For some buildings, sustainability is, at best, a minor consideration when compared to resilience. Resilience and sustainability are buzzwords in the building industry, though their meanings and relationship are often confused. In many discussions, the terms are used interchangeably, but there are significant differences in the scope and application of sustainability and resilience. While sustainability is an important concern that, indeed, plays a role in resilient design, the terms are not interchangeable, and their goals are sometimes in conflict.
As discussed in last month’s column, resilience involves preparing for, absorbing, recovering from, and adapting to extreme events and changes over time. Meanwhile, the United Nations defines sustainability as “meeting the needs of the present without compromising the ability of future generations to meet their own needs.”
As an example of the differences, energy efficiency is one of the pillars of sustainable building design. Designing a building for energy efficiency can directly lead to an increase in resilience. An efficient building has a lower energy demand, making it is easier to provide sufficient on-site generation capacity to allow for operation and recovery after an event. Community resilience is also improved. In addition to the building being available for its intended purpose, it also imposes less demand on the energy grid, allowing for any available energy to be allocated elsewhere.
It is important, however, to recognize that not every design decision that leads to greater sustainability also benefits resilience. An example of the potential tradeoff is windows versus artificial lighting. Windows are inefficient in terms of energy use, which may lead to increased use of artificial lighting; however, artificial lights require energy to function, and operable windows can improve IAQ. So, even if not considering resilience, there is a balancing act required in the design process to determine the best solution regarding natural light versus lighting fixtures. Adding resilience into the mix provides another set of advantages and disadvantages. After an event, windows allow for the use of the building during daytime, even if power is disrupted. In addition, opening windows may help compensate for an HVAC system that is not able to function as designed. However, windows are also subject to damage by windborne debris, blast, and seismic events. Broken windows can allow rain in and cause further damage.
Examples of facilities where resilience requirements greatly outweigh sustainability include hospitals, emergency response centers, some military facilities, etc. When developing designs for those facilities, we should, of course, consider sustainability and try to minimize energy use, embodied carbon, life cycle environmental costs, etc., but we may have to sacrifice one or more of those goals to ensure the building will fulfill its function after an event.
In the end, how do we balance resilience and sustainability in our designs? We need to talk to the owners and jurisdictions to determine their goals in both areas. Once we have a good understanding of the requirements, we need to explore different alternatives and the trade-offs involved in each to find the solution that best fits the needs of the client. That is the usual design process but perhaps with some different objectives. It is possible to balance resilience and sustainability, we just have to approach them as we do other design aspects.