The Rush to Install High MERV Rated Filters Could be a Costly Mistake

Introduction - Pandemic Puts New York on Pause

On March 20, 2020, the state of New York was shut down due to the coronavirus. New York City and the state have been at the epicenter of the pandemic with more than 400,000 confirmed cases and 30,000 deaths over the last four months according to the Centers for Disease Control. As the hardest hit state in the country, New York has gone from complete closure with millions sheltering in place to a strategic, but cautious, plan to reopen. Unlike many other parts of the country, New York is seeing the number of cases declining. In response, NYS implemented a 4-Phase reopening plan. It has prioritized industries and locations starting with those that are the lowest risk of infection for employees and customers. High-volume commercial interiors are seen as a high risk and are being targeted with more extreme requirements, especially their HVAC systems.

Phase 1 allowed construction, manufacturing, and wholesale supply-chain businesses to reopen, as well as many retailers for curbside pickup, in-store pickup, or drop-off.

Phase 2 allowed more businesses to reopen, including offices, outdoor dining, places of worship (at 25 percent capacity), storefront retailers, and businesses in professional services, finance and insurance, administrative support, and real estate and rental-leasing industries.

Phase 3 focused on the hospitality industry, allowing restaurants and other food-service businesses to reopen for dine-in service at 50 percent capacity. (In New York City, however, indoor dining was not allowed in this phase.) Diners are required to be separated by at least six feet, or by a barrier when that is not possible, and must wear masks until they sit down. Gatherings of as many as 25 people, up from 10, were also allowed in this phase.

Phase 4 was initially slated to allow schools and low-risk arts, entertainment, and recreation businesses to reopen — all requiring social distancing — but not movie theaters, shopping malls, or gyms. Gatherings of up to 50 people will also be allowed. This has been changed due to recent hospitalization spikes in other parts of the country.[1]

[1] Source: As of Friday July 10, 2020, malls were given the green light to reopen if they adhere to these guidelines:

“For malls that are greater than 800,000 square feet, ensure building HVAC system filtration meets the highest-rated filtration compatible with the currently installed filter rack and air handling systems, at a minimum MERV-13, or industry equivalent or greater.

If a mall greater than 800,000 square feet is unable to meet a building HVAC system filtration rating of MERV-13 or greater, malls must have a certified HVAC technician, professional, or company, ASHRAE-certified professional, certified retro-commissioning professional, or New York licensed professional building engineer certify and document that the currently installed filter rack and air handling system would be unable to perform to the minimum level of heating and cooling that it was otherwise able to provide prior to the COVID-19 public health emergency if such a high degree of filtration (i.e., MERV-13 or greater) was installed.”[2]

To read the full summary guidelines, click on the link below to the Air Filtration and Building Systems section on Page 2.

Why is Air Filtration a Mandated Requirement?

If the typical homeowner wants fresh air, he or she can open a window. That is not the case for most commercial buildings; they depend on Heating Ventilation and Air Conditioning systems, or more commonly known as HVAC. Many people do not realize that Ventilation is an important part of any HVAC system. How it works for most commercial buildings is a large fan forces outside air through a unit where it gets filtered, conditioned, and supplied to different areas of the building through duct work.

New Covid-19 mandates are calling for upgrading or installing new MERV filters to commercial systems, but it is not just a “set it and forget it” solution. As I will outline in this paper, upgrading a filter can have a negative impact and increase costs. We are also not even sure what is really needed or appropriate as we are getting new information every day about the coronavirus. America is not the only place dealing with this challenge, and many countries are months ahead of us in effectively managing their reopening. It is paramount to learn what other countries have done, not only how they have dealt with the pandemic, but also if they modified THEIR ventilation systems.

The HVAC industry is a necessary commodity and systems installed in buildings affect everyone. Decisions cannot be taken lightly. Public safety needs to supersede profits. One must understand that there is a ripple effect when a retrofit is required, and it affects the entire system. The objective is to educate everyone, not just those in the industry. The proposed solution is much simpler and can save money and lives.

[2] Source:

Why Use MERV-Rated Filters?

Air filters are inserted directly into an air conditioning system airflow path to trap the particles that flow through the filter. MERV, which stands for Minimum Efficiency Reporting Value, is an ASHRAE (American Society Heating Refrigeration Air-Condition Engineers) Standard 52.2-2017 testing protocol used to measure how effective an air filter is at stopping contaminants from passing through it.[3]

The Chart below shows the different MERV Ratings. The top row shows the range of MERV ratings, up to the Particle Size it captures. Below it is the Typical Controlled Contaminant, and under that is the Typical Applications and Limitations. What you will notice, the higher the MERV rating, the smaller particulate it captures.[4]

[3] Source: [4] Source:

To get a better understanding of just how small a particulate is, the image above[5] provides a good perspective of Covid-19’s size in relation to a red blood cell. Scientists used electron microscopes to measure how big the coronavirus is. The smallest virus particles are 0.06 microns, while the largest are 0.14 microns. Information on this and the image can be found in the same article.

