386bebeb-dbd9-40f5-ba73-d309c0253e28.pdf

Good research on design considerations

1. MODULE 4
•Design considerations
•Preparation of lighting & electrical scheme
•Floodlighting Problems

2. The purpose of lighting scheme is that it should provide good lighting, give proper
illumination, have absence of glare .
It depends on the kind of occupancy, type of lighting fixtures, arrangement of fittings , size
of the room , number of fittings used etc.
Every lighting installation should serve a specific purpose.
In the home ,lighting system should facilitate domestic activities.Decorative arrangement
can also be selected to make the interior attractive.
In store or shop , lighting depends on the goods that are stored .
In factory , lighting arrangements are planned to increase productivity and improve the
quality of production. Safety should be given importance.
In offices ,glare should be minimum.
In hospitals, good distribution of light is required .In operation theatres , minimum glare
should be taken into consideration. In case of failure of supply , alternative arrangements
should be immediately available.
Lighting system considerations for different occupancies

3. The lighting scheme should be such that it may,
Provide adequate illumination,
Provide light distribution all over the working plane as uniform as possible,
Provide light of suitable colourand
Avoid glare and hard shadows as far as possible.
Design considerations of a good lighting scheme

4. In designing good lighting scheme , we have to consider mainly
Illumination level
Uniformity of illumination
Colourof light
Shadows
Glare
Mounting height
Selection of required lamp and fitting & their spacing
Size of the room
Colourof surrounding walls
Design considerations of a good lighting scheme

5. IlluminationLevel:Intensityofilluminationrequiredfordifferenttypesofworkdiffer.Foreach
typeofworkthereisarangeofbrightnessmostfavorabletooutputi.ewhichcausesminimum
fatigueandgivesmaximumoutputintermsofqualityandquantity
Tableshowstherecommendedintensityofilluminationfordifferenttypesofwork.
UniformityofIllumination:Thehumaneyeadjustsitselfautomaticallytothebrightnesswithin
thefieldofvision.Ifthereisalackofuniformity,pupiloririsoftheeyehastoadjustmore
frequentlyandthusfatigueiscausedtotheeyeandproductivityisreduced.Locallightingwithout
usingmatchinggenerallightingcreatespsychologicalfeelingsofloneliness,gloomand
unfriendliness.
ColoroftheLight:Theappearanceofthebodycolorentirelydependsuponthecolorofthe
incidentlight.Ingeneralcompositionofthelightshouldbesuchthatthecolorappearsnatural.
Daylightfluorescenttubesnowadaymakeitpossibletoilluminateeconomicallyevenlarge
spaceswithartificialdaylightgivinggoodcolorrendingandatsufficientlyhighlevel.
Design considerations of a good lighting scheme

6. Design considerations of a good lighting scheme

7. Shadows:Acertainamountofshadowsisdesirableinartificiallightingasithelpstogiveshape
tothesolidobjectsandmakesthemeasilyrecognized.
Glare:Itmaybedirect(or)reflected.Directglarefromasourceoflightisthemorecommon,and
ismoreoftenahindrancetovision.Aglanceatthesunprovesthatanextremelybrightlight
sourcecausesacuteeyediscomfort
MountingHeight:Inthecaseofdirectlightingintheroomsoflargefloorarea,theluminaries
shouldbemountedasclosetotheceilingaspossible.Inthecaseofindirectlightingitwouldof
coursebedesirabletosuspendluminariesfarenoughdownfromtheceilinginordertogive
reasonablyuniformontheceiling.
SpacingofLuminaries:Correctspacingisoneofgreatimportancetoprovideuniform
illuminationoverthewholeareaandthusdoawaywithcomparativelydarkareaswhichareso
oftenwhenthefittingsarebadlyspaced.
Design considerations of a good lighting scheme

8. Selectionofluminaries–Aluminaireistheapparatuswhichdistributes,filters,transformsthe
lightgivenbyalamp.Selectionoflampsfordifferenttypesofoccupanciesdiffer.
Forsmallpremisestubularfluorescentlampsortungstenfilamentlampscanbeused.
Inlargepremises,lightingcanbecarriedoutbyusinghighintensitysourcessuchas
mercuryorsodiumdischargelamps.Dependingonthetypeofilluminationrequired,
(direct,indirectetc)reflectortypescanbeselected
Sizeoftheroom–Thelumenoutputofthesourcesisnotfullyutilizedattheworkplace.Partof
itislostinthefittings,partisdirectedtowallsandceilingswherepartwillbeabsorbedandpart
willbereflected.Thisistakenintoaccountbyafactorcalledcoefficientofutilization.Coefficient
ofutilizationdependsonthelumenoutputofthefitting,sizeandshapeoftheroom,reflection
factorsofwall,ceiling,heightoftheceiling,arrangementoffittingsetc.
ColorofSurroundingWalls:Theilluminationinanyroomdependsuponthelightreflectedfrom
thewallsandceilings.Whitewallsandceilingsreflectmorelightascomparedtocoloredones.
Design considerations of a good lighting scheme

