Like many other industries, the COVID-19 pandemic has forced the HVAC industry to reevaluate many strategies. COVID-19 is spread primarily through moisture droplets, making it imperative for HVAC systems to circulate correctly and cleanly.
Recently a call for office, school, and institutional building managers to reevaluate their HVAC strategies for mitigating COVID-19 in light of the updated guidance to ensure desired exposure reduction while minimizing associated energy penalties.
On Jan. 6, 2021 ASHRAE’s ETF posted a refined and concise summary of its recommendations across its many detailed guidance documents, including its Commercial Guide and School Guide. As stated in the ASHRAE press release, the Core Recommendations are “based on the concept that ventilation, filtration and air cleaners can be combined flexibly to achieve exposure reduction goals subject to constraints that may include comfort, energy use and costs.”
Core Recommendations for Ventilation, Filtration, and Air Cleaning
- Provide and maintain at least the required minimum outdoor airflow rates for ventilation as specified by applicable codes and standards.
- Use combinations of filters and air cleaners that achieve MERV 13 or better levels of performance for air recirculated by HVAC systems.
- Only use air cleaners for which evidence of effectiveness and safety is clear.
- Select control options, including standalone filters and air cleaners, that provide desired exposure reduction while minimizing associated energy penalties.
“With this important update, ASHRAE makes clear that buildings can achieve safe air exchange rates with a mix of ventilation, filtration, and air cleaners to mitigate aerosol transmission,” said Christian Weeks, CEO of enVerid Systems. “Additionally, the ETF emphasizes that energy expenditure is a critical factor in determining an optimal HVAC strategy for COVID mitigation. We applaud the ETF’s rigorous effort to evolve their recommendations to account for key operational considerations, and we encourage building managers to reevaluate their HVAC COVID-19 strategies to align with ASHRAE’s updated guidance to deliver safe indoor air without the high energy penalty of ventilation-only approaches.”
Recommendation Changes During the COVID-19 Pandemic
In the early days of the pandemic, the ASHRAE ETF released preliminary guidance that called for maximizing outside air ventilation. This strategy has several drawbacks including high energy penalties and increased carbon emissions. During an October webinar, Prof. William Bahnfleth, Chair of ASHRAE’s Epidemic Task Force, explained that initial guidance from ASHRAE was very conservative without consideration for cost, operational, and seasonal weather impacts. Over time the ASHRAE ETF has evolved its guidance, and the Core Recommendations refine the ETF’s findings into a streamlined prescription to mitigate the transmission of infectious airborne aerosols in commercial buildings.
According to Prof. Bahnfleth, “ASHRAE’s Core Recommendations are based on an equivalent clean air supply approach that allows the effects of filters, air cleaners other removal mechanisms to be added together to achieve an exposure reduction target.” Experts from Harvard Chan School of Public Health recommend 6 air changes per hour (ACH) as the ideal exposure reduction target for schools. Six ACH means the air inside building spaces will be exchanged for clean air once every 10 minutes. Clean air is defined as outside air or recirculated air that has been filtered by high-efficiency filters such as MERV-13 filters and local HEPA filters.
“We welcome the new ASHRAE ETF Core Recommendations, and the emphasis on a flexible combination of HVAC strategies to address indoor air quality allowing important considerations such as energy penalties, outside air quality, and other factors to be part of the equation,” said Robert Ioanna, Senior Principal at Syska Hennessy. “Today’s priority is halting transmission of SARS-CoV-2. Tomorrow’s will be ensuring HVAC systems address the dual priorities of pandemic proofing and maximizing energy efficiency – with the end goal of high IAQ, lower operating costs and reduced carbon emissions.”
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It is for this reason that IECA members keep a close eye on regulatory issues, legal situations, and new regulations from news sources across the country. This is especially true when it comes to issues that everyone should be aware of.Tags: Chicago, COVID-19, HVAC, Recommendations, Worksite Cleanup