We know the coronavirus is an airborne virus that is highly contagious. It is transmitted when infected people sneeze, cough, loudly speak or even sing in close proximity. The article Can Masks Capture Coronavirus Particles? says some masks can filter particles as small as 0.007 microns – 10 times smaller than viruses. Data shows if worn correctly, they work!

The transmission of the virus in the air becomes critical when looking at the filtration requirement for an interior space. Studies are determining the size and how long it remains viable in the air.

“The virus can linger as droplets in the air for up to three hours, according to the New England Journal of Medicine; and it can travel at least 13 feet by aerosols that are emitted by breathing or speaking — twice as far as established physical distancing guidelines, based on a report by the CDC.

Talking can release thousands of fluid droplets per second that can remain suspended in the air for 8 to 14 minutes, according to a study conducted under experimental conditions by the Proceedings of the National Academy of Sciences.

Masks are effective in blocking or at least limiting your exposure to these contagious viral droplets and aerosol particles.”[6]

[5] Source: [6] Source: The locations where the Phase 4 mandates are being implemented hold large volumes of people, and even though there are mask requirements, many people may not comply. As an additional level of protection, commercial building owners are being told to replace their filters with a higher MERV-rated filter if they want to reopen. The problem is installing the upgraded filters will create a significant pressure drop.

What is “Air Filter Pressure Drop?”

“The more dense and tightly knit an air filter’s material is, the more particles it will be able to trap. However, this comes at a cost. One tradeoff that you have to make when you increase the density (and often the MERV rating) of a filter is that the filter will slow down your system’s airflow rate. This is known as an air filter’s pressure drop, and a high pressure drop means that your air handler has to work harder and consume more energy in order to maintain proper airflow.

Another thing you need to consider about air filters is that the pressure drop that they create only increases as the filter gets dirty. As dirt builds up on the filter, there is less and less space for air to flow through the filter. That’s a big reason that we remind our customers about the importance of checking, changing or cleaning their filters every month.

Not all air filters are created equal. In fact, even two air filters with the same MERV rating can cause different amounts of pressure drop.

The pressure drop that is acceptable for your air conditioner depends entirely on what type of system you have installed. Your air conditioner is designed to handle a certain amount of air filter pressure drop, and you can refer to your manufacturer’s guide...”[7]

The bottom line is you get problems installing a denser filter in a unit that was never designed for it. The pressure drop reduces the airflow rate, which means the motor on the fan works harder to keep up and consumes more energy. When the filters get clogged, they exceed the acceptable pressure drop and can reduce the life of the unit. If the system is old or poorly maintained, it can break down in only a few months. Unfortunately, this unforeseen issue forces business owners to temporarily shut their doors once again to replace their Air Handling Unit; a costly replacement that often takes weeks to resolve.

[7] Source:

Where are MERV Filters Installed?

MERV air filters are installed inside Air Handling Units (AHUs). AHU’s are found in Medium and Large Buildings (See EMS image 1). They are in the basement, roof, different floors of a building or on all three in some large applications (See EMS image 2). The purpose of an AHU is to provide conditioned air to different areas of a building. It takes fresh air from outside, cleans it through the filters, heats it or cools it, sometimes humidify or dehumidify it, then forces it through ductwork to different parts of the building. There are different configurations on how some of these units are built. Some provide 100% of the air that is being supplied to different areas from outside. Others use a mixture of outside air and recycled air, controlled by the ductwork configuration, dampers and automation. Fans inside AHUs are designed and sized to overcome the resistance of all internal components that include the modular devices to redirect the air and stationary coils that heat and condition the air.

In the following screen grabs, The Engineering graphically lays out the system in its YouTube video: How Air Handling Units Work AHU working principle HVAC ventilation.

(EMS image 1)

(EMS image 2)

(EMS image 3)

This cut-away shows where most filters are typically installed.

What about HEPA Filters?

