There is no lack of data when it comes to sunlight striking a building’s surface, which means that the software tools used for daylighting modeling must be suited to the specific task at hand. Architects relish tools that emphasize a graphical interface and provide them with immediate feedback on how a design decision affects daylighting and vice versa—whereas engineers may prefer tools that enable them to manipulate raw daylighting data at the code level. Four designers spoke to architect to shed some light on which daylighting modeling software tools they use, and why.

Peter Arkle

Gustavo Brunelli, BDSP Partnership

An associate in the environmental group at engineering firm BDSP Partnership with a background in architecture, Gustavo Brunelli says that his firm uses Rhino (Rhinoceros 4.0, $995) as its primary modeling tool. “It’s very smooth for building in 3D,” Brunelli says.

Brunelli and BDSP Partnership worked with Hopkins Architects to maximize the energy-saving features of the roof lights for the Hopkins-designed velodrome for the 2012 Olympic and Paralympic Games in London. The building features a dramatic, sloping roof design that incorporates natural cooling, water harvesting, and daylighting—features that BDSP modeled using Rhino.

Brunelli says that BDSP uses other tools, including the open-source Unix emulator Radiance, for various daylighting modeling tasks. But the work often winds up back in Rhino, one way or another. “We can do all the simulation for the design using Rhino, including the energy-saving and water-saving features,” he says. “We help the architects realize their design. We can give it to them as something they can read.”

Surface engineers, lighting architects, and environmental engineers at BDSP use different tools, but Rhino serves as the lingua franca. “Ecotect exports directly into Rhino,” Brunelli says, making it useful for quick adjustments on a number of projects.

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Brian Court, The Miller Hull Partnership For Seattle-based Brian Court, AIA, an associate at the Miller Hull Partnership, finding enough daylight can be a challege in itself. The firm’s design for the Cascadia Center for Sustainable Design and Construction in Seattle incorporates a solar array encompassing an area 40 percent larger than the site area: The array overhangs the building’s edge. It will provide 100 percent of the building’s energy, but it presents a daylighting challenge.

“We have the photovoltaic array stretching out to grab every drop of sunshine on the site,” Court says. Tilting the array improves its efficiency but requires that the panels be spaced farther apart. Court has used the Grasshopper plug-in (version 0.8, requires Rhino 4 SR8) for Rhino in order to determine the most efficient solar-panel arrangement—for energy and for daylighting.

Rhino allows him to experiment with the formal geometry of the array, Court says. But Grasshopper allows him to generate efficiency rates for different permutations of panel orientations. “It was a long learning process to determine where the useful daylight was coming through the sky and how to balance that with really strict power-generation requirements,” he says. “It’s an iterative, back-and-forth process.”

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Jason Olsen, EYP Architecture & Engineering

The engineers at EYP use a variety of tools for daylighting modeling, says senior designer Jason Olsen, AIA—but the architects use Ecotect Analysis (Autodesk, $1,495). “It’s basically a graphic visualization of how daylight penetrates a space,” he says. “It gives you really clear diagrammatic results.”

In the early conceptual stages of a project, Ecotect allows designers to see directly how opening up walls or introducing skylights affects daylighting. “You can build natively within Ecotect, or you can import files and use it as the interface,” he says. It’s especially useful for doing clear comparative studies for orientation. “One of the great advantages beyond the graphical interface,” Olsen says, “is that it produces some pretty rich imagery for client presentation. We use it in all phases in our design process.”

Peter Arkle

Giulio Antonutto, Arup

An open-source software tool developed in 1985 by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, Radiance is still widely used today, says Giulio Antonutto, senior lighting designer for Arup. He says that its resilience is a testament to its versatility.

“You can do anything with it,” Antonutto says. “It’s very powerful. You can measure volume or calculate sound. We use it for sound modeling, reflections, simulating complex optical systems.” In part, its power as a daylighting modeling engine stems from the fact that designers can customize Radiance to any number of tasks. “We have a unified directory of the latest version, but there are lots of unofficial releases that anyone can modify to use for his own computer,” Antonutto says. Arup uses hundreds of custom Radiance scripts for tasks such as modeling solar exposure.

Radiance lacks a graphical interface, Antonutto explains, and it requires heavy Unix coding—so it’s not for the faint of heart. But programmers working with Radiance can import models from any program, and designers continue to modify it to keep up with other systems. “It adapts over time.”