University of Southern California Dissertations and Theses

Integrating non-visual effects of lighting in the evaluation of electrical lighting designs for commercial offices

(USC Thesis Other)

Integrating non-visual effects of lighting in the evaluation of electrical lighting designs for commercial offices

PDF

Download a page range

Download transcript

Copy asset link

Request this asset

Transcript (if available)

Content 1

INTEGRATING NON-VISUAL EFFECTS OF LIGHTING IN THE EVALUATION OF ELECTRICAL
LIGHTING DESIGNS FOR COMMERCIAL OFFICES.

by

AMOL SARDESHPANDE

A Thesis Presented to
SCHOOL OF ARCHITECTURE
UNIVERSITY OF SOUTHERN CALIFORNIA

In Partial Fulfillment of the
Requirements for the Degree
MASTER OF BUILDING SCIENCE

MAY 2017

2

COMMITTEE
Kyle Konis, Ph.D, AIA
Assistant Professor
USC School of Architecture
kkonis@usc.edu

Marc Schiler, FASES
Professor
USC School of Architecture
marcs@usc.edu
(213)740-4591

Karen M. Kensek, LEED AP BD+C, Assoc. AIA
Associate Professor of the Practice of Architecture
USC School of Architecture
kensek@usc.edu
(213)740-2081

3

DEDICATION

To my loving Grandfather, Grandmother, Mother and Father.
Thank you for your support along the way.

4

ACKNOWLEDGEMENTS
This project would not have been possible without the support of many people. First and foremost, I would like to
express my deepest gratitude towards my thesis chair, Professor Kyle Konis, who has been an excellent mentor
throughout the entire thesis process. His great ideas and suggestions helped me in finding the right research path for
my thesis. His creative and positive thinking, keen eye for details, valuable inputs/comments on earlier version of
thesis and guidance during my initial stage of confusion, benefitted my thesis in many ways.
I would also like to convey my special appreciation towards my committee members, Prof. Marc Schiler and Prof.
Karen Kensek. They provided great support, time and advice on my project issues and also helped in improving my
writing skills for the thesis book. I am grateful to them for taking out valuable time from their busy schedule to
review my work and provide me with suggestions.
I am honored that all the committee members have always shown confidence in me during this thesis process. Thank
you all the committee members for such a great support and encouragement.
I would like to thank the MBS family of USC School of Architecture. They made the time spent here extremely
enjoyable and memorable.
Last but not the least, I would like to thank my Grandfather, Grandmother, Mother and Father back in India. Thank
you for always being there for me during my best and worst days and I am very grateful to you all for supporting me
in every possible way.
5

ABSTRACT
Humans need to be exposed to a certain amount of light, and overexposure to light may lead to various disorders in
bodies. The human circadian system is considered rarely in designing the lighting for a place. Usually the main
issues of vision, glare, illuminance and luminance are considered. Whether the provided lighting system is useful for
the human bodies using them or not is also one of the most important points that every lighting designer should
consider. Every single space is different than another, and hence every space should have its unique lighting. The
research was helpful to the lighting designers in determining whether the lighting designed by them for a place is
going to help the humans using that space or its going to affect them in an opposite negative manner. The main
objective was to design an easily accessible workflow for the lighting designers to evaluate their design in terms of
circadian system. Using this workflow, three different configurations of lighting design with four different light
sources were evaluated and compared with each other to give outputs in relation with the circadian system. There is
currently limited guidance to help the lighting designers to judge their design and find its suitable level for the
humans in that space. So, the thesis was like a stepping stone in this positive direction.
A test model was created as a replica of commercial office for the research. The test model was linked with various
software programs like Rhino, Grasshopper and Ladybug + Honeybee to carry out different simulations. Three
different lighting design test cases and four different types of light sources were considered during the research. The
EML (Equivalent Melanopic Lux) and LPD (Lighting Power Density) values were collected for each type of design
test case and each type of lighting source. Workflow was developed for the lighting designers to evaluate their
design in relation to its effect on the circadian system of the occupants in terms of the EML values. The comparison
between the design configurations and light sources, helped to determine the better among them for the circadian
system and for the energy consumption. The workflow and data collected, led in the formation of an easy accessible
tool for the lighting designers. The newly created calculator could evaluate a particular design to verify whether the
design would disturb the circadian pattern or would enhance and maintain the circadian cycle along with its energy
efficiency.
HYPOTHESIS
Circadian lighting evaluation tools will provide lighting designers with an easy accessible source to evaluate their
design in terms of circadian effect and energy efficiency.

6

Table of Contents
1 INTRODUCTION ................................................................................................................................................ 13
1.1 Circadian system ........................................................................................................................................ 13
1.2 Lighting ...................................................................................................................................................... 15
1.3 Light and circadian system ......................................................................................................................... 16
1.4 Equivalent Melanopic Lux (EML) ............................................................................................................. 17
1.5 Causes of circadian disruption ................................................................................................................... 18
1.6 Effects of light on health ............................................................................................................................ 19
1.7 Importance of blue light ............................................................................................................................. 20
1.8 Scope of thesis ........................................................................................................................................... 20
1.9 Objectives of thesis .................................................................................................................................... 20
1.10 Thesis role in Design cycle ........................................................................................................................ 21
1.11 Thesis outline ............................................................................................................................................. 22
1.12 Important terminology ............................................................................................................................... 22
2 BACKGROUND AND LITERATURE REVIEW ............................................................................................ 24
2.1 Introduction ................................................................................................................................................ 24
2.2 Photobiology- ............................................................................................................................................. 25
2.2.1 ‘Light as regulator of physiology and behavior’ (Lucas et.al, 2014). .......................................... 25
2.2.2 Non-visual lighting effects and solutions .................................................................................... 26
2.3 Standards-................................................................................................................................................... 28
2.3.1 WELL Building Standards- ......................................................................................................... 28
2.4 Circadian lighting ....................................................................................................................................... 29
2.4.1 Designing with circadian stimulus .............................................................................................. 29
2.4.2 Designing with tunable lighting- Case studies of Health care centers. ........................................ 31
2.5 Simulations................................................................................................................................................. 34
2.5.1 Rhino and Honeybee + Ladybug ................................................................................................. 34
2.5.2 LARK .......................................................................................................................................... 34
2.5.3 Circadian Stimulus calculator ...................................................................................................... 35
2.5.4 Circadian daylight in practice ...................................................................................................... 36
2.6 Summary .................................................................................................................................................... 38
3 METHODOLOGY ............................................................................................................................................... 39
3.1 Test geometry ............................................................................................................................................. 40
3.2 What is an IES file?.................................................................................................................................... 41
3.3 Test lab ....................................................................................................................................................... 43
3.4 Creating model ........................................................................................................................................... 44
3.5 Grasshopper script ...................................................................................................................................... 45
3.5.1 ‘Model specification’ and ‘Bottom grid and Eyepoint’ script. .................................................... 46
3.5.2 ‘Top grid’ script ........................................................................................................................... 47
3.5.3 ‘Simulation’ and ‘Output’ script. ................................................................................................. 48
3.6 Circadian ratio chart. .................................................................................................................................. 49
3.7 (EML + LPD) Calculator ........................................................................................................................... 51
3.8 Four different light source. ......................................................................................................................... 53
3.8.1 LED ............................................................................................................................................. 54
3.8.2 Fluorescent light .......................................................................................................................... 54
3.8.3 Incandescent bulb ........................................................................................................................ 54
3.8.4 Halogen Bulbs ............................................................................................................................. 54
3.9 Three different lighting design test cases ................................................................................................... 54
3.9.1 Ceiling mounted luminaires (First design) .................................................................................. 54
3.9.2 Hanging Pendant luminaires (Second design) ............................................................................. 55
3.9.3 Indirect lighting (Third design) ................................................................................................... 55
3.10 Summary. ................................................................................................................................................... 56

7

4 DATA COLLECTION ........................................................................................................................................ 57
4.1 Ceiling mounted fixture design (1st Test case). ......................................................................................... 57
4.2 Pendant Design test case ............................................................................................................................ 58
4.3 Indirect lighting design test case ................................................................................................................ 59
4.4 Summary .................................................................................................................................................... 60
5 ANALYSIS AND EVALUATION ...................................................................................................................... 62
5.1 To develop a methodology that a lighting designer can use to easily find out the values of EML at eye
point for a design. ...................................................................................................................................... 62
5.2 To determine the zone required for the lighting fixture to be energy efficient and capable enough to avoid
the disruption in circadian patterns of the occupants? ............................................................................... 63
5.3 To evaluate design outputs in terms of EML and LPD for three different lighting methods- ceiling
mounted design, pendant design and indirect lighting design. .................................................................. 64
5.4 To examine the better type of light source in terms of EML and energy efficiency between the four
different light sources. ............................................................................................................................... 66
5.4.1 LED light source ......................................................................................................................... 67
5.4.2 Fluorescent light source ............................................................................................................... 69
5.4.3 Halogen light source .................................................................................................................... 71
5.4.4 Incandescent light source ............................................................................................................ 73
5.5 Comparison between four light sources in each design ............................................................................. 75
5.6 What is the percentage increase or decrease in the values of EML and LPD between the four light sources
for each design? ......................................................................................................................................... 77
5.7 (EML + LPD) Calculator - Coefficients..................................................................................................... 78
5.8 Summary .................................................................................................................................................... 81
6 CONCLUSION ..................................................................................................................................................... 82
7 FUTURE WORK ................................................................................................................................................. 84
7.1 Future works for methodology ................................................................................................................... 84
7.2 Future works for EML + LPD calculator. .................................................................................................. 84
7.3 Future works for outputs ............................................................................................................................ 85
7.4 Summary .................................................................................................................................................... 85
8 REFERENCES ..................................................................................................................................................... 86

8

List of Figures
Figure 1 Schematic Diagram explaining the cycle of Circadian System (Iglesia, 2007). ..................................... 13
Figure 2 Melatonin Graph showing the rise and fall of melatonin during different hours of day (Mastin, 2013).
................................................................................................................................................................ 14
Figure 3 Light and Day rhythm patterns and free running rhythm patterns (Pedersen et.al., 2005). .................... 15
Figure 4 Impact of light on different parts of brain (Abrahamson & Moore, 2001). ............................................ 16
Figure 5 48-hour cycle graph showing the rise and fall of melatonin, cortisol and growth hormone during the
different hours of day. (ILP, 2015)......................................................................................................... 17
Figure 6 Melanopic sensitivity vs Visual Sensitivity Curves. Melanopic sensitivity reaches its 100% relative
response at 485nm before the visual sensitivity at 550nm (WELL, 2014). ............................................ 18
Figure 7 Causes of Circadian disturbance. 1. Jetlag (Jetlag hacks, 2016), 2. Night shift work (Healthy Living,
2013), 3. Exposure to bright light in evening (Murgia, 2016), 4. Street lighting (Yanko Design, n.d),
5.Old age (Tharp, 2017). ........................................................................................................................ 19
Figure 8 Different spectrums in light (ILP,2015). ................................................................................................ 20
Figure 9 Design process explaining the role of this research. .............................................................................. 21
Figure 10 Flowchart for literature study. ................................................................................................................ 25
Figure 11 Mechanism of spectral sensitivity. (Information from- Lucas et al., 2014). ......................................... 26
Figure 12 Left figure- Photo of light goggle engineered by the Lighting research Centre. Blue, short wavelength
light has the greatest impact on the circadin system (Figueiro, 2013). Right figure- Photo of
Daysimeter-D on the wrist and as a pin (Figueiro, 2013). ..................................................................... 28
Figure 13 WELL Building standard. (WELL, 2014). ............................................................................................. 29
Figure 14 Time Scheduled for experimental space. The colour temperatures and the light output levels changes
according to the time. (Figueiro, Gonzales & Pedler, Oct. 2016). ......................................................... 31
Figure 15 The corridor’s tunable lighting, shown at the morning (6500k at 66% output), afternoon (4000k at 66%
output) and evening (2700k at 20% output) setting (James Brodrick, Oct. 2016). ................................ 32
Figure 16 The Circadian and lighting quality deisgn strategies applied to a healthcare patient room. (Siminovitch
& Graeber, August 2016). ...................................................................................................................... 33
Figure 17 Software programs and plugins used in the research field of circadian lighting. 1.LARK, 2. RHINO,
3.GRASSHOPPER and 4. LADYBUG + HONEYBEE. ....................................................................... 35
Figure 18 Circadian Stimulus Calculator designed by Lighting Research Centre to calculate the circadian
stimulus of light source (LRC, 2016). .................................................................................................... 36
9

Figure 19 Left figure- Method 1 circadian daylight results. The areas in the red are projected to meet the
threshold of at least 4 hours per day every day of the year. Right figure- Method 2 circadian daylight
results. A point with a view facing any of the yellow orientations in each location meets the WELL
circadian threshold (Hagen & Richardson, 2016). ................................................................................. 37
Figure 20 Results showing direct details comparison of the both simulation methods. Left figure- Method 1
results. Right figure- Method 2 results. (Hagen and Richardson, 2016). .............................................. 38
Figure 21 Workflow for the methodology of the thesis .......................................................................................... 39
Figure 22 Test Geometry depicting three different grids ........................................................................................ 41
Figure 23 Left Figure - Angular spread of the luminous intensity from a fixture (Talking Photometry:
Understanding Photometric Data Formats,2017). Middle figure- Example of Polar intensity diagram
(Ransen, 2017). Right figure- Example of a cone intensity diagram (Cooper lighting design guide,
2009). ..................................................................................................................................................... 42
Figure 24 Example of an IES file in the text format used in the Grasshopper script. ............................................. 43
Figure 25 FLEX LAB, Berkeley (McNeil et al., Dec. 2014). ................................................................................. 44
Figure 26 FLEX LAB- Inside view, Berkeley ( McNeil et al., Dec. 2014). ........................................................... 44
Figure 27 Test lab plan with Gridpoints. ................................................................................................................ 45
Figure 28 Elevation & 3D view of the Test lab along with its gridpoints and furniture. ........................................ 45
Figure 29 Grasshopper script used in the workflow. .............................................................................................. 46
Figure 30 Flowchart of the full grasshopper script, showing the links between the small scripts. ......................... 46
Figure 31 Left figure- Model specification in the script. Right figure- Script for the bottom grid in the test model.
Light sensors in the test model were organized using this script. Also, the eye point in the Test lab is
controlled by this script. ......................................................................................................................... 47
Figure 32 Grasshopper script for the top grid in the test model. The luminaires in the test model were organized
using this part of the Grasshopper script. ............................................................................................... 48
Figure 33 Left figure- Script for the electric grid based lighting. Right figure- Outputs in the Grasshopper script.
................................................................................................................................................................ 49
Figure 34 Left figure- Light wavelengths showing 100% relative sensitivity. Right figure- Circadian ratio chart
by WELL Standard. This helps in finding out the circadian lux values from the known illuminance
values. (WELL, 2014) ............................................................................................................................ 50
Figure 35 Melanopic and visual response chart used to find the circadian ratio for light source. (WELL, Oct.
2014). ..................................................................................................................................................... 51
Figure 36 Flowchart depicting the working of the calculator. ................................................................................ 52
10

