air filterWhy MERV ratings matter to your air conditioner filter – to a point

Your air conditioner depends on it to run efficiently and cleanly.

You depend on it to breathe clean air and stay healthy.

Yet the HVAC filter remains one of those “mystery components” that confounds and confuses many homeowners.
And little wonder, considering the conflicting advice that emanates from myriad sources – from air quality experts to well-intentioned sales associates at home improvement stores who know how dizzying it can be to confront their vast selection.

The confusion often centers on a filter’s MERV rating, an abbreviation that stands for Minimum Efficiency Reporting Value and that mostly signifies a filter’s ability to trap airborne particles.

Charlie’s Tropic Heating & Air Conditioning is determined to clarify the issue while ensuring that our customers’ HVAC systems run efficiently and meet if not exceed the lifespan projected by the manufacturer. These were the motivations behind a new service that allows our customers to order fresh filters through our website – and then have them delivered right to their front door. (We touted the full benefits of this service in a previous article, “Charlie’s new delivery service underscores importance of monthly filter checks.”)

Charlie’s will help you choose the right filter for your HVAC system – all while educating you about what that mysterious MERV rating is all about.

We take our cues from the EPA
Taking it from the top, when Charlie’s refers to HVAC filters, we mean the soft mesh, disposal-type, and not top-of-the-line HEPA filters. High Efficiency Particulate Air filters are used with whole-house HEPA filtration systems (and usually cannot be installed without extensive modifications.)
Most disposable filters carry MERV ratings of between 1 and 16, though the upper number is sometimes extended to 20, depending on the manufacturer. As a general rule of thumb, the higher the MERV rating, the more efficient the filter. The efficiency quotient is based on three criteria established by the American Society of Heating, Refrigerating and Air-Conditioning Engineers:

• The filter’s ability to remove airborne particles
• The filter’s resistance to air flow
• The filter’s expected lifespan

All things considered, the U.S. Department of Energy says that “medium efficiency filters with a MERV of 5 to 13 are reasonably efficient at removing small to large airborne particles. Filters with a MERV between 7 and 13 are likely to be nearly as effective as true HEPA filters at controlling most airborne indoor particles.”

The National Air Filtration Association endorses these numbers, recommending a range of between 9 and 12 for homes. Filters with higher MERV ratings are better suited to hospitals and commercial buildings, the association says.

Consider a proviso
Charlie’s Tropic Heating & Air Conditioning takes into account a sensible proviso from NAFA – and so should you. Noting that the MERV rating is partially based on a filter’s ability to target airborne particles, NAFA points out that “not all indoor air pollution is particle-based, however. Gasses contribute significantly to pollution as well.”

Put another way, if you home is subjected to special conditions – such as the regular use of strong chemicals or cleaners or the presence of heavy smokers – you may want to choose an HVAC filter with extra care.

There’s no doubt that frequent air filter changes will reduce stress on your AC motor, reduce the frequency and severity of repairs, help you save money on your electric bill and increase the lifespan of your HVAC system. That’s a tall order – and one that Charlie’s will help you fill, right to your front door.