With a scale of 16 different classifications in MERV through the ASHRAE 52.2 test method, the industry only actively uses about half of them. At the high end of the spectrum we see more filters made with more options than anywhere else. MERV 13, MERV 14, and MERV 16 are all very common with many different options/styles, but in this mix there is a glaring omission - MERV 15.
So what happend to MERV 15? With as much focus as there is on high efficiency HVAC filtration and plenty of options at the next three closest MERV how did MERV 15 get skipped over? Is it a useless or redundant? Not really, it is in fact a nice place to be from an occupant health view - espicially in more critical areas like Hospitals, Clinics, and just-under-cleanroom clean manufacturing. MERV 15's problem is that it lacks regulatory agencies or help from other filter rating standards to help boost it's profile.
MERV-13 has become a boom efficiency because agencies like LEED, the EPA, OSHA, and many state and local authorities have set the "preferred minimum efficiency" at this level. And with that much demand created the air filter manufacturers responded - there are more options for MERV-13 filters than any other efficiency.
MERV-14 is resting on the laurels of hospital regulations through it's requirment in the ASHRAE Design Handbook, ASHRAE 170, Joint Commission, and that it has been established as a standard of care in the healthcare industry.
Then we get to MERV-16, which is also able to be labeled/called a 95% DOP filter as they stop 95% of 0.3 micron particles when tested under conditions that we'd test HEPA filters. So when someone needs near-HEPA filtraiton in an HVAC system the answer is MERV-16.
This leaves a hole at 15 where regualtors and industry professionals have skipped over. Which is too bad, because in most scenarios it offers a substantial improvement over 13 or 14, with a minmal added static pressure penalty, and a similar price-point while offering significantly improved particle removal. Sitting right between the particle removal efficiency of 14 and 16, this offers a filter that is close to HEPA filtration without having to undergo the DOP testing. This leeway results in a filter with much lower static pressure than it's MERV-16 counterpart while being very close in particle removal efficiency - most HVAC systems wouldn't experiance a noticable difference - meaning the upgrade to 15 from 14 especially is of little cost but huge value.
Next time you are considering High Efficiency Filtration - give some thought to this forgotten efficeincy MERV 15 - your HVAC system and building occupants will appreciate it.
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