Figure 37 (EML+LPD) Calculator design with the graph. ..................................................................................... 53
Figure 38 Four type of light sources used in the three lighting design configurations. (Ramin, April 2013)......... 53
Figure 39 Elevation of first design with ceiling mounted luminaires. .................................................................... 55
Figure 40 Elevation of Second design method with hanging pendant luminaires. ................................................. 55
Figure 41 Elevation of third design method with indirect lighting luminaires. ...................................................... 56
Figure 42 Left Figure- Values for the LPD and EML from the data of Figure 40. Right Figure- Graphical
representation of the values (shown in the left figure) with LPD as X-axis and EML as Y-axis for the
first design method. The horizontal illuminance at desk surface level is kept constant at approximately
450 lux for all the simulations. ............................................................................................................... 58
Figure 43 Left figure- Values for the LPD and EML from the data of Figure 39. Right Figure- Graphical
representation of the values (shown in the left figure) with LPD as X-axis and EML as Y-axis for the
second design method. The horizontal illuminance at desk surface level is kept constant at
approximately 450 lux for all the simulations. ....................................................................................... 59
Figure 44 Left Figure- Values for the LPD and EML from the data of Figure 41. Right Figure- Graphical
representation of the values (shown in the left figure) with LPD as X-axis and EML as Y-axis for the
third design method. The horizontal illuminance at desk surface level is kept constant at approximately
450 lux for all the simulations. ............................................................................................................... 60
Figure 45 Flowchart of the workflow ..................................................................................................................... 63
Figure 46 Zone description for the analysis process. .............................................................................................. 64
Figure 47 Comparsion of three lighting design methods- Ceiling mounted lighting, hanging pendants and indirect
lightigng. The horizontal illuminace at the desk surface is kept constant at 450 lux. ............................ 65
Figure 48 Graphical representation of Table 6 ....................................................................................................... 66
Figure 49 Comparison of all LED light sources for the three different lighting methods. The maximum dotted
line for LPD is at 1.1watts/sqft. The minimum dotted line for EML is at 250lux. ................................. 68
Figure 50 Comparison of LPD values of all LED light sources for three different lighting methods. The
maximum dotted line for LPD is at 1.1watts/sqft. .................................................................................. 68
Figure 51 Comparison of EML values of all LED light sources for three different lighting methods. The
minimum dotted line for EML is at 250lux. ........................................................................................... 68
Figure 52 Comparison of all fluorescent lamps for the three different lighting methods. The maximum dotted line
for LPD is at 1.1watts/sqft. The minimum dotted line for EML is at 250lux. ........................................ 70
Figure 53 Comparison of LPD values of all fluorescent lamps for three different lighting methods. The maximum
dotted line for LPD is at 1.1watts/sqft. ................................................................................................... 70
11

Figure 54 Comparison of EML values of all fluorescent lamps for three different lighting methods. The minimum
dotted line for EML is at 250lux. ........................................................................................................... 70
Figure 55 Comparison of all halogens for the three different lighting methods. The maximum dotted line for LPD
is at 1.1watts/sqft. The minimum dotted line for EML is at 250lux. ...................................................... 72
Figure 56 Comparison of LPD values of halogens for three different lighting methods. The maximum dotted line
for LPD is at 1.1watts/sqft...................................................................................................................... 72
Figure 57 Comparison of EML values of all halogens for three different lighting methods. The minimum dotted
line for EML is at 250lux. ...................................................................................................................... 72
Figure 58 Comparison of all incandescent bulbs for the three different lighting methods. The maximum dotted
line for LPD is at 1.1watts/sqft. The minimum dotted line for EML is at 250lux. ................................. 74
Figure 59 Comparison of LPD values of halogens for three different lighting methods. The maximum dotted line
for LPD is at 1.1watts/sqft...................................................................................................................... 74
Figure 60 Comparison of EML values of all halogens for three different lighting methods. The minimum dotted
line for EML is at 250lux. ...................................................................................................................... 74
Figure 61 Comparison of all light sources used in celling mounted lighting design in percentage for different
aspects. ................................................................................................................................................... 75
Figure 62 Comparison of all light sources used in pendant design in percentage for different aspects. ................ 76
Figure 63 Comparison of all light sources used in indirect lighting design in percentage for different aspects. .... 77
Figure 64 Example of EML +LPD calculator. ....................................................................................................... 80
Figure 65 Comparison of flowcharts between the 'workflow with simulations' and '(EML +LPD) calculator.' .... 81
Figure 66 Examples of false colour rendering images of lighting. (Left figure- Light+Architecture, New DIALux
EVO, April 2012, http://blog.lightingvanguard.com/2012/04/new-dialux-evo-review-with-
screenshoots.html )(Right figure- Lighting as a service, Designed solution,
http://www.lightingasaservice.com/design-solution/ ) ........................................................................... 85

12

List of Tables
Table 1 Comparison of effect of light on Visual and Circadian system (Information from- Figueiro, 2013). .... 27
Table 2 Comparative analysis of both the simulation methods for circadian daylight analysis. (Hagen and
Richardson, 2016). ................................................................................................................................. 37
Table 3 Descriptive Data for the first design method (Ceiling Mounted luminaires). ......................................... 58
Table 4 Descriptive Data for the Second Design method (Pendant luminaires). ................................................. 59
Table 5 Descriptive Data for the Third Design method (Indirect lighting method with luminaires uplighting on
the ceiling). ............................................................................................................................................. 60
Table 6 Data describing the percentage levels of each lighting design method for each different aspect. .......... 66
Table 7 Percentage decrease and increase in EML and LPD values between four light sources for each lighting
design method. The values highlighted in the blue color are the best values for EML and LPD as
compared to others in every design, and the percentage of increase and decrease was calculated by
using those values as reference. ............................................................................................................. 78
Table 8 Co-efficient values for all three lighting designs. These are the co-efficient between the horizontal
illuminance at the desk and the vertical illuminance at the eye point. ................................................... 79

13

CHAPTER 1
1 INTRODUCTION
The thesis details the development of a method that determines the various design aspects that should be taken into
consideration while designing for circadian lighting. This tool is an effective method which offers an improvement
over conventional design tools that do not account for circadian lighting effects. The lighting designers can score
their design on the basis of its circadian effect.
Light is essential. It enables us in the recognition of form, colour, and texture. Light is considered to be the
important source for our vision, which is the result of complex interactions between the light sources, eye, object,
and surfaces and brain. Humans have developed technologies, devices, applications using this knowledge of light for
resulting in more advanced vision. Light plays the same role in the field of architecture. The primary goal of the
lighting designer while designing a space is to increase the performance and productivity of the space by improving
the vision and perception. But another dimension has been added to these studies in the recent years- ‘LIGHT IS
NOT JUST FOR VISION ANYMORE’ (Figuerio, 2013). The scientists from LRC (Lighting Research Centre) have
discovered that light and dark patterns reaching the retina in the eye have many impacts on the brain leading to
various human health issues. Circadian rhythm is one of the factors that is affected by the light reaching the brain
through the retina (Figuerio, 2013). Circadian rhythms repeat themselves after every 24 hours forming a continuous
cycle. They play an important role in the human body as they are related to the behavior, moods. and many other
functions in the human health (Figuerio, 2013). Light is mainly considered to have the ‘visual effects’ on the body
but by the discovery of light affecting other parts in human body like circadian rhythms, they are also recognized to
have ‘non-visual’ effects on the body (Figuerio, 2013). This chapter introduces the concept of a circadian system. It
defines the functioning of circadian system, interrelation between light and the circadian system, and the causes and
effects of light on circadian system
1.1 Circadian system
Circadian rhythms describe body’s physical, psychological and psychological changes over a 24 hour period. – (ILP,
2015) (Figure 1).

Figure 1 Schematic Diagram explaining the cycle of Circadian System (Iglesia, 2007).
The circadian system is named after the circadian rhythms which are important in determining the patterns like
eating and sleeping in all living beings. A circadian system is common in the living beings, plants, animals, fungi
and cyanobacteria (Edgar et al., 2012). It’s a 24 hour cycle that is internally generated and can be adjusted or
changed by the external cues like sunlight and temperature (Circadian rhythms-Biological clock, n.d). This daily
cycle of the circadian rhythm is linked with brain wave activity, hormone production, cell regeneration and other
biological activities (Circadian rhythms -Biological clock, n.d). Those all coordinates in processing the 24 hour
cycle of living being.
The pattern of the circadian rhythms is based on the light-dark cycles and some other cues present in the organism’s
environment (The American Heritage Stedman’s Medical Dictionary, 1995). This sets up a cycle in the body which
leads in waking up every day at the same time and start feeling sleepy at the same time (The American Heritage
Stedman’s Medical Dictionary, 1995). Due to this circadian cycle, we sometimes wake up at the same time in
morning without the need of an alarm. This cycle is set by the circadian rhythms in our body and we designate them
14

as the circadian system. Circadian rhythm is mainly controlled by the release of hormones (Mastin, 2013). Light and
darkness exposure plays a vital role in the 24 hour cycle. Exposure to light, activates a nerve pathway from the
retina in the eye to another part of the brain known as hypothalamus (Mastin, 2013). In this part, a special center
called the suprachiasmatic nucleus (SCN) has an important role in sleep-wake cycle. It controls the sleep-wake cycle
by sending the signals to various parts of the brain that control the hormone production or the body temperatures
(Mastin, 2013). Melatonin is the hormone responsible for human sleep. This hormone is made by a pea-sized gland
known as the pineal gland, which is located above the middle of the brain (Figuerio, 2013). During the day, it’s
inactive, but when darkness occurs, it becomes active and produces melatonin, which is released in the blood. As a
result, the melatonin levels in the blood increase and humans begin to feel less alert (Figuerio, 2013). Once the
retina is exposed to the first light in the morning, the pineal gland becomes inactive and the level of melatonin drops
in the blood resulting in more alertness (Figuerio, 2013). This is the 24-hour cycle of sleep that is controlled by light
and darkness. Night time causes melatonin secretion to rise, while daylight hinders it (Figuerio, 2013). The graph
(Figure 2) represents that the production of the melatonin begins by starting of 8pm in the night and reaches its peak
at around 3am. This is the time when the person feels very sleepy because of the peak production of melatonin
hormone in the body (Mastin, 2013). As the time approaches to sunrise, the melatonin levels start decreasing, and it
reaches very low level around 7am in morning, when the person wake up and start feeling more alert. This results
because of the low levels of melatonin in the body (Mastin, 2013). Circadian rhythms are disrupted by change in the
normal continuous schedule. For example, biologists have observed in their research that birds that are exposed to a
lot of electrical light, sometimes presume the fall season as the spring and starts building their nests (The American
Heritage Stedman’s Medical Dictionary, 1995). The increase and decrease in the melatonin levels on the basis of the
day and night cycle was explained through graphical form (Figure 2).

Figure 2 Melatonin Graph showing the rise and fall of melatonin during different hours of day (Mastin, 2013).
Circadian rhythms are present in diverse organisms and have the same function. These rhythms are formed from
multiple oscillators (Pedersen et.al., 2005). In the body, the various biological process which occurs in the cells and
tissues have the ability to oscillate within fixed span intervals. Such cells, tissues and the molecules which carries
out this functions are called as the ‘oscillators’ (Pedersen et.al., 2005). The term ‘circadian oscillators’ are used to
express the span intervals of around 24hours and to form a biological clock (Pedersen et.al., 2005). Circadian
oscillators depend on the environmental cue and arrange their intervals according to it. Such cues are known as
‘zeitgeber’ (Pedersen et.al., 2005). These oscillators respond and depends on the environmental reference point to
carry out its functions. This property is known as the ‘relative phase’ (Pedersen et.al., 2005). Such environmental
reference is mostly the ‘day and night cycle’ for most of the organisms and some specialized photoreceptive and
phototransductive mechanism that have evolved in the biological clock systems (Pedersen et.al., 2005). These
oscillators who responds to the environmental references regulates the downstream oscillators and helps in the
functioning of the downstream rhythmic events (Pedersen et.al., 2005). The other example for the environmental
15

references is the ‘temperature changes.’ In such situation, the intervals of the rhythms depend on the variations of
the temperature (Pedersen et.al., 2005).
The rhythm patterns for the circadian oscillators and the normal oscillators are explained in the light-dark cycle. The
cue shown below (Figure 3) is the light and dark cycle (LD- entrained rhythm). The other free running rhythm is the
cycle without any cue. The circadian rhythms in LD entrained system is observed to change according to the patterns
of the light and dark and don’t have any specific span for the repetition of intervals. It all depends on the light and
dark cycle. The circadian rhythm for free running rhythm has a specific span repeating after certain intervals with the
same amplitude. Light and darkness plays a very vital role in the circadian cycle of humans, and it very important cue
to affect the person’s circadian rhythms and 24hour cycle (Figure 3).

