The Higher the MERV the Better: With Some Exceptions

2/12/2024

Before the COVID-19 pandemic, if someone mentioned Merv, they were probably talking about Griffin, the longtime television personality. 

After the pandemic, MERV, as in the minimum efficiency rating value of air filters, became a popular topic beyond facility managers and HVAC contractors, as people who work in institutional and commercial buildings or send their children to K-12 schools started talking about air filters and their effectiveness keeping unhealthy particles out of the air that circulates throughout buildings. 

One of the silver linings that emerged from the pandemic was an increased awareness of indoor air quality (IAQ) among building occupants. Suddenly people who were only worried if their workspace was too hot or too cold were asking, “what kind of air am I breathing right now, and how quality is that air?” 

Priorities change 

Kevin Delahunt has worked in the air filtration industry for more than 30 years and has seen a transformation emerge in the last three years. 

“We’ve evolved from being a mechanical discipline, looking at what was put into the unit to protect the coils, protect the fan, protect the humidifier, that sort of thing, to one now of health and safety,” Delahunt, a senior technical advisor for the National Air Filtration Association, said during an educational session at the AHR Expo, an HVAC industry conference, in January. “What is in the quality of the air that goes through that filter was never a discussion that we had in a hospital or healthcare facility prior to 2020.” 

Delahunt presented a session on air filters and the importance of matching up systems with the quality of filters to achieve maximum efficiency. Before COVID, most facilities used MERV 6 or MERV 8 filters. In the ratings system, filters rated MERV 5-12 are considered medium efficiency and designed to serve as more of a mechanical filter designed to keep the equipment clean.  

Related Content: Rethinking Indoor Health: ‘COVID Changed Things’

The filters graded MERV 13-16 place more emphasis on health and comfort of occupants. 

“As soon as you do something to your system, such as upgrade a filter or do something to an integrity of the filter, it’s an immediate (positive) result,” Delahunt says. “It doesn’t take much time. If I go from a MERV 8 to a MERV 13 and all the filters go in, I go from a particle penetration from 80 percent down to 20 percent. That’s an amazing result, and a quick response to it.” 

Looking for leaks 

While swapping out filters for a more efficient option seems like a no-brainer, there are factors managers need to consider before completely jumping on board. 

According to Delahunt, a MERV 15 filter can cost upwards of $125 each, while MERV 8s are closer to $8. So, to make sure managers are getting their money’s worth, they need to be sure the system using the filters can handle them. 

“During all COVID, the responses were, ‘I’ve got to put a MERV 13 in it,’ so we’ve seen, especially with school boards, that they want to put MERV 13s in a unit that probably at best had a MERV 6,” Delahunt says. “The average age of the HVAC systems is probably about 38.5 years old, so it’s getting the proverbial lipstick on a pig.” 

Delahunt says managers should ensure that their systems can handle the increased pressure of operating with the new filters. The new filters must also be fitted to achieve maximum efficiency. 

“If it doesn’t fit, it doesn’t filter,” he says bluntly. “It’s that simple. If the air isn’t going 100 percent through the filter, you don’t have the filter efficiency that you think you’re doing. Air will always take the path of least resistance, as water will. The more efficient the filter as we start to go up in efficiency, the more air is going to want to bypass it. 

“All we’ve heard the last few years is MERV 13, MERV 13, but not once have I ever heard someone talk about the fit. And they’re of equal importance. If you don’t have fit, you’ve wasted your money on a MERV 13 system.” 

Money matters 

Due to federal funding options such as the Inflation Reduction Act and several school initiatives offered by the Department of Energy, now is the best time for facilities to address their HVAC systems and IAQ. 

“It’s unprecedented right now,” Delahunt says. 

Matching new filters with old technology can be a problem. Delahunt emphasizes the need for better sealing mechanisms for HVAC systems, some of which haven’t changed in design in 50 years. 

“Throwing in a good filter in bad housing, that doesn’t really do you a lot of favors,” he says. 

But sometimes a new system isn’t an option and alternative measures are required. In these instances, Delahunt suggests some simple measures that managers can use to help achieve the maximum efficiency they’re seeking with their filters. 

“A MERV 13 filter with a 2-inch gap will not do what it’s supposed to do,” Delahunt says. “A tube of caulking will work for 18-20 months. Duct tape is fantastic.” 

Dave Lubach is the executive editor for the facilities market. He has more than eight years of experience writing on facility management and maintenance issues.