The campus
design for this high tech corporation includes 10 buildings totaling 1.6 million
square feet, with five buildings and the campus commons in the first phase (design
completed 2001). As the architect stated: "The challenge was to design an environment
that is technically advanced but architecturally calm and harmonious. These goals
informed every scale of the project, from the master plan to the architectural
details" (www.mcdounoughpartners.com/projects). The master site plan develops
an extensive network of exterior paths and outdoor rooms. The four story buildings
include office floors facing eight cardinal and inter-cardinal orientations (N,E,S,W,
and NE,SE,SW,NW). We worked with the design team starting shortly after
the site planning was completed to consult on daylighting, shading and glazing,
with coordination of electric lighting controls and curtain wall strategies. Extensive
collaboration with the architects, structural engineers and mechanical engineers
developed the initial scheme to support the daylighting requirements in an overall
energy saving context. The office buildings are based on a narrow section of 63
feet and increased to 93 feet for areas containing core functions such as elevators,
rest rooms and stairwells. Coupled with a floor-to-floor dimension of 13'-0",
this positions the floor plates for successful daylighting from the beginning.
This integrated design process resulted in upturning the structural beams
in the curtain wall, so that the solid beam area could be enclosed in the spandrel
section below the lighting work plane (30" or top of desk) rather than at the
top of the window head as is usual practice. The design also includes the strategy
of underfloor air delivery, which contains the mechanical space in the section
to 1'-6" rather than the typical 3'-0" hung air plenum. As a result, the floor
to ceiling is a clear 10'-9" to enable significant daylight penetration into the
office floor. The ceiling which meets the top of the window is finished as a white
diffusing surface and helps to minimize glare by providing a smooth lighting gradient
between inside and outside. Daylighting simulations with Radiance show that daylighting
provides a minimum of 22 footcandles even in the center of the floorplate and
visual comfort due to a controlled light gradient is provided with the design
of the window wall. The ground floor offices see much less of the sky and
more of the grass and landscape, which typically are low in light reflectance.
In many cases, the ground floor receives only indirect daylighting. To work with
this, the floor to ceiling was increased to 13'-9", providing greater daylight
illumination levels and a deeper penetration into the office floor than if the
section has remained the same as on floors above. The curtain wall was
developed with a terra cotta rainscreen cladding that addressed both the client's
desire for "traditional and timeless design aesthetic" and the concern for non-toxic
sustainability as the wall sheds molecules during rain storms. A similar approach
combining an advanced technical understanding and traditional design informed
the curtain wall development. The plane of glazing is pushed back from the surface
toward the interior to gain some shade and reveal from the wall thickness. Exterior
overhangs and interior lightshelves are included to address sun penetration and
glare issues in the offices, but do not provide 100% shade at all times shade
is required. San Jose can be a hot and dry climate in the summer, especially
during California heat storm periods when the wind comes off the Central Valley.
Winters are mild but with rain and overcast conditions common. Shading for the
predominantly clear skies is a critical aspect of daylighting design, especially
with so many orientations of the office curtain walls. We identified and defined
shading conditions and requirements for every floor and every orientation for
Phase I. For complete control of the view windows below the clerestories, manually
controlled diffusing shades are specified for the vision glass. Shade for the
clerestories is handled by the combination of the glazing setback in the wall
depth and the interior light shelves. Together, these prevent direct sun from
entering the interior office zone for most orientations and times of day. Diffusing
shades can still be lowered on the view glass |