Figure 3 Light and Day rhythm patterns and free running rhythm patterns (Pedersen et.al., 2005).
Circadian rhythm has definite properties in all organisms. Some of the main properties are as follows:
 A rhythm with a periodicity of about 24 hours, even in the absence of an environmental cycle (called a free-
running rhythm).
 The ability of the clock to be entrained in a time-dependent manner by environmental stimuli.
 And compensation of period length for changes in an organism's natural environment (Pedersen et.al., 2005).
These are the main properties of a biological timing mechanism that responds to various environmental factors in
order to maintain the phase relationship with environmental cycles (Pedersen et.al., 2005).
1.2 Lighting
One factor that is mandatory while designing a structure is its lighting. Designing lighting for a particular space adds
to its aesthetic value as well as towards the working of the space. Lighting gives a very prominent value to the
designed phase. An architectural building is incomplete without its lighting design. Lighting has the power of
turning a negative dull space into positive happening space. A better lighting design for a space is the bonus which
an architect receives for his structure. In the era of sustainability, lighting plays a very important role in energy
efficiency. Using daylighting, energy efficient electrical lighting and good controls to energy demands are all the
16

present strategies for sustainability through lighting (Ander, 2016). Such strategies help in saving the energy of the
building and making it a more beautiful space. Daylighting and electrical lighting both have their uniqueness in the
design. Scientists have discovered that as lighting matters to the energy and sustainability of the building, it also
matters to the health of the people using it (Ander, 2016) (Rea, 2000). Lighting has a very vital role in affecting the
health of the humans (Rea, 2000). Hence, a good lighting design is crucial for maintaining the health of humans.
Lighting mainly affects the circadian system of the person (Rea, 2000). It is the responsibility of the lighting
designers to engage in lighting designs that are beneficial for human health and to pay attention to the effects of their
lighting designs on the people using it (Figuerio, 2016).
1.3 Light and circadian system
The concepts of lighting and circadian system are interrelated to each other. Lighting plays a vital role in the
functioning of circadian system (Figuerio, 2016). The eyes of the person can get disturbed by bad or uncomfortable
lighting. Light does not have impact just on the eyes of the humans but a lot more than that (Figuerio, 2013). There
is a non-visual pathway from the eyes to the brain that has no relation with the vision of the person (Figuerio, 2013).
The SCN (Suprachiasmatic nucleus) controls the circadian system in the body. It is like a master pacemaker,
coordinating all the cellular clocks in the body through the endocrine system that produces various hormones with a
span interval of 24 hours (ILP, 2015).
When the light falls on the SCN (suprachiasmatic nucleus), the pineal gland gets activated. The pineal gland controls
the level of melatonin in the body (ILP, 2015). The pineal gland releases melatonin hormone in the body when the
body is less exposed to light (Mastin, 2013). During the night level, the melatonin level in the body starts increasing
and reaches peak level and starts reducing during the dawn (Mastin, 2013). Hence exposure to proper light in the
morning will help to set the circadian cycle in a 24 hour motion leading to various functions of the body to work
smoothly. If the person is not exposed to proper daylight in the morning, it affects many of the functions like the
sleep, hunger, mood, blood pressure, alertness and tiredness (Wettergerg,1993) (Zatz, 20015) (Lam,1996)
(Tuunainen,2004) (Lucas et.al,2014). The cell replacement and the body growth occurs during the sleeping hours of
night. If the sleep is affected by the unsynchronized circadian patterns, it ultimately affects the production of cells
and the body growth (ILP, 2015).
When the light falls on the SCN, various signals are sent to the neurotransmitters which controls different aspects in
the body (Abrahamson & Moore, 2001). Some of the neurotransmitters like ‘5 HT serotonin’ that controls the mood
of the person, ‘NPY (Neuropeptide)’ that controls the appetite of the person, and ‘Dopamine’ that controls many
neurological functions like learning and memory (Abrahamson & Moore, 2001). When the circadian system is
affected, it indirectly affects the SCN, eventually affecting all these neurotransmitters leading in several hindrances
in the activities of body. The schematic diagram of link between the light, SCN and other neurotransmitters (as
mentioned above) showing that how they lead to various neurological functions of the body was shown below
(Figure 4).

Figure 4 Impact of light on different parts of brain (Abrahamson & Moore, 2001).
LIGHT
17

Below is the graph (Figure 5) showing a 48 hour cycle of the body’s circadian system and the production of the
melatonin and cortisol (the hormone that maintains the alertness during the day) and the growth hormone for cell
production and replacement (ILP, 2015). The melatonin level increases and decreases from day to night. The cortisol
levels are high during the day and starts reducing towards the night time and are the lowest during night. The growth
hormone is at its peak point in the night proving that the growth mainly happens in night during sleep (Figure 6).
This helped in supporting the importance of synchronized circadian patterns for the human body (ILP, 2015).

Figure 5 48-hour cycle graph showing the rise and fall of melatonin, cortisol and growth hormone during the
different hours of day. (ILP, 2015).
1.4 Equivalent Melanopic Lux (EML)
EML stands for Equivalent Melanopic Lux. EML is the metric unit which is used to indicate the biological effects of
light on humans. This unit was proposed by Lucas (Lucas et al., Jan 2014). Photosensitive retinal ganglion cells
(ipRGCs) works in relation with the human circadian system when they are exposed to light (Lucas et al., Jan
2014). Lucas mentioned in his research that these photoreceptors does not produce any image. EML as a metric is
weighted to the ipRGCs response to light and translates how much spectrum of a light stimulates ipRGCs and
affects the circadian system (Zofchek, 2016) (Hagen & Richardson, 2016). It measures the circadian lux falling on
the eye of the human and how much its affecting the circadian system inside the brain (WELL, 2014). The sensitivity
curves for the EML and visual lux are different. The melanopic sensitivity curve reaches its 100% relative
sensitivity at 480nm and visual sensitive curve reaches at 555nm (WELL, 2014) (Figure 6).
18

Figure 6 Melanopic sensitivity vs Visual Sensitivity Curves. Melanopic sensitivity reaches its 100% relative
response at 485nm before the visual sensitivity at 550nm (WELL, 2014).
1.5 Causes of circadian disruption
Jet lag
The best known example of change in circadian rhythms is jet lag. Jet lag is suffered by people after they travel to
another time zone. The circadian rhythms forms a specific pattern for eating, sleeping, body tempertaure differences
and hormone regulation (ILP, 2015). Due to such change in time zones, the whole circadian cycle gets disturbed.
The person feels groggy, tired, disoriented and have poor concentration (ILP, 2015). It takes some time for the body
to adjust to the new time zone patterns. This is short term disrupton in circadian rhythms.
Night shift work
The night shift workers have circadian patterns as opposite to the normal patterns of people. The worst part is that
these people never get used to the cycle of working at night as they are constantly under the electrical lights. If such
pattern is repeated for a longer time, it can result into various dangerous diseases like peptic ulcers, cardiovascular
mortality and cancers. Also, the people lose their concentration and alertness during the day time. (ILP, 2015).
Office work in winter
Working indoors all the time during the winter season also causes the disruption in the circadian patterns. In the
winter month, the day is shorter and the nights is longer. Hence many a times people go to work in dark and return
in dark without being exposed to sunlight for a longer time. These leads to disturbance in their daily cycle, leading
to poor sleep, less alertness, low concentration, less appetite and lack of performance. (ILP, 2015).
Exposure to bright light in the evening
Exposure to bright light levels in the evening is one of the increasing concerns for the disruption in the circadian
cycle of people. The people are exposing themselves to levels of light with a high blue content shortly before
bedtime through laptops, TVs and LED task lights. This is sufficient to suppress melatonin levels in the blood,
making it harder for the person to sleep (ILP, 2015).
Modern street lighting
The modern street lighting is also considered as one of the problem for the disruption of the daily circadian rhythm.
The old street lamps have sodium based lighting and also LEDs in it . This leads to more content of blue light
through it (ILP, 2015). The people staying near the roads and who are exposed to streetlights during nights tends to
19

have effect on their circadian patterns (ILP, 2015). One hour’s exposure to 100lux of light from cold (6900k) street
light can suppress melatonin levels in people by up to 15% (ILP, 2015).
Old age
The older people are very less exposed to daylight if they are spending most of the time sitting indoors. Due to the
age, the condition of their retina is weakened (Rea M., 2000). Hence very less light reaches on the backside of the eye
eventually affecting the circadian system as well. The other eye problems like cornea and thickening of the eye lens
are very common (Rea M., 2000). One of the reasons for such low light levels in older people houses is the energy
codes (ILP, 2015). In order to save energy of the building, the same designs of younger people are being applied to
the older people which in general is the failure of the design (ILP, 2015). Various design methods have been introduced
in the circadian lighting just for the older people. Such designs help in choosing the type of colors needed and suitable
for older people’s eyes and also it should trigger their daily circadian system (Figuerio, 2016).

Figure 7 Causes of Circadian disturbance. 1. Jetlag (Jetlag hacks, 2016), 2. Night shift work (Healthy Living, 2013),
3. Exposure to bright light in evening (Murgia, 2016), 4. Street lighting (Yanko Design, n.d), 5.Old age (Tharp,
2017).
1.6 Effects of light on health
Light has both the positive and negative effects on the health. It totally depends on the use of light. If the light is
used in considerate manner, it can be beneficial for the health, but if it used in disruptive manner, it can affect the
health. Lighting helps in the visualization of objects; it makes the objects and spaces look aesthetically magnificent.
This research concerns about the light and its relation with the circadian system. If the body is exposed to required
light levels, it enhances the circadian system and maintain its circadian patterns (Figuerio, 2016). Exposure to
daylight for a proper limited period is the best method to maintain the circadian cycle in the human body (Hagen &
Richardson, 2016). But at the same time, light proves harmful to the body if not used in appropriate required
manner. The wrong type of light at the wrong time can disrupt the circadian rhythms. For example, large doses of
blue light in the early evening can keep the people awake for a long time in night without sleep (ILP, 2015).

Disruption of the ‘light-dark’ cycle is caused by exposure to too much light during the day or bright light at the
wrong time at night. This disruption of sleep patterns may lead to various health problems. The long-term sleep
problems and circadian disruption can lead to chronic maladies such as diabetes, obesity and hypertension (ILP,
2015). Circadian disruption leads to the decrease in the resistance power of the immune system. The white ‘killer
cells’ in the blood are reduced in their activity by around 28% which affects the immune system of the body (ILP,
2015). The uncomfortable levels of lighting disturb the circadian cycle leading to various effects on the human body.
Some of the effects of the chronic circadian disruption are- drowsiness and unintended sleep, mood shifts and
irritability, anxiety and depression, weight gain, decreased socialization skills and communication skills and sense of
humor, decreased motor and cognitive performance, poor concentration and memory, increase risk tasking,
decreased creativity and productivity, reduced immunity to disease and viral infection, reduced ability to multitask ,
increased risk of substance abuse (ILP, 2015).
20

1.7 Importance of blue light
Visibility is mostly in the blue light spectrum. Blue light has a significant effect on the circadian cycle (ILP, 2015).
Proper amount of blue light enhances the circadian patterns but a lot of blue light during night time harms the
circadian cycle. The exposed light either sets a pattern on the ‘body clock’ or damages it. Daylight has a large
amount of blue component. Also, cold fluorescents, metal halide lamps and LEDs fixture have a lot of blue light in
it. Warm lamps, such as HPS, LPS, tungsten halogen are least effective and are most effective in setting body clocks
(ILP, 2015). The non-visible spectrum in light is from 100-380 nm and the blue light spectrum from 380-500nm
(Figure 8).

Figure 8 Different spectrums in light (ILP,2015).
1.8 Scope of thesis
The scope of the thesis was to determine a workflow that could be used by a lighting designer to evaluate their
design in terms of circadian system. The workflow would help the lighting designer to find that whether their design
is disturbing the circadian system of the occupants or its enhancing and maintaining their circadian patterns. This
research is done only for commercial office space and no other type of space was included. Daylighting was not
incorporated in the design. The research is based on the impact of electrical lighting on the circadian system of
humans. No practical experiments were conducted using the subjects to know the effect of light on circadian system.
A virtual test model of commercial space without door and windows was created in the software program. This
model was used for the entire research process. The effect of electric lighting on the circadian system was evaluated
based on Equivalent Melanopic Lux (EML) values, and no other factor like age and body condition of the occupant
was considered.
1.9 Objectives of thesis
The two-important objective of the research are as follow:
 To develop a method that could be easily accessed by the lighting designers to record the EML values
produced at the occupants’ eye by a particular lighting design. The method should help lighting designers
to determine whether their design is enhancing and maintaining the circadian cycle of the occupants or its
affecting their circadian system. It should also examine the energy efficiency of the lighting design along
with the effect on the circadian system helping the lighting designers to create an energy efficient circadian
positive lighting design.

