As the global health pandemic highlights the need for healthier, well-ventilated indoor spaces to reduce or mitigate the transmission of pathogens, could passive design become a mainstream building practice?
Incorporating passive design into building construction is certainly nothing new, with ancient civilizations developing basic principles of architecture around the relationship between humans, the climate and their environment. Passive design strategies are integrated into the architectural design of a building’s orientation, form and exterior shell in order to optimize the use of natural energy sources such as the sun, wind and light. Unfortunately, for most of this modern age, passive design has not been incorporated or prioritized in the architecture design process which has resulted in poorly performing building stock in the United States.
But as the global health pandemic highlights the need for healthier, well-ventilated indoor spaces to reduce or mitigate the transmission of pathogens, could passive design, once again, become more of a mainstream building practice? Designing commercial buildings to have operable windows (with the appropriate level of control) provides a wide range of benefits including occupant thermal comfort, productivity and overall healthier wellbeing.
As Covid-19 forces us to consider the impact that indoor environments can have on an occupant’s health and safety, I believe that this could be the awakening that the building architecture industry needs.
Why Passive Design Hasn’t Been a Priority
In an industry driven by cost, schedule, and efficiency, optimizing a building’s passive design is low on the list of priorities for many building owners, even though it can greatly benefit all three. While many want to reduce their carbon footprint and energy consumption, financial concerns about maximizing square footage and ROI have been the main decision drivers when it comes to building design.
For the first half of the 20th century, it was actually common practice for commercial buildings in the US to use natural ventilation as the primary method for cooling. Office buildings had extended perimeter zones so that every office would have access to fresh air and daylight. However, with the increase in availability of HVAC equipment and emergence of new control technology, by the 1970s, more than half of the commercial buildings in the US had air conditioning systems installed that provided equivalent amounts of ventilation. Design teams viewed prioritizing a building’s orientation, mass and floor plan for natural ventilation as more of a restriction than a benefit. HVAC systems were understood to provide more controllability and predictability of temperature and airflow than the outdoor environment. In 1975, as response to the oil crisis that prompted an assessment of building energy consumption, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) released the first energy efficiency standard to provide guidelines on how we were consuming (and wasting) energy in buildings. However, these early energy efficiency standards focused on strategies to tighten the building envelope and decrease the size of the outside air intakes to the building in order to reduce the wastage of conditioned air. Unfortunately, this lowered indoor air quality for the occupants, which dropped significantly as a result of the poor ventilation strategies. Consequently, increasing the amount of bacteria and airborne contaminants which caused occupants to fall ill with ‘sick building syndrome’. We had set ourselves up for failure. The majority of the US’s existing building stock was poorly designed with no passive benefits and we were limited to providing a band-aid approach to reducing energy consumption at the sacrifice of occupants’ health and comfort.
Prioritizing Occupant Health
Post-COVID-19, once people feel safe to occupy commercial buildings again, there will most definitely be a greater focus on an occupants’ health and comfort. Many building professional associations are already recommending indoor air quality strategies such as increasing fresh air and higher filtration in order to reduce the contamination of aerosols in interior building spaces.
ASHRAE released updated protocols and MERV filtration guidance to help facility owners and operators improve the indoor air quality of their buildings by eliminating recirculated air systems and increasing the run time of fresh air ventilation systems in order to reduce the cross contamination of aerosols. However, these new protocols will result in additional installation and operation costs due to increase in the quantity and size of supply fans needed to circulate larger volumes of air through the building.
Rethinking traditional design
Renewed focus on the health and safety of interior spaces and continual energy efficiency requirement, is just another push for designers, architects, engineers, developers, and building owners to apply passive design principles on their new construction projects. Considering passive design strategies such as building’s orientation, massing and façade that optimize the use of free energy such as sun for heating, wind for cooling and daylight for natural lighting can have a big impact on reducing the operational costs of a building. For example, the best orientation for a rectangular building in the northern hemisphere is east-west orientation with respect to the long axis of the building. This ‘optimizes your gains and losses’ based on the climate. Thoughtful design into the quantity and positioning of window openings on each of the building’s facades based on the site’s topography and predominant wind conditions could provide both improved airflow and free cooling to the interior spaces.
Consider the benefits that incorporating natural ventilation and mixed-mode ventilation have on improving indoor air quality and comfort for building occupants while reducing energy and operation costs. In addition to thermal comfort, the ability to open windows and circulate fresh air is proven to increase productivity by up to 11%, reduce sick days, and create a better work experience. Orienting a building to capture predominant wind conditions, maximizes airflow within a space that can be used to naturally exhaust aerosols. This is a much more efficient option than increasing the operation time of mechanical systems or recirculating stale air and pathogens through filters—important when dealing with highly contagious viruses like COVID-19.
Giving occupants access to daylight is also important and improves their visual comfort. Studies show that students who work in school buildings that incorporate daylighting strategies into their building design, have better test scores. Optimizing the amount of usable natural light (and eliminated glare conditions) means a reduced operation time for hardwired lighting systems, which saves money and energy.
The benefits of passive design, resulting in healthier, more energy-efficient buildings are undeniable. In the post-pandemic world, my hope is that the new construction industry is reawakened to these benefits and embraces passive design strategies as standard practice. To see for yourself how passive design strategies produce better outcomes, I urge you to check out case studies such as this office building in Phoenix, Arizona.