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PIER Lighting Research Program
California Energy Commission
Contract # 500-01-041
Common Classroom Electric
Lighting and Daylighting
Configurations for California Report
Deliverable 3.3.2b
March 14, 2003
Submitted To:
Accounting Office, MS-2
California Energy Commission
1516 Ninth Street, 1st Floor
Sacramento, California 95814
Submitted By:
Architectural Energy Corporation
2540 Frontier Avenue, Suite 201
Boulder, Colorado 80301
Deliverable 3.3.2b Classroom Lighting Configurations Architectural Energy Corporation
Table of Contents
Executive Summary ...........................................................................................................3
Introduction ......................................................................................................................3
Current California Design Recommendations........................................................................4
Methods ...........................................................................................................................5
Results - Classroom Features ..............................................................................................5
Portable Classrooms...........................................................................................................9
Conclusions ....................................................................................................................10
Next Steps – 3-D Model Development ...............................................................................11
Additional Resources .......................................................................................................12
Appendix A – Guide form Questionnaire............................................................................13
Appendix B – Interview List .............................................................................................15
Appendix C - Photos ........................................................................................................16
Contact Information:
Subcontract Project Manager AEC Program Director
Doug Paton Judie Porter
The Watt Stopper Architectural Energy Corporation
2800 De La Cruz Blvd. 2540 Frontier Avenue
Santa Clara, CA 95050 Boulder, CO 80301
925-454-8224 voice 303-444-4149 voice
925-243-8912 fax 303-444-4304 fax
[email protected] [email protected]
Prepared by:
Dr. Richard G. Mistrick, Associate Professor of Architectural Engineering, Pennsylvania State University
Dorene Maniccia, Manager, Market Segment Development, The Watt Stopper
Project Team:
Dr. Richard G. Mistrick, Associate Professor of Architectural Engineering, Pennsylvania State University
Dorene Maniccia, Manager, Market Segment Development, The Watt Stopper
Francis Rubinstein, Building Technologies Department, Lawrence Berkeley National Laboratory
Doug Paton, Product Line Manager, The Watt Stopper
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Common Classroom Electric Lighting and Daylighting
Configurations for California Report
Executive Summary
This report summarizes information collected on the typical configurations of classrooms
being built in new K-12 schools in California. It concentrates on the design decisions,
which influence the use of daylighting in a classroom including classroom size and
ceiling height, window configuration, glazing type, window treatments, skylights and
reflectance conditions. Also collected was information on common electric lighting
configurations. This work was done in preparation for creating 3-D models and running
computer simulations of five common classroom configurations.
We found that the typical classroom size is 960 ft2, and that sidelighting daylighting
strategies are currently more popular than top-lighting and light shelves. Preference is
given to bringing natural light in from two parallel directions rather than one. High
performance schools are currently limited in number, but high performance design
strategies encouraged by the CHPS (Collaborative for High Performance Schools)
Program are beginning to gain popularity. Pendant mounted electric lighting
configurations are preferred, although recessed lensed and parabolic luminaires are used
when budget is an issue. Finally, although photosensor control systems are frequently
desired, they are often value-engineered out of the design near the end of the project.
The goal of Project 3.3 is to develop a photosensor and lighting control system that is
optimized for common classroom electric lighting solutions (recessed and pendant
lighting) and daylighting configurations (side-lighting only, top-lighting only, side- and
top-lighting), that can be simply and easily commissioned, and that effectively operates
with manual controls and occupancy sensors. The Watt Stopper intends to incorporate
this public knowledge into a new family of daylighting controls.
This document is an interim report, summarizing the results of Task 2. The goal of this
task is to develop an understanding of the common electric and daylighting
configurations currently employed for new classrooms in California. Five common
configurations will be identified and used for optimizing the design of the Classroom
Photosensor System.
Once the five common configurations are determined, 3-D models using Radiance and
Penn State software will be developed that will facilitate the daylighting and electric
lighting analyses. These models will be used for running computer simulations of
daylighting and electric lighting illuminance levels and distributions, and determining the
classroom photosensor system performance criteria.
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Current California Design Recommendations
The California Advanced Lighting Guidelines, and CHPS Program both offer design
guidance for lighting and controls in classrooms. Although the purpose of this report is to
identify and summarize current design practice, a summary of the recommendations of
these programs is warranted.