 To evaluate three light design test cases with four different types of light sources per design with the help
of the developed methodology in terms of energy efficiency and circadian effect.
21

1.10 Thesis role in Design cycle

Figure 9 Design process explaining the role of this research.
The above schematic figure gives the rough idea regarding the role of this thesis in a lighting design process. It
demonstrates the position where this thesis will be used by the lighting designers. The main objective of the thesis is
to find a process that will help the lighting designers to evaluate their design in accordance with the occupant’s
circadian system. The process is explained through the schematic diagram, right from the client handling the project
to architect to the final design from the lighting designer. The process is described in detail in the following-
 At the start of every project a client hires an architect and gives the brief for the desired structure. Those
guidelines are used by the architect to land up on a design and getting it finalized from the client.
 The next step is introducing the lighting to the project. The architect hands over the project drawings to the
lighting designer with some rough ideas in mind. The lighting designer works on it with various ideas of
aesthetics and IESNA (Illuminating Engineering Society of North America) recommendations to reach a
final design. The specifications of the selected fixtures will be mentioned in the fixture schedule along with
the required cut sheets.
 After this stage, the role of this thesis comes into picture. The calculator created at the end of this thesis
will help the lighting designer to determine the effect of their design on the circadian system of the
occupants based on the Equivalent Melanopic Lux (EML) values. If the results are satisfactory then the
22

design will be finalized by the lighting designer in terms of positive effects on circadian system. But if the
results are unsatisfactory then again the lighting designer works on the design until the results end up to be
satisfactory.
 This schematic diagram helps to understand the position of this research in the design process of a project.
Also, it describes that how the lighting designer will be using this thesis output to satisfy the project in
terms of the requirements for the circadian system of humans. The research plays an important role for
between the different lighting design options and the finalization of design. The ‘(EML +LPD) calculator’
is a tool created as a result of this research. It is an easy accessible tool for the lighting designers to evaluate
their design in terms of its effect on circadian system of humans and its energy efficiency.
1.11 Thesis outline
Chapter 1 Introduction- It introduces the topic of circadian system in the human body and describes in detail its
functioning. It explains the interrelation between the light and the circadian system of humans. It describes various
causes that leads to the disruption of circadian system because of the light, and the effects that are caused because of
it. It summarizes that why it is necessary for lighting designers to consider the factor of circadian lighting during
designing.
Chapter 2 Background and literature review- It describes about the various research done in this field and helps to
get the knowledge of the lighting and circadian system in depth. The research appears on the photobiology,
standards in the field of lighting and health, circadian lighting design and circadian lighting simulations. The gaps in
the research papers are noted and are filled by this research.
Chapter 3 Methodology- The workflow of the whole research right from the selection of test model up to the
collection of final data is explained in this chapter. The Grasshopper script used in the workflow is explained in
detail. The detailed explanation of the used three lighting design test cases and the four light t sources.
Chapter 4 Data Collection- The outputs from the workflow are collected into this chapter. The data from this
chapter is the base for the next chapter. The result from the simulation of three different lights designs are displayed
in this chapter. The data is plotted on the graph in terms of EML and LPD values.
Chapter 5 Analysis- The data from the chapter 4 is analyzed through various perspectives. It discusses the
comparison of three lighting designs and four light sources in accordance with the circadian system. The concept of
the new created calculator is explained in this chapter.
Chapter 6 Conclusions- The overall output of the thesis is mentioned.
Chapter 7 Future works- The scope of work that could be continued in future using this research is explained.
1.12 Important terminology
Illuminance- It is the measure of how much light is striking a surface (Houser et.al, 2012). For example, when a
desk is incident with light. The light levels on the desk surface are said to be its illuminance values.
Horizontal illuminance- It is the amount of light landing on a horizontal surface like floor, desk etc.
(Ashdown,2016).
Vertical illuminance- It is the amount of light oriented on a vertical surface (Ashdown, 2016). For vertical
illuminance, the positon and the orientation of the surface should always be mentioned (Ashdown, 2016). The
vertical illuminance is calculated on walls, partitions etc.
Equivalent Melanopic Lux (EML)- EML is the metric unit used to indicate the biological effects of light on humans
(circadian system). This unit was proposed by Lucas (Lucas et al., Jan 2014). In biological terms, EML as a metric
is weighted to the ipRGCs (Intrinsically Photosensitive Retinal ganglion cells) (located in brain) response to light
and translates how much spectrum of a light stimulates ipRGCs and affects the circadian system (Zofchek, 2016)
(Hagen & Richardson, 2016).
23

Light Power Density (LPD)- It is the wattages consumed per unit area. It defines that how much energy is consumed
by the fixture in the room. Its SI unit is watts/square foot (Houser et.al, 2012).

24

CHAPTER 2
2 BACKGROUND AND LITERATURE REVIEW
Chapter 2 describes about the various research done in this field and helps to get the knowledge of the lighting and
circadian system in depth. The research appears on the photobiology, standards in the field of lighting and health,
circadian lighting design, and circadian lighting simulations.
2.1 Introduction
Light has a great impact on the functioning of the human body (Iglesia, 2007). A proper amount of exposure to
daylight or electric lighting helps a person to maintain his/her health and wellbeing (Figuerio, 2016). The circadian
system is a biological process in the human body which keeps recurring itself naturally on a twenty-four-hour cycle
(Iglesia, 2007). In simple words, the circadian system governs the 24-hour cycle of the human body like the day-
night cycle (sleep-awake cycle). The Institution of Lighting Professionals states from their research that when a
person is exposed to insufficient intensity of light for excess interval of time at the wrong time of the day, it may
lead to the disturbance in the circadian system that can affect the human body in many ways (ILP, 2015). Also,
Mariana G. Figueiro from LRC (Lighting Research Centre) states the same facts about effects on the circadian
system through her research. The short-term effects of the circadian system disturbance are less sleep, mood swings
and loss of appetite. In longer run, one may suffer from more serious disease like Alzheimer’s disease, dementia,
and many more (Wettergerg,1993) (Lam,1996) (Zatz,2005) (Tuunainen,2004) (Lucas et.al,2014). Lighting should be
designed in order to maintain and enhance the 24 hour cycle of the human body. Light plays a major role in
maintaining the health of a person, and hence a well-designed lighting system will help to maintain the circadian
system and its daily cycle (Figuerio, 2016).
Lighting designers often do not take the circadian system into account while designing. The factors of aesthetics and
mood overlap the importance of the circadian system. Lighting designers should start giving importance to the
effects caused to the circadian system by improper lighting methods and should try to avoid them. One of the
reasons for this problem is their lack of knowledge and awareness regarding this topic. The more lighting designers
know about the seriousness of this topic, the more it will be used in the design (Figuerio, 2016). No software
programs are available to predict the impact of the electric lighting design on the circadian system, right from the
beginning stage of design to the calculation of EML (Equivalent Melanopic Lux) values. This is one of the hurdles
leading to negligence of this topic. The thesis fills these gaps in the field of circadian lighting. One of the objectives
of this research was to provide the lighting designers with a workflow in software programs that helps them in
verifying their electric lighting design in accordance with the circadian system of the occupants. It is followed by
analyzing three different lighting design methods with different light sources in accordance with the circadian
system requirements.
The concept of circadian lighting is a combination of three main topics and the knowledge of these will help to
create a clear idea regarding the circadian lighting. The three topics are photobiology, standards, and circadian
lighting (design and simulations). Understanding these topics and finding the interrelation between them, helped to
understand and analyze the gaps in the present available work of circadian lighting. This helped in formulating a
workflow for this thesis that aims to fill the gaps and to add new values in the field of circadian lighting (Figure 10).
25

Figure 10 Flowchart for literature study.
2.2 Photobiology-
Photobiology is the study of the effects of light on the living organisms (Wolken, 1969). The research related to the
light and the circadian system of humans is covered in this section.
2.2.1 ‘Light as regulator of physiology and behavior’ (Lucas et.al, 2014).
Dr. Robert J. Lucas has explained the functionality of the eyes and brain in regards to light (Lucas et.al, 2014). The
paper described the process of light falling on the retina of the eye and a signal reaching to the brain. Light is
considered to be the regulator of physiology and behavior (Lucas et.al, 2014). Light falling on the eyes has lot to do
more than just vision and affects other activities in the human body (Lucas et.al, 2014). Light can be used for a
treatment in some of the disorders like depression, seasonal affective disorder, Alzheimer’s, circadian rhythm sleep
disorders, jet lag, bulimia nervosa, space flight, menstrual cycle related problems, non- seasonal depression, shift
work, and cognitive and fatigue problems related to senile dementia, chemotherapy and traumatic brain injury
(Wettergerg,1993) (Lam,1996) (Tuunainen,2004) (Lucas et.al,2014). Dr. Lucas also mentioned the concept of non-
visual effects of light. The paper explains the mechanism of the light falling on the pupil of a human eye and how it
reaches different parts of the eye leading to various functions other than just vision (Lucas et.al, 2014).
Each mechanism has a different spectral sensitivity, defined by the spectral efficiency by its photo pigment (Lucas
et.al, 2014). The bottom part (Figure 11) explains the methods of light calculation techniques. Radiometry and
photometry were the two methods used for light calculations. The ipRGCs (Intrinsically photosensitive retinal
ganglion cells) are the parts of the non-visual system of the retina and are not related with the vision of the person
(Lucas et.al, 2014). The further part of the research declares that these ipRGCs can detect light even when they were
not in contact with the retina. Spectral sensitivity of the non-visual system can be different from that of the visual
system (Lucas et.al, 2014). The research paper indicates that the circadian and other behavioral responses have a
different spectral sensitivity. It was discovered that the peak sensitivity for the non-visual system is around 480nm
whereas the predicted ones according to the light measuring calculations were 555nm (Lucas et.al, 2014). The
devices used for calculating the illuminance for the visual system, do not provide the necessary values required for
the non-visual system. The summary for the different mechanisms of spectral sensitivity were explained in the form
of a flowchart (Figure 11).
26

Figure 11 Mechanism of spectral sensitivity. (Information from- Lucas et al., 2014).
A relation should be derived between the visual and non-visual systems to calculate the lighting levels for both. The
peak sensitivities of both systems should have an equation that can be used to formulate a relationship between
them. Such ratios for determining the comfort light levels for non-visual system based on the light levels of visual
system were derived in WELL Building Standard guide. The light required for the comfortable vision is greater than
that required for the non-visual system (WELL, 2014). The recommendations offered in the research paper by Dr.
Lucas, were based on the research findings, could be further refined.
2.2.2 Non-visual lighting effects and solutions
Mariana Figueiro from Lighting Research Centre (LRC) had published a research paper on the non-visual lighting
effects and its impact on the health of humans. The main aim of the paper was to describe the photobiology related
to the circadian system. The second part of the paper explained the non-visual effects of lighting on the human body
(Figueiro, 2013). Vision for humans is a complex interaction between a source of light, objects and their surfaces,
the retina and the brain. The recent findings elaborate that light also has many more impacts on the brain than just
vision (Figueiro, 2013). To study the impacts on the circadian system due to lighting methods, is the rising topic in
the lighting field. The circadian rhythms are the repetition of the biological rhythms after a certain interval of time
(Circadian rhythms- Biological clock). In humans, the circadian rhythms are regulated by suprachiasmatic nuclei
(SCN) of the hypothalamus of the brain (Figueiro, 2013). The sleep-wake cycle of the body is regulated by the
circadian system depending on day and night cycle (Figueiro, 2013). The sleep driving force and the alerting force
were the terms described in the research paper by Mariana Figueiro to describe the sleep-wake cycle. Melatonin in
the body plays a vital role in the sleep and wake cycle (Mastin, 2013). Melatonin is produced by the pineal gland
whose primary function is to convey light and dark information to the body through the secretion of hormones
27

(Mastin, 2013). Core body temperature also follows a circadian pattern. It is high during the day, reaches its top in
the evening, and starts lowering in night. The lowest point is nearly 2 hours before, the person wakes up according
to the sleep wake cycle (Figueiro, 2013). Both the melatonin and core body temperatures are interrelated to each
other, but the circadian system depends highly on external factors. Light is one of the factors which can be used to
either set up a healthy circadian system or to destroy a circadian pattern (Figueiro, 2013). Light has its effects on
both the visual and the non-visual system (circadian system). The retina in the eye provides light information to both
the visual and the circadian system but both the systems functions differently (Figueiro, 2013). The comparison of
both the visual and non-visual systems is described below (Table 1).
Table 1 Comparison of effect of light on Visual and Circadian system (Information from- Figueiro, 2013).
Visual system Circadian system
 The amount of polychromatic white light that
activates the visual system is at least ‘two
orders of magnitude’ lesser than that required
for the circadian system.
 The amount of polychromatic white light that
activates the circadian system is at least ‘two
orders of magnitude’ greater than that required
for the visual system.
 Peak spectral sensitivity at 555nm.  Peak spectral sensitivity at 460nm.
 It does not depend on what time of the
day/night, the system is exposed to light.
 It depends on what time of the day/night, the
system is exposed to light.
 Responds to light stimulus in milliseconds.  Responds to light stimulus in some minutes.
 Sensitivity of visual system is the same during
the whole day.
 Sensitivity of circadian system changes
according to its exposure to light. For
example, the sensitivity of system reduces, if
exposed to higher amount of electric lighting
during day.

The research paper by Mariana Figueiro has described some of the effects on the circadian patterns due to
insufficient or over-lighted exposure. Light exposure is referred to as both the natural daylight and the electrical
light (Figueiro, 2013). Seasonal Affective Disorder (SAD) is a form of depression which changes from season to
season. It is mostly seen in winters when the days are short and the nights are long (Figueiro, 2013). During winter,
people are less exposed to daylight during the day time, causing the disturbance of the circadian patterns and
resulting in depression, change of moods, and less appetite (Figueiro, 2013). Exposure to available daylight during
the maximum hours of the day is the best solution for this disorder (Hagen & Richardson, 2016). Jet lagged people
changing time zones eventually change their circadian patterns. This is the temporary effect of the change in
circadian cycle (ILP, 2015). Exposure to more bright light on the arrival at westward locations and the exposure to
less bright light on arrival at the eastward locations are the provided solutions for jet-lag problems (Figueiro, 2013).
Delayed Sleep Phase Disorder (DSPD) is caused when people work late at nights or have night duties (Figueiro,
2013). Most of their time is exposed to the electrical bright light at night, that causes the change of their circadian
patterns affecting them to form disorders. The alternatives for this situation is exposing themselves to more bright
light in the mornings and less bright light in the evenings (Figueiro, 2013). Figueiro provides measures to avoid
excess or less lighting that can damage the daily circadian cycle. The measures like having ‘Daysimeter- D’ on their
hand or on the neck or using light goggles, to measure the light levels at the eye (Figueiro, 2013) (Figure 12).
28

