Home AEC Resilience Is the New Sustainability

Resilience Is the New Sustainability

The US Resiliency Council, Bullitt Center, Seattle, Puget Sound, Washington, USRC, San Francisco, Bay Area
“Concentric braced frames in Seattle’s Bullitt Center” Image courtesy of Nic Lehoux

Evan Reis, SE
Executive Director, US Resiliency Council

Green design alone is not sustainable

Ihad a discussion with a friend a few years back who really wanted to buy a new Prius because it was so environmentally friendly. I commented, to her chagrin, that she might be better off buying a used Corolla that got 50 mpg, because the car was already built. Regardless of a building’s “green” features, which are intended to reduce the use of or impact on finite resources over the building’s lifetime – water, energy, clean air – the biggest environmental impact a building has is during its construction. Renewable and recycled materials used in many buildings reduce this impact, but the energy cost of manufacturing and assembling the building components is still the largest contributor. Therefore, the longer a building lasts before it needs to be replaced, the more sustainable it will be.

Consider the example of the Bullitt Center in Seattle, hailed as “the greenest commercial building in the world” by its developers. The building, dedicated on Earth Day, 2013, is an energy net-positive space boasting some of the most state-of-the art, environmentally friendly features that include solar panels, rainwater catchment, use of sustainable wood framing materials, and even self-composting toilets. According to Dennis Hayes, the Bullitt Foundation CEO, “The building was designed to last 250 years, so we expect many decades of favorable economic returns.”

However, Seattle and the rest of western Washington are at substantial risk of a major earthquake along the Cascadia Subduction Zone Fault, which is capable of producing a Magnitude 9.0 earthquake that would generate nearly fifty times more energy than what was released during the 1906 Great San Francisco Earthquake. Experts estimate the probability of such an event occurring over the next fifty years at between one in three and one in ten.

The Bullitt Center was engineered with a structural system employing concentric steel braced frames (CBF). Studies over the past ten years suggest that CBF’s can be among the poorer performing modern structural systems in earthquakes. Brace buckling, gusset plate fracture and yielding of the beams above the braces may result in large permanent building deformations that could render buildings a total economic loss after a major seismic event. The Bullitt Center website makes no mention of the building’s expected seismic performance over its intended “250 year” lifetime.

The question this raises is obvious. If there is a 10 percent-33 percent chance of a catastrophic earthquake hitting the Seattle area in the next fifty years that could render some buildings with CBF’s as total losses, can a building truly be considered green and sustainable if it generates thousands of tons of debris and a huge environmental cost should it have to be demolished and rebuilt after just fifty years?

The US Resiliency Council promotes resilience based design

The Building Code is often misunderstood as a standard that ensures a building is “earthquake proof.” In fact, the stated goal of codes for standard occupancy structures is to produce buildings that are safe and will not collapse under extreme loading. It is possible, even probable in many instances, that the buildings will be so heavily damaged that they are not economical to repair and will have to be replaced. Furthermore, in a large city like San Francisco, as many as 90 percent of the buildings were built before the adoption of modern building codes. Consider the February 11, 2011 earthquake in Christchurch, New Zealand. Only two modern buildings collapsed, but 50 percent of the buildings in the central business district were eventually demolished as a result of heavy damage.

The US Resiliency Council has become the leading organization promoting resilience based design through its Building Rating System for earthquakes. Resilience based design measures and improves building performance across the dimensions of damage and recovery as well as safety.

The US Resiliency Council, Bullitt Center, Seattle, Puget Sound, Washington, USRC, San Francisco, Bay Area
“The USRC Rating System evaluates performance across the dimensions of Safety, Damage and Recovery”

Resilience based design is an economical solution

Several studies suggest that the construction and design costs for a building that achieves a LEED Platinum rating are on the order of 5-10 percent above a building that is not LEED Certified. The marketplace has absorbed this cost because of the high public demand for sustainable buildings. What might be surprising to learn, however, is that the cost to achieve resilient design that considers the value of reducing damage, recovery time and ultimately the probability of having to replace a building after a major natural disaster, is similarly on the order of 1-5 percent above a building that meets only minimum Code standards. Designing a building that will be expected to suffer only minimal damage and can be immediately functional after a large earthquake or hurricane can result in major savings over its lifetime.

The New San Bernardino Justice Center, a $300 million courthouse, was completed in 2014 and represents an example of resilience based design. The 11-story building was founded on base isolators that will allow it to achieve the highest level of performance in a major Southern California earthquake, likely commensurate with a USRC Platinum Rating. The additional cost of employing the base isolation system was on the order of only 1 percent of the total construction cost.

Sustainability and resilience – complementary strategies

The commercial building marketplace has adopted sustainable design as a required approach to development, both because of recent code changes and because it is good business. But events like the Christchurch Earthquake and Superstorm Sandy highlight the fact that green features alone are not enough to make a building truly sustainable. Tenants and buyers are beginning to ask about resilient design as well. Developers, REITs, lenders, brokers and others will benefit from being more aware of resilience based design, incorporating resilience features into their buildings, and seeking USRC certification of properties that meet higher performance standards. You can learn more about the USRC’s mission at www.usrc.org.

The US Resiliency Council, Bullitt Center, Seattle, Puget Sound, Washington, USRC, San Francisco, Bay Area
“The base isolated San Bernardino Justice Center”