9. •Mounting heights and spacing of fittings : Distance of light source from the wall should be
equal to one half the distance between 2 adjacent light sources. Also distance between light
fittings should not exceed 1.5 times the mounting height.
•Conditions of use : In different types of installations , conditions of use of light fittings vary .
Dust and dirt of the surroundings may get deposited on the light fittings and hence deteriorate
the lamp efficiency.
If regular periodic cleaning and assuming good atmospheric conditions , the value of
maintenance factor may be taken as 0.8.
But for dusty atmospheres, the factor may be assumed as 0.4.
Depreciation factor = 1/(maintenance factor)
Design considerations of a good lighting scheme

10. Basic Design technique-
•Determination of Quantity
–Point by point method (Inverse Square law &Lambert’s Cosine law)
–Lumen method
–Light loss factor (LLF) or Maintenance factor (M.F.)
•Determination of Quality
–Visual Comfort Probability
–Glare
Methods of lighting calculations

11. 1. WATTS PER SQUARE METER METHOD
This is principally the rule of thumb method. Very handy for rough calculations and checking.
It consists of making an allowance of Watts/sqmof area to be illuminated according to the
illumination desired on the assumption of an average figure of overall efficiency of the
system.
(Eg-Suppose u have a 15x6m hall , to be illuminated .
Area of the hall = 15x6=90sqm.
Assume 10 watt/sqmas the illumination requirement. So we require 900Watts.
That means, if you are using 60W lamps , then we require 15 lamps.)
Methods of lighting calculations

12. 2. LUMEN METHOD
This method is applicable in cases where the sources of light are such as to produce an
approximate uniform illumination over the working plane.
Lumen on working plane = No.oflamps x wattage of each lamp x efficiency of each lamp in
terms of lumens/watt x coeffof utilisationx maintenance factor.
3. POINT TO POINT METHOD
this method is applicable where illumination at a point due to one or more sources of light
is required. If 2 and more than 2 lamps are illuminating the same working plane , then
illumination due to each can be calculated and added. This method is adopted in some special
cases like flood lighting and yard lighting.
Methods of lighting calculations

13. •Depreciation factor –ratio of net illumination output after a certain gap of time to
illumination output under normal condition of new installation.
–Light emitted by source reduces due to dust or dust decomposition on light
–So quantity of light reflected also get reduced.
–This reduction of light can be minimized by cleaning the light fittings or white washing.
–But absolute cleanliness is not possible hence we need to consider depreciation factor.
This is also known as soiling factor or loss factor. This is not only due to evaporation of
filament material and reflector coating but due to fluctuation of voltage also.
•Maintenance factor –is the reciprocal of depreciation factor. It dependent on soiling effect
and also on the cleaning schedule.
The illumination produced by a light source decreases due to ageing and accumulation of
dust on the lamp surface, reflectors, etc.
MF = Illumination under normal working condition / Illumination when everything is clean
MF = 1/ DF (Depreciation factor)
Methods of lighting calculations

14. Absorption factor –In case of places having smoke, steam, dust, fumes, fogs etc , light flux
emitted is partially absorbed by these contaminations present in the air.
Absorption factor for various types of atmospheres
For clean atmosphere = 1
Fog laden atmosphere = 0.75
Steam / fume/ contaminated atmosphere in factories = 0.5
Reflection factor –is the ratio of reflected luminous flux to total incidental luminous flux.
Ceiling reflection factor values
70% for very light colours and white
50% for light colours
30% for medium shades
Wall reflection factor values
50% for very light colours and white
10% for light colours
30% for medium shades
Methods of lighting calculations

15. •Coefficient of Utilization ( Utilization factor)
All light flux emitted by a lamp or luminairedoes not reach surface or working plane being
illuminated.Amajor portion of light output goes to the wall and ceiling and will be reflected
back to the working plane.
The ratio of effective luminous flux reaching working table to total luminous flux emitted is
known as utilization factor or coefficient of utilization
Direct fixture or downlight–CU = .85
Indirect fixture –CU = .50
Spot or Accent –CU = .95
Ambient or Wash –CU =.75
Methods of lighting calculations