Figure 12 Left figure- Photo of light goggle engineered by the Lighting research Centre. Blue, short wavelength
light has the greatest impact on the circadin system (Figueiro, 2013). Right figure- Photo of Daysimeter-D on the
wrist and as a pin (Figueiro, 2013).
These options of ‘Daysimeter-D’ or light goggles proved helpful for calculating the light at the eye level and for the
circadian system. These helped the user as a notification that the light levels reaching the eyes are not suitable for
the circadian system and solutions must be provided to adjust them (Figueiro, 2013). But the drawback with this
options were that it can be used only after setting up the whole lighting design in a room. The alternatives provided
by Mariana Figueiro works in the retrofitting of buildings and very less in the new construction projects. The
lighting designers cannot use this solution while designing. They need a source to verify their design results in terms
of the circadian system requirements. The solutions provided for the effects of the circadian system are a formwork
for general audience and not for a person (Figueiro, 2013). The amount of light exposure will change from person to
person considering their physique, age, body factors and many other factors (Figueiro, 2013). The solution provided
can be used as a general guideline. The lighting for a room depends upon the daylight available in that room. The
electrical lighting must be programmed to change from time to time according to the conditions of the room and
should not be kept constant for the whole time (Brodrick, 2016). Attention should be given to IES (Illuminating
Engineering Society) recommendations available for that room and to see whether they satisfy the results needed for
the circadian system.
2.3 Standards
Various standards are available in the field of lighting and in healthcare (circadian system). This section helped in
figuring out the standards that are supposed to be referred and followed in this research. The ‘WELL Building
Standard’ is the recent guiding standard which have the concept of circadian lighting as one of its agenda.
2.3.1 WELL Building Standards
The ‘Well Building Standard’ was developed by Delos Living LLC and is managed by the International WELL
Building Institute (IWBI). The WELL Building Standard is third party certified by IWBI, in collaboration with
Green Building Certification Institute (GBCI) (WELL, 2014). The main purpose of this certification is to look for the
wellbeing and the comfort level of the people using the building and to grade the strategies and the designs imposed
into the structure according to its comfort level for human health (WELL, 2014). Its main focus is on enhancing the
health of the occupants through different beneficial strategies, useful programs and advanced technologies in the
built environment (WELL, 2014). The main focusing points of the ‘WELL Building Standard guide’ are as follows:
1. This is the first standard of its kind that focuses attention solely on the health and wellness of building
occupants (WELL, 2014).
2. WELL identifies 102 performance metrics, design strategies, and procedures that can be implemented
by the owners, designers, engineers, contractors, users and operators of a building (WELL, 2014).
3. WELL is based on a thorough review of the existing research on the effects of indoor spaces on
individuals, and has been advanced through a comprehensive peer review (WELL, 2014).
29

4. In order to achieve the requirements of the WELL Building Standard, the space must undergo a process
that includes an onsite assessment and performance testing by a third party (WELL, 2014).

Figure 13 WELL Building standard. (WELL, 2014).
The aim of the WELL Building Standard is to look for the best practices in design for the health and well being of
occupants. WELL Certified spaces and WELL Compliant core and shell developments help in increasing and
improving the fitness, sleep-wake patterns, moods, appetite and the work performance of the people using it (WELL,
2014). Circadian lighting plays a very important role in the section of lighting under WELL Building Standard.
Providing the right amount of light so that it should not adversely affect the people using that space is the main
concern of these standards (WELL, 2014).
The WELL Building Standard has formulated ratios which helps the lighting designers to find the value for the EML
(equivalent melanopic lux) for a particular room. Based on the colour temperatures and the type of fixtures, the
values for the EML can be calculated (WELL, 2014). The WELL Building Standard has provided a positive point by
the introduction of such ratios. The WELL building standard does not provide any framework about the type of
fixture to be used, the amount of light to be exposed, and the better colour temperatures to be used for the circadian
lighting (WELL, 2014). It does not speak in regards of any particular type of space like commercial, residential,
industrial or any other. The lighting for each space is different and the users of each place are also different. Hence,
the circadian values will change from place to place depending on the type of space (Figueiro, 2008). WELL
Building standard depicts the values in its guide as general values and not for a particular space (WELL, 2014). The
thesis will help to get the right amount of values for the commercial working spaces and it can be part of the refined
WELL building Standard guide. This will help the lighting designers to figure out the better type of fixtures for their
designs. This research fulfills the gap of comparison and analysis of different types of light sources. This thesis will
help to add some informative values to the WELL standard guide to explain the aspects of circadian lighting widely.
2.4 Circadian lighting
Many researchers are developing lighting methods and strategies for the enhancement of circadian system of
humans. The practical experiments of such strategies are mostly carried in commercial spaces and healthcare centers
(Rea M., 2000) (Figueiro et.al, 2016). Some of the case studies of such experiments are explained below.
2.4.1 Designing with circadian stimulus
Mariana G. Figueiro, Kassandra Gonzales and David Pedler are the researches at the Lighting Research Centre (LRC),
Rensselaer Polytechnic Institute. The research paper published by them in October 2016, introduced the new terms
for the calculation of circadian light and the strategies that could be used by lighting designers while designing. The
article explained the concept of non-visual effects of light, that affects the circadian system and alertness. The 24 hour
dark and light cycle is one of the most important functions of the circadian system and its disturbance can lead to
cardiovascular disease, diabetes and even some forms of cancers (Figueiro et.al, 2016). These consequences make it
one of the important topic that needs to be included during lighting design.
The LRC has proposed a new metric for circadian lighting by name ‘Circadian Stimulus (CS).’ The CS can be
determined by first calculating the spectral irradiance distribution of light at the cornea of eye (Figueiro et.al, 2016).
30

This spectral irradiance helps to calculate the circadian light(CLA). Circadian light is equal to the spectral sensitivity
of the human circadian system, and CS is the efficiency of the spectral irradiance from the beginning (CS=0.1) to the
end (CS=0.7) (Figueiro et.al, 2016). For example, exposure to CS of 0.3 or greater at the eye for at least 1 hour in
the morning will help in balancing the wake and sleep cycle and also the improve mood and behavior (Figueiro
et.al, 2016). Some of the considerations made by the LRC are as follows –
 The light with higher colour temperature will not always provide the greater CS. Spectral power density
(SPD) of light is the deciding factor for the CS (Figueiro et.al, 2016).
 The ratio between the vertical illuminance and the horizontal illuminance is important. The experiments
carried out by LRC propose for the direct-indirect lighting methods with the best ratio of horizontal
illuminance to vertical illuminance (Figueiro et.al, 2016).
 The light with lower light levels will generally generate lower CS. But SPD with more short wavelengths
can change the situation. For the space with light level restrictions, in order to meet the CS, lights with more
short wavelengths are recommended (Figueiro et.al, 2016).
 Daylight is the main factor for balancing the circadian system. Sufficient amounts of daylight in the morning
should be accessed for the better sleep and moods. Exposure to daylight for about one hour in the morning is
the best proposed solution for the maintenance of circadian system (Figueiro et.al, 2016).
 LEDs can be used to adjust the CS in the places which are site restricted and do not have sufficient exposure
to sunlight. The light from the source is adjusted for sufficient exposure to the occupant (Figueiro et.al,
2016).
The color temperature and the output percentage of the light used for the experimental space were represented in
graphical form (Figure 14). It depicts the change in CS at several times of the day because of the change in the
illuminance levels of the space. LRC proposed this chart after experimenting for an office area and explained, that the
color temperatures and illuminance levels were adjusted to reach the desired CS value (Figueiro et.al, 2016). The
required CS of 0.3 is kept constant for a longer span of the day, mostly during the morning hours. The CS value is
lowered during the evening when the occupants should be exposed to less amount of light levels (Figueiro et.al, 2016).
The colour temperatures along with the horizontal and vertical illuminance values were changed according to
requirements of the occupants (Figure 14).
31

Figure 14 Time Scheduled for experimental space. The colour temperatures and the light output levels changes
according to the time. (Figueiro, Gonzales & Pedler, Oct. 2016).
2.4.2 Designing with tunable lighting- Case studies of Health care centers.
Practical experiments were carried out regarding the effects of lighting on the circadian system (Brodrick, 2016)
(Figueiro et.al, 2016) (Lucas et.al, 2014). Most of the experiments are in the healthcare field. It is indeed important
that the lighting in the healthcare centers should be suitable for the patients to relax and to be used against their
sickness (Rea M., 2000). The living inpatient care facilities rank fourth in energy use in the United States of
America (Brodrick, 2016). Lighting a space was just for the purpose of vision before, but through the recent findings
of growing importance of the non-visual effects on human body there is a need for the upgradation of lighting
methods in the healthcare centers (Figueiro, 2013). The quality of vision of a person decreases as the age increases.
Hence, the light that falls on the retina of the eye is not received by the brain for the vision (Rea M., 2000).
Therefore, the older people need more amount of light for good quality vision. In older eyes, the size of the pupil
also reduces, resulting in less light reaching to the back of the eye and more scattering in the eye (Rea M., 2000).
The statistics explains that for the same amount of light, a 60 year old receives only about 30-40% as much light at
the retina as a 20 year old (Rea M., 2000). The unnecessary light for older people can easily disrupt their circadian
system leading them to sleepless nights, depression, mood change, less concentration, less alertness in mornings,
dementia, insomnia and Alzheimer (Brodrick,2016).
The U.S Department of Energy (DOE) Gateway program participated in a trial installation of tunable white LED
lighting systems at Sacramento’s (California) ACC Care center, which is a rehabilitation and nursing care place for
the senior citizens (Brodrick,2016). The project was coordinated by Sacramento Municipal Utility District (SMUD)
(Brodrick,2016). The purpose of the experiment was to change the type of fixtures from fluorescent to white LEDs
in order to save energy, to increase the quality of vision, to control the colour temperatures throughout the day in
accordance with the non-visual effects on the circadian system and to determine the effects of all these changes in
the care center (Brodrick, 2016). The people in the health care were the patients of Alzheimer’s disease. The spaces
selected for the experiment were the corridors, nurse stations, family rooms, administrative office and resident’s
rooms. The fluorescent lights in the corridors were substituted with the tunable LED with colour temperature range
of 2700-6500k (Brodrick, 2016). The corridor lighting was designed to change the colour temperatures and light
32

output, according to the different times of the day. The scheduled programmed was explained below (Figure 15)
(Brodrick,2016)-
 7am – 2pm:6500 k @ 66% output
 2pm- 6pm: 4000k @ 66% output
 6pm- 7am: 2700k @ 20% output

Figure 15 The corridor’s tunable lighting, shown at the morning (6500k at 66% output), afternoon (4000k at 66%
output) and evening (2700k at 20% output) setting (Brodrick, Oct. 2016).
The change in the colour temperatures and light output was automatically designed through a programmed script
(Brodrick,2016). The same changes were made in the nurse station, family room and the administrative rooms. Only
the changes in colour temperatures and light outputs were controlled manually in these rooms (Brodrick,2016). In the
patient’s rooms, ambient cove lighting was provided with automatic and the manual dim control. The scheduled set
for an automatic programmed script for patient’s room (Brodrick,2016)-
 7 am – 2pm :6000 k
 2pm- 6pm: 4100k
 6pm- 7am: 2700k
 Night light option- 2400k
Task lighting was provided to each patient for personal use with a fixed color temperature of 3500k. Bathroom
lighting was provided with fixed color temperature 3000k and 90 CRI (colour rendering index) with full dimmable
facility (Brodrick,2016). The main purpose of the bathroom lighting was to provide proper vision to the patients
while they are in the bathroom (Brodrick,2016). For night safety, night lighting in the form of recessed lighting
fixtures were provided with motion sensors. It gets activated when patient moves out of the bed or when a nurse
enters the room. The main aim of night lighting was to provide proper vision to the patients and help them to
navigate safely to the bathroom (Brodrick, 2016).
The annual energy used by the fluorescent bulbs was 3,641kWh (Brodrick,2016). After replacing the fluorescent
with the LEDs, the energy consumption was down to 1,182kWh, a 68% reduction relative to fluorescent (Brodrick,
2016). A good amount of energy saving was benefited by the experiment. The project team had made no attempt to
measure the actual biological effect of lighting on the patients of the care center and hence the different levels of
melanopic illuminance were not known (Brodrick,2016). The nurses noticed the behavior changes in the patients
staying in the patient’s room. In three months after the installation for LEDs, the patients staying in the experiment
rooms had reduced yelling, agitation, and crying by 41% as compared to their previous behavior (Brodrick, 2016).
33

All the patients in the experiment rooms started consistently sleeping throughout the night ever since the installation
of LEDs. The accidents of people, falling while navigating to bathrooms has also reduced. Five falls was noted in
three months before installation of LEDs and only three falls were registered within 5 months after installation of
LEDs (Brodrick,2016). The circulation of the people in the corridors had increased because of the changing light
levels. One of the failure in the replacement of LEDs were that the light levels in some of the spaces were unable to
meet the IES recommendations (Brodrick, 2016).
Betty Irene Moore School of Nursing at UC Davis has adopted the lighting methods required for the benefits of
patients for vision and non-vision purposes. Three key elements of emerging healthcare lighting design are circadian
wellness, dark adaptation and a high fidelity visual environment for patient care (Siminovitch and Graeber 2016).
The healthcare has adopted the practice of tunable light fixtures for the common rooms. During the day, the patients
have the fixtures with high color temperatures and during the night with low colour temperatures (Siminovitch and
Graeber 2016). The red amber light LEDs with a relatively low intensity was used as a navigator for patients during
the nights (Siminovitch and Graeber 2016). The circadian lighting design strategies adopted by Betty Irene Moore
School of Nursing at UC Davis were combined to show in a diagrammatic form (Figure 16).

