United States Courthouse, Los Angeles
The new United States Courthouse in Los Angeles uses an innovative structural engineering concept to make the glass cube structure appear as if it’s “floating” above a stone base, making the courthouse contemporary in material, technology and form.
© Bruce Damonte
The design of the new United States Courthouse in downtown Los Angeles is modern in spirit yet rooted in classic principles of federal architecture. It features processional steps, grand public spaces and enduring finish materials that give it a strong civic identity. It also uses an innovative structural engineering concept to make the glass cube structure appear as if it’s “floating” above a stone base, making the courthouse contemporary in material, technology and form.
Located on a prominent block in Los Angeles’ downtown civic center neighborhood, the 10-story, 633,000-square-foot building contains 24 courtrooms and 32 judicial chambers. It houses the U.S. District Court of the Central District of California, accommodates the needs of the U.S. Marshals Service and provides trial preparation space for the U.S. Attorney’s Office and Federal Public Defender.
The courthouse achieved LEED® Platinum certification and meets the GSA’s 2020 energy objective. Sustainable design features include its distinct pleated glass façade, rooftop photovoltaic array, use of LED lighting and control systems, drought tolerant landscaping, water conservation, and daylight harvesting. The composite structural design also enhances security and seismic performance, and resulted in a reduced carbon footprint compared to all-steel or all-concrete construction.
Façade. The building’s pleated glass façade is one of the project’s most visible energy-efficiency features. A key challenge in designing the courthouse was managing the site’s sun exposure. The downtown Los Angeles street grid is rotated 38 degrees from a true north/south orientation, and buildings aligned with that orientation suffer from harsh east/west solar impact.
The facade design incorporates opaque “hot” glass panels in east- and west-facing pleats to minimize solar thermal gain. At the same time, it uses transparent “cool” glass panels in north- and south-facing pleats to maximize views and natural daylight inside the courthouse. This design, coupled with the use of ultra-high-performing, low-e insulated glass, reduces the annual solar radiation load by 47% and decreases central plant load by 9%.
The façade is designed to mitigate the harsh east/west solar impact from the street grid being rotated 38 degrees from a true north/south orientation.
© John Gaylord
Energy roof. The courthouse roof is dedicated to sunlight harvesting. A central skylight provides natural illumination that filters down to the main lobby during most operating hours. The harvested light allows artificial sources to be dimmed or turned off during normal business hours. Natural light illuminates most of the central public circulation areas and reflects into the courtrooms.
Surrounding the skylight on the roof are 900 mono-crystalline photovoltaic panels that supply approximately 507,000 kWh of electricity annually. The panels are supported on racks that are tilted 10 degrees and face to the southwest. The clean renewable energy generated from the solar panels provides approximately 8% of the building’s annual electrical needs.
LED lighting and control systems. The project initially called for the use of compact and linear fluorescent lights, but the team recognized that LED technology would provide the best long-term benefit in terms of energy performance and durability.
A life-cycle analysis showed the cost premium associated with using LEDs could be reclaimed in a 10 to 15-year period. The payback period is further reduced when LEDs are used with dimming controls. The team installed an energy management control system to provide dimming capabilities controlled by daylight sensors throughout the space.
The use of longer-life LEDs also reduces maintenance costs. Due to
the courthouse’s tall ceiling heights—16 ft in typical public areas and courtrooms—use of LEDs reduces downtime and labor associated with maintaining ceiling fixtures. The cost savings result from reducing the amount of staff and equipment needed for this type of upkeep.
Automated plug load control system. Plug loads for equipment such as computers, printers, task lights and desk fans are often overlooked when reviewing energy reduction strategies. So, the team looked to a government study that demonstrates it’s possible to achieve energy savings by using scheduled timer controls and load sensing controls. They also installed advanced power strips at the client’s existing offices and collected energy use data on a web-based platform.
The results of the client study showed using plug load controls could achieve probable savings from 12% in open office areas to 30% in judicial chambers.
The final design solution targeted 25% savings, and connected approximately two-thirds of receptacles in open office cubicles, enclosed offices and chamber suites to the energy management control system. The control system was evaluated and found to have a significant contribution to annual energy savings and relatively short payback period.
Landscape design and water conservation. The terraced landscape uses native, drought-tolerant plants that represent three California biomes including: chaparral, desert and woodland. The diverse southern California species were also selected to attract specific birds and insects to increase their urban habitat.
The site’s tilted garden planes provide access to the building and allow the natural topography of the ground to flow under the cubic structure. The design enhances physical and visual connections between the site and building, while supporting the project’s sustainable design objectives.
To conserve water in the dry Southern California climate, the project captures water from the cooling tower condensate and directs it to a 105,000-gallon cistern located below the sloped garden on the building’s South Broadway side. The captured water, including collected rainwater, is then filtered and used for irrigation. The design provides all of the site’s annual irrigation needs.
Collected surplus water is routed to a flow-through planter on the site’s eastern edge. The planters serve as a bio-filtration/retention system, filtering water prior to it flowing to street storm drain culverts. The flow-through planter wall is seamlessly integrated into the site design and doubles as a security barrier along the public street.
Additionally, ultra-low flow toilet fixtures and low-flow faucets conserve water within the building. These measures result in water savings of approximately 40% over EPAct 1992.
The team wanted to capitalize on the positive benefits of southern California’s strong sunlight and mitigate negative qualities such as heat gain and glare. So, they developed a central light court design to ensure building occupants maintain a connection with the natural, outdoor environment. Functionally, the design saves energy by introducing natural light to interior public zones and courtrooms. Daylight also can have a calming effect on environments that often get tense during court proceedings.
