As I have been working from home during the current viral pandemic crisis, I began to consider the architectural strategies that might play a role in reducing the transmission of viruses. What are those strategies, and how readily can they be implemented?
Building Codes and permit processes tend to focus on life safety in the event of a catastrophic fire. Now that we have all become acutely aware of the latent danger of viral transmission, especially in more public spaces, some clients may want to pay more attention to other health and safety factors. My research shows that there are several design and material choices architects can recommend to inhibit the spread of viruses, however these methods may not be advisable in all situations.
A vigilant cleaning regime is perhaps best, as recommended in this editorial from the Center For Active Design: https://centerforactivedesign.org/5-ways-to-optimize-buildings. However, as time goes on and lives return to “normal”, such practices may begin to be overlooked. Surfaces that we directly touch regularly, such as door knobs, could be made of materials or coatings that reduce the viability of viruses that land on them.
Aside from door hardware, other surfaces can include faucets, keypads such as at kiosks or on electronic locks, countertops where the public might linger (such as at an airline check-in counter), and perhaps other surfaces depending on the building type. These building elements should be designed to facilitate easy cleaning, being smooth or flat and lacking indentations or other hard-to-clean features. Some, like faucets, hand dryers, or even drinking fountains, can be a “no-touch” design that activates based on proximity.
Materials and Coatings
Where touching cannot be avoided, recent research has shown that copper (and alloys such as bronze or brass) has anti-microbial properties that may affect viruses as well as bacteria. Blaine Brownell, writing for The Journal of The American Institute of Architects, https://www.architectmagazine.com/technology/materials-and-coatings-that-reduce-surface-transmission-of-bacteria-and-viruses_o provides an overview of effective materials and coatings that can be used in the built environment.
While the SARS-CoV-2 virus (otherwise known as COVID-19) can be viable for several days on plastic or stainless steel surfaces, on copper it is viable only for about four hours, and related coronavirus may last only as much as eight hours. When our office first looked into the reported health benefits of copper (almost ten years ago), most of the literature touted its successes against bacteria, without much mention of viruses. With the world’s attention now on combating a specific virus it is good to see that copper is as effective as it is.
Not every surface can be copper, though. Coatings are being developed that can be applied to other materials, or included in paint finishes. However, the Centers for Disease Control is not yet persuaded as to the efficacy of such coatings, recommending conventional cleaning and hand-washing instead. Claims that a given coating inhibits “microbial growth” should be understood as a claim regarding bacteria and not viruses, since a virus does not grow or reproduce outside of an infected living cell. It may be the case that a product touted as “antimicrobial” is 99% effective against bacteria, yet relatively untested against viruses.
HVAC Systems and Daylighting
Viruses can accumulate on surfaces that we touch, but they can also ride on the microscopic droplets that emanate from our breathing, larger droplets cascading down in a zone that surrounds us while really fine droplets linger in the air. HVAC systems can play a role in setting the relative humidity as well as controlling air flow.
Sick Building Syndrome has been a topic of conversation for some time, noting that factors such as a high relative humidity (RH) or moisture within the building envelope can contribute to the growth of bacteria, fungus, or mold spores. In conjunction with more air-tight construction methods, the recirculation of indoor air can expose inhabitants to elevated levels of these irritants. Some viruses, however, may prefer a lower RH, which is why they are associated with seasonal outbreaks. During the winter months, lower humidity causes our mucous membranes to dry and thereby fail to protect us as they should. A common recommendation is to maintain RH between 40% and 60%, as the best compromise between inhibiting mold and bacteria, and protecting against viruses. This article by Peter Yost, for the Green Building Advisor website, goes into more detail and also points out that more research is needed with respect to HVAC and viruses.
It has long been known that ultraviolet light can quickly kill most microbes. This fact might encourage the current trend of introducing more natural daylight into spaces, as well as the creation of more outdoor spaces for functional use rather than just decoration. However, the UV provided by daylight is UV-A and UV-B, while UV-C is blocked by atmospheric ozone, and it is UV-C that produces the strongest germicidal effect. The actual benefits of daylight and open spaces has more to do with fresh air changes that dilute the airborne microbes, assuming that an increase in daylighting corresponds to more operable windows.