Figure 16 The Circadian and lighting quality deisgn strategies applied to a healthcare patient room. (Siminovitch &
Graeber, August 2016).
The city of Davis has also taken measures on urban level lighting. The city has substituted the fluorescent street lights
with the new LED lights for some part of the city. The effects of these substitutions were recorded by the positive
reviews of the people living in the neighborhoods (Siminovitch and Graeber 2016).
The conclusion of the experiment at ACC care center was based only on the changes noticed by the nurses at the
center. No biological measurements showing the effects of the light on the melanopsin in the patient’s body were
recorded (Brodrick, 2016). The same condition was of the UC Davis nursing school and the UC Davis street lighting
(Siminovitch and Graeber 2016. The change in the fixture from fluorescent to LEDs has led into the energy savings
in the ACC care center (Brodrick, 2016). The common observations in the above experiments were that the LEDs
are proving useful in context of the energy savings and for the circadian system, but no practical data was recorded
34

to prove it. The experiments mentioned above are of the healthcare centers, and it’s likely to be seen that the
healthcare is trying to formulate some guidelines or research in the field of light and the circadian system (Brodrick,
2016). Data was collected from the methodology of the research, which was used as firm support for the
conclusions. Various such practical experiments are carried out all over the world (Brodrick, 2016) (Figueiro et.al,
2016) (Lucas et.al, 2014) regarding the topic of circadian system and hence this research is like taking a step ahead
in this topic. The practical experiments for commercial offices can be the future step of this thesis. The change in
color temperatures for the same space can be the positive point used for the research (Brodrick, 2016) (Siminovitch
and Graeber 2016), but the points of spectrum, light intensity and the duration of exposure should not be neglected
while designing.
2.5 Simulations
The topic of circadian lighting has shown up in the computational world too. As the lighting designers are taking the
topic of circadian lighting into account in their design methods, they need software programs that will help them in
designing and determining the values of circadian effects (Figueiro et.al, 2016). Some software programs are being
developed mainly just for calculating the effect of light on the circadian system, and there are other plugins which
were designed to work for a portion of this topic (Inanici et.al, 2015). Very few lighting designers are aware of
circadian lighting, and even fewer use this concept in their designing. Hence, plugin development is rare. The
software programs will start developing faster when a large amount of lighting designers will start showing interest
in this topic. Due to the interest of lighting designers, the computational field will also involve themselves deeply in
this topic. This cycle will help the circadian lighting to become one of the important topics for lighting designers.
Some companies have started developing plugins for circadian lighting. The details of these plugins are described
below.
2.5.1 Rhino and Honeybee + Ladybug
Rhino is a commercial 3D computer graphics and computer aided design (CAD) application software developed by
Robert McNeel & Associates (Robert McNeel & Associates). Rhino is based on NURBS (Non-uniform rational basis
spline) mathematical model. The function of NURBS is to produce and generate surfaces and curves in the software
program (Robert McNeel & Associates). Rhino is used in many applications like 3D modelling, CAD, Architectural
design and many more (Robert McNeel & Associates). Rhino helps in forming any desired shape with accuracy. A
visual scripting language is developed by Rhino which is used as a plugin (Tedeschi Arturo, 2011). It is known as
Grasshopper. Grasshopper plugin is a visual programming language developed by David Rutten at Robert McNeel
and associates (Tedeschi Arturo, 2011). The first version of Grasshopper was released in September 2007 (Rutten
David, 2013). The programs in this were created by uniting the functions of various components into each other. The
primary purpose of Grasshopper is to build generative algorithms (Loomis Mark, 2010). Grasshopper is also used to
create 3d modeling and the advance version is used in the parametric modeling for structures, architecture, lighting
analysis and building energy consumption (Echarri,V., 2016).
Ladybug and honeybee are the two other plugins for the Grasshopper 3D. They were developed by Mostapha
Sadeghipour Roudasri (Mostapha, 2016). Ladybug is an environmental plugin for Grasshopper 3D that helps the
architects and the engineers for sustainable architecture design. Ladybug helps in importing ‘Eneryplus weather’
(.EPW) files into Grasshopper and helps in creating different 3D models (Mostapha,2016). Honeybee connects
Grasshopper 3D to Energy plus, Daysim, Radiance and Openstudio for building energy and daylighting simulations
(Mostapha, 2016). These plugins work along with Rhino and Grasshopper (Mostapha,2016). All these software
programs and plugins are useful in demonstrating the analysis of a specific lighting design to the lighting designers
and play an important role in this thesis. These are used as a source tool for the functioning of the desired
methodology for making the output successful. Rhino is used for making of the model. Ladybug and Honeybee are
used for the analysis part regarding the electric lighting for the model. Grasshopper script is used as a connection to
link, the Rhino model to Ladybug and Honeybee.
2.5.2 LARK
Some of the plugins for the Rhino model are made specially for circadian lighting. One of those plugin is known as
‘LARK’. LARK is used as a plugin to grasshopper that helps the lighting designers to determine the circadian effect
of daylight on a certain space (Inanici et.al, 2015). LARK Spectral Lighting is the product with combined efforts of
35

University of Washington and ZGF Architects LLP (Inanici et.al, 2015). LARK is mainly related with the
daylighting and it provides the options to the users to choose the color of skies, the climate, the period of the year,
glazing and building materials (Inanici et.al, 2015). The outputs of the LARK are in the form of the luminance
renderings and irradiance data. It helps in finding out the circadian metrics for the design with respect to daylight
(Inanici et.al, 2015). LARK has restrictions of using the circadian metrics just for daylighting and the analysis of the
circadian metrics for the electric lighting cannot be achieved (Inanici et.al, 2015).

Figure 17 Software programs and plugins used in the research field of circadian lighting. 1.LARK, 2. RHINO,
3.GRASSHOPPER and 4. LADYBUG + HONEYBEE.
2.5.3 Circadian Stimulus calculator
The ‘Circadian Stimulus calculator’ is used to calculate the circadian stimulus of any combination of source type
and light level in photopic lux (LRC, 2016). This tool is helpful to the lighting designers to select the type of light
source and to decide the illuminance level that will benefit the circadian system of the occupants. The calculator is
based on the concept of converting the light falling on the retina of the human eye to neural signals for the circadian
system (LRC, 2016). The input values for this calculator is the type of light source and the visual lux. These will
give out the circadian lux for the room. The time span considered is one hour of exposure to the selected light source
(LRC, 2016). The ‘Circadian Stimulus calculator’ shows the graph with the relative SPD on its screen (Figure 18).
36

Figure 18 Circadian Stimulus Calculator designed by Lighting Research Centre to calculate the circadian stimulus
of light source (LRC, 2016).
2.5.4 Circadian daylight in practice
The circadian lighting concept should be included in the design, right at the beginning stage. Computational
workflows should be used to determine the effect of designed lighting on the occupants (Inanici et.al, 2015). This
will help the lighting designers to provide changes right at the early stage. People spend a lot of time in buildings,
accessed to electric lighting as all the spaces in the building are not exposed to daylight (Hagen & Richardson,
2016). LEDs are used as the source of light in electric lighting to make the building energy efficient (Savov, 2017).
To use less amount of energy is the principle of green architecture. Daylight does not require energy input and is
available in large quantity. If daylight is made available within the building through its design, the building will be
more self-sufficient (Houser et.al, 2012). Daylight is also beneficial for the human circadian system (Hagen &
Richardson, 2016). It is considered better than the electric lighting according to the WELL standards.
Emilie Hagen and Henry Richardson are the two researches who worked on the circadian daylight practices and
have determined two simulation methods required for calculating the daylight, comfortable for human circadian
system in a given office space (Hagen and Richardson, 2016). These two methods are compared to determine the
easy and the better method. They believe that these methods should be included in the initial stages of design, so that
the circadian lighting values obtained from these methods can be utilized. Equivalent Melanopic Lux (EML) metric
was used in the design. The limitation for the study during this research paper was that the other variables of
daylight like creating glare and thermal comfort were not considered during the process. (Hagen and Richardson,
2016).
Method 1- Transformed horizontal illuminance
The WELL Building Standard guidelines described that the lux level of circadian lighting should be above 250 lux
(WELL, 2014). Considering the WELL appendix Table L1 for daylight, the lux level should be 227 lux. The vertical
illuminance at eye level should be half of that of the horizontal illuminance level, based on the calculation method
described in ‘Conceptual design metrics for daylight’ (Leslie et al., 2011). Based on the above calculation, the
horizontal illuminance level should be 466 lux for at least four hours of the day. A typical office was created in
DIVA for Rhino with grid points placed on the horizontal floorplate and annual daylight analysis was conducted
(Hagen and Richardson, 2016). Initially, each grid point was having the daylight illuminance using Radiance in the
37

software program. The illuminance was for every hour of the year (Hagen and Richardson, 2016). This was
followed by the python script to determine which of the points on the grid satisfy the requirement of the circadian
daylight for minimum hours of the day (Hagen and Richardson, 2016). A person should be exposed to daylight for
at least 4 hours in the morning to enhance and maintain the circadian system (WELL, 2014). This time span was
considered as the minimum hours during the analysis process. The different circadian daylight in the room was
depicted by using different colours (Figure 19, left).
Method 2- Multi directional vertical illuminance
Horizontal illuminance was not used to calculate vertical illuminance in this method. Eight orientations were used to
find the vertical illuminance on the floor plate for every hour of the year through software programs like Rhino,
Honeybee and Grasshopper (Hagen and Richardson, 2016). The objective was to determine that for how many days
in the year, each grid point in any of the orientations satisfy the required WELL Building Standards (Hagen and
Richardson, 2016). The grid points fulfilling the required values were depicted using one color and was the portion
was made solid only for the orientations satisfying the requirement (Figure 19, right).

Figure 19 Left figure- Method 1 circadian daylight results. The areas in the red are projected to meet the threshold
of at least 4 hours per day every day of the year. Right figure- Method 2 circadian daylight results. A point with a
view facing any of the yellow orientations in each location meets the WELL circadian threshold (Hagen &
Richardson, 2016).
Based on the results from the simulations, the two methods were compared to each other in order to find the better
among them (Table 2) (Figure 20).
Table 2 Comparative analysis of both the simulation methods for circadian daylight analysis. (Hagen and
Richardson, 2016).
Method 1 Method 2
 Appropriate for quick circadian study  Appropriate for detailed circadian study.
 Very less accuracy in reflecting the calculated
result of circadian light for the occupants.
 Eight times more accurate than method 1 and
reflect the amount of circadian light available
for occupants.
 Can be used in the initial stages of design  Can be used for making detailed decisions.
 Appropriate for comparison of different
design options.
 Appropriate for finalizing floor plan layout,
zoning and workstation orientation for
occupants.

38

Figure 20 Results showing direct details comparison of the both simulation methods. Left figure- Method 1 results.
Right figure- Method 2 results. (Hagen and Richardson, 2016).
Method 2 is considered to be more accurate and useful for making fine decisions for the design layouts. Such kinds
of circadian study before the finalization of designs will help the design to develop and explore. This will benefit
human health. Hagen and Richardson are working in the field of circadian daylight and trying out various strategies
for fine circadian daylight values required for the designs.
2.6 Summary
The concept of circadian lighting is very vast and a lot of research was conducted in the past and still going on in the
present. Some of the points from the chapter 2 that are to be focused on are as follows:
 The research in the field of photobiology focuses on the functioning of both the visual and non- visual systems
in the brain. Hence, a relation should be derived between the visual and non-visual systems by formulating
equations in order to calculate the dependency of both on one another.

 The tools created by Marian Figueiro like ‘Daysimeter-D’ are more useful in the finding out the values of
light levels in order to predict the circadian effect on the body (Figueiro, 2013). But these tools cannot be
used in the initial stage of design when there is no light for the ‘Daysimeter-D’ to measure.

 The standards and guidelines that are formulated by WELL Building Standards are used as general
framework for the concept of circadian lighting. There is no specification for a particular type of space,
particular age group people, particular health conditions of people and such factors.

 Different design strategies implied by researchers by experimenting in various places in order to predict the
different systems of circadian lighting.

 Facilities provided by the computational world by setting up various software programs and plugins are
assisting lighting designers in the field of circadian lighting. A new approach for the creation of an easy
accessible tool for the lighting designers can be initiated through this research.

39

CHAPTER 3
3 METHODOLOGY
One objective of the thesis is to design a system that can evaluate a lighting design in terms of its effect on the
circadian system. This chapter explains in detail the methodology used to get the values of EML (Equivalent
Melanopic Lux) for three different types of lighting designs. The methodology is an important step for the whole
research as it defines the process that was conducted to get the data and values for the next steps of research (Figure
21).

Figure 21 Workflow for the methodology of the thesis.
First a test model is created that can be used to run parametric lighting simulations. The model was attached with the
Grasshopper script to calculate the values for the horizontal illuminance at the desk surface, vertical illuminance at
the eye level, and the EML (Equivalent Melanopic Lux) at the eye point. Three different lighting designs were
added to the model individually for running simulations. After determining the photopic lux, the next step was to
refer the ‘Circadian ratio chart’ from WELL Building Standard guidebook to determine the value of EML. The
output at this stage was the horizontal illuminance at the desk surface, vertical illuminance at the eye level and the
EML at the eye. Data for the three lighting designs were collected. The collected data is compared to each other
based on two components- LPD (Light Power Density) of the room and the EML for the eye point. The LPD and
EML for the designs are sketched in the form of graphs, for better comparison. The process helped in comparing
three lighting designs and to verify their efficiency in terms of their effects on the circadian system of the occupants.
It also helped in explaining the ‘Healthy and Energy Efficient’ zone required for a particular design in accordance
with LPD and EML. By comparing the four different fixture types, a range of difference in the EML values for each
type is noted for three different lighting designs.
40