Advanced Lighting Guidelines
The 2001 version of the Advanced Lighting Guidelines (ALG) lists the 30’ X 32’ room
configuration as being typical for California classrooms with typical lighting power
densities of 1.5 W/ft2. The ALG provides the following example lighting application
layouts for classrooms:
• pendant mounted direct/indirect luminaires for general lighting with independent
chalkboard lighting;
• recessed “donut” layouts for low-cost lighting solutions that achieve good vertical
surface illuminance and high light levels;
• pendant mounted direct/indirect luminaires coupled with a uni-directional side-
lighting daylighting strategy illustrating how luminaires can be dimmed to take
advantage of daylight illuminance
The ALG suggests using one of three gradations of lighting control. These include
“minimal” lighting controls using basic switching with automatic shutoff, “good “ control
using multi-level switching, and “optimal” control using continuous dimming when
daylighting strategies are employed.
Collaborative for High Performance Schools Program (CHPS)
The CHPS Best Practices Manual provides similar lighting design recommendations as
the ALG. The CHPS recommendations for controls are more specific than the ALG.
CHPS recommends using occupancy sensors in all classroom applications for
automatically turning lights off when the space is unoccupied. It also recommends
providing manual override for turning lights off when needed, and manual control of
luminaires in the daylit zone, consistent with the ALG.
CHPS also provides design guidance for daylighting and fenestration design. The
daylighting strategies recommended by CHPS include:
• Using view windows to provide access to exterior views,
• Using clerestories to introduce daylight deeper into classroom spaces,
• Using light shelves or louvers with clerestories to improve daylight distribution;
• Using wall wash top-lighting to balance daylight from vertical glazing,
• Using centralized top-lighting strategies for single-story classrooms,
• Using patterned top-lighting strategies in large areas such as gymnasiums,
• Using linear top lighting in corridors to direct movement and/or provide cues for
visual orientation.
• Using tubular skylights for top-lighting in buildings with deep roof cavities and/or
for low-cost retrofits
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Telephone interviews with designers and decision makers were the primary method used
for gathering information on common classroom design strategies. Design practice
feedback and information garnered through The Watt Stopper’s customer visits
conducted in 2002 is also included in the summary.
Questionnaire Development
The Guide Form Questionnaire, shown in Appendix A, was used for conducting the
telephone interviews. Key architectural and lighting design elements were included on
the questionnaire. Interviews were conducted in an open-ended conversational manner,
with the interviewer using the questionnaire to guide the discussion and obtain
information about the key architectural and lighting design elements.
Telephone interviews
The top school designers and consultants in California were targeted for the interviews.
Telephone interviews were conducted with the architects, consulting engineers, school
districts and electric utility personnel listed in Appendix B. A total of 24 professionals
were interviewed in January of 2003. Interview candidates were selected based upon their
level of experience with designing schools, and their level of involvement in State-funded
school initiatives such as the CHPS Program. The architects represented major firms who
specialize in school design such as Fields Devereaux Architects, Perkins & Will, Boora
Architects and Quattrocchi-Kwalk Architects. Key consulting engineering firms who
specialize in schools such as O’Mahoney & Myer, and Harry Yee & Associates were
interviewed. Utility personnel who are involved in providing design assistance to
architects and engineers, and researchers who are involved in similar work were also
contacted. These included organizations such as PG&E, SC Gas and SDG&E, Heschong-
Mahone Group, Eley & Associates, etc.
Results - Classroom Features
Size and ceiling height
Classroom sizes are commonly a 32’ X 30’ (960 ft2) or 30’ X 30’ footprint (900 ft2).
Ceiling heights vary and depend upon the architectural configuration. Classrooms with
flat ceilings have ceiling heights of at least 9’0”, with 9’-6” being a rather common
finished ceiling height, while those incorporating architectural daylighting strategies,
such as shed roofs, or clerestories, will be higher, typically up to 15 feet for single-story
Window Configuration
For typical side-lighting configurations, there are commonly two rectangular windows
along the outside wall. Placement is typically “punched” rather than continuous. These
designs typically employ two windows in each classroom, which are approximately 6’ X
6’ or 6’ X 7’, and start at a minimum of three feet above the floor. This provides a
window area of approximately 30 percent of the exterior wall. Continuous glazing is also
used, but is not as common as “punched” designs.
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Clerestories and skylights have been employed in a few high performance designs, and
are generally employed in designs where attempts were made to illuminate a large
fraction of the floor area. In the spaces where clerestories were applied, the ceiling is
either one continuous plane sloping up to the clerestory wall, or a ridge roof is applied, as
was typically done in many of the old finger-plan designs. The height of the clerestory
glazing areas is typically about three to four feet across the glass area.
Glazing Type
High performance designs commonly employ Viracon’s Solarscreen 2000 VE 1-2M #2
clear low-E insulating glass or a similar product for vertical glazing providing a view.
