enhance your vision: lighting in librariesweb.stanford.edu/dept/sul/library/institute21/...lighting...
TRANSCRIPT
Enhance Your Vision:Lighting in Libraries
Patricia Fitzgerald, AIA, andJeffrey Scherer, FAIA,Meyer, Scherer & Rockcastle, Ltd.,Library Architects and Interior Designers
Evolution of Lighting theLibrary
• Daylight Source Sized Proportionally toCollection and Task
• Amount of Light Needed Relative to Era
• Task was Primary in Early Age ofArtificial of Illumination
• Form of Building Shaped by Daylight
The Technical Stuff
• Know the “Terms of Art”
• Challenge Assumptions
• Ask for “In-place” examples and actualfixtures
• Check and Double Check
• Use Computer Modeling
Historical Perspective onElectrical Illumination
• The Roles of the Librarian, Engineerand Architect defined by “jobdescription”—in other words strictterritories of expertise
• Manufacturers created the solutions
• Subjectivity and multiple influences nottaken fully into account
Looking Back to the Future
• Lighting is major concern
• Glare, daylight and variations
• Impact of shelving heights
• Controversy over lighting quantity andquality (foot-candle vs. visual acuity)
• General vs. task
• What you see is what you get
Lessons from the Past 40Years
• Too Much Light—cooking the staff• Lighting the ceiling not the task• Too Little Light• Not in the Right Place or Type• Costly—too many fixture• Less skepticism and in-depth
Understanding—Letting the industryand engineers dictate
Architecture or the Library
• Subservient to Architecture
• Function Follows Form
• Fixture Performance Inadequate
• Contrast Too High or Too Low
• Lack of Understanding of Fixture Impacton Staff and Space
• Integration of Architecture & Lighting
Daylight & Electric Light
• Monumental Form not matched to Task
• High Contrast Ratio
• Integrate Sources
• Daylight Matched to Circulation
• Glare and Uncontrolled Illumination
M S & R• Integrate with history• Task Specific—but allowing for flexibility• Daylight Controlled—orientation and
shading devices• Understanding human
needs—welcoming, easy on the eyes,heliotropes, intimate
• Uniformity—with attention to glare,brightness ratios, fixture variety
Summary: DevelopingUniform and Better Lighting
• Minimize different lamp types andfixtures—insist on illustrations, physicalsamples and photographs of proposedfixtures
• Lighting system should maximize acousticalperformance of ceiling
• Flexibility of Space: desk locations, activities,shelving, seating and patron visual comfort
Summary: DevelopingUniform and Better Lighting
• Provide lighting system within stacksthat does not interfere with future stackreorganization
• Where possible use task lighting andmotion detectors to reduce connectedloads and increase local control
• Integrate power system with lighting toensure flexibility and compatibility
Summary: DevelopingUniform and Better Lighting
• Stress coordinated aestheticcharacteristics of the fixture with thedesign of the library
• During the design process—be adoubter and tough questioner!
Thanks!
PowerPoint presentation isavailable on our website.
www.msrltd.com
Terms of Art
Color TemperatureColor Rendering IndexVeiling ReflectionsVertical IlluminationRoom Surface BrightnessTask LightingLamps & LuminairesEfficacy (Lumen per Watt)DistributionFootcandles
Color Temperature Scale
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
North LightOvercastNoon DaylightCool WhiteWhiteWarm WhiteIncandescent SunriseCandlelight
The correlated color temperature scale provides a roughindication of the color balance of various sources ofwhite light.
The higher the degree Kelvin, the bluer the light.
360 400 440 480 520 560 600 640 680 720 760 800Wavelength
1800
1600
1400
1200
1000
800
600
400
200
0
Rel
ativ
e S
ensi
tivity
80
70
60
50
40
30
20
10
0
S/P
Photopic Sensitivity Function Scotopic Sensitivity FunctionS/P Ratio
BERMAN STUDY: COLOR SPECTRUM AND VISUAL SENSITIVITYEnergy and Environment Division, Lawrence Berkley National Laboratory
Pupil efficiency is affected by the colorspectrum of the light source
5000 K fluorescent is 25% more pupilaryefficient than common cool white
5000K fluorescent lamps could operatewith 14% less energy to achieve the samebrightness perception
Consider the visual value of daylightwhich has a color temperature of between6000K and 1000K.
Photometric means of measuring thesestudy results are not available.
Color and Vision Performance
Direct Glare
95
55
Overhead Glare
4’-
0”
Glare is the sensation producedwhen a source of light within a person’s field of view is so much brighter that the light level to which the eyes are adapted that the persons experienced discomfort of loss in visual performance.
If you can eliminate glareyou can improve visual acuityat lower light levels
Veiling Reflections
Veiling Reflections are reflections of a light source that partially or totally obscures details (such as words printed on a page) by reducing the contrast between details and their background.
