When There’s No MERV Rating on Your Air Filter, How Efficient Is It?

Air filters keep dust and other airborne pollutants out of your HVAC system and your home. An air filter is an important first defense for proper functioning of your HVAC system and indoor air quality. As not all filters are created equal, you should understand air filter ratings so you know what you’re purchasing with your hard-earned money.

What Is MERV?

The ratings system known as the minimum efficiency reporting value (MERV) lets you know how efficient a particular filter will be at keeping particulates out. The higher the MERV rating, the smaller the particle it can capture. This rating system was incorporated by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) to create a standard that would help consumers buying air filters.

For most households and HVAC systems, a filter with a MERV rating between 7 and 13 is ideal. Choose higher than that and you might run into compatibility problems, as there’s increased airflow resistance. Lower-rated filters keep out large particles but might let enough mold spores and small dust particles through to keep allergies going strong.

Beware of Other Ratings

Unfortunately, you won’t find a MERV rating on all filters available. Some are rated under different systems, which can be a problem if you’re simply looking at the numbers on the packaging. A filter rated 7 under another rating system may not be as efficient as a MERV 7 filter. By keeping this in mind, you can avoid paying inflated prices for a lower quality filter.

You can always ask the store staff about the ratings, but understand that the average store clerk may not be able to tell you what the MERV equivalent would be. When you’re unable to determine the true efficiency of a filter, sometimes your best choice is to buy filters elsewhere, from a place that sells filters with MERV ratings.

Lastly, remember that no matter the MERV rating, a dirty filter is never an efficient filter, so check and change them regularly.

For more advice about air filter ratings and your HVAC system, please contact us at HVAC & Plumbing Unlimited Heating & Air Conditioning.