Façade Consultant: Eckersley O’Callaghan
Client: Private
Architect: Michael Green Architecture
Façade Contractor: Permasteelisa North America / Scheldebouw B.V
Mass Timber 1 is a groundbreaking project located in Sunnyvale, California, representing a significant leap forward in facade design and construction. The project was developed through a collaborative effort by several organisations, including Eckersley O'Callaghan as the facade engineer, Michael Green Architecture as the concept architect, and SERA as the executive/delivery architect. With XL Construction as the main contractor and Permasteelisa North America handling the cladding, this project is a true testament to innovative building practices.
The project was executed on an accelerated timeline, which required a high level of collaboration and integration among all team members. The concept design to construction was completed in approximately a year, necessitating early involvement from key stakeholders, particularly the facade contractor, during the schematic design phase.
At the heart of Mass Timber 1's design is the Closed Cavity Facade (CCF) system, a pioneering approach that was implemented for the first time in North America through this project. This facade system integrates timber venetian blinds within a glass cavity, offering significant advantages in solar performance and transparency. The use of a CCF system with timber blinds was selected to improve thermal performance while also ensuring compliance with fire safety standards.
The dynamic nature of the facade allows for adaptive management of solar gain and natural light, enhancing the building's energy efficiency and occupant comfort. This innovation is particularly suited for the climate in Northern California, where temperature fluctuations demand flexible and efficient building systems. The facade system achieves a U-factor of 0.24 Btu/(h⋅ft²⋅°F), surpassing California's standard requirement of 0.41 Btu/(h⋅ft²⋅°F).
Sustainability was a core consideration in the design and execution of Mass Timber 1. By using timber as the primary structural material, the project achieved a reduction in Global Warming Potential (GWP) of 96% compared to a baseline steel superstructure design. The CCF system further complements this sustainable approach by significantly lowering the building's operational carbon footprint through its insulating properties.
In terms of material use, the project replaced traditional extruded polystyrene insulation with mineral wool, further enhancing its environmental credentials. This choice not only reduced embodied carbon emissions but also improved the building's overall energy efficiency. In addition, the focus on occupant health and well-being was paramount, with the facade design minimising glare and excessive heat, thus promoting a comfortable indoor environment.
The technical achievements of the project are noteworthy, particularly in the realm of thermal efficiency and air tightness. The CCF system's maximum air leakage rate of 0.008 cfm/sf is a remarkable improvement over traditional curtain wall systems, which typically exhibit air leakage rates around 0.06 cfm/sf. This performance is attributed to the precise engineering and integration of the facade system, which aligns with the building's structural and mechanical systems.
Seismic considerations were also a critical aspect of the design process, given California's earthquake-prone environment. A rigorous dynamic testing regime ensured that the venetian blinds within the cavity would remain operational and undamaged during seismic events, safeguarding the building's occupants and integrity.
The design development process for Mass Timber 1 involved comprehensive research methodologies, particularly regarding the feasibility of the CCF system in California's climate. This included both steady-state and transient thermal analyses, utilising advanced simulation software to predict temperature profiles and optimise the facade's performance.
The success of the project can be attributed to the integrated and collaborative design approach adopted from the project's inception. Close coordination with mechanical engineers, sustainability consultants, and the facade contractor ensured a cohesive and efficient design process. This collaboration allowed the team to align the facade's performance with the project's sustainability goals, achieving a balance between operational and embodied carbon considerations.
