LdG-1 Lighting design Guide for offices

LdG_1

The importance of office lighting to achieve basic requirements relating to the health and safety of people at work is crucial, that is why it is the first one in my series of lighting guides.

In this guide I will be addressing the following

  1. The European standard about lighting EN 12464-1: “The Lighting of Workplaces” with explanation of different parts.
  2. The DIAL investigation (a research carried out to show the effect of different lighting scenes in office lighting).
  3. Case Study of office lighting.
  4. How to use DIALux evo to calculate the requirements of office lighting.

EN 12464-1: “The Lighting of Workplaces”

This European standard is about the quality aspects of lighting workstations and their direct environment. It also has tables with lighting requirements in accordance with the type of work and the visual task.

1-Working Plane

The working plane in office area is considered 0.75 or 0.8 form floor level which is the standard height of a table.

When standard is asking for 500 Lux it should be achieved at this height for the office area.

In this guide 0.75 will be considered as the height for the office area.

The working plane for a corridor is 0.2

 01_Ldg_1 office lighting Task Area working palne

2-Task Area

The task defines the size of the working plane for calculation inside a space and could have of the following situation

A.    the location of the workstation is not known during design stage then the whole room will be taken as a task Area

The wall Zone of 0.5 could be ignored if the workstation is not placed near wall.

The wall zone will not be taken into consideration for the average value of Lux or uniformity.

 02_Ldg_1 office lighting Task Area 1
B.     The location of the workstation is not known during design stage and there is a possibility to place work station near wall then the whole room will be taken as a task Area.  02_Ldg_1 office lighting Task Area 2
C.     The location of the workstation is known then task area is above the desk typically 1.8 m x 1.8 m (the blue area in the side image) the minimum dimensions of an office desk are 1.6 m x 0.8 m.

The surrounding area is an area around the task area with at least 0.5 meter form all sides (the purple area in the next image)

Background area is the area of the other space and should be at least It should be at least 3.0 m wide.

Wall zone of 0.5 m could be considered

 02_Ldg_1 office lighting Task Area 3

3-Lighting requirements for office area

The table below has the regiments of different office spaces where

Em is the Minimum Illuminance in lux

UGRL is maximum limit for Unified Glare Rating

U­­o is the uniformity of lighting (Emin / Eaverage)

Ra is the minimum color rendering of the lamp

Interior type, task or activity Em (lx) UGRL Uo Ra
Filing, copying, etc. 300 19 0.4 80
Writing, typing, reading, data processing 500 19 0.6 80
Technical drawing 750 16 0.7 80
CAD work stations 500 19 0.6 80
Conference and meeting rooms 500 19 0.6 80
Reception desk 300 22 0.6 80
The requirement  of Em  (minimum Illuminance value In lux) could be taken form the table

Example of office area where the requirement is 500 lx for  data processing

500 Lux for the Task Area

300 Lux for Surrounding area

100 Lux for the Background area

The U­­o  for the task area should be 0.6 which means that the minimum value should not be less than 60% of the average Value , e.g. if the achieved  average value is 520 lx then the minimum should not be less than 312 lx

 05_Ldg_1 office lighting Task Area Surrounding area and background area

The UGR is an approximate model that express the chance of direct glare by Luminaire, the higher the figure, the greater the chance of glare.

Example of office area where the requirement of UGR limit is 19 then value should not exceed 19; it could be lower or equal 19

It is good to understand the glare to understand the UGR formula

Glare

Glare is difficulty seeing in the presence of bright light against darker surrounding.

Glare is caused by a significant ratio of luminance between the task and the background

The high contrast make seeing more difficult and a good example is the head light of the car where at day time there is no high contrast between the headlight and the background then there is no glare, but at night where headlight is much higher than the surrounding (background) then it could cause glare especially if there is no street light (darker background)

 06_Ldg_1 office lighting UGR contrast and Glare car headlights  07_Ldg_1 office lighting UGR contrast and Glare car headlights daylight
High contrast at night between the headlight and the background Low contrast at day time

Glare could be classified as

  • Disability glare
  • Discomfort glare

Where the disability glare could be found mostly outdoor and can cause disability of vision, the discomfort glare where present will not disable the vision but will make the environment not comfortable.

