Many architects and designers have proffered ideas about how to design healthy buildings in light of COVID 19. However, the current pandemic need not be the motivation to design structures that support salubrious living. There should be an ongoing effort to strive for buildings and spaces that are beautiful, safe, and healthy for all.
Accordingly, architects, planners, and designers should rethink what constitutes a healthy building with particular reference to its culture, resources, and climate. In developed nations structures usually begin with a program that considers design, safety, comfort, a healthy environment, and perhaps a LEED certification. However, this may not be feasible in parts of the world where resources are scarcer. In such places, architects must triage priorities when it comes to designing healthy buildings. This is particularly important in healthcare buildings, where design strategies employed in developed nations may not be feasible in other parts of the world.
What This Pandemic Taught Us
Aerosolized droplets that contain the virus can travel long distances through the airstream and linger, where they can be inhaled. The closer individuals are to each other, the higher the risk of infection.
Most infections occur indoors, on public transit, or during social gatherings. However, the risk indoors is significantly reduced through well-designed ventilation systems. A well-ventilated space, either mechanically or naturally, will do the following:
- Dilute the virus by increasing air exchange rates. Diluted pathogens are less likely to infect.
- Contain the virus through decentralized systems and providing pressurization between spaces.
- Saturate the virus through humidification. By maintaining high relative humidity, studies show that aerosolized droplets fall to the floor where they are less likely to be inhaled.
Ventilation is needed to remove water vapor produced by respiration, burning, and cooking, and for removing odors. In the absence of adequate ventilation, irritating or harmful contaminants can build up, causing health problems.
According to the World Health Organization, when assessing ventilation performance in buildings, the following four aspects shall be evaluated: (1)
- Does the system provide sufficient ventilation rates as required?
- Is the overall airflow direction in a building from clean to dirty zones?
- How efficient is the system in delivering air to each location in the room/building?
- How efficient is the system in removing the airborne pollutants from each location in the room?
Mechanical ventilation is a method where outside air is processed through devices to achieve desired temperature, humidity, and flow.
If well designed, installed and maintained, mechanical ventilation is reliable in delivering desired results regardless of variable wind and ambient temperature. Filtration systems can also be installed to mitigate harmful microorganisms, particulates, gases, and vapors. Further, the airflow path on mechanical ventilation systems can be controlled, allowing the separation of infectious areas from clean areas.
However, if not well designed, installed, and maintained, the system will not perform as expected. Normal operation may be interrupted or underperform for numerous reasons, including equipment failure or utility service interruptions.
Because of these problems, mechanical ventilation systems may, ironically, result in the spread of infectious diseases through buildings, especially healthcare facilities, instead of being an essential tool for infection control.
Natural ventilation is a method of allowing fresh outdoor air into indoor living spaces by natural means without the use of mechanical devices.
Natural ventilation can provide an appropriate ventilation rate economically due to the use of natural forces doing the work. No electricity or fossil fuels are needed. As such, the operating costs are negligible. Natural ventilation usually results in more natural light, which has proven therapeutic benefits. Due to its simplicity, natural ventilation is generally reliable.
However, similar to mechanical ventilation, natural ventilation has its drawbacks. Natural ventilation depends on external climatic conditions. Wind and temperature vary randomly. As a result, natural ventilation may be difficult to control, with airflow being uncomfortably high in some locations, and stagnant in others. With natural ventilation, it is challenging to control airflow. Contamination of corridors and adjacent rooms is therefore a risk. Additionally, natural ventilation may be interrupted for numerous reasons, including windows or doors not being open, or poor sizing and location of openings. Other potential drawbacks include noise, air pollution, insect and vermin infestation (not all cultures use screens), and security/safety from nefarious actors.
Rethinking Healthcare Facilities
The decision to use mechanical or natural ventilation for infection control should be based on needs and available resources.
For example, in the United Kingdom, the National Health Service policy limits the adoption of mechanical ventilation to the principal medical treatment areas such as airborne infection isolation rooms, operating theatres, and associated rooms. Patient wards are usually not required to be mechanically ventilated and natural ventilation through operable windows is commonly employed.
In another example, in Butaro District Hospital (Rwanda), MASS Design Group provided a layout that mitigates and reduces the transmission of airborne disease through natural cross-ventilation. All hallways are located along the building’s exterior so that patients and staff can move in the open-air. Inside, the hospital wards are inverted, giving each patient a large window with a view in addition to increasing natural light and ventilation. High-volume, low-speed fans, louvers, and large operable windows support cross-ventilation. High ceilings further facilitate air circulation. These measures reduce the infection rate among patients and staff. (2)
Architects and designers should reexamine dogma when it comes to providing healthier buildings, particularly healthcare facilities. Although codes such as ASHRAE would require all healthcare facilities to rely only on mechanical ventilation, we should keep in mind that natural ventilation would accomplish many of the same goals with the added benefits of simplicity, economy, and affordability.
(1): “Natural Ventilation for Infection Control in Health-Care Settings,” James Atkinson, et al. Eds. WHO 2009.
Written by: Paulina Beeche, AIA, LEED AP, CDT, Senior Associate
Edited by: Greg Andoll, Architectural Associate