Vertical Illumination
Lights placed parallel to the stacks limit flexibility and provide good vertical uniformity at lower average light levels.
Lights placed perpendicular to the stacks provide flexibility in arrangement and higheraverage light levels with lower vertical uniformity.
Perpendicular - 84 light fixtures
Average = 46fcMaximum = 74fcMinimum = 20fcMax:Min = 3.74
Parallel - 84 light fixtures
Average = 38fcMaximum = 54fcMinimum = 21fcMax:Min = 2.59
Reading Tasks
Surface Brightness Ratios
Task to Immediate Surroundings 3:1Book to Desk
Task to General Surroundings 5:1Book to Partitions
Task to Remote Surroundings 10:1Book to Remote Wall
Light Source to Large Adjacent Area 20:1Window to Adjacent Wall
Task Lighting
DISTRIBUTION ADVANTAGES DISADVANTAGES USE AREA
DIRECT
DownlightsRecessed LensRecessed Parabolic
Adds sparkle/CharacterDefines TextureDefinition of ShadowsHigh Vertical Illumination
Direct GlareLighting Cut-Off
Lobbies & CorridorsConference RoomsChildren & YouthPerformance / Story TellingStacks
INDIRECT
Pendant LinearPendant RoundSurface Wall
Eliminates GlareBest Visual PerformanceLights Walls & Ceiling
Requires High CeilingsEliminates ShadowsRequires Reflective Surfaces
ResearchSpecial CollectionsAdmin Offices
DIRECT/INDIRECT
Pendant LinearPendant RoundSemi-Recessed
Reduces GlareGood Visual PerformAdds Shadow DefinitionLights Walls & CeilingGood Vertical Illumination
Potential GlarePendant Requires High CeilingsSemi-Recessed Cuts Off Lighting
General CollectionsChildren & TeensMeeting RoomsAdmin Offices
Comparison of Lighting Types
Comparison of Lamps
LightSource
ColorTemperature(Kelvin)
ColorRenderingIndex (CRI) Dimming Start-up
Lamp Life(Hours)
Efficacy(Lumen/Watt)
Disposal
Daylight6000K –9000K
98 - 100WindowCoverings
Cyclical Renewable
IncandescentArgon 2800K 98
Continuousto 1%
Instant On 3,000 3 - 21
Incandescent Halogen 3000K 98
Continuousto 1%
Instant On 3,000-6,000 10 - 22
Fluorescent3000K-5000K
70 - 90Continuousto 5%
Rapid OnInstant On
10,000 –20,000
40 104ToxicWaste*
Metal Halide3000K –4800KColor Shifts
60 – 92Bi-level Step
10 - 15Minutes
7,000 –15,000
44 - 95ToxicWaste
HighPressureSodium**
2800K -3000K
21 - 85Bi-LevelStep
10 – 15Minutes 24,0000 36 - 114
ToxicWaste
* Low mercury lamps that meet TLCP tests have been exempt in many states.** Not recommended for indoor use.
System Cost Comparison
Legend
Incandescent Halogen
Metal Halide
Fluorescent Indirect - 3 Lamp
Fluorescent Direct/Indirect - 2 Lamp
Task
5000 Square Feet
Base = Cost to Install Energy Cost 10 yr. Maintenance Cost 10 yr.
$250,000.00
$200,000.00
$150,000.00
$100,000.00
$50,000.00
$0.00
8ft 10ft 12ft 14ft 16ft
70 fc Average
Ceiling Height
$250,000.00
$200,000.00
$150,000.00
$100,000.00
$50,000.00
$ 0.00
8ft 10ft 12ft 14ft 16ft
40 fc Average with Task Lights
Ceiling Height
Comparison of Lighting Controls
Switches Occupancy Sensors Daylight Control Automated Control
Common , easy touse.
Turns lights off whenarea is not occupied
Dims electric lightwhen daylight ispresent.
Switches lights onand off based ontime schedule.
Low initial cost Low initial cost High initial cost High initial cost.
Lights may be left on.Potential for highenergy cost andshort useable lamplife.
Energy savings andextended lamp lifebased on occupancytime.
Significant savings inenergy and lamp life.
Energy savings andextended lamp lifebased on timescheduled
One Footcandle
One footcandle is the intensity of one candela onone square foot surface one foot away.
The flame of a wax candle of standard composition = 1.02 candela.
One Footcandle Four Footcandlesor Four Lumen/ft2
How Much Light?
Visual task, occupant age, and task accuracy are the primary criteria for establishing required light levels.
Ambient IlluminationPublic Circulation 30fcLibrary Areas 40fc
Task Illumination (Print/Contrast)Large/High 30fcSmall/Medium 75fcVery Small/Low 150fc
Recommended Light Levels