EVALUATION OF ZENGUARD MERV9 FILTERS: Impact on Outdoor Air Requirements and Operational Carbon Footprint in Buildings By D. Sridhar, R. Shacklock, C. van der Kuur
Method and Discussion
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 120
1A.
OA%
80 60
40%
40
20% 0%
80%
20 Office space
Bank
Warehouse
Gym
0
120
1B.
100
60%
80 60
40%
40
20% 0%
CO2eq, t/year
100
60%
CO2eq, t/year
80%
OA%
T
he 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.
20 70
133.33 200 ft2/person
300
0
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 ISSUE 6 2023 FILTNEWS.COM 11
