A dramatic example of sustainable design principles, the San Francisco Federal Building’s shape and orientation maximize natural airflow for cooling and ventilation, and take advantage of natural daylight for the majority of the office interior. These features, combined with a number of other energy-saving elements, significantly reduce overall energy consumption compared to conventional commercial office buildings in the United States.
Climate Control
Throughout the year, San Francisco’s design temperature ranges between 44 and 78 degrees Fahrenheit. The new San Francisco Federal Building takes advantage of the temperate climate to provide a comfortable interior environment while reducing energy consumption.
As a whole, the building is best understood as a hybrid that includes different space conditioning strategies appropriate for different locations in the building. The first five levels, with high concentrations of people and equipment, are fully air-conditioned. Above the fifth floor, the windows automatically adjust, allowing fresh air directly into the building for natural ventilation and free cooling. The window system creates a “living skin” that allows the building to breathe. Breezes pass through openings on the windward side and are vented out through the leeward wall, with control based on wind speed and direction.
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A dramatic example of sustainable design principles, the San Francisco Federal Building’s shape and orientation maximize natural airflow for cooling and ventilation, and take advantage of natural daylight for the majority of the office interior. These features, combined with a number of other energy-saving elements, significantly reduce overall energy consumption compared to conventional commercial office buildings in the United States.
Climate Control
Throughout the year, San Francisco’s design temperature ranges between 44 and 78 degrees Fahrenheit. The new San Francisco Federal Building takes advantage of the temperate climate to provide a comfortable interior environment while reducing energy consumption.
As a whole, the building is best understood as a hybrid that includes different space conditioning strategies appropriate for different locations in the building. The first five levels, with high concentrations of people and equipment, are fully air-conditioned. Above the fifth floor, the windows automatically adjust, allowing fresh air directly into the building for natural ventilation and free cooling. The window system creates a “living skin” that allows the building to breathe. Breezes pass through openings on the windward side and are vented out through the leeward wall, with control based on wind speed and direction.
Perforated metal building skin
Skin detail
Building skin with automated windows open
Tower air circulation diagram
A computerized system, known as the building automation system (BAS), controls and monitors all of the building’s mechanical equipment including those devices that are used to maintain internal environmental conditions and lighting levels. On the naturally ventilated floors, the computer system opens and closes windows, vents and sunscreens in response to temperature within the building as well as external environmental conditions. The window wall features manually operated windows for occupant control of the internal environment and includes a heating system integrated into the mullions. A minimal number of central, fully enclosed offices and meeting rooms are served by local, supplemental cooling units to accommodate higher density occupancies. During the night, the BAS opens the windows to flush out heat build-up and allows the nighttime air to cool the building's concrete interior. Throughout the day the thermal mass of the exposed concrete columns, shear walls and wave-form ceilings help cool the occupants of the building.
Wave forms passively cool day lit interiors
BAS operated window diagram
In the tower, the design of the high-performance façades is critical to the functioning of the natural ventilation. At the southeast elevation, a perforated metal sunscreen protects the glass façade from excess solar heat gain; at the northwest elevation, a series of fixed translucent sunshades are attached to an exterior catwalk, breaking the sun’s path to shade the glass These climate specific facades give the building its distinctive appearance.
South façade skin detail
South and north façade juxtaposition
North façade with sunshades
North façade
North façade detail
Nationally, the GSA strives to use no more than 55,000 Btu of energy per square foot per year in its buildings. The new San Francisco Federal Building is expected to surpass the GSA’s target as well as California’s stringent Title 24 Energy Code. The naturally ventilated floors are projected to have an average energy consumption of less than 25,000 Btu per square foot per year, a significant improvement over the national standard.
Electrical
Lighting is typically the largest energy cost for an office building, representing up to 40 percent of a facility's total energy load. The new San Francisco Federal Building's lighting strategies improve the workplace and are a critical facet of this project's sustainable design. Approximately 85 percent of the workspace is illuminated with natural light.
Ambient light, the general illumination in an office, comes from sunlight channeled through the windows and reflected off walls and ceilings to extend its reach with minimum glare and intensity. With an average overall ceiling height in the tower of 13 feet, natural daylight will penetrate deep into work spaces. Powered lights are also provided to supplement the natural light. Through simple sensors, the building's automated systems manage the balance between powered and natural daylight. The powered lights are on only when people are at their workstations. Together, these approaches reduce energy used for lighting by approximately 26 percent.
Daylit interior
Building Materials
The San Francisco Federal Building incorporates building materials and construction strategies that minimize waste and energy consumption.
The building minimizes pollution by replacing high proportions of Portland cement in its concrete foundations and frame. During the manufacturing process, Portland cement is associated with very high levels of greenhouse gas emissions. In the Federal Building’s concrete mixture, 50% of the pollution-intensive Portland cement is replaced with blast furnace slag, a recycled waste product from the steel industry, significantly reducing greenhouse gas emissions resulting from conventional concrete. This environmentally sound choice also results in higher-strength concrete and has a warm, light-colored tone that contributes to the favorable daylight penetration within the office space.
The GSA mandated that 75 percent of materials used during construction be recycled. The project recycled 87 percent of its waste material.
Carpet, paint and furniture were carefully considered with respect to the project's sustainable goals.
Energy Usage Diagram
Energy Savings Comparison Diagram
High Tower Energy Consumption Diagram
Energy Savings Diagram
Reduction in Carbon Dioxide Emissions Diagram
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