Bullitt-proof Geothermal

Advancing environmental protection and conservation with sustainability in large buildings has undergone demanding but rewarding progress during the past decade: first there was the widespread adoption of the LEED scorecard for new building certifications, then Net Zero Energy design (with an ASHRAE goal of net-zero energy for all new buildings by 2030), and the latest criterion, the Living Building Challenge, as important yardsticks applying and verifying evolving best practices wedded to the use of an array of advanced materials and technologies.

In the recently completed Bullitt Center office building in Seattle, Washington, a revolutionary building enterprise experiment owned by the environmentally conscious Bullitt Foundation, net zero energy and net zero water initiatives have been combined with the Living Building Challenge, a rigorous verification process consisting of 20 demands that go beyond LEED requirements.

The Living Building Challenge is a sustainable building certification program created by the non-profit International Living Future Institute. Created in 2006 and launched three years later, it was the brainchild of the Cascadia Green Building Council, which today has its offices in the Bullitt Center along with other like-minded organizations. Currently, there are over 140 Living Building Challenge registered projects in 10 countries, but only three to date in the U.S. have been fully certified and they are much smaller buildings than the six-story, 50,000 sq ft. Bullitt Center.

The $30-million Bullitt Center, which opened on April 22^nd, Earth Day, will undergo a full year of verification against the Challenge’s 20 “Imperatives” that fall under seven performance areas (site, water, energy, health, materials, equity and beauty).

The timber structured Bullitt Center building was designed to be one of the most energy efficient buildings in the U.S., achieving an energy efficiency of 83-percent better than the typical Seattle office building.  Already called the “world’s greenest commercial building,” it is meant to last 250 years, remaining independent of municipal water and sewer connections through its long operational life.

 

To achieve the twin Imperatives of net-zero energy and net-zero water use, the Bullitt Center comes with a geothermal system and in-floor radiant heating, a 14,000 sq. ft. canted and extended rooftop filled with photovoltaic solar capture arrays to make electricity, a rainwater capture/purification system for potable systems with a 56,000-gallon basement cistern, onsite waste management through the use of water saving composting foam flush toilets (a first for a commercial building in the U.S.), and large thermally glazed curtain wall windows that open and close automatically in response to outside conditions and to maximize daylighting. Automatic controls are designed to adjust or turn-off low voltage LEDs when daylight illumination is sufficient to light interior spaces.

The Center’s mechanical requirements led to the design by M/E/P engineering firm PAE of a highly efficient heating and cooling system utilizing geothermal heat exchangers, in-floor radiant heating and a climate control system that depends on natural ventilation and automated windows. The vertical closed loop geothermal system consists of 26 geothermal wells, each 400 feet deep, to tap the consistent earth temperature.

Bosch Thermotechnology’s FHP Manufacturing division‘s water-to-air (W2A) heat pump units were selected by PAE to provide heating and cooling to the Center’s conference rooms, the building’s data center, and elevator machine room. FHP heat pumps connected to Uponor radiant PEX deliver BTUs for radiant heating and cooling and also generate heat recovery for the ventilation system’s 100 percent outside air unit which preconditions incoming fresh air with outgoing air.

FHP Manufacturing ES Series and AP Series W2A heat pumps were specified for the project along with CA Series W2A pumps. All three series pumps come with copper coaxial heat exchangers and 4-way reversing valves for heating/cooling and provide very quiet operation. AP Series pumps feature a state-of-the-art two-stage scroll compressor that when matched to a multistage thermostat, as in the Bullitt Center, matches demand for heating and cooling, making them highly energy efficient. There are a total of 10 FHP heat pumps in the Bullitt Center.

According to Justin Stenkamp, PE of PAE, selection of the FHP products was made on the basis of their performance characteristics along with working relationships and a strong track record for service from Bosch representatives on previous projects.

As electrical plug loads from tenants can account for as much as 50 percent of an office building’s energy use, the Bullitt Center’s occupants are responsible for setting and abiding by a unique lease agreement condition that sets a specific energy use limit per square feet each year.  Other unique features about the Bullitt Center include a transparent glass staircase that affords stunning views of the Seattle skyline in an effort to discourage using the elevator, plus a bicycle garage, quite a step-up from easiest attainable LEED point for an on-site bicycle rack.

But it is the net-zero energy and net-zero water objectives of the Bullitt Center that will have the most impact on the building’s attainment of Living Building certification. Use of a geothermal HVAC system with dedicated on-site solar energy generation – even in cloudy climates like the Pacific Northwest — is a natural choice for Net-Zero Energy Buildings (NZEB).

Proven carbon neutral renewables like solar and geothermal energy along with radiant heating and cooling for indoor air comfort, in tandem with strict energy monitoring, will verify the vision put forth by the owner and the build team to create and sustain a true living laboratory for sustainability in a building that is commercially viable, aesthetically pleasing, and provides a great environment to work in.

Information provided by Bosch Thermotechnology with assistance from PAE.