MERV (Minimum Efficiency Reporting Value) is a filter rating from the ASHRAE 52.2 test standard that measures how well an air filter captures particles between 0.3 and 10 microns. Ratings run from 1 to 16; higher numbers capture smaller particles, but denser filters also add airflow resistance that the blower and ductwork must overcome.
Why it matters to you
During summer wildfire smoke events, fine particles get past basic builder-grade filters, so many Lower Mainland homeowners want a higher MERV. Forcing a dense filter into a system that cannot carry it starves airflow and can freeze a cooling coil.
Practical guidance
For most homes on standard ductwork, MERV 8 to 11 is a practical range; MERV 13 helps with smoke and allergies once the system has been checked for it. A thicker media cabinet usually runs a higher MERV at lower resistance than a dense one-inch filter, and filters should be changed on schedule.
General MERV tiers (ASHRAE 52.2 general guidance)
| MERV range | Typical particles captured | Typical residential use |
|---|---|---|
| MERV 1-4 | Large particles such as lint, carpet fibres, and coarse dust | Basic equipment protection; minimal air cleaning |
| MERV 5-8 | Pollen, dust mite debris, mould spores, and larger dust | Common standard residential filter |
| MERV 9-12 | Finer dust and some fine particles in the 1-3 micron range | Better residential filtration where the system can carry it |
| MERV 13-16 | Fine particles including much of the smoke and bacteria-size range | Allergy and smoke-season filtration; check airflow and static pressure first |