Greenest Office Building Sets a Standard for Energy Efficiency Tech

April 23, 2013
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Bullitt Center exterior

The Bullitt Center features a distinctive overhanging solar “sombrero” that will power the entire building. Photo by Benjamin Benschneider

Denis Hayes coordinated the first Earth Day in 1970, and now, more than 40 years later, he has opened what promises to be the greenest office building on Earth Day.

Hayes now heads up the Bullitt Foundation, and its new building, the Bullitt Center in Seattle, features a collection of cool and practical green technologies geared to save energy. Hayes and others involved with the building design say the point of the building is to propagate other 21st century buildings like it.

The six-floor, 50,000-square-foot building is going for a Living Building designation, which means it must be self-sufficient in its energy and water use for 12 continuous months.

That will be a challenge, even with a 26-well geothermal ground-source heat pump system for heating and cooling through in-floor radiant tubes—and an overhanging 545-panel rooftop solar array that will produce about 230,000 kWh of electricity a year. (Each panel produces 425 watts.)

The geothermal system should heat and cool the building just fine, but the 14,000-square-foot commercial-grade solar array from SunPower will need some help inside of the building to provide all of its electricity.

To meet the self-sustaining goals for water use, the building will collect rainwater from the roof, funnel it into a 56,000-gallon cistern, filter and disinfect it. It will also recycle graywater for irrigation of some gardens on a second-floor rooftop and use foam-flushing composting toilets. The solid waste will be turned to fertilizer. The potable water from rainwater system will be tested first, and for now the building is connected to the public water supply.

Bullitt Schuco windows

The Schuco triple-pane windows are energy-efficient and automatically open a few inches on all sides to help ventilate the building.

Automated Windows

The coolest green tech feature in the Bullitt Center may be its automated, motorized triple-pane windows from Schuco that open a couple of inches on all sides, mostly at night, to “flush” the building with warm air. The windows also activate via moisture, carbon dioxide and temperature sensors, so they can open to help warm or cool the building, for example. “The number one climate design priority is to keep heat in and cold out,” says Robert Pena, Associate Professor of the University of Washington’s Integrated Design Lab, which helped with the design of the building and will be monitoring its performance as one of the tenants.

Solar Blinds Help

Exterior solar blinds from Warema are triggered by an astronomical clock to minimize solar gain before the sun hits the windows, and the slat angles can be adjusted every 15 minutes to control the heat gain, thereby minimizing use of the ground-source heat pump to help cool the building.

Designing for Daylight

Much of the building will be lit by natural daylight, reducing the lighting load. Architectural firm Miller Hull Partnership even pinched the building in from the third floor up to increase the relative amount of space that could be lit naturally, to 82 percent. Automated lighting dimmers will dim the LED and fluorescent lights accordingly. The building isn’t expected to use a lot of electricity for lighting, though it’s still budgeted to be about 23 percent of the load. (Remember that this is for a highly efficient building with an Energy Use Intensity of just 16 kBtus per square foot.)

Smart Strips for Plug Load Reduction

Each tenant will have an energy budget it needs to meet in order for the building to be net zero and produce all of its energy. The Bullitt Foundation will pay the utility bills of tenants that meet their energy budgets. To help do this, aggressive plug-load reduction is planned by using smart power strips by Enmetric that communicate via wireless ZigBee to a bridge, so every receptacle can be monitored. Soon Enmetric will provide detached occupancy sensors for the strips as well, according to Pena. Plug loads just for computer and IT-related purposes will account for about a quarter of the building’s energy usage, making plug load control important.

Bullitt energy use

Reducing lighting and plug loads are big part of the energy savings needed to make the building energy self-sufficient.

Energy Monitoring Dashboards

A building energy dashboard will be available in the lobby and at every workstation so people can see how much energy the building is producing and using. The building uses a circuit-level Climatec Axcess energy monitoring system that interfaces with the building automation system via the BACnet protocol.

Irresistible Stair

A big energy saver may be low-tech but rewarding. Hayes had the designers include an “irresistible” staircase in a glass encasement that offers stunning views of the Seattle skyline, so tenants would be inspired to climb the stairs instead of taking an energy-using elevator.

Some of the building’s designs required the city to relax its codes and laws, such as the extended solar overhang, lack of parking spaces and the use of rainwater as potable water. “Doing sustainable things is illegal in this and other places,” joked Seattle Mayor Michael McGinn.

Bullitt Center video

Click on the image to go to the video.

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