This glass type has high visible light transmittance and filters out most of the ultraviolet
and the infrared radiation, using spectrally sensitive material (Figure 1). Viracon applies
the low-e coating to the inside surface of the outer glass pane (Figure 2). One architect
mentioned that this glass type would likely become standard in California because of its
spectral and insulating characteristics. Examples of other common low-E glazing types
include PPG’s Solex, Solargreen, and Azurlite products. The low-E glass types have
relatively high visible light transmittance properties, and high light to solar gain ratios
(LSG). This ratio is defined by the ratio of visible light transmittance to solar heat gain
coefficient. Higher ratios mean that more visible light is transmitted through the glass
while the heat gain is low. As shown in Table 1, low-E glass types transmit less UV and
heat, and more visible light, than uncoated glass types.
When light shelves are used, low-E glazing with higher transmittance (approximately 70
percent) is commonly used on the upper glazing, and low-E glazing with lower
transmittance (around 40 to 50 percent) is commonly used for the view window.
Figure 1. Spectral transmittance of
Viracon’s glazing types illustrating
the IR and UV reducing properties
of the Solarscreen 2000 glazing.
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Figure 2. Viracon’s window
sandwich illustrating the low-e and
spectral coatings on the inside surface
of the outer windowpane.
Table 1. Examples of Low-E and Uncoated Glass Properties
U-Value3 Solar Heat Light to
Low-E Glass Shading
Gain Solar
Type Coefficient4
Transmittance2 Reflectance2 (Imperial) Coefficient5 Gain6
Total Total
Solar Solar Winter
(SC) (LSG)
Ultraviolet Visible Energy Visible Energy Night Summer
% % % Light % % Time Day Time
Clear Glass 14 69 32 12 28 0.29 0.29 0.44 0.37 1.86
SOLEX Tinted
8 60 24 11 11 0.29 0.30 0.41 0.36 1.67
® 4 52 20 10 8 0.29 0.30 0.35 0.30 1.73
Tinted Glass
10 52 20 9 7 0.29 0.31 0.35 0.3 1.73
Tinted Glass
Viracon VE 1-
10 70 32 11 31 0.29 0.28 0.43 0.37 1.89
U-Value3 Solar Heat Light to
Uncoated Shading
Gain Solar
Glass Type Coefficient4 5
Transmittance2 Reflectance2 (Imperial) Coefficient Gain6
Total Total
Solar Solar Winter
(SC) (LSG)
Ultraviolet Visible Energy Visible Energy Night Summer
% % % Light % % Time Day Time
Clear Glass 50 79 61 15 12 0.48 0.55 0.81 0.70 1.13
SOLEX Tinted
25 69 39 13 8 0.48 0.57 0.56 0.49 1.41
® 13 60 29 11 7 0.48 0.57 0.46 0.39 1.54
Tinted Glass
34 60 27 11 7 0.48 0.57 0.44 0.38 1.58
Tinted Glass
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Daylighting Design Strategies
Presently, the most common architectural daylighting design strategies employ
clerestories or shed roofs, which enable the architect to bring daylight into the space from
as high as possible. Light shelves are not common, primarily because they are a “big
value engineering target” and often are removed from a design because of cost. Other
reasons that light shelves are not utilized include the resistance of school maintenance
staff because they are difficult to clean, become bird havens, and may become “stuff”
depositories by students and teachers. Therefore, clerestory and shed roof designs are
more commonly employed because they provide good daylight distribution, and are
economical compared to the cost of light shelves. Most architects prefer to design a
classroom with daylight entering from two parallel sides of the room. Overhangs are
frequently employed with vertical glazing in an attempt to block direct sunlight from
striking vertical glazing, particularly on the south side of a building.
Light shelves are certainly in the minority, but may be gaining some popularity with the
increase in “high performance” design. When light shelves are used in a high
performance design, the ceiling is typically open with ductwork exposed. This strategy
helps to mitigate indoor air quality issues, such as dust and dirt build up and mold that
sometimes arise with concealed ceilings. In addition, larger duct sizes can be used, which
results in better acoustical performance because the supply air is delivered at a lower
Window treatments
Glare from direct sun is a major obstacle to proper “daylighting” design. Direct and
reflected glare from solar radiation is a major issue to resolve now that whiteboards are
used instead of traditional blackboards. To provide occupant control, and help mitigate
direct glare from the sun, horizontal blinds mesh or opaque shades are common interior
shading strategies. In one high performance design utilizing light shelves, an architect
mentioned that signs were posted at each window shade, asking teachers to keep the
blinds open whenever they weren’t needed for glare control or other “low light” tasks.