16. Tables for Utilization factor for various room indexes and reflection factors of ceiling/wall/floor
are available .
Room Index :
Room Index for a rectangular area is given by
•K
f= LW/(L+W)h
m
L-overall length of room
W –overall width
hm-mounting height of fittings above working plane.
Methods of lighting calculations

17. Light Loss Factor (LLF)
Lightlossduetodeterioratinglamps
Itistheproductofseveralfactors,eachdepreciatinglightoutputatcertainpointintime
inthefuturecomparedtoinitiallightoutput.
LLFhasmainly2components:
i.LLD(Lamplumendepreciation):
Thisrecognizesthefactthatlumenoutputdepreciatesovertime
ii.LDD(LuminaireDirtDepreciation):
Thegreatestlossoflightoutputisduetothedirtaccumulationonlampsandluminaire
reflectingsurface
∴LLF = LLD x LDD
•Industry standard of .85 for a light loss factor
TypicalLLFvalues
Airconditionedoffice-0.8
CleanIndustrial -0.7
DirtyIndustrial -0.6
Methods of lighting calculations

18. Calculation of illumination levels in interiors
The empericalformula to calculate the illumination is
where N = no. of fittings needed.
E= required illumination(lux)
A-working area (sqm)
O-luminous flux produced per lamp(lumens)
Cu-coefficient of utilization
MF-maintenance factor.
Methods of lighting calculations
Total Wattage of fixtures
= No: of lamps * watt of each lamp
Efficacyor Efficiency= Lumens /
Watt

19. •A small assembly shop 15m long , 9m wide and 3m uptothe trusses is to be illuminated to a
level of 200 lux. The coefficient of utilisationis 0.75and maintenance factor is 0.8. Calculate
the no. of lamps , required to illuminate the whole area if the lumen output selected is
3000lumens.
Working Area , A = 15m x 9m
Required Illumination , E = 200 lux
Lumen output of one lamp ,O = 3000 lumens
Coefficient of utilization , CU = 0.75
Maintenance Factor , MF = 0.8
Number of lamps required , N = (EA)/(OxCUxMF)
= (200x15x9)/(3000x0.75x0.8)
= 15
Methods of lighting calculations

20. •An office 30m x 15m is illuminated by 40W fluorescent lamps of lumen output 2700
lumens.theaverage illumination required at the work place is 200lux.Calculate the number of
lamps required to be fitted in the office. Assume coefficient of utilization to be 0.6 and
depreciation factor 1.25.
Working Area , A = 30m x 15m
Required Illumination , E = 200 lux
Lumen output of one lamp ,O = 2700 lumens
Coefficient of utilisation, CU = 0.6
Maintenance Factor , MF = 1/DF = 1/1.25 = 0.8
Number of lamps required , N = (EA)/(OxCUxMF)
= (200x30x15)/(2700x0.6x0.8)
= 70
Methods of lighting calculations

21. •A workshop measure 10m x 25m. The shop is illuminated by 24 lamps of 200 W each. The
lumen efficiency of each lamp is 15lumens/Watt. Maintenance factor is 0.8 and coefficient of
utilization is 0.5Determine the illumination on the working plane.
A = 10m x 25m
Total lumens given by the lamps = No.oflamps x wattage of each lamp x luminous
efficiency of each lamp
= 24x200x15 = 72000lumens
N = (EA)/(OxCUxMF)
E= 24x200x15x0.5x0.8/10x25 = 28800/250 = 115 lux
Methods of lighting calculations

22. Luminous flux Table of different types of light sources.
Methods of lighting calculations

23. Luminous flux Table of different types of light sources.
Methods of lighting calculations

24. Basic Design technique-
•Determination of Quantity
–Point by point method
–Lumen method
–Light loss factor (LLF) or Maintenance factor (M.F.)
•Determination of Quality
–Visual Comfort Probability
–Glare
–CRI
Methods of lighting calculations

25. QualityofIllumination
Threequalityissuesareaddressedinthissection.
•glare
•uniformityofilluminance
•colorrendition
Glare
Glareisasensationcausedbyluminancesinthevisualfieldthataretoobright.Discomfort,
annoyance,orreducedproductivitycanresult.
Abrightobjectalonedoesnotnecessarilycauseglare,butabrightobjectinfrontofadark
background,however,usuallywillcauseglare.
Contrastistherelationshipbetweentheluminanceofanobjectanditsbackground.Althoughthe
visualtaskgenerallybecomeseasierwithincreasedcontrast,toomuchcontrastcausesglareand
makesthevisualtaskmuchmoredifficult.
Methods of lighting calculations

