Building design around the world will need to change in order to reduce transmission of infectious respiratory diseases including COVID, a panel of experts says.
During a recent webinar, the International WELL Building Institute (IWBI) convened a panel to discuss how design of buildings should evolve in response to recent research into infectious respiratory diseases.
The session was chaired by Whitney Austin Grey, Senior Vice President, Research at IWBI. Panellists included Vivien Loftness FAIA, a Professor of Architecture at Carnegie Mellon University in Pittsburgh and a past and present member of ten panels the National Academy of Science; Kevin Van Den Wymelenberg, Professor of Architecture at the University of Oregon; and Kate Davis, Principal and Director of Commercial Interiors at multi-national architecture, engineering and design firm HIKS.
The webinar comes as the IWBI is looking at infectious diseases as part of a twelve topic research agenda which it launched last January.
Several key themes emerged during the webinar.
Let in Outside Air and Natural Light
In terms of specific design strategies, a critical theme which panellists stress is the need to bring in external elements such as outside air and natural light.
Speaking of outside air, Loftness says the importance of this has been underscored during COVID as understanding of transmission shifted from initially being entirely focused on touch points and cleaning to also include airborne transmission.
On this score, she talks of three areas.
First, there is a need for openable windows and other openings.
According to Loftness, there are many examples of how these can be delivered. In catering, some restaurants have moved away from sealed dark glass doors to having entire walls open up and tables spilling out onto sidewalks and footpaths. In schools and offices, openable windows and walls could not only help to manage infection but also to enliven earning and learning spaces.
Next, spatial arrangements should be revaluated to determine which parts of buildings really need to be indoors and air-conditioned and which could be opened to the outside.
Finally, there is a need to rethink heating, ventilation and air-conditioning (HVAC) systems.
In particular, Loftness talks of a need to separate ventilation from thermal conditioning. As things stand, she says traditional approaches have seen heating and cooling supplied with the same air that is used for breathing. With the volume of air needed for air-conditioning often being ten to fourteen times that required for breathing, breathing air often becomes ‘lost in the shuffle’.
Nowadays, however, Loftness says a shift is underway toward outside air conditioning systems along with a dedicated constant volume breathing air system. This will ‘allow people to open windows because we’ll just turn off their thermal system, let them open the windows we’ll still provide them with a dedicated outside air system that’s well filtered and is in some cases dehumidified and in other cases, maybe humidified’ she said.
Indeed, Loftness talks of a shift toward what is known as mixed-mode HVAC in the US or hybrid HVAC in the UK. “Mixed-mode” refers to a hybrid approach to space conditioning that uses a combination of natural ventilation from operable windows (either manually or automatically controlled), and mechanical systems that include air distribution equipment and refrigeration equipment for cooling.
This will require a shift of mindset from mechanical engineers – many of whom Loftness says are accustomed to use of variable air volume and pressurised buildings to distribute breathing air.
Van Den Wymelenberg broadly agrees and talks about the importance of natural ventilation and natural systems.
Even before COVID, research in which he had been involved had highlighted the importance of ‘natural systems’ for things such as HVAC and lighting.
During his research, his team discovered that naturally ventilated spaces have a different indoor microbiome compared with spaces which are mechanically ventilated – the former having a microbiome which more closely matches that of outdoor environments.
Spaces with daylight, meanwhile, have a different microbial community compared with those without. Moreover, darker spaces have a greater abundance of bacteria which is associated with respiratory disease compared with those which saw natural light penetration.
Indeed, one of his studies conducted in dorm rooms showed that natural ventilation delivered a 50 percent reduction in aerosol viral load compared with mechanical ventilation.
On the point of daylight, Loftness says that not only daylight but natural sunlight is critical.
Whilst some designers have expressed concerns about letting too much sun and solar energy into buildings in the face of warming temperatures, she counters that designing spaces around sunshine helps to sterilize those parts of buildings which would otherwise be more concerning from a viral perspective.
Reducing Water and Surface Viral Transmission
Aside from fresh air, Loftness says attention is also needed in regard to water and surfaces.
On water, it is important not only to deliver water of an acceptable quality in order to reduce waterborne disease transmission but also to design buildings to minimise microbial damage which can occur during flooding or hurricanes as water penetration into buildings can breed microbes and mould. This, Loftness says, has become more important as climate change leads to more frequent and more severe weather events.
On surfaces, Loftness talks of a need for hands-free design to avoid hand-to-hand transfer of diseases via doorknobs or keyboards. This is especially important as ordinary colds and flu are transferred via hand-to-hand contact.
Better Building Codes and Information Provision
Beyond specific measures, panellists talked about broader issues regarding building codes and public communication.
On codes, Van Der Wymelenberg would like an approach which clearly defines an acceptable level of viral transmission risk within buildings. This could start, for example, at a 10 percent risk of transmission and be reduced over time.
He says it is critical to measure the risk of infectious respiratory disease transmission and to strategically manage indoor environments around a specific risk profile.
Davis agrees, adding that such an approach will enable clearer communication about the level of risk in buildings. For building owners and managers, this will empower them to assume greater control over infection control management in their buildings. For occupants, it will enable better understanding of potential health risks in coming to work. This in turn will facilitate better informed personal decisions about coming into the workplace or working remotely.
More broadly, Davis talks of a need to shift how corporate real-estate is viewed.
In particular, she would like a movement away from buildings being viewed as a container into which people are forced to come in order to perform their tasks.
Instead, she says buildings should be viewed as a service offering and a place of service. Under this view, design strategies would focus on how the building can best help those coming to work to derive maximum value and productivity.
As part of this, she says greater transparency and provision of data is needed to empower individual occupants to assess their own level of risk from attending. She adds that occupant desire for such data has grown in line with the proliferation of wearable devices.
100 percent outdoor air for breathing?
As mentioned above, Loftness has argued for a shift toward outdoor ventilation. This raises questions about whether or not 100 percent outdoor ventilation is desirable.
On this score, Van Den Wymelenberg acknowledges that the need to reduce viral transmission must be considered along with other issues such as climate, energy consumption and occupant comfort.
Rather than 100 percent outdoor air, he would like codes and standards to define the expected mode of operation within the building. Most likely, this would include an outdoor air ratio.
These specific requirements could be flexible, he adds. They should respond not only to the pathogenic profile of the direct environment but could also be varied across seasons and across regions.
To do this, buildings must be designed to enable facility managers to modulate and to dial in to higher and lower risk modes as the need arises.
Instead, she argues that ventilation systems should be based on 100 percent outside air.
In order for this to happen, Loftness reemphasises her above point about ventilation systems needing to be separated from thermal energy systems. This, she argues, would facilitate provision of outdoor air ventilation systems at a much lower ‘energy penalty’ than would be incurred if 100 percent outdoor systems were enacted without such separation.
She also adds that 100 percent outdoor energy for breathing systems should be accompanied by consideration of energy recovery. Indeed, she says current technology enables 70 to 80 percent of such energy to be recovered from discharged air. Also considered should be high energy particulate air (HEPA) filters.
Loftness says there are many examples of outdoor ventilation systems being included in new construction (but also encourages retrofitting of existing buildings for outdoor air). In Cape town, for example, the convention centre is already 80 percent natural ventilated – air conditioning being applied only in rooms in which people spend short periods in high-density.
“I do fundamentally believe that we need to do 100 percent air ventilation systems,” Loftness said.