This was executed to encourage the teachers to help optimize the architectural
daylighting design strategy.
Large window areas and/or clerestories appear to be more common than using skylights
for maximizing daylighting penetration, especially in urban schools where skylights are
useful only on the top floor of a building. One respondent indicated that in their projects,
skylights are not used for “functional” daylighting, meaning that there is not sufficient
quantity or size to functionally daylight the space. In suburban schools, skylights are
usually discussed at design meetings as a primary option, although often the school
decides not to use them because of maintenance concerns about leakage and access by
vandals. The maintenance and leakage concerns carry over to urban schools as well.
When used, skylights are usually employed in single story school designs, which are
most frequently used in suburban locations. They often include motorized louvers for
shading mechanisms that are under occupant control.
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Sunoptics appears to be the popular skylight manufacturer for products applied in
schools. They also supply product to WalMart. Their skylights use a prismatic, pyramid
shaped lens to distribute the light, and are often coupled with louvers for glare control.
Appendix C illustrates the Sunoptics skylight, and some application photos for a
classroom in the Yamato Colony Elementary School in Livingston, CA, and for a library
in the Mildred Perkins Elementary School in Modesto, CA. Both applications use 4' X 4'
skylights and motorized light control louvers. The skylight wells were splayed to
optimize light distribution. A number of different schools apply this design concept,
which uses the large splayed wells to provide relatively high quantities, and even
distribution of daylight across an entire classroom. This technique provides abundant
daylight on both the work plane and the walls. Small view windows are generally applied
in these designs to provide a view to the exterior environment.
Common Electric Lighting Configurations
Pendant mounted indirect, or indirect/direct lighting systems are becoming more popular,
particularly in high performance schools, but many schools are still constructed with
conventional recessed fluorescent luminaires. Most designers are using T8 lamps and
electronic ballasts, although T5 technology is gaining in popularity in pendant luminaires.
Pendant luminaires are typically laid out in two or three rows, depending on luminaire
lamping, and commonly run parallel to the window. When ceiling heights cannot
accommodate pendant mounted luminaires, or when budget is a significant concern,
recessed direct, or recessed indirect luminaires are commonly used.
Most lighting professionals follow the Illuminating Engineering Society of North
America (IESNA) recommended illuminance levels. The IESNA recommended design
illuminance levels for classrooms vary depending on the classroom activities. Maintained
horizontal illuminance levels of 50 footcandles are recommended for general classroom
activities, and maintained illuminance levels of 30 footcandles are recommended on
vertical surfaces. Special classrooms such as laboratories, art and drafting rooms require
higher horizontal illuminance levels to accommodate more detailed visual tasks. The
typical “non-specialty” classroom in California and other states are commonly designed
using target illuminance levels between 30 and 50 footcandles.
Reflectance Conditions
Most schools designed with daylight in mind have relatively high room surface
reflectance values to help diffuse the light within the space and reflect it to other surfaces.
High reflectance ceilings (about 85 to 90 percent) are often applied with indirect or
indirect/direct lighting systems. In those cases where the ceiling is exposed, it is generally
painted with high reflectance paint. Wall surfaces are either painted or covered with
acoustical panels, with materials that have medium reflectivity (between 40 and
60percent). Color is often used on the walls to provide a visually pleasing and stimulating
learning environment.
Portable Classrooms
Portable classrooms account for a large percentage of classrooms in California. There are
two common designs. One has a 24’ X 40’ footprint, the other a 30’ X 32’ footprint. In
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both designs, two “punched” windows are located along the short walls, adjacent to the
doors. Windows are either 5’ X 4’ or 4’ X 4’. Low-E glazings are not common, although
tinted glass is sometimes used. Ceiling heights are commonly 9’0”, and are flat. Electric
lighting is typically recessed lensed 2’ X 4’ luminaires using three T8 lamps with
electronic ballasts.
One architect is working on prototype portable classrooms incorporating high
performance design principles. These classrooms will use six SunOptics skylights in the
24’ X 40’ designs, and four in the 32’ X 30’ designs.
The common classroom footprint is between 900 and 1000 ft2 with 30’ X 30’ and 32’ X
30’ aspect ratios being the most popular. Ceiling configuration is driven by the desired
daylighting design strategy, with preferences for daylight penetration from high angles,
using vertical glazing strategies. Light shelves are an exception rather than the rule for
most new school designs. This is driven by budgetary and maintenance considerations.
Clerestories and shed roofs with bi-directional daylighting distributions are relatively
common in some of the high performance school designs. Skylights are also applied in a
number of school districts in single story schools, but are frequently not selected because
of leakage concerns. Although the low-E glazing types are highly desirable and
frequently applied, uncoated and clear glazings are also applied in some designs.