Where UV-C is being effectively used currently is in hospital situations, where it is employed as part of a disinfecting regimen. While a patient room is unoccupied, a portable UVGI (Ultraviolet Germicidal Irradiance) fixture can be brought in to expose surfaces to UV-C; this must be moved a few times to expose shadowed areas. Another implementation is within HVAC air ducts, to expose and thereby clean the coils, or just within the air stream. Studies have shown that UV-C disinfecting in HVAC systems can reduce the number of air changes per hour needed to achieve a target level of purity, and coil maintenance is reduced, so energy and maintenance savings can offset the additional cost of the system. For more information on UV-C implementation, see this workshop presentation by the National Institute of Standards and Technology together with the International Ultraviolet Association: https://www.nist.gov/news-events/events/2020/01/workshop-ultraviolet-disinfection-technologies-healthcare-associated
Social Distancing & PLANNING
Due to stay-at-home orders, many have become familiar with video conferencing as a way to hold meetings or get work done. We have dedicated some portion of our living space to serve as both an office and a broadcasting studio of sorts – and you can read this article with considerations for a home studio. Residential design may shift further towards inclusion of genuine home office/studios, with sound-insulated walls, much as there has been a trend of home theaters in recent years.
For other building types, there may be other factors to consider. Movie theaters used to try to pack in as many seats as they could, but when home theaters and streaming options became viable, many theaters redefined themselves by replacing their seats with much more comfortable recliners, spaced more widely, with a greatly reduced audience capacity. A desire to observe social distancing might push this trend even further. Restaurants might consider fewer tables, or fewer chairs per table, but with slim profit margins sensitive to seat count they may need to rely on other methods to protect their patrons. HVAC systems in large public accommodations may need to include UVGI disinfection. Places where crowds gather, like theaters or sports venues, may need first-aid rooms designed for effective isolation.
Many retailers have added markings on the floor to help shoppers to space themselves out, such as at a checkout counter. Rather than being ad-hoc markings, architects might consider flooring patterns that perform a similar role, while fitting in with the overall design aesthetic.
Office spaces may want to favor enclosed individual offices instead of large cubicle-defined open offices. However, those offices might be without doors, to avoid the need for door knobs, and air flow could be planned to minimize potential contamination from one office to another.
Some building types may have the potential to be converted into temporary hospital facilities, either to take on pandemic cases or just to relieve hospitals of non-acute patients to make their beds available. As reported in Healthcare Design Magazine, a task-force evaluation of assets near New York City (see https://www.healthcaredesignmagazine.com/news/awards-events/webinar-covid-19-lessons-from-new-york/) concluded that it doesn’t make sense to consider conversion of a facility that provides less than 25 beds, based on staffing ratios, and a hotel or convention center may lose 15% or more of its bed rooms to ancillary functions like nurse stations, clean supply, soiled laundry, or other programmatic needs. Temporary supplemental HVAC and emergency power can be installed on the exterior of the building, entering patient rooms through window panes that can later be replaced. The estimated cost of conversion should include costs to restore back to original condition, and restoration will likely cost 25% to 33% of the conversion cost. Staffing and supply can be as limiting as the availability of physical space, so communication and coordination among several sectors is needed to achieve a conversion, not just architects and engineers.
All of these measures are aimed at reducing the transmission of viruses in general and many are already adopted in hospitals or other sensitive buildings. Ultimately, though, it is up to the human immune system to produce its own protection against a virus, and this process can only be triggered by exposure. Will it be wise to increase our protection, if it means that we reduce exposure?
The term “herd immunity” refers to the population overall containing enough individuals who have been exposed and developed their own antibodies; the virus doesn’t have enough susceptible individuals to infect and therefore cannot spread at the exponential rate seen at the outset. A population that is protected by its environmental features, rather than by its exposed immune system, might not achieve an appropriate level of herd immunity, remaining susceptible to future outbreaks. Since the threshold for herd immunity is imprecise (and likely to be different for each unique virus), it will be difficult for authorities to establish the right level of protection to recommend.
Still, it may be wise to adopt some of the most effective methods used in hospital settings and extend them to varying degrees in places where the public congregate. Some sectors, like food service / restaurants, might have new regulations imposed as part of maintaining their license to operate. Other buildings, like churches, are not subject to the same level of regulatory compulsion, and may not have a budget that can absorb additional costs. Architects can help to determine an affordable strategy and achievable goals, just as they do for similar concerns like energy efficiency.