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Key
Terms
Acrylic Prismatic Lens
The least expensive and most
typical lens, used on both lay-in and surface mounted fixtures.
CRI
Color Rendition Index
Full Spectrum
Fluorescent lamp with a color temperature
of 5,000 Kelvin or higher, with a CRI of 90 or better.
Indirect light
Light that is reflected, often from the ceiling.
Lay-in Fixture
Fixture that is recessed into a ceiling grid.
Pendant Fixture
Light fixture that is suspended below the ceiling.
T-8 Lamp
Energy efficient 1inch (8/8 inch) diameter fluorescent lamp.
T-12 Lamp
Older style 1 ½ inch (12/8 inch) diameter fluorescent lamp.
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Lighting the Learning
Environment
Randall Fielding
“We want plenty of windows
and full spectrum lighting - not those cold fluorescents.” This is a
request I hear frequently from teachers while planning learning
environments. While the benefits of full spectrum lamps remain
inconclusive, there is a good deal of consensus on the value of daylight
and quality lighting design.
The Daylight Standard:
Daylight has long been the standard measure for lighting quality.
Studies by Kuller and Lindsten (1992), and the Heschong Mahone Group
(1999), demonstrate a positive correlation between day lighting and
academic performance. Daylight gives off a continuous spectrum of all
light wavelengths, including blue, red and green, appearing as a bright
white. Daylight is the standard for color quality in lighting, with a
Color Rendering Index (CRI) of 100. Daylight is free – the most energy
efficient source of illumination.
In contrast, fluorescent lamps give
off a discontinuous spectrum - a flickering light, with spikes of color.
Most fluorescent lamps operate at 3,000 K (warmer) to 4,100 K (cooler),
with a CRI from the low 50’s to 86. While fluorescent light fixtures
with electronic ballasts and T-8 lamps (one inch diameter) provide an
efficient utilization of electricity, they cannot be compared to
daylight, since most electric power relies on fossil fuels or nuclear
power. While natural illumination from windows and skylights is a
preferred standard, most learning environments will require supplemental
electric lighting.
The Wired
Learning Space:
The
movement towards learning spaces developed for notebook computers allows
for tremendous flexibility in the configuration of teams and individual
learner stations. This flexibility can pose a challenge in lighting
design. Ideally, light from an overhead source will be directed from a
learner’s right or left, minimizing glare or “veiling
reflections.” Light directed from the front or behind can reflect off
of computer screens or glossy pages into the learner’s eyes, causing
eyestrain. Light directed from the left or right bounces off a page or
screen to the side, rather than in the learner’s eyes. In a flexible
environment, where team and individual seating arrangements change
often, a directional light source produces poor results. One popular
solution is to provide indirect lighting, with most of the light
reflected off of the ceiling from pendant-mounted fixtures. Pendant
fixtures are typically mounted 18 inches to 24 inches below the ceiling;
requiring ceiling heights of nine foot six inches or more. These
fixtures may include a portion of direct or filtered down light. Since
light is reflected, an efficient installation requires 80% reflectivity
for ceiling materials and 65% reflective paint for major walls.
Lighting
Controls, Accent & Task Light
Indirect lighting, while uniform, can also be monotonous, lacking shadow
and contrast. Accent lighting on display areas or white boards enlivens
a space. Recessed cove lights or pendant mounted directional
fluorescents provide accent and task lighting efficiently. Location of
lighting controls near presentation areas allows presenters to reduce
the light level during media presentations, and increase them for
speaking and discussion.
Switching of selected rows
of fixtures allows for a more efficient use of lighting resources. For
example, fixtures running adjacent to a window wall can be switched
separately; during most seasons and times of the day, these fixtures are
not needed – illumination will be provided by daylight. Another
switching option involves multiple ballasts; with a 3-lamp fixture, one
may turn on one row of lamps, two rows of lamps or all three. During a
media presentation, one row of lamps will be adequate for note taking,
with minimal distraction from the presentation. During active team
collaboration or discussion, all three rows of lamps are desirable.
Laboratory Lighting in
Higher Education
Photo labs, life sciences and hi tech environments involved in the
development of microchips may find that ultraviolet rays contribute to
unwanted chemical reactions and bacterial growth. The same radiation can
have beneficial effects in the absorption of vitamin D, thus the term
the “sunshine vitamin.” Ultraviolet filtering lenses, sometime
referred to as “yellow” lenses, filter out both the blue and
ultraviolet spectrum.
Full-Spectrum Lamps and
Polarized Diffusers
Light from the sun is polarized by the atmosphere, resulting in reduced
glare and the blue color of the sky. Polarizing lenses are available to
filter fluorescent lamps. These chemically treated acrylic lenses,
combined with full spectrum lamps, can achieve artificial illumination
with the spectral energy distribution and light polarization
characteristics of natural daylight. “The lighting has been found to
match natural daylight so closely that one cannot tell the difference
between the artificial illumination and any light entering the windows.
