Advanced Lighting
For Office
Open-Plan Office Applications
High-Density 1
This High-Density 1 lighting application module presents alternative ‘energy
effective’ lighting design options for open-plan offices. These options provide
lighting uniformity, glare control, daylighting and visual comfort—all high
priorities for office environments.
Workers often spend a significant percentage of time in a given office space
so it’s important that these spaces are conducive to occupant health, comfort
and productivity. With regard to lighting design, the perception of natural
color rendering and appropriate facial modeling contribute to effective worker
interactions. Vertical illuminance on wall and partitions enhances the impression of
brightness in the environment. The lighting should be interesting without creating
distractions such as shadows, high contrast, or sudden changes in light levels.
Some important goals to consider:
• The ambient lighting source for the space is separated from the workercontrolled task lighting. This can be accomplished using one luminaire with
separate compartments, or by using one luminaire type for ambient light and
a local task light at the desk.
• The ambient lighting should enhance orientation and continuity, unifying
the space while still allowing variations in functions and layouts. Ambient
lighting should be generally uniform to enable flexibility within open-plan
work areas.
• Low partitions can increase the sense of spaciousness and the occupants’
connection to the windows, as well as utilizing lighting energy more
effectively.
• An educational program should be in place to educate users of the functions
and abilities of the lighting control system.
Approach
Recessed HighPerformance Lensed
Luminaires
lighting power density
LPD = .64 W/SF Standard and .67 W/SF Dimming
concept
Open-Plan offices with high ceilings utilize recessed fixtures
with broad distribution. Interior walls may receive light as
well, potentially reducing the need for additional wallwashing.
Adjustable desk lights may supplement illumination for tasks,
and give users personal control and increased satisfaction.
Lighting Concepts for recessed high-performance lensed luminaires
in open-plan offices with high ceilings and low furniture partitions:
• Recessed luminaires provide ambient lighting. Articulated
desktop luminaires provide higher light levels when
necessary. Local control of task lighting promotes worker
satisfaction.
• The lighting system has an orderly appearance but spacing may
vary. Luminaires are spaced more closely over work areas.
• The selected luminaires distribute light to the vertical
surfaces in addition to horizontal task surfaces.
• All vertical surfaces above 30" AFF are light-colored to
increase brightness and inter-reflections.
• Recessed luminaires are most appropriate for open plan
spaces with ceilings 8'4" or lower, since they do not
illuminate the ceilings and have a greater potential for high
angle glare. Suspended luminaires provide better quality for
open plan ceiling heights above 8'-4".
criteria
Lighting Quality: Uniformity, glare control, daylighting and visual
comfort are high priorities for office environments.
• Horizontal Illuminance (average maintained footcandles) on
the work surface: 30-35 fc ambient, 45-75 fc for paper task
performance
• Uniformity: Task-to-immediate surround: 3:1 preferred; 10:1
acceptable. Max-to-min in field of view: 10:1 preferred; 20:1
acceptable
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• Lamp correlated color temperature (CCT): 3500K-4100K
• Color Rendering Index (CRI): 82 or greater for linear fluorescent
Refer to IESNA DG-18 and IESNA Lighting Handbook 9th Edition,
Chapter 10 Design Guide matrix for more detailed information.
Open Plan Office with a High Density of
workstations, with high ceiling and low partitions,
with recessed high-performance lensed luminaires.
Strategy
Recessed HighPerformance Lensed
Luminaires
lighting power density
c
LPD = .64 W/SF Standard and .67 W/SF Dimming
daylighting
The combination of high ceilings and low partitions is the most
favorable for daylight and electric lighting distribution, and
provides more uniform illumination for less energy. Locate
open-plan areas at building perimeter for greatest effectiveness
of daylight harvesting controls. Proper sun shading is required.
Provide clerestory windows, skylights, or roof monitors when
offices are located on the upper floors. Control the lighting by
zones that are consistent with the daylight distribution. Provide
automated or motorized shade controls for open-plan spaces.
luminaires
a
Task lights located on the desktop are articulated, i.e., allow
adjustment in two or three axis to supplement the ambient
lighting for demanding visual tasks and for any employee who
is older than 40, wears corrective lenses, or simply desires
more light.
