The Bullitt Center

2 September 2013 — Seattle’s Bullitt Center has been designed to be completely self-sustaining in terms of energy and water use.

The building has met the stringent standards of the Living Building Challenge, meaning that for 12 months it must prove energy and water self-sufficience, and meet high standards for green materials and indoor environmental quality.

In CorporateTechDecisions, Steven Castle has described the technology employed in the building to make it “the greenest office building in the world”, including composting toilets, an automated curtain wall, a huge solar PV array and geothermal heating and cooling:

Ground-source Heating and Cooling

What will save the most energy? Start with the geothermal system, which consists of 26 wells and a ground-source heat pump, which will heat and cool the building through in-floor radiant heating tubes that transport heat from the ground to warm the concrete in the winter and remove the heat in the summer. No airconditioning system need apply. The heat pump will still consume about five per cent of the building’s electricity load. However, says Robert Pena, associate professor of the University of Washington’s Integrated Design Lab, which advised on the building’s efficient design and is one of the first tenants, “The heat pump generates three units of heat for about every one unit of electricity it uses.”

Automated Curtain Wall

By far one of the coolest features on the building are its automated motorized windows, which can be triggered to open or close by temperature, humidity or carbon dioxide sensors. The triple-glazed Schuco windows are energy efficient with a rating of R5 and extend outward to open a few inches on all sides to ensure a better seal when closed against the weather stripping. The windows are planned to open primarily at night to “flush” the building with fresh air during the warmer months, though they could open to help cool the building as well.

Warema exterior blinds, triggered by an astronomical clock, will shut to help block the sun to prevent solar gain in the warmer months, which will help cut down on the amount of time the heat pump must run and cool the building. Although exterior blinds are far more common in Europe, Miller Hull Partnership’s Court describes them as “a no-brainer to minimize solar heat before it hits the glass.” Both the motorized windows and blinds are tied to a weather station on the roof, so blinds won’t close on a cloudy day, for example.

Daylighting Tech

Lighting is another big load, and much of that was actually addressed with the building’s design that brings natural light to 82 per cent of the space. An initial U-shaped atrium design was considered to bring daylight into the interior spaces, but daylighting analysis found that the benefits of natural lighting wouldn’t extend lower than a couple of the top floors.

Miller Hull Partnership decided on a more traditional design, using daylighting from only the exterior walls, and pinched in the top four floors’ footprint to light more of the space. Energy-saving fluorescent and LED lights come on automatically when there isn’t enough light, and dim when there is, so the building will have 92 per cent daylight autonomy, or adequate daylight to work in 92 per cent of the time. So little energy is used by others systems in the building, that lighting will still account for about 23 per cent of the load.

The daylight modeling was accomplished using EcoTech software, and that company was consulted frequently during the building design. “Every time we made a decision about windows, we came back to this software and tested it,” says Court.

Plug Load Savings

Nearly a quarter of the electricity in the Bullitt Center will be used by computers and IT equipment, estimates the energy study conducted by PAE Consulting Engineers. To control this, more flat-panel LED monitors and thin clients are encouraged, as well as smart power strips by Enmetric that will be coupled with occupancy sensors to power down certain devices when not in use. Enmetric is expected to introduce the separate occupancy sensing technologies soon.

Each outlet on a four-outlet strip, explains Pena, can be programmed by the user to be controlled remotely or occupancy-switched.

Plug loads in the building will be limited to a maximum of 0.8 watts per square foot, approximately half the typical 1.5W/sq. ft. for new office buildings, states the building’s Energy Performance document.

Energy from Ventilation

There’s also an energy recovery ventilator (ERV) on the roof, which will bring fresh air into the building and keep it circulating. The ERV has a heat wheel inside that transfers heat from the exhaust air stream to the incoming stream, or vice versa.

 Read the full story at CorporateTechDecisions.

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