Buildings

Seattle, United States of America

Seattle Justice Centre - sustainable building regulates temperature with an innovative exterior and green roof

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Summary

The Seattle Justice Centre is 14-story building housing Seattle's municipal courts and police headquarters in a dense urban setting. Seattle mastered its design challenge to create distinct and unique identities for both the courts and the police headquarters within one sustainable building. It has unique features including: naturally vented "double skin" façade that allows light but minimizes heat, and a "green" roof with drought-resistant and low-maintenance plants that remove solar heat, stores rainwater and filters pollutants out of the air while returning some oxygen to the atmosphere. It cuts 445 tons of CO2 annually and saves $17,817 annually.

What is it?

The Seattle Justice Centre is 14-story building within the three-block Civic Centre area of downtown Seattle for 800 people. Owned and occupied by City of Seattle, Local government, the building is occupied by the Seattle Municipal Courts and the headquarters for the Seattle Police Department. Some functions of the Police Department are in constant use, 24 hours a day.

How does it work?

The design challenge was to create distinct and unique identities for the courts and the police headquarters within one building. The combination of programs yielded a structure with two different parts: a primarily glass Courts portion that occupies the southern part of the block and a primarily stone Police portion on the northern part. The bipartite nature of the building is also reflected in the organization of the Civic Centre Master Plan; both building and urban design are inextricably linked.

Recycled content materials were used wherever possible including recycled concrete and recycled content carpet. FSC certified wood, forest products that have been independently assessed as adhering to principles for well-managed forests.

Notable sustainable features include:

Glazed Thermal Buffer Wall: A large section of the West façade of the building was designed as a naturally vented "double skin" façade: two separate planes of glass separated by a 30-inch air space. The "double skin glazed thermal buffer" curtainwall addresses solar heat gain. A shading device within the double skin absorbs solar gain and re-radiates it as heat trapped in the cavity. Apertures at the wall's top and bottom induce air movement. The heat's natural tendency to rise pulls fresh, cool air in at the bottom while exhausting hot air out the top. Controlling the capture or venting of this trapped heat dictates cavity air temperature and, in turn, the inner glass surface temperature.

The air space has automatically controlled louvers at the roof level to release or retain heat as required. Lightshelves at each floor of the curtainwall reflect natural light to the interior as well as acting as shading devices.

The Justice Centre design has taken care to locate the large public lobbies and the major areas of open office space facing the curtain wall- allowing maximum exposure to natural light for as many of the building's occupants as possible.

The thermal flue contains the following elements:

• A curtainwall system with clear, monolithic glazing
• A 30-inch-wide air space with an aluminum catwalk at each floor level
• Programmed semi-transparent shades
• Insulated, clear glazing in the storefront system with an internal light shelf

Additional design strategies further reduce the use of energy.

• Water in the restrooms and the police locker rooms is heated by an energy-efficient boiler
• Fluorescent lights were used throughout the project
• Occupancy sensors in conference rooms automatically turn off lights when people leave
• Light sensors located around the perimeter of the building dim the lights according to the amount of daylight present.

Garden Roof: The principal roof area of the building is designed as a "green" roof and terrace with drought-resistant and low-maintenance plants. The planted roof adds an insulating layer of soil and removes solar heat gain through photosynthesis. It absorbs and stores rainwater and filters pollutants out of the air while returning some oxygen to the atmosphere.

Water Harvesting: Water harvesting is employed as part of a water retention system, storing rainwater for irrigation. Using harvested rainwater to water the public plaza plantings reduces the building's use of municipal potable water.

Costs

Cost data in U.S. dollars as of date of completion.

• Total project cost (land excluded): $91,350,000
• Soft cost: $63 per sq foot ($680 per sq meter)
• Hard cost: $253 per sq foot ($2,720 per sq meter)
• Construction: $247 per sq foot ($2,660 per sq meter)

Application

The curtainwall system of ventilation in the Justice Centre – while rare in the US, has been very effective in Europe for some time and has proven to be highly effective in reducing energy consumption while maintaining high levels of transparency.

The Seattle Justice Centre team initially had to confront the fact that green buildings often involve more up-front expense while demonstrating economy over their life cycles. As the budget for the Justice Centre concentrated on construction costs, and as the funds available for green features were limited, NBBJ and the City of Seattle restated the goals set during pre-design in terms that clarified implicit priorities:

• Pursue any design features that help to achieve a minimum LEED Silver rating
• Emphasize those features that will be legible to people using the building
• Pursue other ideas that have value as demonstration projects