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