EVALUATION OF ZENGUARD MERV9 FILTERS:

By D. Sridhar, R. Shacklock, C. van der Kuur

The annual global building sector is comprised of 242 billion square meters of floor space which produces operational emissions estimated to be ca. 10 GtCO2, and to reach net zero carbon we will require advancement in existing technologies to reduce building emissions1. To put this in perspective, the Canadian province of Ontario alone plans to construct 1.5 million homes in the next 10 years2. Buildings account for approximately 39% of energy-related global CO2 emissions; specifically, 11% is materials used for building and construction, while the remaining 28% comes from operational carbon, resulting from the heating, cooling, lighting and power associated with such systems3. The field of Heating, Ventilation, and Air Conditioning (HVAC) offers opportunities for such improvements, as HVAC systems often dominate a building's operational energy use.

A crucial aspect in this domain is air filters, especially post SARS-COVID-19 pandemic due to increased emphasis on indoor air quality to reduce the spread of airborne pathogens. ZenGUARD4 coated filter medium with patented graphene-based antiviral ink5, enhances the viral filtration efficiency (VFE) of the existing filters, thus requiring less outdoor air (OA) to maintain a determined pathogen-free equivalent clean air, which leads to reduced heating and cooling loads. They need no special adaptation to use in existing HVAC units and offer no additional pressure impedance to the airflow. This work aims to quantify the effect of ZenGUARD coated MERV9 filters’ enhanced VFE over uncoated MERV9 filters in terms of OA% and CO2 equivalent for various building occupancy types, while ensuring comparable indoor transmission rates of infectious viruses.

A space of 10,000 ft2, with a ceiling height of 10 ft, and airflow of 5,000 CFM is considered for this study, which is of ideal size to modify into different occupancy types. An occupancy of 75 (133.3 ft2/person) is considered for all occupancy types. Further, to understand the effect of occupancy density in an office space; 70, 133.3, 200, and 300 ft2/person were used. The minimum required OA% is calculated as per ASHRAE 62.1 guidelines6 for four occupancy categories; office space, bank, warehouse, and gym. These were specifically considered as the people outdoor air rate (Rp) and the outdoor air rate (Ra) for these categories encompass a wide range of occupancy categories. An infection risk calculator used in this work was developed to quantify different scenarios and is similar to the calculations found in the literature using a binomial distribution7 model but with certain modifications. One key adaptation includes equivalent clean air, which is emphasized in ASHRAE 2418, which includes fresh OA and the percentage of air that is virus-free from air recycled through the HVAC filter based on the filters VFE and accounting for various virus removal rates, with a focus on the SARS-COVID19. The model assumes that 10% of the occupants are infected.

Viral filtration efficiency introduced into this model was experimentally determined using a horizontal testing chamber for both coated (ZenGUARD) and uncoated MERV9 filters with dimensions 24”x24”x2”, and

 Figure 1. For the discussed footprint and ventilation in this work; the minimum recommended OA% as per ASHRAE 62.1 calculated for ZenGUARD-coated MERV9, and the corresponding calculated OA% to maintain a similar infection rate using uncoated MERV9 filter: (A) for various occupancy categories (bar chart) and associated calculated CO2eq (scatter plot); (B) for different occupancy densities in an office space (bar chart) and associated calculated CO2eq (scatter plot). ZenGUARD-coated MERV9 and uncoated MERV9 are shown in purple and lavender colours respectively. CO2eq/year is calculated to theoretically heat or cool air by 20 °C for the calculated OA%.

15 pleats per linear foot, and bacteriophage Phi6 was used as the test organism. Tests have shown that coating with ZenGUARD antiviral ink does not change the pressure drop or the MERV rating of the filters. These results are not discussed as it is outside the scope of this article. VFE was experimentally determined along with dust loading for 0,1,2,3,6 months and an average

References:

VFE was estimated for 6 months duration by linear interpolation for every single month. The estimated average VFE for coated and uncoated MERV9 filters were ca. 67% and 44% and were integrated into the infection risk model. Unlike other coated filters9, ZenGUARD’s viral filtration ability has been experimentally evaluated to not decrease with dust loading and increases more on a relative basis compared to the uncoated MERV9 filter10. The OA% of ZenGUARD-coated MERV9 was first determined using ASHRAE 62.16 for the given occupancy type and space. This was then incorporated into the model along with other building operation variables to determine the infection risk rate. This computed infection risk was then used in the same model to find the required OA% using an uncoated MERV9 filter. The CO2eq is estimated by calculating the energy required to heat/cool the outdoor air by 20 °C over a year and using the national U.S. average CO2 emissions per kWh for electricity generation11. Other energy costs related to air handling unit operations or zoning of building spaces are not considered in this work to focus only on the OA temperature adjustment scenario and its general quantification to CO2eq.

