7 Key Steps in Lighting Design Process _ EEP

7 Key Steps In Lighting Design Process7 Key Steps In Lighting Design Process

Structured Design Process //Structured Design Process //

To achieve the best overall outcome in a lighting installation, it is important to avoid theTo achieve the best overall outcome in a lighting installation, it is important to avoid the

tendency of rushing straight into luminaire selection before determining more broadlytendency of rushing straight into luminaire selection before determining more broadly

what is required from the system. The use of a structured design process helps to avoidwhat is required from the system. The use of a structured design process helps to avoid

this.this.

The key steps in the design process are:The key steps in the design process are:

Identify the requirementsIdentify the requirements1.

Determine the method of lightingDetermine the method of lighting2.

Select the lighting equipmentSelect the lighting equipment3.

Calculate the lighting parameters and adjust the design as requiredCalculate the lighting parameters and adjust the design as required4.

Determine the control systemDetermine the control system5.

Choice of luminaireChoice of luminaire6.

Inspect the installation upon completionInspect the installation upon completion

(and if possible, a few months after occupation, to determine what worked and what(and if possible, a few months after occupation, to determine what worked and what

didnt. This is the only way to build up experience to apply to future designs)didnt. This is the only way to build up experience to apply to future designs)

7.

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The five initial stages are considered in more detail in the following lines.The five initial stages are considered in more detail in the following lines.

1. Identifying the requirements1. Identifying the requirements

This involves gaining a full understanding of This involves gaining a full understanding of what the lighting installation is intendedwhat the lighting installation is intended

to achieveto achieve. This includes the following:. This includes the following:

Task Requirements Task Requirements

IlluminanceIlluminance

GlareGlare

Mood of the spaceMood of the space

Relation to shape of spaceRelation to shape of space

Things to be emphasisedThings to be emphasised

Things to hideThings to hide

Direction of lightDirection of light

Interaction of daylightInteraction of daylight

Go back to Index Go back to Index

2. Determine the method of lighting2. Determine the method of lighting

At this stage, consideration is given to At this stage, consideration is given to how the light is to be deliveredhow the light is to be delivered, e.g. will it be, e.g. will it be

recessed, surface mounted, direct or indirect, or will up-lighting be used, and its primaryrecessed, surface mounted, direct or indirect, or will up-lighting be used, and its primary

characteristics, e.g. will it be prismatic, low brightness or mellow light.characteristics, e.g. will it be prismatic, low brightness or mellow light.

Consideration should be given at this stage to the Consideration should be given at this stage to the use of daylightuse of daylight to minimise the need to minimise the need

for artificial light.for artificial light.


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3. Select the lighting equipment3. Select the lighting equipment

Once the method of lighting has been selected, the most appropriate light source canOnce the method of lighting has been selected, the most appropriate light source can

then be chosen followed by the luminaire.then be chosen followed by the luminaire.

The following attributes should be studied when choosing the light source:The following attributes should be studied when choosing the light source:

Light output (lumens)Light output (lumens)

Total input wattageTotal input wattage

Efficacy (lumens per Watt)Efficacy (lumens per Watt)

LifetimeLifetime

Physical sizePhysical size

Surface brightness / glareSurface brightness / glare

Colour characteristicsColour characteristics

Electrical characteristicsElectrical characteristics

Requirement for control gearRequirement for control gear

Compatibility with existing electrical systemCompatibility with existing electrical system

Suitability for the operating environmentSuitability for the operating environment

A number of factors also affect luminaire choice:A number of factors also affect luminaire choice:

Characteristics of the light source and control gearCharacteristics of the light source and control gear

Luminaire efficiency (% lamp light output transmitted out of the fixture)Luminaire efficiency (% lamp light output transmitted out of the fixture)

Light distributionLight distribution

Glare controlGlare control

Finish and appearanceFinish and appearance

SizeSize

Accessibility of components for maintenanceAccessibility of components for maintenance

Ability to handle adverse operating conditionsAbility to handle adverse operating conditions

AestheticsAesthetics

Thermal managementThermal management


4. Calculate the lighting parameters4. Calculate the lighting parameters

Lighting calculation methods fall into three broad categories:Lighting calculation methods fall into three broad categories:

Manual calculation methodsManual calculation methods1.

Three dimensional modellingThree dimensional modelling2.

VisualisationVisualisation3.

Photometric data for light sources and luminaires is commercially available to contributePhotometric data for light sources and luminaires is commercially available to contribute


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to these calculations.to these calculations.

