181 Fremont: A Distinctive New Tower for San Francisco

The third tallest building in San Francisco, and one of the tallest buildings west of the Mississippi River, 181 Fremont began welcoming residents and office tenants in May.

The 57-story mixed-use tower features 435,000 square feet of Class A+ office space on the lower levels and 67 condominiums on the top floors. The condominiums offer unparalleled views of San Francisco and the surrounding Bay Area.

“This building is an important new addition to the Transbay district, providing both residential and commercial real estate inventory in a high-demand area,” said Caroline Fenlon-Harding, WSP’s principal-in-charge on the project. “Its close link to the Salesforce Transit Center—a bridge at the seventh floor connecting directly to the 5.2-acre rooftop park—will provide residents and tenants easy access to recreation, shopping, restaurants and major transportation links.”

The project had high goals for sustainability from the outset. WSP’s mechanical, electrical and plumbing; Built Ecology; and building technology systems teams worked closely with Jay Paul, the owner; and Heller Manus, the architect; to deliver innovative systems with a focus on water and energy reduction.



A fifth floor bridge connects to the adjacent Salesforce Tower and a 5.2-acre rooftop park, providing access to recreation, shopping and transportation links.

Saving Water, Saving Money

Early in the project, the WSP team identified a new option that would have a positive impact on both the amount of water used by tower occupants and the owner’s bottom line.

“A few years ago, the San Francisco Public Utility Commission began offering grants to projects that used alternate water sources,” Fenlon-Harding said. “181 Fremont was the first approved recipient of one of these grants.”

Under the program, a $250,000 grant was secured for the owner, Jay Paul, as a result of an installed on-site graywater treatment system identified by WSP.

“The system collects graywater from commercial and residential fixtures and reuses the treated water for flushing and irrigation throughout the building,” Fenlon-Harding said.

“By combining the installed equipment with low-flow fixtures, we were able to reduce projected water use by about 50 percent.”

The WSP team collaborated with the system manufacturer to size the system appropriately and is working to secure the required agency approvals. In addition to the grant, the water reduction added Leadership in Energy and Environmental Design (LEED) points for the project, putting it on track to achieve LEED Platinum certification from the U.S. Green Building Council.

Measures for Energy Reduction

The mixed-use of the 800-foot-tall building required different systems for the residential and commercial areas.

The office floors feature a dedicated outdoor delivery system on every floor, supplying air to fan-powered terminal units that provide preconditioned and dehumidified air to the fan-powered terminal units installed at each zone.

“The outdoor air delivery system contains a high-temperature chilled water coil that precools the outdoor air in the summer and a secondary DX coil that will provide additional cooling and dehumidification,” said Alan Davis, design engineer on the project. “This also increases efficiency for the chilled water plant, because it allows the chilled water supply temperature to be higher than what would normally be required for dehumidification.”

This system eliminates the need to overcool and reheat supply air during part-load cooling conditions, as is typical of a central variable-air volume system, making it much more efficient.

Meanwhile, residential units are conditioned and ventilated by four-pipe fan coil units that have direct access to fresh air intake through the façade of each condominium.

“Additional energy savings also come about because of the reduced need for fans, since only ventilation air is distributed throughout the building,” Davis said.

The chilled water plant consists of three variable-speed, water-cooled centrifugal chillers, two cooling towers with variable speed fans and two waterside economizers that provide free cooling to office and residential chilled water loops when the outdoor conditions allow.

Additionally, a mini natural gas-fueled cogeneration combined heat and power turbine with 65kW electricity and 118 kW heat generation capacity provides electricity for electrical base loads and heating to meet hot water demand. Due to the utility rate structure in San Francisco, operating the cogeneration turbine results in utility cost savings.



181 Fremont tower is the third tallest building in San Francisco, and the tallest mixed-use building west of the Mississippi River.

A Focus on Technology

It was important to the owners that the building’s technology systems support the commercial and residential uses while also using intelligent systems for the building.

“We employed a converged network approach, which will allow for the integration, automation and optimization of all intelligent building systems and equipment,” said Reza Moghaddasi, lead technology engineer on the project. “This includes the base building data network systems architecture, building management system, electrical sub-metering, access control, electronic safety and security, and lighting control systems, all as integrated technology.”

These converged systems enable remote monitoring and control of all building systems in an enterprise-rated secured network.

A distributed antennae system provides both a reliable cellular network and two-way radio systems coverage for emergency responders throughout the building.

“We used iBwave software during design to analyze obstructions of cellular signals,” said Moghaddasi. “This allowed us to strategically place antennae, ensuring signals are abundantly spread.

Working on a Tight Site

The building’s exoskeleton allows for column-less interiors, allowing for open floorplans. To further maximize floor space, shaft area was reduced by incorporating openings in the curtain wall system to provide ventilation air and residential toilet exhaust.

“Our team detailed a slot integrated in the diagonal exoskeleton to provide the ventilation intake,” Fenlon-Harding said. “Where the slot was restricted toward the top of the tower, we supplemented with a vertical shaft at the perimeter to service the top three floors.”

The WSP team also worked to coordinate the locations of operable windows in the residences with toilet exhaust louvers to meet the required separations.

Additionally, the need to maximize the building’s footprint relative to the size of the lot meant that only one side of the site was available to route and provide all incoming utilities, as well as public entrances to the building.

“To accommodate this, our team coordinated all the water, gas, electrical and telecom utilities in the basement, and secured the necessary accommodations from the utility companies,” Fenlon-Harding said. “This allowed the residential and commercial public entrances, including the entrance ramp to the underground parking garage, to be unaffected.”



181 Fremont has already made a huge impact on the San Francisco skyline and its immediate community.

A New Icon for San Francisco

With its striking form, height and proximity to Salesforce Tower, the tallest building in San Francisco, 181 Fremontthe tallest mixed-use building west of the Mississippi River—has already made a huge impact on the San Francisco skyline and its immediate community.

The building is essentially complete, but WSP is continuing to provide services for the residential interiors, working with architects Hornberger and Worstell, and for the commercial space (all of which has been leased by Facebook) working with architects ODADA. The first group of residential units and the first floors of the commercial office space begin occupancy in May, with additional work continuing in phases.

“I’m so impressed with the dedication and commitment of Jay Paul, and the experience of the design and construction team, to rise to the challenges and hurtles encountered along the way,” said Fenlon-Harding. “The team work was outstanding, and in working together with the local review agencies, inspectors and utility officials, all the complexities were tackled and resolved.”

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