26. VCP
Youcanreduceglareorluminanceratiosbynotexceedingsuggestedlightlevelsandbyusing
lightingequipmentdesignedtoreduceglare.
Alouverorlensiscommonlyusedtoblockdirectviewingofalightsource.Indirectlighting,or
uplighting,cancreatealowglareenvironmentbyuniformlylightingtheceiling.Also,properfixture
placementcanreducereflectedglareonworksurfacesorcomputerscreens.
Standarddatanowprovidedwithluminairespecificationsincludetablesofitsvisualcomfort
probability(VCP)ratingsforvariousroomgeometries.
Visualcomfortprobability(VCP)indicatesthepercentofpeoplewhoarecomfortablewiththe
glarefromafixture.
TheVCPindexprovidesanindicationofthepercentageofpeopleinagivenspacethatwouldfind
theglarefromafixturetobeacceptable.
AminimumVCPof70isrecommendedforcommercialinteriors,whileluminaireswithVCPs
exceeding80arerecommendedincomputerareas.
Methods of lighting calculations

27. Uniformity of Illuminanceon Tasks
The uniformity of illuminanceis a quality issue that addresses how evenly light spreads over a
task area. Although a room's average illuminancemay be appropriate, two factors may
compromise uniformity.
Improper fixture placement based on the luminaire'sspacing criteria(ratio of maxim
recommended fixture spacing distance to mounting height above task height)
Fixtures that are retrofit with reflectors that narrow the light distribution
Non-uniform illuminancecauses several problems:
•Inadequate light levels in some areas
•Visual discomfort when tasks require frequent shifting of view from underlitto overlitareas
•Bright spots and patches of light on floors and walls that cause distraction and generate a low
quality appearance
Methods of lighting calculations

28. Color Rendition
The ability to see colors properly is another aspect of lighting quality.
Light sources vary in their ability to accurately reflect the true colors of people and objects.
The color rendering index (CRI) scale is used to compare the effect of a light source on the
color appearance of its surroundings.
A scale of 0 to 100 defines the CRI.
A higher CRI means better color rendering, or less color shift.
CRIs in the range of 75-100 are considered excellent, while 65-75 are good. The range of 55-65
is fair, and 0-55 is poor.
Under higher CRI sources, surface colors appear brighter, improving the aesthetics of the space.
Sometimes, higher CRI sources create the illusion of higher illuminancelevels.
Methods of lighting calculations

29. Headlightsofoncomingtraffic–directglare
Headlightsinrearviewmirrorwhendrivingatnight–indirectglare
Direct & Indirect Glare
Methods of lighting calculations

30. Direct & Indirect Glare Zones
Thedirectglarezoneisbetween45°and90°
Theindirectglarezoneisbetween0°and45°
Methods of lighting calculations

31. Methods of lighting calculations

32. Strategies for Reducing Unwanted Glare
Strategies commonly employed to reduce unwanted levels of glare include:
•Indirect lighting that throws more light upward than downward, diffusing the light and reducing
glare on computer screens
•Parabolic louvers, special lenses or other diffusing media on fixtures that diffuse the fixture's
light output
•In an office, it may be possible to de-emphasize the ambient lighting system with reduced light
output and diffusing media, while providing adjustable task fixtures at workstations
•Relocating the light source
•Relocating the task or changing its orientation until the glare is removed
Methods of lighting calculations

33. Strategies for Reducing Unwanted Glare
•Changing the surface reflectance of the task
•Use blinds or shades on windows to control the amount or transmittance angle of sunlight
entering the space
•You can reduce glare or luminance ratios by not exceeding suggested light levels and by using
lighting equipment designed to reduce glare.
•A louver or lens is commonly used to block direct viewing of a light source.
•Indirect lighting, or uplighting, can create a low glare environment by uniformly lighting the
ceiling.
•Also, proper fixture placement can reducereflected glareon work surfaces or computer screens.
Methods of lighting calculations