4.1 Manual calculation methods4.1 Manual calculation methods

There are a wide range of manual computation methods for the There are a wide range of manual computation methods for the calculation of differentcalculation of different

lighting aspectslighting aspects. These include complex methods for calculating the illuminance from a. These include complex methods for calculating the illuminance from a

wide variety of shapes of luminous objects. The majority of these have now beenwide variety of shapes of luminous objects. The majority of these have now been

superseded by computer programs (superseded by computer programs (check our free softwarecheck our free software).).

The Lumen MethodThe Lumen Method was the mainstay for interior lighting and has remained in use as a was the mainstay for interior lighting and has remained in use as a

quick and relatively accurate method of quick and relatively accurate method of calculating interior illuminancecalculating interior illuminance..

The Lumen Method calculates The Lumen Method calculates the average illuminance at a specific level in thethe average illuminance at a specific level in the

spacespace, including an allowance for the light reflected from the interior surfaces of the, including an allowance for the light reflected from the interior surfaces of the

room. The calculation method has a set of assumptions that, if followed, gives aroom. The calculation method has a set of assumptions that, if followed, gives a

reasonable visual environment.reasonable visual environment.

Inadequate attention to the assumptions will produce Inadequate attention to the assumptions will produce poor resultspoor results..

The basic assumptions are:The basic assumptions are:

All the luminaires in the room are the same and have the same orientationAll the luminaires in the room are the same and have the same orientation

The luminaires do not have a directional distribution and are aimed directly to theThe luminaires do not have a directional distribution and are aimed directly to the

floorfloor

The luminaires are arranged in a uniform array on the ceiling and have the sameThe luminaires are arranged in a uniform array on the ceiling and have the same

mounting heightmounting height

The luminaires are spaced less than the maximum spacing to mounting height ratioThe luminaires are spaced less than the maximum spacing to mounting height ratio

nominated in the coefficient of utilisation tablesnominated in the coefficient of utilisation tables

The average illuminance produced by a lighting installation, or the number of luminairesThe average illuminance produced by a lighting installation, or the number of luminaires

required to achieve a specific average illuminance, can be calculated required to achieve a specific average illuminance, can be calculated by means ofby means of

utilization factors (UF)utilization factors (UF), a UF being the ratio of the total flux received by a particular, a UF being the ratio of the total flux received by a particular

surface to the total lamp flux of the installation.surface to the total lamp flux of the installation.

Lumen method formula //Lumen method formula //

The The average illuminance E(h)average illuminance E(h) over a over a reference surface sreference surface s can be calculated from the can be calculated from the

lumen method formula.lumen method formula.

where:where:

FF the initial bare lamp flux (lumens) the initial bare lamp flux (lumens)


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nn the number of lamps per luminaire the number of lamps per luminaire

NN the number of luminaires the number of luminaires

LLFLLF the total light loss factor the total light loss factor

UF(s)UF(s) the utilization factor for the reference surface s of the utilization factor for the reference surface s of

the chosen luminairethe chosen luminaire

Utilization factors can be determined for any surface or layout of luminaires. The Utilization factors can be determined for any surface or layout of luminaires. The UFUF

symbolsymbol is normally shown followed by an extra letter in brackets, to denote the surface, is normally shown followed by an extra letter in brackets, to denote the surface,

for example, for example, UF(F) is the utilisation factor for the floor cavityUF(F) is the utilisation factor for the floor cavity and and UF(W) is theUF(W) is the

utilisation factor for the wallsutilisation factor for the walls..

Utilization factors are, in practice, only calculated for general lighting systems Utilization factors are, in practice, only calculated for general lighting systems withwith

regular arrays of luminairesregular arrays of luminaires and for three main room surfaces. The highest of and for three main room surfaces. The highest of

these surfaces, the these surfaces, the C surface (for ceiling cavity)C surface (for ceiling cavity), is an imaginary horizontal plane, is an imaginary horizontal plane

at the level of the luminaires having a reflectance equal to that of the ceiling cavity.at the level of the luminaires having a reflectance equal to that of the ceiling cavity.

The lowest surface, the The lowest surface, the F surfaceF surface (for floor Cavity), is a horizontal plane at normal (for floor Cavity), is a horizontal plane at normal

working height (i.e. table height), which is often assumed to be working height (i.e. table height), which is often assumed to be 0.85 m above the0.85 m above the

floorfloor..

The middle surface, the The middle surface, the W surface (for walls)W surface (for walls), consists of all the walls between, consists of all the walls between

the C and F planes.the C and F planes.

