Basic Concepts of Lighting Design - NY Engineers

Compared with other components like HVAC equipment and plumbing fixtures, the lighting system is special - there is a subjective and ... 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LEDlightingisfrequentlyrecommendedbyenergyconsultants.Thepaybackperiodistypicallylessthanthreeyears,andleadingmanufacturersofferafive-yearwarranty.Sincetheupfrontcostisrecoveredduringthewarrantyperiod,LEDlightingisaverysafeinvestment. GetanLEDlightingdesignforyournextbuildingproject,andsaveonelectricitybills. KnowMore Effectivecommunicationisimportantinanydesign,andthisisonlypossibleifeveryoneisfamiliarizedwithkeytechnicalconcepts.Thisarticlewillprovideanoverviewofthemaintermsusedwhenspecifyingalightingsystem. TheLumen:BasicUnitofLuminousFlux Justlikeelectriccurrentismeasuredinamperes,andwatervolumeismeasuredingallons,thelightoutputofalampismeasuredinlumens.Wattsareoftenusedtodescribelampbrightness,butthisisanincorrectpracticethatcausesconfusion: Afewdecadesago,whenmostlightbulbswereincandescent,brightnesscouldbedescribedwithwatts.Therewasadirectrelationshipbetweenlumensproducedandwattsconsumed. However,thiscausesconfusionwhencomparingdifferenttypesoflamps.Theconversionefficacyfromwattstolumenschangesdependingonthelightingtechnology. Forexample,thelumenoutputisroughlythesamefora60Wincandescentbulb,a15Wcompactfluorescentlight,anda9WLEDbulb. AcommonmisconceptionaboutLEDlightingisthatyouendupwithadarkerroomduetothelowerwattage.However,thiscomesfromtheoldpracticeofdescribingbrightnesswithwatts,whenthecorrectunitisthelumen. Theconceptofluminousefficacydescribeshowwellalampconvertswattsintolumens,similartothegasmileage(MPG)ofacar.Ifthethreelightbulbsdescribedaboveproduce900lumenseach,theirluminousefficacyvaluesarethefollowing: LIGHTINGTYPE LUMENS WATTS EFFICACY Incandescent 900lm 60W 900lm/60W=15lm/W Fluorescent 900lm 15W 900lm/15W=60lm/W LED 900lm 9W 900lm/9W=100lm/W JustlikeacarwithahighMPGhasalowerfuelcostpermile,alightsourcethatproducesmanylumensperwatthasalowerenergycost.Fromafinancialstandpoint,LEDupgradesareamongthebestenergyefficiencymeasuresforbuildings.  Lumensareusefulwhendescribingtheoutputoflamps.However,adifferentmeasurementunitisusedtodescribethelightingneededbyaspecificarea.Forexample,10,000lumensaremorethanenoughlightforasmalloffice,buttheireffectisbarelynoticeableinalargewarehouse. Theconceptofilluminanceisusedtodescribe therequiredlightinginbuiltenvironments. Illuminance:LumensperUnitofArea Thelightingneedsagivenoccupancyaredescribedwithanilluminancevalue,whichisunaffectedbysize.Therearetwocommonmeasurementunitsforilluminance: Lux(lx)-lumenspersquaremeter. Footcandle(fc)-lumenspersquarefoot. 1fc=10.7639lx Sinceilluminanceisspecifiedperunitofarea,roomsizedoesnotmatter-anilluminanceof50fchasthesamemeaningfor500sq.ft.and2500sq.ft.offices.Thedifferenceisthatthelargerofficeneedsmorefixturestoreach50fc.TheIESNALightingHandbookprovidesilluminancedesignvaluesforeachoccupancyclassification. Inactuallightingdesigns,illuminancevariesduetothespacingoffixturesandtheirbeamshapes.However,slightvariationsareacceptable,unlesssomeareasaretoodarkortoobright.Illuminanceisdeterminednotonlybythelightingdistribution,butalsobyroomfeatureslikeceilingheightandsurfacecolors.Manuallightingcalculationsarecomplex,buttheprocessisautomatedwithsoftwareinmoderndesigns. Photometry:WhatistheBeamShapeofLamps? Lightbeamshapeisanotherimportantaspectconsideredbylightingdesigners.Forexample,spotlightsconcentratetheiroutputintoanarrowbeamfacingdownwards,whiletroffersspreadtheiroutputoverthelargestpossibleareaforuniformlighting. Donotassumethattwolightbulbscanbeusedforthesameapplication,justbecausetheirbaseshavethesameshape. Lampswiththewrongbeamshapewillresultinunevenlighting,eveniftheirtotallumenoutputiscorrect. Thebeamshapeofalampisthree-dimensional,anditcanbesimulatedbylightingdesignsoftware.Lightingcutsheetsdescribethebeamwith2Dshapes,parallelandperpendiculartothelamp,sincea3Dbeamcannotberepresentedfully.However,theproductmodelsusedforsoftwarehavethefullbeamsimulatedin3D. ColorTemperatureandColorRenderingIndex