• NREL's Research Support Facility
• Chabot College Community and Student Services Center
• The Terry Thomas
• Phoenix Central Library
• Seattle Justice Center
• Debis Tower
• Hoffmann-La Roche Office Building
• Florida Solar Energy Center
• Cambria Office Facility
• Xilinx Development Center

Hoffmann-La Roche Office Building

Maximizing building surface area is one response to designing for effective daylighting, and this approach was necessary before the advent of reliable electric lighting, extensive mechanical services, and cheap energy. Traditionally, building designers were mindful that spaces had to be in close proximity to windows, with daylighting only possible within 15 to 25 feet of a window—given a standard window head height of 8 feet. This "daylight dimension" limited building depth.

Designing with such a precept in mind, however, has drawbacks. Long, thin buildings are more expensive to construct because their shape requires more exterior wall area to enclose the same volume of space compared to a structure with a square plan. For instance, a floor of 40,000 square feet can be enclosed in an area of 200 by 200 feet, or 80 by 500 feet. The latter requires a 1,160-foot perimeter, while the former only requires an 800-foot perimeter, significantly impacting initial building cost.

A common challenge, given the economic realities of construction, is to design a deep-plan building while still offering day-lighting. The Hoffmann-La Roche Ltd. Office Building in Nutley, New Jersey, by Hillier, is a seven-story building with a 185-by-185-foot footprint—a square administration building. The goal of designing with effective daylight in mind is addressed through several basic strategies:

• The building is planned with a central core to maximize the perimeter for daylighting. In addition, the core is offset at the north side where daylight penetrates the least and to accommodate the design of a skylit atrium stair to the south of the core where the occupiable office space is furthest from the wall.
• Two-story work studios anchor each of the building's four sides. With their tall glass openings, these spaces admit daylight deep into the building's center. As a more conventional 13-foot floor-to-floor height predominates (9.5 feet from floor to finish ceiling), the work studios increase daylight penetration to adjacent spaces.
• Within the standard office areas, interior and exterior light shelves redirect light onto the ceiling, bouncing light back further into space, as well as offering shade and glare protection. Prismatic glazing in the transom window is angled to redirect sunlight and ambient light onto the ceiling plane, so that it becomes an indirect light source.

These basic design decisions were made recognizing the sun's movement throughout the year and the impact adjacent buildings would have—both in terms of shading or reflecting light upon the new facility.

The project does not feature any active elements such as heliostats tracking the sun to maximize daylight. Rather, passive daylighting strategies work in concert to provide a comfortable work environment. Computer modeling and other studies helped refine the strategies, which were reinforced throughout the design process. For instance, at the interior design level, careful attention was given to interior finishes, which were designed to optimize brightness and reduce glare and contrast. Similarly, the open interior was planned without perimeter offices in order to maximize daylight penetration.

Given the emphasis on daylighting, glazing selection and specification, and even window mock-ups, required thoughtful consideration.

• The standard glazing is low-E insulating glass, with a U-factor of 0.29 Btu/hr-sf-°F, a shading coefficient of 0.44 (SHGC=0.38), and visible light transmittance of 0.70. It was used on all the building faces, in the vision glass panels of the regular office windows and in the work studio curtain walls.
• The specialty glass for transom windows is ECOSS glass type—an acronym for "Ecological Sunlight System" manufactured by Figla. The window assembly is a set of acrylic prisms sandwiched between two sheets of glass.

Daylight sensors engage roller shades to help control brightness and glare when there is too much daylight entering the curtain walls in the work studios. On the other hand, photosensors do not control the electrical lighting, to tune down or turn off the lights when there is sufficient daylight in the space. Such elements were not integrated into the final design.

Despite this, overall the design illustrates an integrated lighting solution and how design decisions must work in concert to yield such a result. Client and design team interest and proper use of daylighting studies and tools contribute to a design where daylighting supplements electric lighting in a dynamic and energy-efficient manner.

Source:
Carmody, J. S. Selkowitz, E. Lee, D. Arasteh, T. Willmert. Window Systems for High-performance Buildings. Norton, 2004.