There are two types of discomfort glare

Direct glare

  • Reflected glare
  07_Ldg_1 office lighting reflected glare  07_Ldg_1 office lighting dirict glare
Reflected glare Direct glare for luminaires

To reduce glare

Fist selects the right luminaire that reduces the light that is coming to the eyes

The light coming from the angles between 45o and 85o  should be minimum

The light form 45o to 65o  is less critical than the light from 650 to 85o

 07_Ldg_1 office lighting glare zone and cut off angle
 11_Ldg_1 office lighting glare zone and cut off angle ERCO dark light reflector darklight  12_Ldg_1 office lighting glare zone and cut off angle ERCO dark light reflector darklight
Luminaire with good cut-off angles that cut the light above 65o  Luminaire without cut off angle

Secondly reduce the contrast between the luminaire and the background by ensuring good light at ceiling and walls.

UGR factors

Let us have a look at the factors that could increase or decrease the UGR values

 13_Ldg_1 office lighting UGR factors The “8“ is just a constant factor that gives the UGR numbers which normally sit in a range between 10 and 30
 14_Ldg_1 office lighting UGR factors This takes into account that our eyes respond logarythmically to light
 15_Ldg_1 office lighting UGR factors This is the background luminance, the higher it is the lower is the UGR value
 16_Ldg_1 office lighting UGR factors The luminance of one luminaire squared
 17_Ldg_1 office lighting UGR factors The solid angle of the lumi-naire from the observer‘s position represents the size of the glare source
 18_Ldg_1 office lighting UGR factors The so-called Guth index represents the position of the luminaire in relation to the line of sight of the observer. It gets bigger the further it is away.

Form the formula above, we can see that the following will affect the UGR

  1. Luminance of the luminaire
  2. The luminance of the background
  3. The position of the luminaries

So to keep the UGR low we have to follow the following steps

  1. Select the right luminaire with low luminance (low brightness) at angles between 65o and 85o.
  2. Consider a good position for luminaire in relation to the observer (software like DIALux could be helpful in this case).
  3. Increasing the brightness of the background (walls and ceiling)

For more information on luminance you can see the following link

https://ezzatbaroudi.wordpress.com/2013/06/21/using-a-quantitative-measure-to-achieve-a-qualitative-lighting-design-effect/

Luminaire

The standard set new values for the maximum luminance of luminaires as shown in the following table

Table 4 gives the limits of the average luminaire luminance at elevation angles of 65° and above from the downward vertical, radially around the luminaires, for work stations where display screens which are vertical or inclined up to 15° tilt angle are used.
 001_Ldg_1 office lighting Luminance
Nowadays most if not all computer screen has high luminance so we can neglect the right column and use the left one where in case A the luminaire Luminance has to be less than 3000 cd/m2 at elevation angles of 65° of the luminaire.  002_Ldg_1 office lighting Luminance
You can evaluate this value by using the photometric data in a computer software like DIALux evo you could see the curve that represents the values at different angles

Red for 65°

Blue for 75°

Green for 85°

All the values has to be less than 3000 cd/m2

In case the user is going to use negative polarity software like AutoCAD with black background the values has to be less than 1500cd/m2

For more information on this topic see

https://ezzatbaroudi.wordpress.com/2013/06/21/using-a-quantitative-measure-to-achieve-a-qualitative-lighting-design-effect/

 003_Ldg_1 office lighting Luminance Luminaire diagram

4-Vertical surfaces, Vertical task Area

Shelving systems and cabinets need to be regarded vertical task areas if visual tasks need to be performed there over an extended period of time (e.g. ticket-issuing

or bookkeeping). The vertical task area reference surface starts 0.5 m above floor level and, in the case of an office shelving system, ends 2.0 m above floor level

 0001_Ldg_1 office lighting vertical task area
Where visual tasks are performed mainly on a vertical plane, that plane is the task area.

The vertical task area reference surface starts 0.5 m above floor level and, in the case of an office shelving system, ends 2.0 m above floor level

  • Illuminance for walls and ceilings

One new requirement in EN 12464-1 is balanced luminance distribution. This is achieved by taking account of the luminance of all surfaces, which is determined by the reflectance of the surfaces and the Illuminance on them. To avoid gloom, raise adaptation levels and

Enhance visual comfort; room surfaces should be bright.

Wall washing is a good technic to ensure bight walls and achieving good visual comfort

 30_Ldg_1 office lighting wallwasher  30_Ldg_1 office lighting wallwasher effect
Using wallwasher- A luminaire that distribute the light to walls is a good technic to ensure bight walls

The EN-12464-1 recommends a minimum value wall and ceiling as follows, however for brighter appearance a higher value is considered good practice

Wall     75 lx U0 ≥ 0,10

Ceiling 50 lx U0 ≥ 0,10

0.5 meter could be excluded form top and bottom of the wall and could be away 0.5 meter form the wall.

