.