There is none of the eyestrain and fatigue typical of conventional
cool-white illumination, which dives fluorescent lamps with core coil
ballasts in unpublicized fixtures.” (Karpen, 1991
A full-spectrum lamp is generally defined as a lamp having a
Color-Rendering Index (CRI) of 90 or above and a color temperature of
5,000 degrees Kelvin or above. Full-spectrum lamps and polarized lenses
are more costly, and have not been widely accepted commercially. In the
last decade, high efficiency electronic ballasts with reduced flicker
and lamps with improved color rendering have become readily available.
T-8 Lamps with a color temperature of 3,000 to 4,200 K are available
with a CRI as high as 86. One study concluded that there was little
consistent difference between conventional lamps with a good CRI and
full spectrum lamps with a polarizing diffuser (Veitch, 1994).
Cost
Factors & Efficiency
Lighting quality is closely linked to fixture costs. Lay in fixtures
with acrylic prismatic lenses are cost as little as $35 for a four foot
fixture, and are generally considered to provide the poorest quality of
light, with the highest glare. A similar fixture with a parabolic louver
produces less glare, and can be purchased for as little as $50. A steel
pendant mounted fixture that produces indirect, reflected light starts
at about $80. A steel pendant fixture with a mix of up light and down light
starts at about $140. Extruded aluminum pendants, producing a much
straighter line when installed in a line may cost even more. While
installation costs are lower for pendant fixtures, the overall cost is
still typically higher.
According to Tom Lyman, Director of Lighting Design at the Princeton,
New Jersey-based firm CUH2A, when overall efficiency is considered, an
installation of steel indirect pendants will outperform lay in fixtures
and result in a superior lighting quality. The efficiency of a lay in
fixture is in the 50% to 70% range. The efficiency of a pendant indirect
is in the 70% to 85% range. The efficiency of a bi-directional pendant,
with both up and down light is in the 80 – 95% range.
Conclusions
Utilize day lighting wherever possible, providing windows on one or two
walls; where window walls are limited, utilize skylights. For all but
northern exposures, provide overhangs or blinds to allow for control of
direct light.
Provide ceilings at nine foot six inches or higher. Provide a
combination of pendant direct/indirect fixtures for general illumination
and linear strips of accent light along display areas and white boards
along one or two walls. With breakout or learning alcoves, provide a
unique directional pendant that focuses light on the center of the
discussion area. If the budget does not allow for this, provide indirect
lighting in least a portion of the learning spaces, such as
technology-rich areas or collaborative common areas.
Consider making the study of
light a curriculum elective. Numerous study programs have been developed
around the study of water and air quality. Sunlight is an essential
element in life, and warrants the same attention as water and air
quality. The physics of light and the effects of lighting on behavior
are rich sources of study.
Randall Fielding is an educational
planner, architect and the editor of Design Share. He can be reached at fielding@designshare.com
References:
Heschong Mahone Group. 1999.
“Daylighting in Schools: An Investigation into the Relationship
Between Daylighting and Human Performance.” Pacific Gas and
Electric Company Report, on Behalf of the California Board for Energy
Efficiency Third Party Program. (August 20), pp. 24-29. http://www.pge.com/pec/daylight/valid.html
Karpen, Daniel. 1991.
“Full-Spectrum Polarized Tackles Computer Screen Glare.” AIP
Facilities (March/April), pp. 35-38
Kuller, R and Lindsten, C.
1992. “Health and Behavior of Children in Classrooms with and without
Windows.” Journal of Environmental Psychology (12), pp. 305 -
317
Veitch,
Jennifer A. and McColl, Shelley L. 1994. "Full-Spectrum Fluorescent
Lighting Effects on People: A Critical Review.” National Research
Institute in Construction, Ottawa, ON K1A OR6
IRC Report No. 659,
(June), pp. 53-100 http://www.nrc.ca/irc/fulltext/ir659/contents.html
Lighting Designers and
Engineers Interviewed:
Tom Lyman, Director of Lighting Design, CUH2A, a Princeton, New Jersey
firm specializing in higher education facilities. tlyman@cuh2a.com
Wilson Dau, Manager,
Applications Engineering Department, >
Ledalite Architectural Products, Langley, British Columbia, wdau@ledalite.com,
www.ledalite.com
William Boland, Lighting
Designer, Fletcher Thompson, Inc, a Connecticut-based firm specializing
in higher education facilities bboland@ftae.com
Lily del Berrios, Director,
Education Studio, an Atlanta-based form specializing in higher education
facilities. lilb@sizemorefloyd.com
David Black, Design
Principal, Flad Associates, a Madison, Wisconsin-based firm specializing
inn higher education facilities. David_balck@fald.com
Myron Kaplan, CEO, Polarized
Lighting International, a Tarzana, California-based manufacturer,
specializing in polarized lenses. myronkahn@aol.com
, http://www.polarizedighting.com
Additional Information
On-line:
The National Clearinghouse
on Educational facilities, a leading indexer of educational planning
issues. http://www.edfacilities.org/rl/lighting.cfm
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