Maintenance Issues
“Super T8” lamps provide extended lamp life exceeding
30,000 hours, and the lumen output does not depreciate
more than 5% over the rated life of the lamp. Ballasts with
higher or lower Ballasts Factors may be considered to tailor
the luminaires to the project. However, the same ballast
should be used for all applications, or limited to specific areas,
to prevent confusion during replacement or maintenance.
The number of different types of lamps and ballasts should
be minimized for ease of maintenance and to ensure that
components are correctly replaced.
The luminaires selected for this application are recessed for
use in low ceilings, and have a wide distribution to enhance
the brightness of vertical surfaces for
LUMINAIRE SCHEDULE FOR OPEN-PLAN OFFICE APPLICATIONS
increased comfort. These luminaires use highHIGH DENSITY1
performance lenses and splayed sides and are
significantly more efficient than those with
 Recessed 2-lamp 2'x4' high performance
 CCT: 3500-4100K
A
lensed troffer
 CRI: 80+
open-celled parabolic louvers, reducing energy
 Direct wide distribution
 Ballast Factor: .88
 Non-planar curved or angled lenses
 System Input Watts: 55
consumption and the quantity of luminaires
 (2) 32 watt T8 fluorescent lamp
 Mean Lamp Lumens per Watt: 94
needed for a space.
(F32T8/835) in cross section
 Minimum Luminaire Efficiency: 88%
 High Performance (3100 lumens) lamps,
Low Mercury/Extended Life
 Electronic NEMA Premium instant-start
ballast
b
Same as luminaire A, except these luminaires
contain dimming ballasts, providing continuous
reduction of light down to 10% or lower of full
output. These luminaires are used for daylight
harvesting, are capable of reducing electric light
in response to the availability of natural light,
and are located less than 15' from the window
wall, as shown on the plan.
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B
C
 Same as Type A above, except with
electronic dimming
 Ballast Factor: .88
 (1) 2-lamp ballast, 2-wire or 0-10V 4-wire,
10% dimming ballast
 System Input Watts: 60
 Mean Lamp Lumens per Watt: 87
 LED desktop task luminaire with remote
electronic power supply
 Articulated movement so that luminaire
head is adjustable in at least two planes of
motion (three planes preferred)
 Adjustable height and extension 10" to 20"
 Uniform pool of light 11"x17" minimum
area in size
 (9) 1 watt LEDs, Initial lumens: 379





CCT: 3000-3700K
CRI: 75+
Electronic Power Supply
System Input Watts: 10.4
Mean System Lumens per Watt: 36
Controls
Recessed HighPerformance Lensed
Luminaires
lighting power density
LPD = .64 W/SF Standard and .67 W/SF Dimming
control strategies
This module could be controlled by a variety of control
options. Vacancy sensors are seen as a typical consideration,
where luminaires are grouped into zones that are turned on
by occupants using manual switches and automatically turned
off when not in use by networked sensors. A more advanced
option would be to add dimmable perimeter daylight zones
controlled by photosensors to the vacancy sensors. The strategy
featured below is a basic option that uses daylight dimming with
photosensors coupled with the less granular On/Off control of
a time clock. This option applies when occupancy is consistent
through work hours.
control strategies: scheduling, daylight
harvesting
In this basic option, lighting is automatically turned on and off
based on a set occupancy schedule. Daylight control zones dim
when possible, while occupants use manual switches to control
their local lighting. Graphics and details support the design
development.
A time clock turns lights on according to a schedule, only when
the space is occupied. During hours of occupancy, energy is
saved through daylight harvesting.
• Consider digital lighting control, which enables remote
programming while providing other advantages such
as energy reporting and diagnostics and simple future
integration of additional control strategies.
• The microprocessor-based CPU should be conveniently
accessible to the facility operator to enable future
programming changes. Override switches shall be located so
that users can see controlled lighting.
• Photosensors may be connected to controllers via lowvoltage wiring or may be wireless. In some cases avoiding
the need for power wiring by either using batteries or
4 | Advanced Lighting for Office
harvesting light energy in the space to generate the energy
required to produce the signal.
Time clocks should be programmed based on building operation
hours. Override switches are available for after-hours building
occupancy.
Design
Parameters
applying this module to your project
The design modules shown in the ALG are intended
to serve as examples of best practices in lighting
for common spaces with typical conditions. They
provide a starting point for design teams, but are
not intended to replace the design team or process.