Although Although the lighting designerthe lighting designer can calculate utilization factors, lighting companies can calculate utilization factors, lighting companies

publish utilization factors for standard conditions for their luminaires. The standardpublish utilization factors for standard conditions for their luminaires. The standard

method of presentation is shown below. To use this table, it is only necessary to knowmethod of presentation is shown below. To use this table, it is only necessary to know

the Room Index and the effective reflectance of the three standard surfaces (floor cavity,the Room Index and the effective reflectance of the three standard surfaces (floor cavity,

walls and ceiling cavity).walls and ceiling cavity).


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Room Index //Room Index //

The Room Index is a The Room Index is a measure of the angular size of the roommeasure of the angular size of the room, and is the ratio of the, and is the ratio of the

sum of the plan areas of the F and C surfaces to the area of the W surface. Forsum of the plan areas of the F and C surfaces to the area of the W surface. For

rectangular rooms the room index is given by:rectangular rooms the room index is given by:

Where:Where:

LL the length of the room the length of the room

WW the width of the room the width of the room

HHmm the height of the luminaire plane above the horizontal reference the height of the luminaire plane above the horizontal reference

plane.plane.

If the room is re-entrant in shape, If the room is re-entrant in shape, for example L shapedfor example L shaped, then it must be divided into, then it must be divided into

two or more non-re- entrant sections, which can be treated separately.two or more non-re- entrant sections, which can be treated separately.

Spacing to Mounting Height Ratio (SHR)Spacing to Mounting Height Ratio (SHR)

The Spacing to Mounting Height Ratio (SHR) is the The Spacing to Mounting Height Ratio (SHR) is the spacing between luminairesspacing between luminaires

divided by their height above the horizontal reference planedivided by their height above the horizontal reference plane..

It affects the It affects the uniformity of illuminance on that planeuniformity of illuminance on that plane. When the UF tables. When the UF tables

are determined, for a nominal spacing to height ratio SHR NOM, the maximumare determined, for a nominal spacing to height ratio SHR NOM, the maximum

spacing to height ratio SHR MAX of the luminaire is also calculated, and is aspacing to height ratio SHR MAX of the luminaire is also calculated, and is a

value that should not be exceeded if the uniformity is to be acceptable.value that should not be exceeded if the uniformity is to be acceptable.

Go back to Lighting parameters Go back to Lighting parameters

4.2 Three dimensional modelling4.2 Three dimensional modelling

Although it was possible to calculate the luminance of all the surfaces in a room, theAlthough it was possible to calculate the luminance of all the surfaces in a room, the

calculations were extremely laborious and could only be justified in the most specialcalculations were extremely laborious and could only be justified in the most special

cases. However, cases. However, the advent of computer modellingthe advent of computer modelling enabled a more flexible approach to enabled a more flexible approach to

lighting design and significantly increased the information available to the designer.lighting design and significantly increased the information available to the designer.


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In contrast to the Lumen Method, lighting programs enable the lightingIn contrast to the Lumen Method, lighting programs enable the lighting

designer to broaden the assumptions:designer to broaden the assumptions:

A mixture of luminaires can be usedA mixture of luminaires can be used

The luminaires no longer have to be arranged in a regular arrayThe luminaires no longer have to be arranged in a regular array

Directional luminaires can be modelledDirectional luminaires can be modelled

A large number of calculation points can be considered to give a meaningfulA large number of calculation points can be considered to give a meaningful

uniformity calculationuniformity calculation

The illuminance and luminance of all surfaces can be calculateThe illuminance and luminance of all surfaces can be calculate

This gives the lighting designer a much greater understanding of what is happeningThis gives the lighting designer a much greater understanding of what is happening

in the room.in the room.

However there has been considerable research, experience and documentation over theHowever there has been considerable research, experience and documentation over the

past 80 years that has developed the current thinking in the adequacy of variouspast 80 years that has developed the current thinking in the adequacy of various

illuminance levels for various tasks and functions.illuminance levels for various tasks and functions.

Although there is some general understanding of the need for appropriateAlthough there is some general understanding of the need for appropriate

luminance distribution in the vertical plane, there is little information, experience orluminance distribution in the vertical plane, there is little information, experience or

understanding for many designers to determine:understanding for many designers to determine:

What the luminance of surfaces should be in varying situationsWhat the luminance of surfaces should be in varying situations

What is an acceptable luminance uniformityWhat is an acceptable luminance uniformity


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Whether there should there be a maximum luminance uniformityWhether there should there be a maximum luminance uniformity

What is the desired graduation in luminanceWhat is the desired graduation in luminance

At what point is the luminance distribution of the wall unacceptableAt what point is the luminance distribution of the wall unacceptable

It is important in using a It is important in using a lighting calculation programlighting calculation program that the output records the type that the output records the type

of luminaire used, the location of the luminaires, the assumed lumen output of the lamp,of luminaire used, the location of the luminaires, the assumed lumen output of the lamp,

the light loss factor and the aiming points. If this is not recorded you have a prettythe light loss factor and the aiming points. If this is not recorded you have a pretty

picture of the installation and no way of making it a reality.picture of the installation and no way of making it a reality.

