Sun-drenched may be an attractive notion to Florida's oranges and snowbirds, but it's not quite what one thinks of when considering the state's art museums. Still, when Miami's Florida International University (FIU) hired Yann Weymouth of HOK's Tampa office to design the new Patricia & Phillip Frost Art Museum, he and his gallery lighting consultants from London-based Arup became strong advocates for using daylight wherever possible.

"It can be too much," admits museum director Carol Damian of the region's abundant sunshine. But the conditions at the previous exhibition space made Damian, an art historian and curator at FIU for a decade and a half, an early advocate for a daylit solution. That gallery was several steps below grade, in what Damian calls Florida's version of a basement, and windows had been covered to provide exhibition walls. The only natural light was borrowed from the below-grade entry door.

The new, three-story, 46,000-square-foot building contains 10,000 square feet of exhibition space on the second and third floors—to protect the exhibited works from potential flooding. Nine galleries form the heart of the L-shaped museum. Wall heights range from 13 feet 4 inches to 28 feet 8 inches in the five galleries that receive natural light through the Frost's signature skylight design with petal arrays. "We had to convince the museum that daylighting would be desirable and could be controlled," says Weymouth. Arup had recently completed a retrofit of The Rothko Chapel in Houston, where the intensity of the sunlight is similar to that in Miami. The success of that project helped FIU decide to go with natural lighting. Miami's natural light provides other advantages beyond brightness. Compared with a northern city such as London or Paris, the length of the day doesn't vary that much—so there aren't many museum hours during the year when it's dark outside. "You get a lot of use from daylight," says Arup's Jeff Shaw.

Each of the petals under the skylights is constructed of a fiberglass shell using the same technology as surfboard construction. The designers even spoke to local surfboard makers about manufacturing them (although they eventually hired a more conventional subcontractor). Arup used computer modeling to determine the exact form that utilizes parabolic curvature—slightly more curved on top than bottom. The petals are finished with a gray silver metallic automobile paint, chosen for its neutral qualities so as not to affect the color of the daylight.

While the drooping petals are the primary aesthetic device that gives the Frost galleries their image, less sophisticated but equally important things occur above the array in each skylit room. The skylights themselves, glazed with a polycarbonate material to meet hurricane wind loads, also provide critical light diffusion to protect the artwork on the wall. It's the combination of diffusion at the skylight with the redirection of light by the petals that delivers the exact quantity and quality of light to each gallery wall.

For the designers, with the limited budget typical of a public institutional project, a full-scale mock-up of the galleries was not an option. As expected by HOK and Arup, some fine-tuning of the system has been necessary to get the assembly just right. Initial tests after building completion revealed a lighting level of 29 foot-candles in the galleries, slightly higher than the target of 25. Simple coatings of paint have been applied to the skylight surfaces to increase diffusion and reduce the light level to the appropriate range.

Arup also designed the artificial lighting for all the galleries. In those without natural lighting, the desire was to create an effect that didn't dramatically vary from adjacent daylit spaces. When a room is naturally lit, supplemental artificial lighting is provided from two sources—one seen, one concealed. Simple spot fixtures hang between the petals for more dramatic needs on cloudy days or occasional evenings. But the effect of diffused light through the skylights can also be achieved at these times through a distinctly low-tech solution. Ceramic metal halide floodlights mounted on poles—not unlike a street or parking lot fixture—surround each skylight on the roof. When used, they can simulate the effect of daylight coming through the tall skylight structure, are easily relamped and maintained, and don't add any heat load to the building interior.

HOK's Weymouth notes that they expect little need for the artificial lights. "Seventy percent of the year, they won't even need to turn on the lights," he says. "That's when you get the most energy savings," says Arup's Shaw. Which gives their silvery fiberglass petals a metaphoric shade of green, too.