With stricter energy codes, tighter budgets, and growing interest in LEED, building owners are being challenged to do more with less, particularly in the realm of lighting design. In order to meet lighting-level requirements with increasingly lower lighting power density targets, ceiling systems are becoming a key component of energy conservation.
Fortunately, with well-designed and coordinated ceilings, high light reflectance can go a long way toward boosting space illumination, which reduces the number of fixtures, required electrical light output, maintenance, and cooling load.
Patricia Kazinski, principal at RTKL in Washington, D.C., explains, “Once energy conservation strategies and a construction budget are set, [you] can explore ceiling and lighting options that get the most bang for the buck – matching ceiling systems with the highest reflectance and lighting fixtures with the highest efficiency possible.”
Offering some general guidelines for ceiling systems, experts advise building owners and facility managers to choose:
- A ceiling reflectance of greater than 80 percent.
- A smooth, matte finish.
- No heavy patterns or textures.
- Floor-to-ceiling heights at a minimum of 9 feet (10 to 12 feet is preferred).
“These types of ceilings greatly contribute to the uniformity and spread of lighting in the space, and help give the space depth and volume,” says Kazinski.
In terms of lighting design coordination, direct high-efficiency or indirect lighting generally work well with high ceiling reflectance to optimize lighting levels.
For example, one strategy is combining direct high-efficiency luminaires and direct fixtures. Designed with “high-reflectance surface materials, this provides the optimal combination for decreased energy consumption,” says Angela Nudy, lighting and electrical designer at EwingCole, Philadelphia. “Overall, the combination also allows the design to reduce the number of fixtures and lamps required, which creates savings through reduced energy and maintenance.”
Meanwhile, the other approach – indirect lighting – employs the ceiling surface as a reflector for ambient lighting, although ceiling reflectance levels of at least 90 percent may be required to achieve desired light levels.
RTKL designers discovered (via a LEED-CI Platinum project with pendant-mounted fluorescent T5HO direct/indirect lighting and a LEED-CI Silver building with recessed semi-indirect T5 fluorescent fixtures) that acoustical ceiling tile with little texture, light reflectance of greater than 80 percent, and a matte, smooth finish enabled energy conservation strategies to be met for both projects.
Kazinski has also found that well-coordinated lighting and ceiling system design, with energy conservation goals set early in the project, enables a 25- to 35-percent increase over ASHRAE 90.1 lighting power density requirements.
Similarly, Rik Master, architectural systems manager at USG in Chicago, notes that, through the use of T8 compact fluorescent bulbs and highly light reflective ceilings, savings of 30 percent have been documented. And now, with T5 technology and creative design, Master projects potential lighting operation savings as high as 60 percent.
In addition to ongoing operational costs, savings can also come from the initial lighting design itself. For example, with a highly reflective ceiling and high-efficiency luminaires, the design of the LEED-NC Silver Geisinger Center for Health Research in Danville, PA, utilized direct lighting fixtures housed with high-output lamps, which enabled EwingCole to reduce the fixture count by nearly 50 percent (for a construction savings of $80,000).
Aesthetics and Style
While optimizing energy savings is a key goal, if architectural style and effect are also desired, sometimes the approach will be different.
For instance, according to Tom Lyman, senior associate and director of lighting design at HDR CUH2A, Princeton, NJ, “An asymmetric wash of light grazing across a textured ceiling will create visual interest while providing comfortable ambient light. Or a point source of light on a glossy ceiling panel will form strong brightness patterns, creating sparkle and attracting attention.”
While choosing a textured or glossy ceiling may mitigate the ceiling’s ability to reflect light, every project has its unique set of requirements.
Barbara Horwitz-Bennett is a frequent contributor to building and construction publications (www.BHBennett.com).