Incorporating a modern glass facade, the new GSA Federal Building in San Francisco will be a 600,000 square foot building 240 feet high, 120 feet long, but just 60 feet wide. Among the many green features, this narrow, 18-story glass tower will showcase a natural ventilation system designed to replace the mechanical heating and cooling system. The building management system will monitor interior temperatures then automatically open and close large floor air vents during warm months. Radiant floor heating will help keep the occupants warm during the colder months.
One challenge created by this natural (and quiet) heating and cooling system is that the overall background noise levels within the open plan office areas will be extremely low. The natural system will also require passive airflow, so the open plan offices will incorporate low-height cubical walls. In addition, the concrete floor/ceiling slabs will serve to absorb and release heat back into the building. Therefore, the slabs are required to be exposed, which means there can be no traditional acoustical tile ceiling. These three elements create a situation where speech privacy between cubicles is almost non-existent, requiring the addition of a sound masking system.
To help increase the amount of absorption within the space, supplemental sound absorptive material will be located on top of the ceiling of private offices and conference rooms in the core of each floor.
Another challenge is the amount of exterior noise audible within the facility. With extremely low background noise levels, exterior noises are more easily heard and understood. This increases the distraction level of employees. With the proper attention to window and wall details, and the addition of the sound masking system, this challenge was resolved.
While these alternative systems added 5 percent to the overall cost of the building, energy savings will more than pay for the added expense during the construction phase.
Thom Mayne of Santa Monica-based Morphosis designed the building in conjunction with executive architect SmithGroup, San Francisco. Thorburn Associates provided acoustical design, sound masking system design, and audiovisual system bridging documents.