Go back to Lighting parameters Go back to Lighting parameters

4.3 Visualisation4.3 Visualisation

These are programs that create a These are programs that create a perspective rendering of the space in levels ofperspective rendering of the space in levels of

detaildetail that vary from a block representation of the space, to photographic quality that vary from a block representation of the space, to photographic quality

renderings, depending on the sophistication of the program and the level of detail of therenderings, depending on the sophistication of the program and the level of detail of the

interior to be entered.interior to be entered.

The programs fall into two basic types:The programs fall into two basic types:

Flux transfer or radiosity calculationsFlux transfer or radiosity calculations

Ray tracing calculationsRay tracing calculations

The major difference being in The major difference being in how they interpret light from reflectivehow they interpret light from reflective

surfacessurfaces..


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A A Lambertian surfaceLambertian surface is a perfect diffuser, where light is reflected in all directions, is a perfect diffuser, where light is reflected in all directions,

irrespective of the angle of incidence of the light such that irrespective of the viewingirrespective of the angle of incidence of the light such that irrespective of the viewing

angle the surface has the same luminance. A specular surface is a mirror like surface,angle the surface has the same luminance. A specular surface is a mirror like surface,

where the angle of reflection of the light is the same as the angle of incidence.where the angle of reflection of the light is the same as the angle of incidence.

A real life surface is a combination of both surfaces (semi-specular) and has bothA real life surface is a combination of both surfaces (semi-specular) and has both

specular and diffuse characteristics. Some materials are more specular while others arespecular and diffuse characteristics. Some materials are more specular while others are

more diffuse.more diffuse.

A A flux transfer or radiosity programflux transfer or radiosity program treats all surfaces as diffuse or Lambertian treats all surfaces as diffuse or Lambertian

surfaces, as a result their rendering tends to appear flat with soft shadow details. It willsurfaces, as a result their rendering tends to appear flat with soft shadow details. It will

tend to overestimate the uniformity. Ray tracing traces the individual rays of light from thetend to overestimate the uniformity. Ray tracing traces the individual rays of light from the

source to the eye as it reflects from surface to surface around the room. As a result raysource to the eye as it reflects from surface to surface around the room. As a result ray

tracing can allow for the specular component of the surfaces.tracing can allow for the specular component of the surfaces.

Some programs calculate Some programs calculate the entire lighting by ray tracingthe entire lighting by ray tracing while others calculate while others calculate thethe

space on a flux transfer basisspace on a flux transfer basis and have an overlay of ray tracing of specific areas to and have an overlay of ray tracing of specific areas to

improve the quality of the rendering. When ray tracing is added, reflections are added inimprove the quality of the rendering. When ray tracing is added, reflections are added in

polished surfaces and shadows become sharper.polished surfaces and shadows become sharper.

Visualisation programsVisualisation programs are a useful tool in the presentation of a design, as a tool are a useful tool in the presentation of a design, as a tool

for the designer to check that the design is consistent with his own visualisation offor the designer to check that the design is consistent with his own visualisation of

the space, and to model specific lighting solutions. The programs are stillthe space, and to model specific lighting solutions. The programs are still

calculation tools and not design programs.calculation tools and not design programs.

The programs can show the designer how a specific design will perform butThe programs can show the designer how a specific design will perform but

that they cannot reliably be used to assess the acceptability of a design.that they cannot reliably be used to assess the acceptability of a design.

Irrespective of the form of the visualisation output, it is important that the programIrrespective of the form of the visualisation output, it is important that the program

provides adequate information to enable the construction and verification of the lightingprovides adequate information to enable the construction and verification of the lighting

design.design.

The output should include:The output should include:


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Installation informationInstallation information the type and location of all luminaires and the aiming the type and location of all luminaires and the aiming

information. The lamp details should be included as well as the specific catalogueinformation. The lamp details should be included as well as the specific catalogue

number of photometric file that has been used.number of photometric file that has been used.

Light technical parametersLight technical parameters the illuminance, uniformity and other parameters that the illuminance, uniformity and other parameters that

have been calculated to achieve the design.have been calculated to achieve the design.

