The Basics of HVAC Air Filter Ratings

A well-functioning HVAC system is essential for comfort, efficiency, and proper humidity control, and the air filter plays a critically important role in its reliable operation. Choosing the right HVAC air filter isn’t always easy when you’re faced with a complicated rating system and different industry acronyms. Learning these air filter basics can help.

MERV: The HVAC Filter Rating System

Air filters are rated by a minimum efficiency reporting value or MERV, a numerical scale ranging from 1 to 20 that tells you their effectiveness at capturing particles within a certain size range. The higher the rating, the greater the effectiveness.

What Does HEPA Mean?

Another commonly-heard acronym is HEPA, which stands for high-efficiency particulate arrestance. These filters have the highest MERV ratings between 17 and 20 and can trap up to 99.97 percent of particulates down to 0.3 microns. Because they restrict airflow significantly, HEPA filters aren’t compatible with central HVAC systems.

Which Filter Does Your System Need?

When choosing a filter, you can go by the rating range recommended by your equipment’s manufacturer or ask for your HVAC technician’s advice. To help clarify your choices, here’s a brief guide to the MERV ratings for different types of air filters:

• Flat filters: These inexpensive fiberglass filters range from MERV 1–4. They only trap about 80 percent of larger particles over 10 microns in size, so they keep harmful debris off of sensitive HVAC components but they don’t help with air quality.
• Pleated filters: Medium-efficiency pleated filters have MERV ratings from 5–13. The higher-rated ones can capture up to 95 percent of airborne debris as small as 3.0 microns, so they’re more effective at cleaning your indoor air.
• Higher-efficiency filters: If you want even greater filtering capabilities, you can go with a higher-efficiency pleated filter rated from MERV 14–16, but your HVAC system will need to be professionally modified to prevent airflow restrictions and costly component damage.

For advice about which HVAC air filter is best for the system in your Martin, Palm Beach, or Indian River County home, contact us at NisAir Air Conditioning and Heating.