The following article was developed through the collaboration of several Arup experts: Fiona Cousins, Gideon D'Arcangelo, Rebecca Hatchadorian, Meaghan Kahnert, Jamey Lyzun, Ray Quinn, and Mark Walsh-Cooke.
As we contemplate returning to the workplace, businesses continue to wrestle with many unanswered questions. Recently there has been an explosion of articles addressing these topics — some from industry experts, others from commercial service providers and equipment manufacturers. Sorting through occasionally conflicting and sometimes inaccurate information can make it difficult to find a clear path forward.
This three-article series provides guidance for making indoor environments healthier both during the COVID-19 crisis and beyond. These recommendations are informed by reliable sources and augmented by the on-the-ground experience of Arup’s building system engineers, sustainability consultants, and integrated planning experts.
Six months after COVID-19 triggered its first shut down in Wuhan, China, some parts of the world have begun to emerge from the worst of the crisis. With no clear end in sight, policy makers and business leaders in re-opening areas are now faced with the challenge of determining how to safely loosen restrictions in urban centers.
Fortunately, we don’t need to know everything about COVID-19 to help prevent its spread. The novel coronavirus is similar to other, better understood, respiratory viruses that infectious disease experts already know how to contain and kill, and experts agree these strategies can guide us.
We know that reducing the risk of transmitting COVID-19 indoors hinges on three actions: maximizing ventilation and improving indoor air quality, sanitizing high-touch surfaces, and minimizing close person-to-person contact.
Expert sources recommend implementing a combination of strategies to accomplish these goals, including:
- Strict cleaning and hygiene protocols
- Social distancing
- Personal protective equipment
- HVAC system upgrades
- Specialized disinfection technology, such as UV irradiation, as appropriate
Why HVAC upgrades are crucial to prevention
When it comes to containing the spread of the novel coronavirus indoors, maintaining high levels of air quality and air flow is critical. Why? Because infectious disease experts agree that the rate of virus transmission is influenced by several factors, including:
The dose of the pathogen
The virulence of the pathogen
The time the pathogen has been in the air or on a surface
The resistance level of the host
Based on these findings, we can deduce that a more densely populated room is likelier to have a higher number of infected individuals and therefore a higher concentration (or dosage) of pathogenic particles. We can also conclude that the risk of infection in that room will be reduced by increasing air flow and diluting the concentration of pathogens in the air.
The key takeaway here is that your HVAC system’s level of performance directly impacts your ability to control the spread of the virus indoors; the higher the level of performance, the lower the risk of spreading the virus. Ideally, we could redesign all buildings to be more resilient to viral outbreaks. Instead, we must work with what we have, reverse engineering our systems to boost their performance as much as possible.
With this in mind, in April 2020 ASHRAE released guidance on how to upgrade HVAC systems to help prevent the spread of COVID-19 in the workplace.
- Increasing outdoor air ventilation rates
- Implementing pressure control
- Improving filtration in central air handlers
- Optimizing air flow patterns
- 24/7 system operation
- Controlling humidity at 40–60%
- Increasing air changing rates
- Adding UV irradiation (ultraviolet germicidal irradiation) in air-handling units or occupied spaces
It’s important to note that the measures endorsed by ASHRAE are designed to reduce the risk of indoor transmission. There is currently no way to eliminate the risk of indoor contagion entirely. Are the upgrades still worth doing? Absolutely, according to Dr. Joseph Allen, Deputy Director of the Harvard Education and Research Center for Occupational Safety & Health. During Green Buildings in the Age of Coronavirus, a recent webinar hosted by the Urban Green Council, Professor Allen emphasized that the COVID-19 crisis has put today’s building owners on the frontlines of public healthcare, “The person who manages your building has a bigger impact on your health than your doctor.”
Will this knowledge be enough to prompt most businesses to undertake a series of complicated and potentially costly HVAC modifications in the lead up to a long-awaited reopening? It remains to be seen. There is speculation that some percentage of building owners will opt for an easier solution — recalibrating their systems to maximize outdoor air rates and dialing up run hours. But this blunt approach to air-quality enhancement has some obvious disadvantages, such as compromising your ability to control humidity and maintain the thermal comfort of occupants in the summer and winter months. It can also easily result in soaring energy costs.
How to get the most from your HVAC system
There are more efficient and affordable ways to improve indoor air quality and flow than running HVAC systems at full capacity 24/7. But implementing many of these solutions will require some construction and expert guidance. The installation of a new or upgraded filter rack or a larger fan motor in an air-handling unit can significantly boost performance, for example. To further limit the risk of contagion, these upgrades can be augmented by electronic air cleaners and disinfectors that remove or inactivate particles within a space or airstream. Ultraviolet Germicidal Irradiance (UVGI) is one example. UVGI is already widely deployed in healthcare settings to degrade organic material and inactivate microorganisms. Other electronic technologies designed to remove, inactivate, or capture ultra-fine pathogenic particles are currently being developed and tested.
