Q: What are your top recommendations to reduce virus spread through HVAC modifications?
A: Top 3 recommendations for businesses, public gathering places, and homes:
- Increase air flow of outside air. The target is 40 cfm per person fresh air, resulting in 800 ppm of carbon dioxide concentration with occupants at sedentary metabolism. This is easiest to achieve through "smart" or demand control ventilation that adjusts to building occupancy level.
- Improve filtration. At least MERV 11 filters, but preferably MERV 13 filters to manage particulates and to filter out 90% of infectious particles.
- Add ultraviolet germicidal irradiation (UVGI) to recirculation air stream. 0.02 Wuv per cfm of building airflow for 85% single pass kill efficiency. Conversion of electric energy to UV irradiation is approximately 25%, so UV sanitation of 200cfm of air requires ~4Wuv, or 16W electricity to sanitize.
Of course, these measures are no substitute for face masks, physical distancing, and hygiene, which are essential.
Q: Are there any special guidelines for hospitals and other medical facilities?
A: Hospital-acquired infections are a growing concern with today's drug-resistant bacteria and immune suppression treatments that increase patients' susceptibility to bacteria, virus and fungal infections. Medical facilities should have systems reviewed to be sure components and system operations meet guidelines for ventilation (ASHRAE 62.1). Medical facilities should be operating with high ACH (air changes per hour) with enhanced filtering that meets or exceeds our guidelines. Airflow patterns should be examined in high-risk spaces.
Q: Any special recommendations for schools?
A: It's hard to provide specific guidance because each school is so unique. Contact SEDAC for specific recommendations. See also the CDC's guidance on reopening k-12 schools.
Q: Do these measures apply to homes as well?
A: Yes. Increased air flow, improved filtration (above MERV 11) and UVGI will reduce the probability of someone in your household catching a cold, the flu or COVID-19, and are well worth the cost, even if they downgrade your home's energy certification rating.
Q: Do you recommend keeping these measures in place after the pandemic is over? What are the benefits in non-virus periods?
A: We recommend that the increased ventilation, improved filtration, and UVGI be continued after the pandemic ends. The recommendations for increased ventilation and improved filtration will help dilute any future pathogens, along with the current COVID-19 pathogen, as well as improve employee productivity and reduce sick days (see below). UVGI in addition to killing viruses helps keep the coil and condensate pan clean of biofilms that tend to build up over time, reducing maintenance costs for cleaning the coil system .
Q: How can I make the case that measures to improve air quality and reduce virus spread are beneficial and cost effective, beyond the pandemic?
A: Pandemic concerns aside, improving air quality in buildings should be a much bigger priority for organizations that care about the well being of their building occupants. A study by the Harvard TH Chan School of Public Health found that doubling fresh air flow (decreasing building CO2 from ~1100 ppm to 800 ppm) resulted in employee productivity gain valued at $6500/employee per year, far exceeding the added energy cost of the measure. Potential operational cost increases for improved comfort, fresh air, and air filtration/sanitation generally amount to ~$0.01/employee hour of operational cost and a similar level of capital cost with significantly higher return (~$2.5/employee-hour) due to improved productivity (~10%) and reduced sick days. (~40%). We recommend that facility managers and HR personnel work together to make the case for these improvements.
Q: Are there roles for private sector service providers to help with these efforts?
A: Absolutely! Improving and maintaining a building's indoor air quality (IAQ) and energy systems at a higher quality level will require the assistance of a variety of service providers, from mechanical engineers, those who install or sell "smart" online monitoring systems, to boots-on-the-ground HVAC contractors and maintenance workers.
Q: Spraying disinfectants between every customer makes me dizzy. Any recommendations on disinfectants?
A: We use 70% ethanol wipes to avoid this problem.
Filtration and air cleaning
Have a question about building modifications during COVID-19? Contact SEDAC at firstname.lastname@example.org or 800.214.7954.
Interested in receiving a COVID-19 Readiness Building Assessment? SEDAC's COVID-19 Readiness Assessments give you the independent, expert advice you need to identify medium to high risk spaces and make building modifications to reduce the risk of virus transmission.