See the Matrix of Variations below (end of section)
for variations in module characteristics such as
partition height, ceiling height, workstation density,
task lighting, ballast factor, dimming ballasts, and
resulting changes in connected load (LPD).
parameters used to develop the design
This lighting design was developed and modeled
with the following parameters and assumptions. If
these factors are different in your space, it will be
necessary to make modifications to address the
actual conditions.
• 9'-6" dropped ceiling, ACT, some GWB or plaster.
80% reflective.
• 42” high furniture partitions, opaque, with no
overhead shelves or bins.
• Floors 20% reflective, matte finish (carpet).
• Full height walls 70% reflective. Walls around
windows 80% reflective.
• Desktop 60% reflective.
• Ballast factor (BF): This vignette assumes
normal BF ballasts (nominal 0.88) for T8 lamps.
• Light Loss Factor (LLF) for linear T8 luminaires,
not including ballast factor = 0.84.
• Due to the low partitions, no undercabinet
lights were assumed for this vignette.
• Due to the ambient light levels calculated for this
specific vignette, it was assumed that 55% of the
workstations were supplied with an articulated
desk-top task lights. Task lights should be made
available to any workers who request them.
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Critical factors that will require modifications from this design include room
dimensions, spacing and height of the workstation partitions, lack of overhead
bins or shelves, colors and reflectances of the surfaces.
matrix of variations
The first row (yellow) represents the module as shown, additional rows
represent variations.
Partition Ceiling
Ht
Ht
Workstn
Density*
W/SF
W/SF daylight
dimming**
% Task
lights***
Notes
42"
9'-6"
<100 sf
0.64
0.67
55%
1
42"
8'-6"
<100 sf
0.64
0.67
55%
42"
9'-6"
100-150
sf
0.56
0.58
85%
42"
8'-6"
100-150
sf
0.55
0.57
70%
64"
8'-6"
100-150
sf
0.63
0.65
100%
1
2, 3
Ballast Factor (BF) of T8 lamps: Normal NEMA Premium ballast and dimming ballast = 0.88.
*
Total area of open plan space (sf) divided by total number of work cubicles.
** Assumes dimming ballasts for daylight harvesting in zone 15’ from windows.
*** Percentage of workstations with desk top LED task lights (8W each). Higher percentage of task
lights required.
1. High ceilings are preferred in spaces with windows for better distribution
of daylight and potential energy savings from daylight harvesting.
2. High furniture partitions absorb more light and create shadows. Underbin
LED lights (8W) are needed to reduce shadows.
3. High furniture partitions and low ceilings are the least efficient
combination.
Quicktips
About
New Buildings
Institute
• Recessed luminaires with wide distribution characteristics
can be spaced on wide centers. However, since they do not
provide desirable light to the ceilings, their usage should be
limited to those configurations with ceilings lower than 8'-4"
AFF and partitions higher than 56" tall.
• The use of high furniture partitions is the least favorable
for daylighting or electric lighting distribution. This
configuration will always consume more energy. Consider
using glass or translucent furniture partitions and lowering
the partitions that are parallel to the window wall.
• More light is distributed perpendicular to the length of the
luminaire, so the layout should be coordinated with the
orientation of the computer monitors.
• Running luminaires with the long side parallel to the window
wall will make the daylighting harvesting system more
effective and less distracting.
• Light the perimeter walls in the open-plan space to increase
the impression of brightness in the space, to improve
visibility and comfort, and to add visual interest to the
environment.
• Interior finishes must be very light in color for open plan
configurations.
• Luminaires should have concealed labels indicating the
correct lamp and ballast numbers for replacement.
• Incorporate lamp recycling into operating budgets.
For more advanced lighting design information for open-plan
offices, including daylighting, interior design considerations,
controls, maintenance issues and operation, go to: http://
algonline.org/index.php?open-plan-office
ALG Online is one of the design guides offered by New Buildings Institute (NBI) through its Advanced Buildings® suite of tools and resources. NBI is a
nonprofit organization working to improve the energy performance of commercial buildings. The organization works collaboratively with commercial
building market players—governments, utilities, energy efficiency advocates and building professionals—to remove barriers to energy efficiency, including
promoting advanced design practices, improved technologies, public policies and programs that improve energy efficiency.
NBI works nationally with offices located in White Salmon, Seattle and Vancouver, Washington. Visit us for more information about New Buildings Institute
at newbuildings.org, ALG Online at algonline.org and Advanced Buildings at advancedbuildings.net.
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