Chapter 3 is divided into two main parts. The first part is the detailed description about the methodology, and the
second part is the detailed explanation of three different lighting design methods and the four different types of light
sources used in the test model for simulations. The summary of the two steps are as follows:
 First part- It consists of test model, Grasshopper script, and all the simulations.
 Second part- It consists of three different lighting test cases and four different light sources.
The first part of this chapter deals with the main working methodology section and was the most important part of
the thesis. This part depicts the process required for the outputs which were used as the base for the next chapters. In
this step, the illuminance values and EML values were calculated for a particular test geometry using different
lighting design configurations. The detailed description of the test geometry and the used software programs are
explained in the following section.
3.1 Test geometry
A model was created that could be used to run simulations and to get data. A square box was created initially to get
a rough sketch of the various grids which was later used in the final test geometry model. The grids here define the
positions of various vectors which were then connected with the Grasshopper script to calculate various values
during the simulations.
The first grid with the ‘Light Fixtures Points’, is the topmost grid in the model. The grid was linked with the ceiling
surface. The ceiling was used as the base of the grid and all the functions were carried out in relation with the
ceiling, like the offset from the ceiling and the size of the grid. This grid was designed specifically for the lighting
fixtures used in the model. The points in the grid depict the lighting fixtures in the model. The IES files (explained
below) of different lighting fixtures were further connected in the Grasshopper script, and the topmost grid points
functions as the fixtures for the room. The vectors used in this grid were facing in downward direction, depicting
that the light was directed towards the floor surface of the model. The gird points depend on the number of fixtures
to be used in the model and can be changed using the Grasshopper script.
The bottom grid, ‘Light Sensor Points’ was the grid that depicts the surface illuminance measurement points. The
grid was linked with the floor surface. The floor was used as the base of this grid, and all the functions were carried
out in relation with the floor surface, like the distance of the grid from the floor and the size of the grid. This grid
was used to calculate the surface illuminance in the room or for a particular point in the simulations. The vectors of
these bottom grid were pointing in the upward direction to calculate the horizontal illuminance at the desk surface in
the test room. The number of grid points depend upon the user and can be changed in the Grasshopper script when
required.
The single point in the centre of the top and bottom grid is ‘Single View Point.’ It depicts the position of human eye
in the Test lab. The point is linked with the floor surface. The floor is used as the base of this point and all the
functions were carried out in relation with the floor surface. The distance of the eye point is calculated from the floor
surface. To understand the effect of the light on the circadian system of humans, it was required to measure the light
at the human eye level (Figuerio, 2016). The height of the single point was considered to be at the eye position of a
sitting human being in a chair. The vector was pointing in the front direction, depicting that the human was looking
in the front direction, neither towards the light fixtures on ceiling nor towards the floor. It was assumed to be the
position of a human being sitting and working in a commercial hub in front of the computer. This point was used to
measure the vertical illuminance at the eye level and the EML at a human eye. The position of this point was moved
according to the user. These three grids were the basics of the test model and the data for the research depends on
the outputs of these grids. These three grids were created finally in the test geometry (Figure. 22).
41

Figure 22 Test Geometry depicting three different grids.
3.2 What is an IES file?
A file with the IES file extension is an IES Photometric file that stands for Illuminating Engineering Society. IES
files contain data on light for architectural programs that can simulate light. They hold information about how light
will appear, like on roads or in buildings (Fisher, 2016). The IES files have the extension of ‘.IES.’
The Illuminating Engineering Society of North America (IESNA) has introduced the concept of IES files by
creating the standard LM-63-86, ‘IES Recommended Standard File Format for Electronic Transfer of Photometric
Data’, in the year 1986 (Talking Photometry: Understanding Photometric Data Formats, n.d). It has been updated in
the year 1995 and again in 2003 (Talking Photometry: Understanding Photometric Data Formats, n.d). It is the
most common format used in the North America (Talking Photometry: Understanding Photometric Data Formats,
n.d). IES file also known as photometric data file. In simple words, the file that represents the photometric data of
the light source is the IES file (Talking Photometry: Understanding Photometric Data Formats, n.d). Two
photometric units are considered in the file, total luminous flux and luminous intensity (Talking Photometry:
Understanding Photometric Data Formats, n.d). Total luminous flux is the total amount of light emitted from a light
source, corrected for the spectral response of the human eye to light. It is measured in lumens. The luminous
intensity defines the amount of lumens in a given direction, per solid angle. This is measured in lumens per candela
(Talking Photometry: Understanding Photometric Data Formats, n.d). The typical photometric file contains
luminous intensity values for 855 different angles (Talking Photometry: Understanding Photometric Data Formats,
n.d). It also mentions the wattage for the particular file.
The luminous intensity data in the IES files are useful for lighting designers as it describes the total light output from
the fixture and the angular spread of the light (Talking Photometry: Understanding Photometric Data Formats, n.d).
In the specification sheets of the light fixtures, the angular spread of the light is typically described by two forms of
diagrams- polar diagrams or cone diagrams (Talking Photometry: Understanding Photometric Data Formats, n.d).
The image (Middle – figure 23) is an example of a polar intensity diagram. The shape marked from the center point
on the angles of the diagram is the light output showing in the downward direction (Ransen, 2017). The width of the
diagram shows the light spread, and it can be measured by the marked angles on the diagram (Ransen, 2017). The
example of the cone illuminance diagram is mentioned bellow (Right side- Figure 23). It shows the beam angle at
different distances and also the intensity of light at different intervals (Cooper lighting design guide, 2009). This all
information is included in the IES files.
42

Figure 23 Left Figure - Angular spread of the luminous intensity from a fixture (Talking Photometry:
Understanding Photometric Data Formats,2017). Middle figure- Example of Polar intensity diagram (Ransen, 2017).
Right figure- Example of a cone intensity diagram (Cooper lighting design guide, 2009).
The example of an IES file in the text format is presented below. It describes the name of the manufacturer, the
wattages, the lumen levels and the spread of the light at various angles. Such IES files are used to install fixtures in
the Grasshopper script as mentioned above (Figure 24).
43

Figure 24 Example of an IES file in the text format used in the Grasshopper script.
3.3 Test lab
The U.S. Department of Energy’s FLEXLAB is situated at Berkeley Lab (Figure 25). The main use of the
FLEXLAB is to test individual or combined systems before the actual construction (McNeil et.al., 2014). It allows
the FLEXLAB users to test the performance of a specific building configuration. The results can be known right
before the construction, that helps in modifying the particular systems. The results also help to understand the real
performance of the building configuration rather than just achieving it from the simulations alone (McNeil et.al.,
2014). The FLEXLAB helps in the testing of various configurations like that of the daylighting, electrical lighting
and HVAC systems (Figure 25).

44

Figure 25 FLEX LAB, Berkeley (McNeil et al., Dec. 2014).
One of the test cells in the FLEXLAB was considered for this research project. No actual performance of the test
cell was tested, only the setup of the test cell was used for creating the test model in the software program for
simulations. The selected test cell was 20 feet wide by 30 feet deep by 13 feet high (McNeil et.al., 2014). None of
the windows and doors of the FLEXLAB were considered in the test model. The test model was furnished same as
that of the FLEXLAB. The furniture was set in such a way that it depicts the test model as a commercial office. The
plan and the view of the FLEXLAB shows that it was tried to give the look of a commercial office (Figure 26).
(McNeil et.al., 2014).

Figure 26 FLEX LAB- Inside view, Berkeley ( McNeil et al., Dec. 2014).
3.4 Creating model
FLEX lab was considered as the reference model for this research project. A replica of such model was created as a
testing model in the software program, to run simulations for lighting designs, and to study the effect of circadian
system. The model was created with identical dimensions and furniture as that of FLEX lab in the Rhino (Andrew
et.al, 2014). The furniture and tables were for the purpose of considering it as a commercial place to study its
results.

45

The test model in Rhino software was linked along with the plugin, by name, Grasshopper and three grids had been
formed. The three grids, as above mentioned in this chapter (Section 1.1) were created inside the model for
collecting the required data. The top grid was for the fixtures which emit light, the bottom grid at the desk level to
calculate the horizontal illuminance level at the desk surface, and the third grid which consists of one point is placed
at an eye level. The position of the third point (Figure 28 - Elevation) indicates that a human is sitting in a chair and
is looking in the front direction. The grid point indicates the human eye. This point was used to calculate the light
levels which reach the eye from the above light sources. This test model was the base for simulations. This model is
a replica of the commercial office, and hence the results and analysis from the collected data can be used to
formulate conclusions just for the commercial offices in the outside world. The plan, elevation and the view for the
Test lab in Rhino were presented for easy understanding (Figure 27 and 28).

Figure 27 Test lab plan with Gridpoints.

Figure 28 Elevation & 3D view of the Test lab along with its gridpoints and furniture.
3.5 Grasshopper script-
Grasshopper was used as a plugin in Rhino software. A plugin is a component that helps the existing software
program to function with the new features which the software program cannot provide, making it more useful (Plug-
in Computing, n.d). It helps the existing software program to function with the new features which the software
program cannot provide, making it more useful. Rhino created the test model of FLEX lab and then Grasshopper
script was added as a plugin to that Rhino model. It facilitates the test model to carry out the simulations for electric
lighting. Along with Grasshopper, the other plugins used were Honeybee and Ladybug. These were used to calculate
the light levels in the room. The three grids in the model was formatted with the help of Grasshopper script.
Many sections in the grasshopper script were grouped together. These groups in the script depicts that each section
is responsible for some working section in the test model. The purpose behind grouping the sections in the script
was that when a particular element in the test model needs to be modified, that particular section in the script can be
easily located and changed without confusions. Further in the thesis, modifications were made in some of the groups
46

for each and every simulation. During those times, this idea of forming the groups in Grasshopper made the work
easier (Figure 29).

Figure 29 Grasshopper script used in the workflow.
The grasshopper script is a combination of various small scripts in it (Figure 29). The Rhino model links with the
‘Model Specification’ script of Grasshopper. It is then connected to ‘Top grid script’ and the “Bottom grid script’.
All these scripts were connected again to the main ‘Simulation script’ where all the simulation takes place. Then it is
finally connected to the ‘Outputs’ required for the research. The flowchart of the various scripts and its interrelation
with each other helps in understanding the full grasshopper script (Figure 30).

Figure 30 Flowchart of the full grasshopper script, showing the links between the small scripts.
3.5.1 ‘Model specification’ and ‘Bottom grid and Eyepoint’ script.
Each section of the Grasshopper script was explained in detail to give a brief description of its working in section
3.5. The image (Figure 31) on the left was of the group by name ‘Model Specification’. This group deals with the
specifications of the created model. It also links the model to the Grasshopper script. The model was linked with the
script by various forms like the walls, floor and ceiling. The walls were linked together with the specification like
the reflectance for RGB. The same specification was considered for the floor and ceiling. The RGB reflectance was
47

considered to be 0.6. The properties assigned to the surfaces were material, reflectivity, transitivity, absorptivity,
insulation details and door-window specifications. This helped in creating a proper model with specifications as per
the Test lab and appropriately link the model in Rhino and Grasshopper. The criteria chosen for the specifications
was kept constant throughout the entire thesis. The scope of the thesis regarding the specification of model was
limited to the materials used in the FLEX lab. But when a different model is to be linked in future, changing the
specifications will help to connect the model easily and within no time. The zoom in views of the ‘Model
specification’ script and ‘Bottom grid and eyepoint’ script is presented below (Figure 31).
The script (Right Figure 31), describes one of the grids in the model. It manages the bottom grid, the grid which was
at the desk level (work level) and was used to calculate the horizontal illuminance at the desk surface level.
Illuminance is the total luminous flux incident on a surface, per unit area. It is the measure of how much the incident
light illuminates the surface (Houser et.al, 2012). The SI unit for measuring the illuminance is lux. Calculation of
the illuminance in the room was important for two reasons. The first reason was that it should fulfill the IES
(Illuminating Engineering Society) recommendations for commercial office which was used as the test model for
this thesis. The main purpose of fulfilling the IES recommendations was to provide a clear visibility for the
occupants while working (Houser et.al, 2012). The second reason for calculating the horizontal illuminance in the
Test lab was for the further analysis of data. The horizontal illuminance at desk surface is kept constant for all the
three lighting designs used for the Test lab. These two reasons made it mandatory for the calculation of horizontal
illuminance for the Test lab at desk level. The points that calculate the horizontal illuminance were known as the
‘light sensors’.
The mentioned script (right side Figure 31) was also used to calculate the vertical illuminance reaching the eye of a
person sitting in a chair in the Test lab. The calculation of the vertical illuminance was important, as it was required
for the calculation of EML (WELL, 2014). Such illuminance level at eye point should be calculated for all three
lighting designs. The light sensors were adjusted in the Grasshopper script to calculate the horizontal illuminance
level for the room and then to calculate the vertical illuminance at an eye point. The ‘grid size pointer’ is used to
control the distance between the light sensors in the grid. More the light sensors, the more accurate value of
illuminance in the room. The ‘distance surface pointer’ is used to adjust the distance of the grid from the floor
surface. The horizontal illuminance of the room was calculated at the working desk surface as it was the main
surface for the commercial space. Hence, the distance surface for the calculation of horizontal illuminance of room
is kept at 0.9metres from the floor surface. To calculate the light at an eye level, the light sensor was at a distance of
1.2metres from the floor level. It’s the level at which the human eye will be when a human sit in a chair. Hence, the
script in the second figure was used to calculate the horizontal illuminance level at the working surface and vertical
illuminance at the eye level. The zoom in views of the ‘Model Specification’ script and ‘Bottom grid and eye point’
script was explained in detail (Figure 31).

Figure 31 Left figure- Model specification in the script. Right figure- Script for the bottom grid in the test model.
Light sensors in the test model were organized using this script. Also, the eye point in the Test lab is controlled by
this script.
3.5.2 ‘Top grid’ script
The script shown (Figure 32), was grouped with the name, ‘Light Fixtures grid’. The script was used to function as
the topmost grid in the test model. This grid was of the lighting fixtures that were used in the design. For collecting
the data, various types of light sources were used. A Grasshopper script for electric lighting grid base calculations
48

has the facility to attach IES files to it, along with its specifications (Subraminiam,2016). The top left yellow box
was used to link the lighting fixtures to the grid and can be changed as per the designs. The right yellow box shows
the details of the light sources, with all its specifications. The main input of the script was linking the lighting
fixtures to the test model. The values of illuminance for the desk and for the eye, varies with a change in the type or
the position of the fixtures (Houser et.al, 2012). For collecting the data, three designs with four types of light
sources were used. The ‘grid size pointer’ in the left was used to control the grid of the fixtures in the ceiling. The
scope is limited to the square grid design for the lighting fixtures on the ceiling. The change in the grid size changes
the position and the quantity of the fixtures on the top grid, changing the values of the illuminance. The smaller the
grid size, the greater the number of fixtures. The greater the quantity of fixtures, the higher the illuminance value of
the room. The ‘distance surface pointer’ was used to control the distance for the grid from the ceiling surface. The
distance was increased when the fixtures used in the design were hanging like pendants and similarly it was
modified for other designs. Hence, the main importance of this part of the script was to give details regarding the
fixtures used in the design and to control them according to the verifications in the design (Figure 32).

