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How Often Should You Change Your Filters?

Updated: Aug 22, 2018

We’ve all heard before how important it is to change air filters. Changing your air filters regularly boosts the efficiency of your HVAC system and prolongs its life. Failing to do so can clog your HVAC units and harm the air quality in your home. However, many homeowners wonder how often exactly “regularly” is. The answer is: it depends on the filter. The filter size, the home’s HVAC system, and MERV ratings all factor into how often your filter needs to be changed.

MERV Ratings

MERV stands for Minimum Efficiency Reporting Value. It’s a rating system that was developed by the American Society of Heating, Refrigeration, and Air Conditioner Engineers (ASHRAE) to rate the efficiency of certain air filters at catching airborne particles. The rating scale runs from 1-16, and the higher the number, the more efficient the filter is found to be.

A filter with a MERV rating of 3 or 4 traps about 20% of airborne particles or less, typically things like dust and pollen or carpet fibers; meanwhile, a filter with a MERV rating of 16 catches 90% of airborne particles, including bacteria and even tobacco smoke. Because they catch more particles, air filters with higher MERV ratings need to be changed more often than those with lower MERV ratings.

Filter Size

Air filters come in a variety of sizes, from 1-2 inches to 5 or 6 inches. Size also impacts how often your filters will need to be changed. Smaller filters will fill up more quickly, of course, and thus they’ll need to be changed more often. If you have a 1 inch air filter with a high MERV rating, for instance, you’ll have to change that much more frequently than a 5 inch air filter with a low MERV rating. It’s best to choose one or the other — 1 inch air filters or larger air filters, rather than trying to have a combination of both. 1 inch air filters should be changed about once a month.

Ducts or Not

In-duct air filters are cut to fit inside the vent. They go inside both the intake and return vents of the home to stop air particles that could damage your indoor air quality before they exit the vents. These types of filters typically have longer life spans and only need to be changed every 6 months. However, again, take MERV ratings into consideration. If your MERV rating is particularly high, you may want to check your in-duct air filters sooner than 6 months to make sure they’re not beginning to clog. On the other hand, you may have a ductless system with a cabinet air filter, in which case you can gauge the replacement time by the appearance of the filter.

There’s no one clear answer when it comes to replacing your air filters. It depends on the kind of filter you have, the quality of that filter, and of course your HVAC system itself. Want to know if it’s time to replace your filters — or possibly seek out more efficient air filters? Contact Air Solutions in Bryan-College Station today for more information.

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