Figure 1A shows the calculated OA% for ZenGUARD MERV9 following ASHRAE 62.1 guidelines for the building size described in this work, and the calculated OA% required to maintain the same infection risk using an uncoated MERV9. The required OA% nearly doubles when uncoated MERV filters are used for all occupancy categories except for gyms, where the increase is about

1. United Nations Environment Programme, “2022 Global Status Report for Buildings and Construction: Towards a Zero-emission, Efficient and Resilient Buildings and Construction Sector” (2022), (available at https://wedocs. unep.org/20.500.11822/41133.).

2. More Homes Built Faster (2022), (available at https://www.ontario.ca/ page/more-homes-built-faster).

3. “Bringing embodied carbon upfront: Coordinated action for the building and construction sector to tackle embodied carbon” (London, 2019), (available at https://www.worldgbc.org/sites/ default/files/WorldGBC_Bringing_ Embodied_Carbon_Upfront.pdf).

4. Home | Zentek Ltd., (available at https://www.zentek.com/).

5. A. Hadidi, C. Van Der Kuur, J. Korkis, D. Sridhar, Graphene-silver nanocomposites and uses for same as an antimicrobial composition (2021).

6. ASHRAE, “Ventilation and acceptable indoor air quality: ASHRAE Standard 62.1–2022” (ASHRAE, Atlanta, 2022).

7. J. Lelieveld, F. Helleis, S. Borrmann, Y. Cheng, F. Drewnick, G. Haug, T. Klimach, J. Sciare, H. Su, U. Pöschl,

Model calculations of aerosol transmission and infection risk of COVID-19 in indoor environments. Int. J. Environ. Res. Public Health. 17, 1–18 (2020).

8. ASHRAE, “Control of infectious aerosols: ASHRAE Standard 241-2023” (Atlanta, 2023).

9. Y. H. Joe, D. H. Park, J. Hwang, Evaluation of Ag nanoparticle coated air filter against aerosolized virus: Anti-viral efficiency with dust loading. J. Hazard. Mater. 301, 547–553 (2016).

10. Zentek Ltd., Zentek Announces Breakthrough Results in Viral Filtration Efficiency with Dust Loading (2023), (available at https://www.zentek.com/ news/zentek-announces-breakthroughresults-in-viral-filtration-efficiencywith-dust-loading/).

11. How much carbon dioxide is produced per kilowatthour of U.S. electricity generation? U.S. Energy Inf. Adm. (2022), (available at https://www.eia. gov/tools/faqs/faq.php?id=74&t=11).

12. H. Ritchie, Which form of transport has the smallest carbon footprint? Our World Data (2023), (available at https://ourworldindata.org/travelcarbon-footprint).

15%, which is still significant considering high metabolic activity in these spaces that demand significant ventilation. This result translates to savings of ca. 32.5, 30.8, 29.1 and 14.5 tonnes/year of CO2eq for the above-defined office space, bank, warehouse, and gym respectively.

A similar trend can be expected if higher MERV-rated filters are coated with ZenGUARD, with no additional pressure drops or mechanical fittings that are used for uncoated filters. It should be further noted that MERV ratings are estimated using ASHRAE 52.2 guidelines and are limited to particle efficiency, thus an additional VFE for the desired filter will be required for a full analysis if other filters need to be studied.

In Figure 1B, considering the office space type of occupancy category, with occupancy density of 70, 133.3, 200 and 300 ft2/person, the OA requirement is lower for less-dense occupations, with the use of ZenGUARD coated or uncoated filters, which is expected. Additionally, the OA increment between the use of coated and uncoated MERV9 filters is substantial and becomes more pronounced and plateaus as the occupancy density decreases. This result translates to a saving of ca. 29.8, 32.5, 33.9 and 33.6 tonnes/year of CO2eq for the above-mentioned occupancy densities respectively. Drawing a parallel to the transportation sector, 33.6 tonnes CO2eq/year is almost equal to a savings of 197,647 kilometres of petrol car driving12

This study highlights the effectiveness of ZenGUARD coated filters in achieving improved indoor air quality without an increase in energy consumption. The ZenGUARD MERV9 filter provides significant advantages in terms of improved indoor air quality and environmental sustainability when compared to an uncoated equivalent. ZenGUARD is versatile, suitable for integration with almost any air filter, and delivers superior VFE without incurring additional capital costs or causing pressure impedance to airflow. As a result, buildings equipped with ZenGUARD filters require less OA, leading to decreased fan usage and considerable energy and CO2 savings. Such reductions are critical for advancing toward net-zero operational carbon in buildings. Adopting ZenGUARD should be a strategic move for those aiming to construct energy-efficient buildings, particularly when leveraging existing air-handling infrastructure. Moreover, this technology is cost-effective and can seamlessly align with current building codes with minimal modifications. www.zentek.com

We acknowledge LMS Technologies, Inc., Bloomington, USA for the VFE analysis of our air filters. Special thanks to Dr. Paul Lebbin of the National Research Council Canada and his team for the phase one testing of filters for viral filtration activity ZenGUARD. Additionally, we extend our sincere appreciation to Zentek’s Research, Product Development and Manufacturing teams for their efforts in ZenGUARD filter development and production.