Let the (Indirect) Sun Shine In

A highly collaborative design process and in-depth analysis produce daylighting systems for two expanding art museums on opposite coasts
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From Architectural Record
Joann Gonchar, AIA
Hanging Light Reflector, Isometric View

The QMA skylight's fabric baffles and the frosted-glass fins of the hanging structure surrounding the central gallery will reflect, refract, and diffuse daylight and direct it to flanking exhibition spaces.

Image courtesy Grimshaw

 

Another design-team concern was control of the relative daylighting levels throughout the museum. The architects and their consultants wanted to be sure that within the individual exhibition spaces, the ratio of the brightest to the darkest wall (or between parts of walls) was no more than three to one. The ratio is derived from the measure of light arriving at these surfaces, or their illuminance. "This is an aesthetic issue," says Gallagher, explaining that to the human eye, a ratio of three to one would appear relatively uniform.

The team also paid special attention to the experience of visitors moving throughout the museum, from the lobby to the large-works gallery and on to the smaller galleries, striving "to create a sequence that avoided abrupt changes between spaces," says Husser. The goal was to limit the contrast ratio between adjacent spaces to 10 to one. But in this case, the designers were comparing luminance, or the amount of light leaving a surface. "This is generally considered a visitor comfort issue. If the contrast is too great, eyes have trouble adapting, causing fatigue," says Gallagher.

 

In order to ensure that they achieved the desired contrast ratio in these smaller side galleries, team members performed extensive modeling, including studies of illuminance levels at various times of the day and throughout the year.

Images courtesy Grimshaw

 

In order to produce a scheme that would realize their performance targets, the design team conducted extensive modeling of the museum's proposed spaces and the architectural elements. One such study was an examination of the relationship between roof aperture configuration and side-gallery daylighting levels. Using the simulation program Radiance, consultants placed virtual sensors in each gallery. They then manipulated the skylight size and shape while charting the amount of light falling on wall surfaces. The goal of the study was to come as close as possible to the annual reciprocity target without exceeding it, explains Matthew Herman, senior building physicist in the New York City office of Buro Happold, the project's environmental consultant.

Team members also closely examined the aluminum louvers over the smaller galleries, conducting a solar-ray analysis for various shapes, angles, and spacing. Ultimately, the designers selected louvers with elliptical sections, varying their slant and spacing them closer together near the wall adjacent to the large-works gallery. The arrangement provides reflective surface area where it is needed most to direct light back toward the wall closest to the light source, one that would otherwise be in shadow, explains Husser.

Sensor Points

To refine the design for the QMA skylight, the team virtually manipulated its configuration and charted light levels at sensor points in the side galleries.

Image courtesy Grimshaw

 

After virtually modeling the components and spaces, the environmental consultant built a physical model and brought it to Flushing Meadows Park during summer solstice to measure actual light levels on-site. "The simulations were very effective in telling us if we were on the right track," says Herman. "But they have their limitations." He notes that their accuracy depends on the computational power of hardware and is hampered by the difficulty of mathematically describing the way various materials bounce light, especially when the simulated daylighting scheme includes multiple filters, as does the design for QMA.

These layers, and especially the 30-foot-tall suspended structure surrounding the skylight, will be the defining elements of QMA's interior. The light diffuser "will be a hanging object of the same scale as the panorama," points out QMA executive director Tom Finkelpearl, referring to the 9,300-square-foot model of New York City that is the best-known piece in the museum's collection. "The method of directing light into the galleries will be an enormous sculptural statement."

 

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Originally published in Architectural Record
Originally published in May 2008

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