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Your Lighting Vocabulary1Luminous IntensitySam Wanamaker Theatre, LondonBased on the intensity of an ordinary wax candle1 candlepower or candela (cd)Candlepower2Luminous FluxQuantity of light measured inLumensDefinition:1 lumen falls on 1 square footof a 1 foot radius spherewith a 1 candela source at its centerSince the surface area ofa 1 foot radius sphere is 12.57 sqft,a 1 candela source creates 12.57 lumensFormula: S 4πr2Lumens31
Density of Luminous Flux1 footcandle 1 lumen/ sq. foot1 lux 1 lumen/ sq. meterFootcandles (Lux)( International )4IlluminationMeasured with an illuminance meterin footcandles or lux5Luminance (surface brightness)Measured with aluminance meterin footlamberts orcd/m2.Illuminance is light striking a surfaceLuminance is light reflecting off a surface62
Reflectance ( ) & Transmittance (t)For a reflector:f.l. f.c. x reflectanceOrFor a transmitter:f.l. f.c. x transmittanceReflectors vs. TransmittersWhite Reflects 90%; Clear Transmits 90%Black Reflects 4%; Tinted Transmits 4%7Daylight Factor (DF).Here A/B x 100 DF Percentage of Interior Light vs. Exterior Light DF Interior f.c./Exterior f.c. x 1008Daylight SourcesSky Component(SC)(ERC)Internal ReflectedComponent (IRC)Sun Component usually unwanted!93
Daylighting Sky ConditionsDesign for worst case and best case 10Sunny SkyCloudy Sky11Domes with oculisimulate cloudy skies!Bibliotéque National, Paris—Labrouste124
Design Guidelines—Sky Component1. Exclude Sun or use for drama2. Skylight in cloudy climates3. Sidelight in clear climatesCloudy DayClear Day Less Light Most Light From Above- More Light- Most Light from.- Horizon- Sun13Design Guidelines—ERC1. Natural, dark, and textured materials absorb light2. Neighboring buildings can be significant14Design Guidelines—IRC1. Walls and ceiling most important2. Use surfaces to distribute lightDavid LawrenceConvention Center,Pittsburgh—Rafael ViñolyArchitects155
The Importance of Reflected LightImagine a 5,000 lumen source in tworooms with 1,000 sqft of surface area.Room 1 has 80% reflective surfaces.Room 2 has 20% reflective surfaces.How much brighter is room 1? (4x?)“Ambient Illumination: A Thought Experiment” by Kit Cuttle.16We don’t see incident light, we see reflected light.So, in Room 1In Room 25,000 lumens x 0.8 4,000 lumens5,000 lumens x 0.2 1,000 lumensBut that’s only the effect of direct light on the surfaces,the surfaces reflect light to each other, increasing theluminous flux.Room 1Room 2Initial Flux (F)5,000 lumens5,000 lumens1st Reflection4,0001,0002nd Reflection3,2002003rd Reflection2,65040 Total [F/1-ρ]25,000 lumens6,250 lumens17Surface IlluminanceNow we can determine the average surface illuminance ofthe two rooms by dividing the total flux (lumens) by thesurface area of the room.Room 1 25,000 lumens/1,000 sqft 25 f.c.Room 2 6,250 lumens/1,000 sqft 6.25 f.cSurface LuminanceBut that’s the light that strikes the surfaces, we see thereflected light as surface brightness:Room 1Room 225 f.c. x 0.8 20 f.l.6.25 f.c. x 0.2 1.25 f.l.So, Room 1 appears 16 times brighter!186
The Bright Room!One Lux Studio, Bernhardt Design19Solar Control & Shading DevicesOlgyay & Olgyay (1957)20217
22Del MarSchool,El Cerrito1957—Barbachano,Ivanitsky,Watanabe23248
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28Rosa Parks Elementary SchoolPortland, OR—DOWA Architects293010
Millennium Primary SchoolGreenwich Peninsula, UK—Edward Cullinan Architects31323311
Moonwalk, Renan Ozturk, Nat Geo3412
Your Lighting Vocabulary 1 candlepower or candela (cd) Luminous Intensity Based on the intensity of an ordinary wax candle Candlepower Sam Wanamaker Theatre, London Luminous Flux Quantity of light measured i
