Examining various types of architectural and exhibition lighting
Though located in Europe, for exhibit lighting sources, the children’s science center is typical of best-practice U.S. venues. As in many such projects, the push to use efficient LEDs is often restrained by the need for solutions more appropriate for the given application or effect. Here, Available Light employed LED sources for general track spot and wash lighting, as well as for mini-downlights in some headers and ceilings.
As many LED sources can be specified in a native color of light, LED lamps are well-suited to colored lighting applications, and blue PAR38 LEDs are used to illuminate the walls and interiors of several exhibits, including an outer space-themed area. (PAR stands for ‘parabolic aluminized reflector,’ and it is a widely used source in commercial and institutional projects—the number indicates the diameter of the housing in eighths of an inch). Red and amber LED PAR38s create an intense colored effect to illuminate the simulated surface of Mars for an interactive rover activity at Muzeiko. A large ‘tree’ display creates a signature element in the museum’s lobby. Comprising varied materials such as steel, acrylic, and plastics, green LED PAR lamps housed within cylindrical fixtures to mask the lamps from view, shine down through its ‘leaves,’ which are suspended hexagonal green acrylic panels.
The PAR38 LEDs use only about 16 watts, and are rated to last 30,000 hours, or about 27.4 years. In some places, these lamps can be clustered to create areas of intense illumination or other effects. Combo LED fixtures are arrays of LED sources in a single housing, and may have three sources or up to 80 or more. These can be recessed into walls for general illumination.
Smaller-profile LED fixtures can be used behind and under exhibits, such as beneath a glass walkway in Muzeiko’s cave exhibit. At the science museum, another type—narrow-beam LED track fixtures—produces dramatic high-contrast shafts of light. The layouts of the overhead fixtures often mimic the shapes of the architecture or exhibit envelope. One such application at Muzeiko recesses these fixtures in the varied faceted planes of the dome-like lobby ceiling.
When the science center lighting was originally specified in 2013, some LED technologies related to museum exhibition lighting were still in their infancy, so many of those primary light sources were specified as low-wattage ceramic metal halide (CMH), which is a type of HID source. These sources are significantly more efficient than traditional tungsten halogen lamps; like LEDs, however, they deliver excellent color rendition—about 80 to 96 CRI, according to a specialty fixture manufacturer the authors consulted.
As controlling color temperature is among the most important aspects of museum exhibition lighting selection, fixtures with high CRI are often critical to the design and specification of art galleries and other sensitive installations. In some cases, holding the spec on the CRI may be more important than holding the actual fixture spec.
Special conditions and details
Another way exhibition lighting may greatly differ from art gallery lighting is in its use of concealed, special effect, and thematic fixtures. The listings and ratings for these fixtures may vary significantly from standard lighting products, and specification teams should carefully review the manufacturer data and confirm the product’s track record.
Museums tend to prefer ‘set-and-forget-fixtures that require minimal maintenance and relamping. For LEDs, thermal management (i.e. efficient removal of heat generated at the point where the LED chip is mounted to a substrate) is vital to fixture longevity; poorly designed fixtures and installations can cut LED chip lifespan by as much as 80 percent.
For CRI, good manufacturers provide verified photometric test results. Safety certifications include UL listing and hazardous substance registries such as Electronic Waste Recycling Act (EWRA) in the United States and Restriction of Hazardous Substances (RoHS) directive in the European Union. Test reports must verify claims of brightness and longevity, such as IES LM-79, Approved Method for the Electrical and Photometric Measurements of Solid-state Lighting Products. Also vital to performance is the quality of the materials, such as the thickness and componentry used in wires, reflectors, and housings.
Concealed fixture applications in museum exhibitions may include backlit substrate and see-through conditions, as well as fixtures in the floor assembly for uplighting exhibits and signage above or overhead. At the children’s science center, the design called for dozens of lamps hidden in the faux tree to light up key features. Some of these were color-changing sources or fixtures, which add the effect of animation to the whole tree, with sweeps of color passing over in a coordinated sequence. Another tool used is the wire coil fixture spiraling around the upper limbs; it is made of electroluminescent (EL) wire in various static colors.
I had no idea that lighting choices were taken so seriously but it’s really nice to see. Thanks so much for sharing!