Designed to be the most resilient tall condominium on the West Coast, every square inch of 181 Fremont’s 435,000 square feet was engineered for superior performance, including the innovative, unitized curtain wall system.
Pre-certified as LEED Platinum, 181 Fremont, located in San Francisco, was designed to enhance the energy performance of the 55-floor, mixed-use tower by incorporating a floor-to-ceiling façade, fully glazed with Solarban 70XL glass (now Solarban 70 glass) by Vitro Architectural Glass—an advanced, triple-silver-coated, low-emissivity (low-E) glass that blocks 73% of the sun’s heat energy in a 1-inch insulating glass unit (IGU) while still enabling 64% of the ambient daylight to pass through.
The design by Heller Manus Architects creates a sawtooth pattern with window mullions that are angled to face slightly inward against one another throughout the curtain wall—a curtain wall that acts as a passive solar control system. Due to its ability to block heat while still allowing light to pass through, the low-E glass accentuates the performance of the angled window mullions, which function as a shading device as the sun passes over the building each day.
Glazing contractor Benson Industries took an active role in working through the complex glass geometry with the design team, providing models, renderings, and many versions of proposed elements. Glass fabricator Hartung Glass Industries, a member of the Vitro Certified Network, worked closely with Benson Industries to make the project a success.
“With the proposed sawtooth adjoined diagonal panels, it created hundreds of unique curtain wall units,” said Jeffrey Heymann, vice president of business development for Benson Industries. “Each unique unit had its own 3D model, where the connections and milling could be studied in depth.”
With the steel exoskeleton, the diagonal elements required retention cages that encroached on a typically clear anchor zone. Getting the right fit took several months of modeling, yet the finished result is a resilient façade that can handle high wind forces and seismic events up to 8.0 magnitude.
“When we design a façade in a high seismic zone, we talk about resiliency. We accommodate large lateral movements to mitigate damage to the frames so the building can be repaired quickly,” Heymann said. “For 181 Fremont, the sealant joint between the glass and the aluminum frame is a half-inch larger than for a typical Benson project. This design ensures that, at the most extreme seismic racking, the glass never touches aluminum.”
This innovative design also minimizes wind load. Traditional smooth-sided buildings accelerate winds and increase stress on the buildings. The angled glass design of 181 Fremont disrupts airflow and reduces such stresses.
About 500 feet from the ground, the tower is bisected by a chevron-shaped support configuration framing a glass-walled amenity terrace that dissipates wind forces. Due to the open nature of the terrace, wide panels of Solarban 70XL glass were required to achieve the prescribed level of wind deflection.
To maximize overall tower resilience, the engineers used a 44-caisson system in conjunction with a series of dampers to conserve the structural weight. Individual caissons were driven an average of 262 feet into the ground to enhance structural and nonstructural design to limit damage and improve egress systems—earning it a Resilience-based Earthquake Design Initiative (REDi) Gold rating.
Occupant Evacuation Operation (OEO) elevators were used in place of stair towers, maximizing availability of office and residential leasing space.
As the tallest mixed-use high-rise on the West Coast, 181 Fremont includes 435,000 square feet of Class A office space and 17 floors of luxury condominiums—including a $42 million penthouse.
The building’s office space has been fully leased by Facebook since it was completed in May 2018. In addition, homeowners have purchased almost all of the dozen residential units, which offer bridge-to-bridge views of San Francisco and the bay.