As workplaces adapt in the wake of COVID-19, mindful decisions when designing mechanical, electrical and plumbing systems can have a positive impact on limiting the spread of disease. Some technologies are already available, but the designer must be forward thinking about how decisions can impact the health of the building.
There are many options available in the electrical and plumbing products industry which, when used appropriately, can limit the spread of disease by limiting or eliminating the need for contact with the fixture. Occupancy or vacancy sensor light switches are commonplace in commercial applications. Sensor-type flushing mechanisms for toilets, as well as sensor-operated faucets, soap dispensers and paper towel dispensers or hand dryers are readily available and often utilized on commercial projects.
Unfortunately, however, the design is only as strong as its weakest link. If an occupant can activate the lighting upon entry and wash their hands without contact after using the restroom, but then needs to pull a door-handle to get out of the restroom, all has been lost. Some projects utilize contact-free entry and exits from restrooms rather than physical doors which is especially helpful. However, in order to maintain visual privacy into the restrooms, the entry/exit path needs to include changes in direction which can take up considerable floor space, so this approach is less often utilized. Other features may be considered for doors such as foot-operated door handles, hands-free door opener sensors (i.e. “Wave to Open” technology, etc.).
Drinking fountains most often require contact to use the bubbler. If a bottle filler is provided, sensor-activated options are readily available. This product line is ripe for improvement, however, to develop complete sensor-operated functionality.
The discussion around heating, ventilation and air conditioning (HVAC) systems can greatly enhance a building’s resistance to the spread of airborne disease. Designers can be strategic with the use of HVAC systems to help reduce airborne exposures. While filtration and ventilation are the most common approaches, there are other creative tactics that can also be used.
Air Filtration Systems
Filtration is a great option for controlling the spread of disease and is required in the design of hospitals and many other types of medical facilities. However, in most commercial, residential and industrial applications, the use of high filtration devices is optional. It is important to understand that filters come in many efficiencies, and the filter efficiency required for capturing bacteria and viruses is extremely high. These high efficiency filters are costly and largely not used except in the medical industry. The higher the filter efficiency, the more powerful the fan must be to push the air through the filters. This can become a limiting factor for many mechanical system types.
Larger packaged and custom air handling units can often be selected with high static fans to overcome this issue, but most products for light commercial and residential applications do not have fans that are suited for the use of high (enough) efficiency filters. Further, while designs for equipment can include accommodations for high efficiency filters in non-critical applications, at some point the high efficiency filters are often removed from the systems due to the high cost of filter replacement and the fan energy associated with pushing the air through those filters.
A second option for controlling the spread of disease is ventilation, or the introduction of outside “fresh” air into a building. Well-ventilated buildings are beneficial to occupants in countless ways, including dilution of contaminants in the air, removal of moisture, odors, carbon dioxide, etc. Studies have also been linked to decreased cognitive performance in poorly ventilated buildings.
While ventilation alone is not capable of addressing all aspects of infection control, current codes regulate minimum ventilation levels by occupancy type. In some applications and in some jurisdictions, “natural ventilation” through operable doors and windows is still allowed. Design teams should consider this carefully, though, because tightly-constructed buildings severely limit the effectiveness of natural ventilation. Ducted ventilation systems add cost and energy use to projects, but the long-term benefits are significant. Also, energy use can be reduced substantially through energy recovery systems.
Another tactic that is not considered as often for disease prevention is optimizing levels of relative humidity within buildings. Hospitals and medical facilities are mandated to be maintained at certain levels of relative humidity for good reason – many viruses have been shown to be sensitive to relative humidity, although the exact reason for this has been a bit elusive to the scientific community. The American Society for Microbiology has published articles and data related to the survival of various virus types at different levels of relative humidity. Low humidity and/or high humidity in spaces can increase the survival of many types of viruses, where mid-levels of humidity often shows a reduction in viability depending on the virus. Also, mid-range humidity levels have been correlated to better immunity against respiratory infections by immunobiologists. Maintaining relative humidity within buildings at 40-60% is generally optimal. In dry climates, this means the HVAC systems design should consider humidification, where design in humid climates should implement dehumidification strategies. Both of these tactics require larger amounts of energy use in the HVAC systems.
Ultraviolet energy, especially in certain wavelengths, can also kill or inactivate microorganisms. HVAC systems designed with ultraviolet germicidal irradiation (UVGI) lamps can be a good consideration, but the maintenance of UVGI products is important. UV-C energy can be damaging to eyes, so the lamps are best installed in ductwork so they are not visible to the occupants. A proper maintenance protocol is critical, because when the lamp life has ended and UVGI lamps require replacement, it’s not immediately obvious since these are concealed in the ductwork.
Design and construction teams for buildings can help influence the health of buildings through the features that are implemented, but there is still no substitute for personal hygiene and cleaning protocols. As we navigate the current COVID-19 pandemic, creative, forward-thinking solutions to maintain a healthy building will undoubtedly continue to receive increased consideration.
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