The case for careful planning
It is possible to undertake some of ASHRAE’s recommended changes without the help of an expert, but it’s not generally advisable. For one thing, not every infection-reduction HVAC solution is suitable to every building. For instance, while early evidence suggests that maintaining a minimum relative humidity above 40% and below 60% can lead to a significant decline in the transmission of respiratory infections, making humidity control potentially useful in combating COVID-19 transmission indoors, this solution will not work for some building types. For buildings located in cold weather climates, attempts to maintain minimum humidity can lead to problems with condensation. Moreover, this strategy would be at odds with the mandate to increase ventilation, since cold incoming outside air is very dry, leading to enormous humidification loads.
The bio-disinfection technologies on offer will also be challenging to implement without expert assistance. For example, the preventative potential of UV irradiation is being much touted at the moment, but this technology has yet to be widely deployed in offices and will be of minimal value if not installed properly.
What is UV irradiation?
UV irradiation (UVI), also known as germicidal ultraviolet irradiance (UVGI), employs ultraviolet radiant energy to inactivate bacteria, mold spores, fungi, and viruses. UVGI works by damaging a pathogen’s genetic source code, destroying a virus’s ability to replicate. UVGI is commonly used in healthcare settings to aid in bio-disinfection. Like other forms of irradiation, UVGI can damage human skin, but it poses limited risk when used properly.
To get the most value from your COVID interventions, it’s useful to partner with an experienced building system designer during the planning and implementation process. Unlike building managers or specialty technicians, building system designers are trained to perform an in-depth evaluation of a range of factors (such as building systems, code requirements, office layout and density, and energy performance) to determine the best strategies for each client.
A COVID intervention plan will also benefit from a multidisciplinary approach. In addition to assessing HVAC system capacity at both the space and building level and reviewing building and energy code limitations, a multidisciplinary team can work with contractors to ensure that your system’s air flow patterns and rates are calibrated to optimize air quality. Modeling experts can quantify the particle concentration reductions delivered by specific HVAC interventions and help you optimize pedestrian flow and layouts to meet social distance requirements. Project management and finance experts can develop detailed cost estimates, work plans, and construction schedules. Under the guidance of building automation specialists, HVAC algorithms can be implemented to help optimize building operations to maintain safety, comfort, and energy efficiency. In addition, sensors can be added to measure ultra-fine particles or volatile organic compounds that may correlate to the level of pathogenic particles inside a space.
Preparing for the new normal
With the COVID crisis still underway, it’s tempting to throw all our resources into designing laboratory-grade ventilation and bio-disinfection systems for commercial and office buildings. But it’s important to remember that the COVID prevention upgrades outlined in ASHRAE’s April guidance document are aimed at fighting a pandemic. These are not the new gold standard in HVAC design. If we fail to make this distinction, we run the risk of overdesigning all our future buildings, which would be unnecessary, expensive, and counterproductive to our long-term goals. After all, the success of any business depends not just on surviving the COVID crisis, but on building lasting resilience — and a key part of building overall resilience is continuing our commitment to creating more sustainable, energy-efficient buildings to help combat climate change.
We don’t have to sacrifice long-term performance to help reduce future outbreaks. By taking a holistic approach to building design we can balance the needs of today against the demands of the future. We can invest in the development of future-proofed design systems — low-energy enhancements that actively kill viruses while still prioritizing sustainability and resource efficiency.
Another powerful way we can help meet both our current and future goals is by promoting the widespread adoption of healthy building practices. Standards like Fitwel and WELL were originally designed to foster sustainability and health and wellness, but it turns out that many of the enhancements that put you on the road to certification also work to reduce the spread of COVID-19. For example, both organizations call for higher air-quality standards, improved filtration, increased ventilation, and stricter, more frequent cleaning protocols.
With many businesses already implementing these upgrades in response to the pandemic — and thus on the way to certification already — we are in a unique position to advocate that healthy building standards become the baseline for all future buildings. Those businesses that choose to act now, and pursue full certification for existing buildings, will not only set an important precedent, they will also reap a host of other rewards. They will help restore the confidence of their employees by clearly signaling a deep commitment to their health and wellbeing and they will create healthier indoor environments that have been proven to increase employee engagement, improve productivity, and boost cognitive function. Put simply, healthy buildings are not just better for the environment, they are better for business.
Our next article will dive into user-centered strategies businesses can leverage to facilitate a smoother, safer return to the office.