The central light court is reminiscent of the grand central spaces of classic public buildings, and serves as one of the main organizing features of the building. The court’s saw-toothed rooftop skylight is designed to provide abundant daylight to each floor level, directing the light downward within the heart of the structure. Courtrooms receive daylight from the light court as well as the perimeter curtainwall.
Clerestories frame both ends of the typical courtroom. Light reflects off the top of the witness/attorney rooms at the public entry side and off a horizontal light shelf that extends along the circulation corridor behind the judge’s bench. Additional natural light enters the central court along the transparent glazing of the north façade.
The court’s saw-toothed rooftop skylight is designed to provide abundant daylight to each floor level, directing the light downward within the heart of the structure.
© Bruce Damonte
The typical floor plan has perimeter lighting zones and controls that automatically dim the chambers and jury deliberation areas when sufficient natural light is present. Glare is controlled in courtrooms by balancing artificial and natural sources of light. The materials and textures on courtroom walls and ceilings help bounce and reflect light. Roller shades are linked to solar tracking window management systems that automatically control the amount of daylight coming through the clearstories.
Indoor Air Quality
The team specified low VOC finishes and furniture throughout the interiors, and used displacement ventilation air distribution to provide better air quality and thermal comfort in courtrooms, the light court, public corridors and waiting areas. The low velocity air-distribution system also enhances interior acoustics.
Public areas are coupled with the light court to encourage stratification in the high floor-to-ceiling spaces. Fresh air is provided to mechanical rooms on each level through intake louvers integrated into the faceted building façade. Direct outside air systems efficiently provide tempered, humidified ventilation to each courtroom air handling unit and provide the primary VAV air handling units with a high level of air quality.
The team performed a pre-occupancy flush out to remove remaining air contaminants. The air handling units are placed in 100% outside air economizer mode and programmed through the building management system. A continuous purge was also performed for 11 days prior to occupancy. New filtration media was provided on the central air-handling equipment prior to and after the purge.
Structural Innovation and Resiliency
Security is a primary requirement in modern courthouse design. This includes planning for blast resistance, resiliency, redundancy and mitigation of progressive collapse. To answer these requirements the structural engineering team suspended the cubic volume above the ground and placed perimeter columns in tension — supported by a roof hat truss — to provide a column-free ground area.
The four central cores that extend to the foundation consist of hardened, reinforced concrete shear walls that house the vertical circulation elements. The column-free ground area and inset core elements increase the blast threat standoff distance from the curb line to the building, protecting the facility and its inhabitants.
Buckling Restrained Braced (BRB) frames located in the hat truss enhance seismic performance by absorbing lateral loads. The BRB frames are an effective way to reduce steel framing quantities and congestion associated with conventional steel bracing. The bracing elements further enhance the resiliency and reduce possible operational downtime of the facility.
The hat truss design was optimized using Maxwell’s Theorem of Load Paths. It uses a bicycle wheel or Michell truss that creates the stiffest members with the least amount of material. It optimizes the flow of forces resulting in reduced steel tonnage. The energy that goes into initial construction can be as much as 45% of the total whole life carbon emissions.
To address structural design impacts on the environment, a proprietary analysis tool was used for calculating the structural carbon footprint and assessing the enhanced seismic systems. The tool considered items such as material harvesting, transportation to the site and speed of erection. The study shows that the building’s composite system, comprised of steel and reinforced concrete, achieves a 23% reduction in carbon footprint over conventional all-steel or all-concrete approaches.
The team was responsible for validating the modeled energy efficiency over the first year of the building’s operations. With the goal of 35 EUI, the team achieved an actual EUI of 30.90—a reduction of 54% over the national average for the building type. Figure 1 shows metered and modeled energy use for the courthouse.
The new United States Courthouse in Los Angeles was awarded LEED® NC v2009 Platinum certification by the U.S. Green Building Council on May 11, 2017. The team exceeded the Platinum threshold by seven credits, achieving 87 of the total 109 credits. For the Energy and Atmosphere – Optimize Energy Performance credit, 17 of 19 credits were awarded, indicating an energy cost savings of approximately 45% over the baseline. Additionally, all credits the team attempted were awarded, including all possible Innovation in Design and Regional Priority categories. •
Collaboration and transparency between members of the courthouse design and construction teams and GSA were the foundation for overcoming project challenges and accomplishing project goals. All parties worked collaboratively and innovatively to deliver a high-value building that optimizes each building system to achieve efficiency in the areas of sustainability, use, operations and maintenance.
One example of the collaborative process is the team beginning the project with the criterion of achieving 47 kBtu/ft2·yr (EUI). After creatively coordinating architectural and system performance objectives, the team then committed to achieving 42 kBtu/ft2·yr. After the project began, the GSA took the energy performance goals to the next level by asking the team to come up with ideas to achieve 35 kBtu/ft2·yr.
To answer the challenge, the team organized a six-week brainstorming charrette to evaluate energy conserving measures. This involved gathering input from all stakeholders including design, construction, tenants and operations teams. The result: The final design more than met the GSA’s goal.
The team has gone on to share their experience about the new courthouse at the Design Build Institute of America Conference, USGBC Greenbuild, ULI Los Angeles, AIA Los Angeles COTE, Facades+, GSA Building Enclosure Workshop, Facade Tectonics Institute, Building Forward Los Angeles and the LA Mayor’s Office of Sustainability. In addition to receiving numerous national awards, the GSA published the project as a case study titled “Integration at its finest, Success in High Performing Building Design and Project Delivery in the Federal Sector, Volume 2.”
About the Author
Steven Zimmerman, AIA, LEED® AP BD+C, is an associate director with Skidmore, Owings & Merrill in Los Angeles.