For the past six years, Paul Lewis of the New York–based firm Lewis. Tsurmaki.Lewis (LTL) Architects has taught an Integrated Building Studio at Princeton University's School of Architecture. Along with his colleagues, engineers Nat Oppenheimer of Robert Silman Associates and Mahadev Raman of Arup, Lewis challenges his graduate students to use building performance as a catalyst for design. “Rather than design a building and then see if it works,” he explains, “we take structural and thermal issues and use them generatively as a key component in the design trajectory.”

It was in this spirit that Lewis wrote a proposal to the High Meadows Fund at Princeton—a philanthropic endowment that offers grants to academic and civic projects that focus on sustainability—suggesting a study of the contradictory pressures put on Princeton's campus lighting. There is a desire for more light to facilitate nighttime activities and improve safety on campus. That creates a demand for more electricity, which is the opposite of the university's sustainability plan. In fact, the light levels on all of the campus' exterior pathways had never been measured. No one could empirically say where there wasn't enough light, or where there was too much. According to the proposal, measuring these conditions and comparing them with factors such as watts used and crime statistics could prove useful to the school's green aspirations while also improving campus quality of life.

Lewis' proposed project also had an educational component. It would have master's students in the architecture school work with the university's facilities department and the campus architect. “My hope was that the project would give the students a greater knowledge and understanding and, frankly, capacity to think about lighting and how it affects perception,” he says. “At LTL we often become lighting designers as well as architects. It's integral to design. But lighting can be easy to miss. It's so ubiquitous, something that you see everyday that it becomes invisible. I wanted the students to give close scrutiny to this aspect of spatial experience and become much more conversant with it, to the point that they could see the nuanced differences.”

The Princeton Sustainability Committee chose to fund the project and Lewis hired three graduate students for eight weeks from June to August this past summer to conduct field research and study alternative strategies for the university's exterior lighting. The first step was to understand Princeton's existing luminaire and lamp equipment. The students worked with the facilities department to identify each of the campus' 1,720 exterior pathway lights. These lights include three different generations of pole types and feature myriad pole heights and lamp types, including mercury vapor, metal halide, high-pressure sodium, and induction. Finding the current lamp identification system obsolete, the students developed a new numbering system and zoning map that divides the campus into four major zones. Before, lamps were identified by their proximity to certain campus landmarks, such as “North of Spelman,” or “South-East Entrance of Whitman,” but the student-generated system assigns each light its own number within its quadrant. The facilities department is adopting the system so that it will be easy to report a lamp outage by the fixture's printed ID number.

The bulk of the research involved mapping and recording existing light levels. The students used off-the-shelf light meters in conjunction with a custom-built machine they call the Luxmetron, a homemade device that is basically a plywood cart on two casters and a repurposed bicycle wheel. A handlebar at the back of the cart is used to push the device, and a steel pole located at the front of the cart supports two light receptors. At 5 feet 6 inches above the ground, these receptors read light at eye level from fore and aft. A third receptor at the base of the pole determines the visibility of light levels at the ground. Each receptor feeds into a separate light meter and measurements are taken once every four revolutions of the bicycle wheel, approximately every 12 feet. Each night for one month from 10 p.m. to 4 a.m., the students worked in shifts, wheeling the Luxmetron around campus taking readings. (The rest of the group's time was spent preparing the identification/zoning and analysis for the final report.) In total, they pushed their “mobile light machine” 124,748 feet and compiled 10,896 readings.

The students entered their findings—footcandle readings as well as pole and lamp types and wattages—into a geographical information system (GIS) database that they set up with help from Michael Tantella, a consultant engineer based in Philadelphia. The GIS created a map rich with easily legible information. Light levels were compared with incidents such as crime statistics—including theft, vandalism, and assaults—and bicycle accidents.

While the team didn't discover anything startling from this data, an examination of electricity use proved more fruitful. The campus' lighting fixtures draw a range of power, from 85W to 1,000W. The most efficient of these lamp types is induction, and the students calculated that switching all of the school's fixtures to this would produce a savings of 38,210W—the equivalent of removing 382 100W incandescent lamps.

Halfway through the project, Princeton hired New York–based lighting firm Fisher Marantz Stone to complete a lighting master plan for the campus. The extensive field research produced by this project will provide essential data for more detailed design and master plan approaches for the campus. Furthermore, the data now gives the facilities and security departments tangible metrics about the campus.

An added value of the exercise is what the students will take away. “Having come into the project with no previous experience or knowledge in the field of lighting, it really was an eye-opener,” says graduate student Yu-Cheng Koh. “It made me realize that there are many contributing factors beyond the measurable ones. Pure numbers and statistics can only approximate the often-subjective experience lighting produces on architecture. This confluence of lighting and architecture is definitely something that I would like to explore further.”

Project Princeton's Exterior Pathways: Lighting Analysis and Sustainable Prototypes, Princeton, N.J.
Project Dates Summer 2009
School Princeton University School of Architecture, Princeton, N.J.
Grant Funding High Meadows Fund: Princeton Sustainability Committee, Princeton University, Princeton, N.J.
Faculty Member Paul Lewis
Student Researchers Jean Choi, Yu-Cheng Koh, Thomas Wong
Images Jean Choi, Yu-Cheng Koh, Thomas Wong