The ceiling as well could exclude 1 m form each side

 30_Ldg_1 office lighting wall task area30_Ldg_1 office lighting wall task area room surfaces
  • Modelling and cylindrical illuminance Ēz

Modelling is a good yardstick for 3D perception of persons and objects in a room. It expresses the balance between diffuse and directional light and is determined by

The ratio of cylindrical illuminance to horizontal illuminance at a given point (normally 1.2 m above floor level). As a rough guide, a value between 0.30 and 0.60 is an indicator

of good modelling: faces and bodies are not too dramatically shaded or sharply illuminated, nor are they cast in a flat, dull light.

 29_Ldg_1 office lighting Modelling and cylindrical illuminance Ēz  29_Ldg_1 office lighting Modelling and cylindrical illuminance Ēz 2
A high cylindrical illuminance is important for the perception of vertical planes and objects. It is enhancing particularly the recognition of faces.

Maintained illuminance must be no lower than 50 lx. In places where good visual communication is crucial, e.g. in an office, meeting room or classroom, maintained

illuminance should be raised to 150 lx.

This requirement needs to be met at 1.2 m above floor level for seated persons and 1.6 m above floor level for persons standing in activity and interior areas.

 29_Ldg_1 office lighting Modelling and cylindrical illuminance Ēz 3  29_Ldg_1 office lighting Modelling and cylindrical illuminance 4
To avoid shadows the cylindrical illuminance should be at least 0.3 of the horizontal illuminance.

DIAL research

The German institute for applied lighting DIAL (http://www.dial.de/DIAL/en/home.html) has carried out a research on The Effect of Different Lighting scenes in Office Lighting.

This investigation had 20 different scenes with combination of ambient and accent lighting as in the following table

5 type of ambient lighting

A.    Direct ambient lighting by Down lighting.

B.     Direct/indirect lighting by suspended luminaire.

C.     Indirect lighting only

D.    Direct ambient lighting and wall-washing

E.     Indirect lighting by wall-washing

 28_Ldg_1 office lighting DIAL research The Effect of Different Lighting scenes in Office Lighting
 28_Ldg_1 office lighting DIAL research The Effect of Different Lighting scenes in Office Lighting_1  28_Ldg_1 office lighting DIAL research photo A
 28_Ldg_1 office lighting DIAL research B  28_Ldg_1 office lighting DIAL research photo b
 28_Ldg_1 office lighting DIAL research c  28_Ldg_1 office lighting DIAL research photo c
 28_Ldg_1 office lighting DIAL research d  28_Ldg_1 office lighting DIAL research photo D
 28_Ldg_1 office lighting DIAL research e  28_Ldg_1 office lighting DIAL research photo e
For the above 5 ambient lighting scenes an accent lighting scene there was added

The four scenes added to the above 5 ambient lighting scenes

1.      No accent lighting at all.

2.      Accent lighting on table.

3.      Accent lighting on wall.

4.      Accent lighting on table and wall.

 27_Ldg_1 office lighting DIAL research Accent lighting
 27_Ldg_1 office lighting DIAL research Accent lighting 4  27_Ldg_1 office lighting DIAL research Accent lighting 4 photo

                           One of the accent lighting scene with ambient lighting

The combination of the ambient and accent lighting scenes give total of 20 scenes  DIAL_Table
For example scene 19 is senses that have ambient of direct by downlight and indirect by wall-washing with accent lighting on table and wall.  DIAL_Table with Numbers Arrows
 26_Ldg_1 office lighting DIAL research Accent lighting 4 photo

Some of the 20 scenes

The purpose of the investigation is to find out, what the best lighting scene is for each one of the following criteria

  1. Brightness
  2. Attractiveness
  3. Activation
  4. Well-being

The results was displayed by tables that have both colors and numbers

Color representation

The greener the color the higher rating has the scene in particular criteria

The other way round the red is the worst.

 DIAL_Table Color1

Number representation

Because color could be similar, a number give more precise rating

The lower the value represents the better rating for the scene in particular criteria.

The other way round the warmer the worse.

The rating was form 1 to 5

1 is the best , 5 is the worst

 25_Ldg_1 office lighting DIAL research Accent lighting 4 photo

The results are show in the following tables

Brightness

For the brightness the best scene was

Ambient wall-wash and Accent (1.93)

While the worst scene for brightness is only direct lighting which is the most common scene you can find in an office!

 1__Brightness_The Effect of Different Lighting scenes in Office Lighting_DIAL research_investigation

Attractiveness

The most attractive scene was with value (2.09)

Ambient lighting (Direct lighting + wall-washing) and accent on table and wall.