“HEPA air filters are not MERV-rated as they exceed the ASHRAE test protocol 52.2 used in determining the MERV ratings. In fact, HEPA air filters are the ONLY mechanical air filters that are tested and certified to meet a specific efficiency at a specific particle size. All HEPA air filters must meet a minimum efficiency of 99.97% at 0.3 microns. ASHRAE or MERV air filters are tested using the Dust Spot tests that incorporate some fine dust, powdered carbon and some cotton linters. The Dust Spot test particle size range is from 0.3 microns to 50 microns, with an average size of approximately 20 microns.

HEPA air filters are tested using DOP, Mineral Oil and other materials that generate mono-dispersed particles that are all 0.3 microns or smaller in size. In essence, if 10,000 0.3 micron-sized particles are blown into a HEPA air filter, only 3 particles are allowed to pass through. Thus, you get the 99.97% at 0.3 micron rating. If you were to use the HEPA test on a 95% ASHRAE air filter, they would be about 50% efficient on 0.3 micron-sized particles once they loaded up with dust. So, HEPA air filters are at least 50% more effective at removing respirable-sized airborne particles than any of the ASHRAE air filters previously available on the market.”[8]

In layman terms, HEPA filters are much more efficient than MERV-rated filters – they are the most efficient filters you can buy. So, why are we not using them? Basically, it is overkill. It would be like putting an entire body cast on a patient who broke his thumb. We are already dealing with cost, pressure drop, airflow and quality when upgrading MERV filters - imagine how these problems can intensify when using a HEPA filter.

[8] Source:

Image source:

What is the Impact?

If we lived in a perfect world, everyone would have isolated themselves for two months when the pandemic broke out and we would be getting back to normal like some other countries. But that is not the reality here in the United States. Instead we have each State operating independently with open borders to each other, a political divide that creates confusion and a capitalistic society that pushes for businesses to open to keep the economy going. There is a price to pay for all this that only ends up costing us more in the long run.

I am sharing the perspective of an owner with nine years working for one who not only built their own buildings but operated them also. I saw first-hand how initial decisions affected us in the long term - this decision-making process forced us all do to our homework. I see the desperation to rush to open and am afraid of how this reactive behavior will pan out in the near future. We saw in 1920 the rush to make changes in the heating industry. A century later, buildings are still paying the price for what turned out to be a big mistake. You would think we had come a long way in the last 100 years, but cultural and social behaviors are repeating themselves regardless of how educated a society is.

Three articles written in the past three years support the point I’ve made. The first shows The Unintended Consequences of High-MERV Filters.[9] It summarizes what high MERV rated filters can do in AHU’s:

Add resistance to the air flow

Increase the pressure in the duct system

Increase the energy use of the system

Reduce the air flow

Cause comfort problems

Freeze the air conditioner coil

Damage the compressor

Dehumidify better

[9] Source: The second article, by the same author, Do High-MERV Filters Always Reduce Air Flow?[10] shows three case studies that emphasizes the point – yes, they do.

The third article, also by the same author, 7 Reasons Your Filter Isn't Improving Your Indoor Air Quality[11], shows what actually happens in the field. And if you read one of my previous LinkedIn videos where I said “Show Me Your Filters,” I spoke of the three scenarios I would find in the field where there was either no filter, the filter was being by-passed or there was a lack of maintenance. His detailed data emphasizes my points even more.

[10] Source: [11] Source:

Image Source: Google

What is the BEST Solution?

The mandate is making owners understand their responsibility to the public and force them to take a look at their HVAC systems. Installing High MERV-rated filters in an Air Handling Unit that was not designed for it, will eventually damage the fans. There are also the recurring costs to replace expensive MERV filters every two to three months. If not replaced, clogged filters reduce the airflow and cause additional strains on the fan. If an owner’s system is on its last leg, it would expedite the replacement. An inoperable fan means no airflow. No airflow means non-compliance, which also means you will once again have to shut down your business. Let us not forget, when the filters get dirty, the pressure drops increases, the air flow decreases, and energy consumption increases to add even more expense to the mechanical nightmare.

The reaction is not surprising considering the historical patterns in the industry. The improperly researched, single perspective, band-aid methods, can cause more harm than good. I encourage all owners to get their systems checked out to determine if they can handle installing higher MERV-rated filters, and IF THEY CAN’T - continue with a proper maintenance schedule and set a new rule for your company.


Masks are a quick and proven solution. Some may protest that it is a violation of their rights, but it is perfectly legal. It is not the first time we have been down this road. It helped during the 1918 pandemic, and it will help us today. Enhanced Building Solutions LLC (EBS) offers training and consulting. Our training methods provide consistent information, saves on employee turnover, and minimizes liabilities. Nothing will ever replace hands-on learning but blending it with online resources will create an IDEAL training solution. Are you ready to be a pioneer in the industry?

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