Verification informationVerification information adequate details to enable the lighting calculation to be adequate details to enable the lighting calculation to be

verified. This should include the luminaire type, the photometric file, surfaceverified. This should include the luminaire type, the photometric file, surface

reflectances that were assumed, light loss factors, lumen output of lamps andreflectances that were assumed, light loss factors, lumen output of lamps and

mounting and aiming locations.mounting and aiming locations.

Go back to Lighting parameters Go back to Lighting parameters | | Go back to Index Go back to Index

5. Determine the control system5. Determine the control system

The The effectiveness and efficiency of any lighting installationeffectiveness and efficiency of any lighting installation is affected as much by is affected as much by

the control system as by the light sources and fixtures chosen.the control system as by the light sources and fixtures chosen.

Give consideration to:Give consideration to:

Providing Providing multiple switches to control the number of lightsmultiple switches to control the number of lights that come on at any that come on at any

one time. Using one switch to turn on all the lights in a large room is veryone time. Using one switch to turn on all the lights in a large room is very

inefficient.inefficient.

Placing switches Placing switches at the exits from roomsat the exits from rooms and using two-way switching to and using two-way switching to

encourage lights to be turned off when leaving the room.encourage lights to be turned off when leaving the room.

Using Using smart light switches and fittingssmart light switches and fittings which use movement sensors to turn which use movement sensors to turn

lights on and off automatically. These are useful in rooms used infrequently wherelights on and off automatically. These are useful in rooms used infrequently where

lights may be left on by mistake, or for the elderly and disabled.lights may be left on by mistake, or for the elderly and disabled.


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Make sure they have Make sure they have a built-in daylight sensora built-in daylight sensor so that the light doesnt so that the light doesnt

turn on unnecessarily. Models which must be turned on manually andturn on unnecessarily. Models which must be turned on manually and

turn off automatically, but with a manual over-ride, are preferable in mostturn off automatically, but with a manual over-ride, are preferable in most

situations. Be aware that the sensors use some power continuously, situations. Be aware that the sensors use some power continuously, upup

to 5W or even 10Wto 5W or even 10W in some cases. in some cases.

Using Using timerstimers, , daylight controlsdaylight controls and and motion sensorsmotion sensors to switch outdoor security to switch outdoor security

lights on and off automatically. controls are particularly useful for common areas,lights on and off automatically. controls are particularly useful for common areas,

such as hallways, corridors and stairwells, in multi-unit housing.such as hallways, corridors and stairwells, in multi-unit housing.

Using Using solar powered lightingsolar powered lighting for garden and security lights. for garden and security lights.

Using Using dimmer controls for incandescent lightsdimmer controls for incandescent lights (including halogens). This can (including halogens). This can

save energy and also increase bulb life. Most standard fluorescent lamps cannot besave energy and also increase bulb life. Most standard fluorescent lamps cannot be

dimmed, but special dimmers and lamps are available. If lamps are to be dimmed itdimmed, but special dimmers and lamps are available. If lamps are to be dimmed it

is important to ensure that the correct equipment is used, especially whenis important to ensure that the correct equipment is used, especially when

retrofitting more energy efficient lamps.retrofitting more energy efficient lamps.


6. Choice of Luminaire6. Choice of Luminaire

The performance of a luminaireThe performance of a luminaire should be considered just as carefully as its cost. In should be considered just as carefully as its cost. In

the long term a well designed, well constructed luminaire will be cheaper than a poorthe long term a well designed, well constructed luminaire will be cheaper than a poor

quality unit; and the salient features of a good quality luminaire are:quality unit; and the salient features of a good quality luminaire are:

Sound mechanical and electrical construction and a durable finishSound mechanical and electrical construction and a durable finish

Adequate screening of high luminance lamps to minimise discomfort and glareAdequate screening of high luminance lamps to minimise discomfort and glare

Adequate heat dissipation to prevent over-heating of the lamp, wiring and ancillaryAdequate heat dissipation to prevent over-heating of the lamp, wiring and ancillary

equipmentequipment

High light output ratio with the appropriate light distributionHigh light output ratio with the appropriate light distribution

Ease of installation, cleaning and maintenanceEase of installation, cleaning and maintenance


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Share with engineers //Share with engineers //


Reference //Reference // The Basics of Efficient Lighting A Reference Manual for Training in The Basics of Efficient Lighting A Reference Manual for Training in

Efficient Lighting Principles National Framework For Energy EfficiencyEfficient Lighting Principles National Framework For Energy Efficiency

Recommended EE articles //Recommended EE articles //

About Author //About Author //

Edvard CsanyiEdvard Csanyi

EdvardEdvard - - Electrical engineer, programmer and founder of Electrical engineer, programmer and founder of EEPEEP. Highly specialized for. Highly specialized for

design of LV high power busbar trunking (

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