The worst is the indirect lighting (3.81)

 2__Attractiveness_The Effect of Different Lighting scenes in Office Lighting_DIAL research_investigation

Activation

The best scene to keep people active is two scene with value of (2.32)

Indirect lighting with accent lighting on table and wall

or Ambient lighting (Direct lighting + wall-washing) and accent on table and wall.

The worst is indirect lighting

 3__Activation_The Effect of Different Lighting scenes in Office Lighting_DIAL research_investigation

Well-being

The best scene for well-being has the value of (2.23) which is

Ambient lighting (Direct lighting + wall-washing) and accent on table and wall

The worst is indirect lighting

 4__Well-being_The Effect of Different Lighting scenes in Office Lighting_DIAL research_investigation

My conclusions

The results are self-explanatory but I would like to highlight some points

1.      The most common office lighting I have experienced in many offices is the direct lighting. Engineers love it!

Despite that the direct lighting being the most cost effective and best for energy efficiency, but it is the worst for brightness perception, the second worst for the rest scenes (attractiveness, activation and well-being)!

01_Ldg_1 office lighting DIAL research Accent lighting 4 photo
2.      Indirect lighting is the worst in 3 scenes (attractiveness, activation and well-being)!

In my career I met many interior designers and Architects who thinks the cove lighting and hidden lighting the best lighting! p

 02_Ldg_1 office lighting DIAL research Accent lighting 4 photo
Just because we don’t see the source of light will never make lighting more attractive!

This is a fact that we see it in day lighting, we don’t like the cloudy atmosphere and we prefer the sunny day in spite of the glare we get by the sun.

Indirect lighting we produce a shadow-less effect similar to the cloudy atmosphere!

 04_Ldg_1 office lighting DIAL research Accent lighting 4 photo  03_Ldg_1 office lighting DIAL research Accent lighting 4 photo
 06_Ldg_1 office lighting DIAL research Accent lighting 4 photo  06_Ldg_1 office lighting DIAL research Accent lighting 4 photo

Cloudy day

Sunny day

   

But when accent lighting was added to indirect lighting, the result was dramatically changed

Adding accent lighting on table and wall changed the indirect lighting from worst scene for attractiveness to be second best!  07_Ldg_1 office lighting DIAL research Accent lighting 4 photo
Adding accent lighting on table and wall changed the indirect lighting from worst for activation to the best!  08_Ldg_1 office lighting DIAL research Accent lighting 4 photo
Adding accent lighting on table and wall changed the indirect lighting from worst for well-being  to be third level!  09_Ldg_1 office lighting DIAL research Accent lighting 4 photo

3.      Many Engineers ask for very high uniformaty in all the room!

Uniformaty is required only in task area and adding accent lighting will change uniformaty a lot and create a hight contrast.

 10_Ldg_1 office lighting DIAL research Accent lighting 4 photo  11_Ldg_1 office lighting DIAL research Accent lighting 4 photo

Uniform lighitng by cloudy day

None-uniform lighting by sunny day

If we want to take the best scene in DIAL results we find that Ambient lighting (Direct lighting + wall-washing) and accent on table and wall is close to the best in brightness and the best in the rest criteria (attractiveness , activation and well being) which makes it very good guideline for designing an office.

Of course there can’t be one rule or scene for every office every time and there are many other factors but it could be very good idea to consider adding wall wash and accent lighting to improve the office lighting in gerneral.

 5__Well-being_The Effect of Different Lighting scenes in Office Lighting_DIAL research_investigation

Case Study

In the plan below we can see 5 deferent areas

1.      Open plan office

2.      Individual office (MD office)

3.      Meeting room

4.      Waiting area

5.      Corridor

 100001_Ldg_1 office lighting DIAL research case study EN12464-1 layout
 100002_Ldg_1 office lighting DIAL research case study EN12464-1 layout
Many engineers like to design all the rooms by just putting 60×60 fluorescent luminaire in a grid system, the follow layout shows the most common lighting design by many engineers, which is fairly simple and doesn’t give any quality of lighting, according to DIAL investigation it is the worst for brightness perception, the second worst for the rest scenes (attractiveness, activation and well-being)!
 100003_Ldg_1 office lighting DIAL research case study EN12464-1 layout
 100004_Ldg_1 office lighting DIAL research case study EN12464-1 layout
 100005_Ldg_1 office lighting DIAL research case study EN12464-1 layout
Calculation and rendering was produced by DIALux evo
The luminaire used is 3x14w T5 fluorescent with very efficient luminaire and the average illuminance is higher than 500 lux in all the room with very uniform lighting!
 100006_Ldg_1 office lighting DIAL research case study EN12464-1 layout false color rendering
In the next layout I am going to purpose an alternative solution that have Ambient lighting (Direct lighting + wall-washing) and accent on table and walls (the secene that was found best in DIAL invastagating for office lighting)
 100007_Ldg_1 office lighting DIAL research case study EN12464-1 layout
The downlight (wf) is a downlight with ERCO 83238 with Extra wide distribution

