The Bullitt Center: Architecture Imitating Ecology
The architecture of the Bullitt Center, one of the world’s greenest buildings, is meticulously crafted to imitate the ecology of the Douglas fir, a tree native to the forests which historically covered Seattle. With exceptional lumber, the Douglas fir was important for the logging industry, propelling Seattle’s early economic growth. Referencing Seattle’s ecological and economic past, the building is designed to function like the forest once did, collecting its energy and water from its immediate surroundings.
With a mission to safeguard the natural environment of the Pacific Northwest, the philanthropic Bullitt Foundation endeavored to create their new headquarters as a deep, green prototype and living laboratory for sustainable design. Under the leadership of CEO and President Denis Hayes, a founder of Earth Day, the Foundation developed the Bullitt Center to showcase the possibilities of synthesizing net zero energy, water and carbon in an urban office setting. The building, which opened on Earth Day in 2013, was designed to meet the Living Building Challenge, a rigorous sustainable building certification process developed by the Living Building Institute. The certification is based on actual, rather than anticipated, environmental performance with a year-long evaluation period once the building is fully occupied.
In April 2015, the Bullitt Center became the first office building in the world to earn Living Building certification.
From the outside the Bullitt Center doesn’t look like a tree. A beautifully crafted timber staircase, surrounded by glass windows with landings that cantilever over the footpath to enable views of downtown Seattle and Puget Sound, greets visitors and workers at the entrance. It’s fondly described by the Bullitt Center as the ‘irresistible staircase’, intended as one of the building’s many behavioral change elements to reduce energy use, enticing people to use the stairs instead of the discretely-located elevator. Once inside, the artistry behind the six-storey building, and its relationship to the architecture of a tree, is illuminated. The inspiration stems from the notion of ‘biomimicry’, a design approach emulating tested patterns found in nature to provide sustainable solutions to complex problems.
Mirroring how the Douglas fir would have captured, absorbed and slowly released rainwater, the Bullitt Center acts as a catchment by harvesting the water that falls upon its site. Rain is collected from the roof and stored in a cistern in the basement which holds over 200,000 litres. The rainwater is purified for drinking quality through a specialized system involving filtration to remove large particulates and viruses, and treatment with ultraviolet light, activated charcoal and a little chlorine. Currently, however, due to legal and health requirements, the rainwater is only used for non-drinking purposes such as toilets and irrigation. Until permission is granted from environmental and health authorities, the building will use the municipal supply for all other purposes.
Applying the versatility of nature, waste-water disposed through sinks and showers is collected and pumped to a small constructed wetland on a rooftop beside the third-floor. This greywater is circulated several times through the wetland’s layers of soil, gravel and horsetail, a sturdy plant suited to Seattle’s climate. The plants absorb the nutrients and harmful materials are removed before the water is directed to bio-swales beside the building. Here the water is filtered through another 6 metres of gravel and plants before entering ground water. Through these processes, water is returned back to the local ecology, just like in the forest.
A bespoke feature of the building is the world’s first six-storey composting toilet system. The toilets significantly reduce water use, requiring only two tablespoons of water combined with biodegradable soap. Human waste enters one of ten large composters in the basement, where it is decomposed through an aerobic process. The liquid and solid waste is carefully mixed with wood chips to ensure enough exposure to oxygen. The compost benefits other landscapes and plants in the region. The liquid is separated into leachate storage tanks and taken monthly to a local treatment plant where it is used to enhance native wetlands and a bird sanctuary. The biosolids will be taken to a local facility, mixed with sawdust and made into fertilizer, once the building has generated a sufficient load.
Mimicking how the site processed sunlight via photosynthesis when it was a forest, the roof spreads over the footpath like a canopy, generating energy via 575 solar panels.
Even in a city notorious for cloudy days, the 1300 square metre roof provides more energy than the building consumes across the year. During summer surplus energy is sold to the grid and in winter it’s purchased back. The solar panels are separated by gaps, evoking the dappled sunlight filtering through the leaves of a tree. The heating and cooling system extends beneath the building, like the roots of a tree. Heat is sourced from geothermal wells over 100 metres below and can be restored back into the ground in summer. To moderate temperature efficiently, a mix of water and glycol is circulated via the building’s hydronic system which branches through concrete slabs on each floor.
Materials were carefully selected to avoid common toxic building products and sourced locally to reduce environmental impacts, as required by the Living Building Challenge. Timber is a structural and interior feature, referencing the regional architectural style. The frame is constructed of timber sourced within 1000km from Seattle, from a forest certified by the Forest Stewardship Council. The beams and columns comprise planks of glued-laminated timbers, a process more efficient in its use of wood. It is estimated that 545 metric tons of carbon dioxide are sequestered in the building’s wood. The Foundation collaborated with a company to produce a new sealant for building exteriors free of harmful phthalates. Instead of the design team purchasing their preferred high-performing windows from Germany, they worked with the company to secure a manufacturing license for a local glazing business. These endeavors have helped strengthen the local green economy, allowing others to access these innovations.
Denis Hayes describes the building, intended to have a lifecycle of 250 years, as a tribute to the craftsmanship of everyone involved.
Emulating design principles from Seattle’s native forests, the architectural and engineering craftsmanship of the Bullitt Center has resulted in a state-of-the-art living building which assists in restoring the local ecosystem and offers sustainable solutions for human habitats. Just as Seattle’s pioneers identified the value in exporting the Douglas fir to the world, the Bullitt Center will help pollinate green buildings inspired by the nature around them, across the globe.