County of San Mateo Office Building 3 is a 208,000-square-foot, five-story government office building in downtown Redwood City designed to accommodate approximately 500 County employees. The facility is constructed with cross-laminated timber, making the mass-timber structure a defining element of both the building’s architecture and sustainability strategy. Designed around aggressive energy-performance goals, the project achieved LEED Platinum certification and incorporates operable windows that allow the building to pre-cool naturally during summer conditions, reducing mechanical loads. The project was also recognized by ENR as the 2024 Best Government/Public Building Project.

CMI delivered mechanical systems designed around energy efficiency, occupant comfort, and long-term lifecycle performance. Air-source heat-recovery units provide both chilled and heating water, while variable primary-only pumping systems distribute water to air-handling units, perimeter fan coils, and VAV terminal units throughout the building. A two-pipe perimeter system provides heating or cooling for envelope loads while the central air-handling systems address interior cooling requirements. Because much of the building infrastructure remains exposed within the mass-timber structure, CMI worked closely with the architect and other trade partners to carefully coordinate overhead utilities so the mechanical systems integrate cleanly with the finished architecture.