A relatively small number of school designs appear to qualify as high performance
schools with regard to daylight utilization. The presence of the CHPS Program may help
to increase the relative number of these schools in the future, but at the present time the
numbers appear somewhat limited. The use of photosensor controls appears to be quite
limited at this time. In many of the schools in which daylight is being addressed,
photosensor controls are often value-engineered out of the design near the end of the
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Next Steps – 3-D Model Development
Given the information garnered through the telephone interviews, the following
classroom configurations are currently being developed in the 3-D models using
Radiance and Penn State software:
• Simple windows (with blinds) – windows on one wall
• Windows with clerestory
• Windows with skylights
• Full skylight system – four large splayed wells covering entire room
• Light shelf system (shown below – this model was developed from a best practice
recommendation found in the CHPS literature)
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Additional Resources
PPG web site
Viracon web site
PG&E’s Daylighting Initiative
Collaborative For High Performance Schools
Illuminating Engineering Society of North America Lighting Handbook, 2000
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Appendix A – Guide form Questionnaire
1. What proportion of your school projects takes advantage of daylight as a light
2. What types of architectural daylighting strategies are commonly used?
3. Architectural elements for sunlight control
• Solid Overhang
• Light shelf
• Louvers - exterior
• Interior shelf
• Other
Side-lighting window geometry
• Band or continuous?
• How far down from the ceiling?
• Dimensions, or approximate size?
• Proportion of roof area devoted to skylights?
• Symmetrical skylight layout?
• Top-lighting – symmetrical for general lighting
• Top-lighting – asymmetrical – wall wash?
Skylight types
• Well….
• Type
• Transmittance
4. Interior shading devices?
• Horizontal blinds
• Vertical blinds
• Mecoshade (translucent fabric)
• Opaque fabric/material
5. How often does a design have relatively uniform groupings of classrooms
oriented north/south?
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6. What types of electric lighting systems are employed with each daylit
a. Recessed
b. Pendant
i. Ind/Dir
ii. Ind
c. Other
d. Perimeter
7. What type of electric daylighting control strategies do you commonly use?
a. Continuous dimming……Get details….
b. Switching…. Get details
8. Typical Classroom DATA
a. Typical room size – Elementary & middle/high school
b. Ceiling Height
c. Typical room surface reflectances?
d. Using chalkboards or whiteboards?
e. Ceiling configuration ( flat, sloped, other…)
9. Would you be willing to share project examples that we can use for
developing our test cases?
a. Drawings – CAD or floor plans/sections, interior details
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Appendix B – Interview List
Name Title/Role Company/Address
Bob Martin San Diego Unified School District
Jim Blomberg Sunoptics
John Zimmer Consultant to LA Unified Schools
Mike Maurizio LA Unified School District
Bill Burke Architect PG&E, San Francisco, CA
Chuck Angyl Architect San Diego Gas & Electric
Dennis Bottum Architect GreenWorks/Fields Devereaux Architects
George Loisos Architect Loisus Ubbelohde Architects
Gregg Ander Architect Southern California Edison
Heinz Rudolph Architect Boora Architects
Jim Theiss Architect Quattrocchi-Kwalk Architects
Lisa Heschong Architect Heschong-Mahone Group
Marvin Taff Architect Consultant, Ex-Gensler Architect, LAUSD
Rob Samish Architect Lionakis Beaumont Design Group
Scott Shell Architect Esherick, Homsey, Dodge & Davis (EHDD)
Steven Ternoey Architect Lightforms, Santa Barbara, CA
Wendell Vaughn Architect Perkins & Will, Pasadena, CA
Charles Eley Engineer Eley Associates
Jon McHugh Engineer Heschong Mahone Group
Randall Higa Engineer Southern California Gas Co.
James Benya Engineer/Ltg.Designer Benya Lighting Design
J. Schanrock Facility Coordinator Oak Ridge High School, El Dorado Union School
David Yu Principal Harry A. Yee & Associates, Sacramento, CA
Junette Kushner Senior Electrical and O’Mahony & Myer, San Rafael, CA
Lighting Designer
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Appendix C - Photos
Sunoptics Product Photos and Application Examples
Sunoptics Prismatic Skylight
Mildred Perkins Elementary School
Modesto, CA
Library using 4' X 4' skylights with splayed
wells and motorized light control louvers.
Yamato Colony Elementary School
Livingston, CA
Classroom using 4' X 4' skylights with
splayed wells and motorized light control
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