Wallwasher (ww) ERCO 84014

Downlight with oval flood distribution for the corridor ERCO 80032

Spot light for accent lighting (S) ERCO 40104 to highlight the painting on the wall and the meeting table on the MD office

 100008_Ldg_1 office lighting DIAL research case study EN12464-1 layout

Spacing and offset for wallwasher and spotlight for accent lighting

The role of thumb , wallwasher should have an offset form the wall of 1/3 the wall height and the spacing between the wall-washers is equal to the offset (if wall height is 3 meter then the offset form wall should be 1 meter and spacing is one meter)

Accent lighting for a 3 meter height wall should be 850-1000 mm as an offset form wall to have 30o tilt.

 100009_Ldg_1 office lighting DIAL research case study EN12464-1 layout  100010_Ldg_1 office lighting DIAL research case study EN12464-1 layout

Offset a is 1/3 of the wall height Spacing d is equal to offset however some new wallwasher form ERCO could be spaced up to 1.5 times the offset

Spotlight offset form wall for

accent lighting for a painting on walls

 100011_Ldg_1 office lighting DIAL research case study EN12464-1 layout  100012_Ldg_1 office lighting DIAL research case study EN12464-1 layout

Downlight 60×60 solution

Downlight+wall-wash and accent lighting

 100013_Ldg_1 office lighting DIAL research case study EN12464-1 layout  100014_Ldg_1 office lighting DIAL research case study EN12464-1 layout

Downlight 60×60 solution

Downlight+wall-wash and accent lighting

 100015_Ldg_1 office lighting DIAL research case study EN12464-1 layout  100016_Ldg_1 office lighting DIAL research case study EN12464-1 layout

Downlight 60×60 solution

Downlight+wall-wash and accent lighting

(blue Colored wall-wash added)

The paintings on wall are much more attractive

Using DIALux evo with EN12464

If you go to assessment tool in DIALux evo and select the room then you can define the area and DIALux evo will list all the requirements according to EN12464-1, this is not only for office but for any type of room.  100017_Ldg_1 office lighting DIAL research case study EN12464-1 layout
If you go to calculation objects mode and select visual task areas you can place on task area and DIALux evo will simply create surrounding area and background area.  100022_Ldg_1 office lighting DIALux evo en 12464 ugr task area
Also you could place area of activity to calculate the cylindrical illuminance.  100018_Ldg_1 office lighting DIAL research case study EN12464-1 layout
You can in place calculation for the walls and ceiling by selecting room main surfaces tool  100019_Ldg_1 office lighting DIAL research case study EN12464-1 layout
In the calculation object tool you can draw a calculation surface and get many results by just selecting what is required for this example a UGR and cylindrical illuminance is selected

It should be noted that UGR and cylindrical illuminance for offices should be at a height of 1.2 meter which is the average height of the eye for a seated person.

 100020_Ldg_1 office lighting DIAL research case study EN12464-1 layout
DIALux evo will show the EN requirements in the summary page
 100021_Ldg_1 office lighting DIAL research case study EN12464-1 layout

Lighting design LdG + LdC Page

LDG and LDC-2

if you are intersected  in  learning lighting design software then you can visit this  page

DIALux evo Tutorials

SM

 

 

17 Comments

  1. good morning mr,baroudi,we want to thank you you at  your information which you tell aboutbut, kindly we from you to speak about  street lighting, and tunnel best regardeng. abdalah

    Like

  2. Dear Eng Ezzat ,
    A novel method developed by Gruppe Nymphenburg Consult AG was applied: Limbic Emotional Assessment, or LEA in brief . Emotional Assessment is based on the methods of neuro-science and psychophysiology. The latter discipline deals with the connections between emotional processes in the brain and the concomitant Physical reactions.

    Like

  3. What do you think of changing the light from warm white to cool daylight, I thought cool daylight is more widely used for office lightning?

    Like

  4. Good morning Mr.Ezzat, Firstly I’d like to thank you for sharing this work. The information is very clear and nicely done. And secondly I can’t find the DIAL reasearch about this topic anywhere, The link you gave in this site is no longer exist. can you help me about this?

    Regards

    Like

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