34. 10WaystoReduceGlare
Glareiscontrolledbyadjustingthelightsourceorthesurfacereflectingitandbyfilteringlight
beforeitreachestheeyes.Thefollowingsolutionsseektocontrolglareintheseways.
•Filter&diffuselight.Usefilteredlightinsteadofdirectlight,whichcausesthemostglare.
Diffuselightwithlampshadesorglobes,anduseadjustablecurtainsorblindsonwindows.
•Adjustworkareas.Makesureworksurfaceshaveadullormattefinishsinceshinysurfaces
reflectlightmore.Evenadjustingcolorsonwallsandceilingscanaddcontrastandreduceglare
inworkareas.
•Wearpolarizedlenses.Polarizedglassesreduceglareinsituationswherebrightlightreflectsoff
ashinysurfacelikewater,snow,glossyprintedpaperorpaintedsurfaces.
•Lookforanti-glarecoatings.Anti-glaretreatmentcanreduceglareatnightandinsidefrom
computerscreensandinsidelight.Askyourophthalmologistforthecoatingforprescription
eyewearorpurchaseanti-glaresafetyglasses.
Methods of lighting calculations

35. •Adjustlightlevel.Althoughlightleveldoesimpactvisualperformance,it’snotalwaysbrighter
lightlevelsthatareneeded.Often,raisingtheoveralllightlevelcanhelpwithcontrastandthus
visibility.
•Addadesklamp.Insomesituations,addingadesklampforviewingpaperdocumentshelps
significantlybyilluminatingthedocumentwhileavoidingexcessivelightonthecomputer
screen.Justmakesurethelampdoesn’tcauseadditionalglareoffacomputermonitor.
•Useadjustablelighting.Makesurelightisadjustablefordimnessorbrightnesstosuitthe
situation.
•Lettechnologyhelp.Usecomputermonitorswithadjustablecontrastsettings,andchangethe
backgroundcoloronthecomputerscreentosuitthelightingsituation.
•Considerplacementofcomputers.Adjusttheangleandplacementofmonitorstoreduceglare
fromoverheadlights.Ideally,placethematarightangletoalllightingsources,including
windows.
•Tryfoamseals&wrap-aroundglasses.Safetyglasseswithfoampaddingandwrap-around
sunglassesandsafetyglasseshelpprotectfromside/angularglare,whichcancauseasmuch
damageasdirectsunlight
Methods of lighting calculations

36. •Flood lighting Calculations
While calculating the number of projectors required for the flood lighting, it is necessary to know
the level of illumination required
Illumination level required –The illumination level in lux(lm/sqm) required depends on the type
of the building, purpose of flood lighting, amount of reflecting light in the vicinity etc.
Waste light factor –When several projectors are illuminating a surface there is bound to be a
certain amount of overlap and also some of the light will fall beyond the area to be illuminated
. These 2 effects are taken into account by multiplying the theoretical lumens by waste light
factor .This is generally taken as 1.2 for rectangular areas and 1.5 for irregular objects like
statues.
Depreciation factor–Ratio of illumination under ideal condition to the illumination under normal
condition. This depreciation is due to the dust and dirt accumulated on the reflector surfaces.
Coefficient of utilisation–Also called the beam factor , is defined as the ratio of beam lumen to
lamp lumen.Itsvalue lies between 0.3 and 0.5
Flood Lighting system

37. Number of projectors-
N=(A x E x DF x Waste light factor)/( CU x wattage of the lamp x luminous
efficiency of the lamps
N-no.ofprojectors
A-Area of surface to be illuminated in sqm
E-illumination level required in lm/sqm
Gross lumen required from lamps
= A x E x Waste light factor x DF / CU
Flood Lighting system

38. •The front of a building 45m x 20m is illuminated by 20 , 1000W lamps
arranged so that uniform illumination on the surface is obtained. Assuming a
luminous efficiency of 18 lumens/Watt, CU = 0.4 , waste light factor 1.2,DF –
1.3,Determine the illumination on the surface.
N=(A x E x DF x Waste light factor)/( CU x wattage of the lamp x luminous
efficiency of the lamps
20 = 45 x 20 x E x 1.3x 1.2/ 0.4 x 1000 x 18
E = 0.4 x 1000 x 18 x 20 /900 x 1.3 x 1.2 = 102.56 lux
Flood Lighting system

39. It is desired to illuminate a drawing hall with an average illumination of 200lux.The hall is
30×20m2 .The lamps are to be fitted 4m from ground floor. Find the number of lamps and
wattage / lamp for the lighting scheme .Given efficiency of the lamps and available as 25
lumens/watt, depreciation factor 0.8 and coefficient of utilization 0.75, space height ratio
between 0.8 and 1.2 .Give satisfactory spacing arrangement.
Submission date: December 11th
Assignment 2