Twometricsareusedtodescribethecolorperformanceoflighting-oneforthelightsource,andanotherfortheobjectsitilluminates. Thecorrelatedcolortemperature(CCT)describesthecolorofthelightsourceitself.EachCCThasdifferentapplications,andthereisnocolorthatcanbeconsidered"thebest". Thecolorrenderingindex(CRI)describeshowfaithfullythelightsourcerendersthecolorsofobjectsandsurfaces.ThemaximumCRIis100,describingalightsourcethatmatchesthequalityofsunlight-ahigherCRIisalwaysbetter,regardlessoftheapplication. UsingTemperatureValuesToDescribeLightingColors Objectsglowinacharacteristiccolordependingontheirtemperature,andthisiswhylavafromavolcanolooksred.Thesameprincipleappliestostars,whereayellowstarliketheSunishotterthanaredstar,andabluestarishotterthanayellowone.Inphysics,thisbehaviorisdescribedwithanabstractconceptcalleda“blackbody”,whichisanobjectthatonlyemitslightwhenheated,andeachtemperaturematchesaspecificcolor. Lampsarenotactuallyheatedtothecorrelatedcolortemperature,butitisaconvenientwaytoassignanumbertotheircolor.IfalamphasaCCTof4000K,itglowswiththesamecolorasa“blackbody”at4000K,butthelightsourceitselfdoesnotreachthattemperature.Inmostresidentialandcommercialbuildings,theCCTrangesfrom2700K(yellowish-white)to6500K(bluish-white). Theoptimallightingcolordependsonpersonalpreferences,butthefollowingprinciplesapplyformostlightingdesigns: Lowcolortemperatureslike2700Kareconsidered“warm”,andtheytendtohavearelaxingeffect.Theyarepreferredinareaslikehomebedrooms,hotelroomsandhigh-endrestaurants.Warmcolorsarenotsuitableforcommercialandindustrialsettings,wheretherelaxingeffectcanbecounterproductive. Highcolortemperatureslike6500Kareconsidered“cool”,andtheytendtohaveanenergizingeffect,boostingawareness.Theyarepreferredinapplicationswheremaximumvisibilityisrequired,suchashigh-precisionmanufacturing.Coolcolorsmaydelaysleepwhenusedinhomesandapartments,andsomepersonsmaybestressedbythesecolorsafteralongexposure. CCTvaluesaround4000Kareperceivedas“neutral”,andtheyareconsideredbalanced.Neutralwhiteistheideallightingcolorforoffices,classrooms,kitchensandotherareaswherepeopleconcentrateforlongperiods. EffectoftheLightSourceonObjectsandSurfaces EveniftwolampshavethesameCCT,theirlightingqualitymaydifferdependingontheircolorrenderingindex.ACRIof100meansthelightsourceisasgoodassunlight. Inspiteoftheirlowenergyefficiency,incandescentandhalogenbulbshaveaCRIof100. FluorescentbulbstendtohavethelowestCRIvalues,andlow-qualitylampsgobelow70. CRIvaluesforLEDbulbscanvaryalotdependingonproductquality.Low-endproductsgobelow70,whilehigh-performanceLEDsreachvaluescloseto100. TheminimumCRIforanENERGYSTARlampis80,whichmeansyoushouldlookforlabeledlampstogethigh-qualitylighting.Thelabelalsomeansalightingproductisreliable,sinceithaspassedrigorouslaboratorytests. WhendealingwithLEDbulbs,ahigherCRInormallycomeswithahigherpricetag.However,thereareplaceswheretheCRImetricisveryimportant,suchasartgalleriesandshoppingmallstores. Conclusion LEDupgradescanreducelightingcostsby30-90%inmostcases,dependingonwhichlamptypesarereplaced.Inspaceswithairconditioning,thereducedheatoutputofLEDsalsoresultsinminorcoolingsavings. ItcanbetemptingtosimplyreplacetheexistinglampswiththemostefficientLEDsavailable,butlightingdesignshouldnotbeoverlooked.Electricitysavingsarewelcome,buttheyshouldnotbeachievedattheexpenseofquality. IfyouhaveapropertyinNYCthatiscoveredbyLocalLaw88,youmustupgradethelightingsystemsaccordingtotheEnergyConservationCodeby2025.However,youcanachieveahigherROIbyexceedingtheefficiencylevelrequiredbycode,whileusingtheopportunitytoimprovelightingquality. Tags LightingEfficiency| LightingDesign| locallaw88 - - - - - RelatedArticles 4MinutesRead LEDLighting:AStartingPointtoReduceBuildingEmissionsinNYC JahnaviSajipJuly28,2021 ReadMore 5MinutesRead HowMEPEngineeringCanImproveHealthandMotivationinOffices MichaelTobiasNovember13,2019 ReadMore 15MinutesRead Top7BenefitsofUsingLEDLightsComparedwithTraditionalLighting NewYorkEngineersJuly30,2021 ReadMore LeaveComment Pleaseavoidaddinglinksincomments.Anycommentwithexternalwebsitelinkswillnotbepublished. Join15,000+FellowArchitectsandContractors Getexpertengineeringtipsstraighttoyourinbox.SubscribetotheNewYorkEngineersBlogbelow.   Join15,000+FellowArchitectsandContractorsGetexpertengineeringtipsstraighttoyourinbox.SubscribetotheNewYorkEngineersBlogbelow. ©2021NearbyEngineersNewYorkEngineers.AllRightReserved.LegalNotice|Trademarks