Figure 32 Grasshopper script for the top grid in the test model. The luminaires in the test model were organized
using this part of the Grasshopper script.
3.5.3 ‘Simulation’ and ‘Output’ script.
The script (left- figure 33) was grouped with the name ‘Simulation’. This was the main processing area for the
whole script. The inputs from all the groups were connected in the middle component to get the output. The ‘run
daylight analysis’ is connected with all the inputs from the test model like the walls, ceilings, floor, fixtures and the
light sensors. The scope of the thesis was restricted to the research of electric lighting and hence the daylighting is
avoided. To avoid the daylight in the script, it was being plugged in with ‘Dark sky’ component. This helped in
collecting the data required for the research topic. This was further connected to the group with outputs.
The script on the other side (right side- figure 33) was grouped with the name, ‘Outputs.’ These were mainly the
boxes that showed the results of simulations. The boxes in the script were placed together to show the results
together, and to collect the data easily. There were mainly three boxes that were the most important outputs, and
were considered in the analysis and plotting of data – average lux, LPD (lighting power density,) and average EML
(equivalent melanopic lux). The yellow box with the ‘LUX data’ tag was to show the illuminance values calculated
in the script. These were the results of the light sensors which were placed on the bottom grid as discussed earlier
3.5.1 chapter. The number of points in the box represents the number of points on the grid, showing the illuminance
value calculated at that particular point. The ‘LUX data’ box was connected to the ‘Average Illuminance’ box that
shows the final value. It was the average of all the values in the ‘LUX data’ box that is used to get an average value
of the illuminance in the Test lab. This process was carried out for the calculation of horizontal illuminance at the
desk surface and vertical illuminance at an eye point. During the calculation of illumination at eye, only one value
was displayed in the ‘LUX data’ box which was considered to be the final value.
49

Another result box was of ‘LPD’ (light power density.) Light power density is the wattage per square foot (Houser
et.al, 2012). It describes the fraction of how much wattage is consumed in a particular space (Houser et.al, 2012).
This was used as one of the data for the analysis as the scope of thesis collaborates with the fundamentals of energy
savings in the lighting design. Hence, the amount of energy consumed by a particular lighting design, helped in
judging the design on its energy efficiency. Finding out the design that does not affect the circadian system of
humans or affects in a minimal manner, and an energy efficient design and consumes less amount of energy were
the important points in this thesis. The LPD was used while plotting the graphs for the data collected, and was
mentioned in the following chapters. The ‘LPD’ yellow box was linked to the wattages of the fixture, its quantities
and the area of the Test lab. The division of both the quantities gave the LPD for the Test lab. The Test lab units in
Rhino software were in meters and hence the LPD was initially calculated in watts per square meter. They are
further converted to watts per square foot using the conversion factor and the final value for LPD was available in
‘LPD watts per sq ft’. The value from ‘LPD watts per sq ft’ is used in the data collection for analysis and for plotting
the graphs.
The third box is the ‘EML data’ box. EML stands for equivalent melanopic lux. EML is the metric unit which is
used to indicate the biological effects of light on humans (WELL, 2014). The EML data box was used during the
calculation of vertical illuminance at eye point. The EML data is calculated using the vertical illuminance at the eye
level. There is no relation of the EML data with the illumination on the desk surface. The ‘Simulation’ script and
‘output’ scripts were presented below (Figure 33).

Figure 33 Left figure- Script for the electric grid based lighting. Right figure- Outputs in the Grasshopper script.
3.6 Circadian ratio chart.
The WELL Building Standards is the organization that certifies the building on the values of how the building is
affecting the humans staying in it and on the basis of their comfort levels (WELL, 2014). It provides certification
similar to the LEED (Leadership in Energy and Environmental Design) organization. LEED is an organization
which is setup by USGBC (U.S Green Building Council) to certify the buildings on the basis of their energy
efficiency and sustainability (USGBC, 2015). The WELL Building Standard has set up its guidelines to help the
designers to design according to the comfort level of humans (WELL, 2014). The WELL building organization has a
separate section related to the lighting of the building. It describes in complete detail how the lighting of the building
should be designed and how to make it comfortable for the occupants (WELL, 2014). The circadian system of the
humans staying in it should not be affected. The guidelines of the WELL building organization has defined
standards to follow and to find out the effect of particular lighting on the human body (WELL, 2014).
50

The WELL Building Standards has used some guidelines from the research paper ‘Measuring and using light in the
melanopsin age’ by Lucas. The research paper explains that all the five photoreceptors (three cones, rod and ipRgcs)
reach to 100% response when light falls on them (Lucas et.al, 2014). The difference is that all of them do not reach
the 100% response at the same time (Lucas et.al, 2014). The WELL Building Standard describes the wavelength
comparison for the non-visual and visual system (Left Figure 34). The ‘Circadian ratio chart’ that has been used in
the workflow is described below (Right figure 34). The light wavelengths (figure 34) was used to depict the concept
of reaching 100% response at different wavelengths. The dotted line is depicted by the ipRGCs (Intrinsically
photosensitive retinal ganglion cells), responsible for the effects on the circadian system (non-visual effects) and the
RGB line depicts the cones which are responsible for the vision (WELL, 2014). When light falls on the eye, the
ipRGCs reach the 100% response level at 480nm and the cones reach at 555nm (WELL, 2014). This proves that the
ipRGCs starts reacting sooner than that of the cones. Hence the light provided for the vision and that for the
circadian system are not the same and should be designed differently. The light levels required for vision and for
circadian effectiveness are not the same (WELL, 2014). The comparison between the light wavelengths reaching
100% relative sensitivity and the WELL Building Standard designed ‘Circadian ratio chart’ are presented below
(Figure 34).

Figure 34 Left figure- Light wavelengths showing 100% relative sensitivity. Right figure- Circadian ratio chart by
WELL Standard. This helps in finding out the circadian lux values from the known illuminance values. (WELL,
2014)
To demonstrate a relation between the vision and non-vision system, the WELL Building Standard has created a
‘circadian ratio’ chart (Figure 34). The ratio chart derived by the WELL Building Standards shows the colour
temperature, the light source and the ratio (WELL, 2014). The result of this chart is the EML value. To calculate the
EML, it is required to have the visual lux and the specifications of the used light source (WELL, 2014). Match the
specifications of the light source with those mentioned in the chart and select the appropriate ratio. The selected ratio
should be multiplied by the visual lux to get the value of EML (WELL, 2014).
EML equals the visual lux multiplied by the ratio in the chart. The WELL Building Standard also explains the
process behind finding out the ratios shown in ‘Circadian ratio chart.’ The whole process is derived by WELL
Building Standard. The table (Figure 35) displays the column of wavelengths, light output, melanopic curve,
melanopic response, visual curve and visual response (WELL, 2014). The wavelengths were given at an interval of
5nm in the chart. The first step was to obtain the value of light output through the light source. This can be found
through the specifications, manufacturer or by using a spectrometer. The value of light output was the basis for this
ratio. Note the value of light output at each 5nm increment (WELL, 2014). Multiply the value of light output with the
melanopic curve to get the value of melanopic response (WELL, 2014). Follow the same process for the visual
response. Multiply the value of light output with the visual curve to get the value of visual response. Get the values
for about 200 wavelengths or more and then add all the values of melanopic response on one side and the visual
response on another (WELL, 2014). Finally divide the total melanopic response by the total visual response to get
the melanopic ratio for that particular light source (WELL, 2014).
 Melanopic response = light output x Melanopic curve
 Visual response = Light output x Visual curve
 Melanopic ratio = Total Melanopic response / Total visual response.
51

The chart used to describe the formation of ‘Circadian ratio chart’ is given below (Figure 35).

Figure 35 Melanopic and visual response chart used to find the circadian ratio for light source. (WELL, Oct. 2014).
The illuminance values at the eye level were collected through various simulations. The light source and the colour
temperature were selected form the ‘Circadian ratio’ chart. Appropriate melanopic ratio was chosen and multiplied
with the illuminance value at eye level to get the EML. The result thus obtained will be another value for plotting on
the graphs.
 EML= Illuminance at eye level x Melanopic ratio (WELL, 2014).
The values obtained at the end of the workflow were horizontal illuminance at the desk surface, vertical illuminance
at the eye point, EML value for the eye and the LPD value for the room. Three different design test cases and four
different light sources were used to run 60 simulations. The collected data was analyzed in chapter 5 and the values
from the data was used in the creation of a new calculator tool known as ‘(EML+ LPD) calculator’.
3.7 (EML + LPD) Calculator
A new methodology was created using the following software programs: Rhino, Grasshopper, Ladybug, and
Honeybee. The objective was to provide a workflow to the lighting designer that can evaluate their design to clarify
that the particular lighting design does not create any hindrances in the circadian cycle and can be used to enhance
and maintain the circadian pattern in the human body. In the present lighting field, ‘AGi 32’ is the widely-used
software program for calculating the illuminance values in the room and other functions of lighting (Bloom, 2014). It
is very rare that the lighting designers will be aware and well informed about the software programs like
Grasshopper and Rhino (Bloom, 2014). These were the main software programs that carries out the whole
methodology in the research. One of the objectives was to find an effective tool which can be easily used by the
lighting designers to find the value of EML for their lighting design. The alternative way for the methodology was to
create a calculator using the calculated data. The main aim was to make an easily accessible tool that can be used by
the lighting designers. The calculator created was in the conceptual stage. The calculator has the data that has been
found in the research through different simulations. The output of the calculator was same as that of the
methodology, but in an easier way. The calculator completely depends on the methodology. The information and the
analysis conducted in chapter 5 was combined and converted to create a calculator.
The concept of the calculator was to input the basic things required and allow the calculator to work on its own to
provide the results. The inputs include, type of design configuration, the horizontal illuminance of the room, and the
light source. In order to get the value for EML, the vertical illuminance at eye point must be known. The vertical
illuminance for eye point was available in the data. The horizontal illuminance for the desk surface was kept
constant to 450lux. Initially, due to grid base ceiling design, a constant value of 450lux was not achieved. The values
closer to 450lux was achieved like 440, 430, 455 and so on. The vertical illuminance values were in respect to such
achieved horizontal illuminance values. The values closer to 450lux were converted to constant 450lux, converting
the values of vertical illuminance by maintaining the same ratio between the horizontal illuminance at desk and the
vertical illuminance at the eye level. For example, the horizontal illuminance 435lux was having a vertical
illuminance of 470lux. The horizontal illuminance was converted to 450lux, converting the vertical illuminance to
52

486lux by maintaining the same ratio between them. A relation was found between the horizontal illuminance at
desk surface and the vertical illuminance at the eye level through the analysis. The relation is expressed in the form
of a co-efficient (explained in Chapter 5.7). The values for co-efficient are determined after all simulations.
The design of the calculator was done in Excel (Figure 37). Software programs like ‘AGi 32’ can easily provide the
horizontal illuminance for the room. A lighting designer should input the horizontal illuminance for the design,
select the appropriate design method and select the light source. By inserting these values, EML and LPD was
available to use in numerical and graphical form. The user should input the horizontal illuminance at the desk
surface in the first column of the calculator. The second column was for the selection of the design method. The
three design test cases (ceiling mounted fixture, pendant design and indirect uplighting) were applied in the
calculator. The choice of options in the third column depends on selection of option in the second column. For
example, if user chooses ‘ceiling mounted design’ in the second column, only the light sources used in the ceiling
mounted design was available in the third column. The choice of 2
nd
and 3
rd
columns automatically updates the co-
efficient in the fourth column. The ‘vertical illuminance at the eye level’ was programmed in such a way that by
using the co-efficient, it automatically calculates the lux at the eye point. The next column of ‘WELL Building
Standard guidelines’ has the ‘Circadian ratio’ chart, attached. The most applicable light source and colour
temperature was selected. This calculates the EML value for the eye. LPD was also calculated. Inputting the values
for the area of the space, the wattage of the light source and number of fixtures used can automatically calculate the
LPD in the calculator. The end results of EML and LPD were displayed in the graphical form (Figure 37). The point
is the indication of the design. The position of point, depicts the level it stands in terms of EML and LPD. The point
adjusts itself when the values of EML and LPD changes. The graph was displayed with the ‘Healthy and Energy
Efficient’ zone required for a design in terms of EPL and LPD. To understand the workflow of the calculator, a
flowchart was presented that shows how the options of light sources and coefficients are linked with the type of
design configuration (Figure 36).

Figure 36 Flowchart depicting the working of the calculator.
53

Figure 37 (EML+LPD) Calculator design with the graph.
3.8 Four different light source.
One goal was to provide a reference source to lighting designers to find out the healthy lighting level for the
occupants in their design. The above mentioned script proved useful in finding the illuminance values required for
the calculation of EML at the eye and LPD for the room. Three design strategies were used to run through the script
to find out their impact on the circadian system of the humans in terms of EML values. The results helped to study
the context that which one of the design was better than the other two designs. The results also helped in analyzing
the design strategies among the three different design configurations that should be implemented by the designers
for the betterment of the circadian cycle of humans. Three design strategies were considered, and 20 simulations of
different types of light sources were run through the script to collect the data. The total data of 60 simulations were
collected and analyzed.
In each design, 4 different types of light sources were used (Fig. 38). Each light source had 5 variations each
(different wattage and lumen levels) with corresponding IES files (Fig. 38).

Figure 38 Four type of light sources used in the three lighting design configurations. (Ramin, April 2013).
54

3.8.1 LED
A light emitting diode (LED) is one of the demanding light source in the modern world. It can provide more light
with the use of less wattage (Savov, 2017). The heat emitted form LEDs is very less as compared to incandescent
bulbs (Savov, 2017). They do not have any ultraviolet light coming out of it unlike the fluorescent bulbs (Savov,
2017). LED can be designed for any desired colour temperature (Savov, 2017). The beam angles of LED can be
varied as the requirement. It can be wide and even shallow (Savov, 2017). The life span of LEDs are more than the
other light sources and also the cost is average as compare to the other light sources (Savov, 2017). Due to all these
benefits, it’s the most commonly used light sources (Savov, 2017).
3.8.2 Fluorescent light
The fluorescent lamps are coated with phosphorous from inside (LRC, 2006). When an electric current pass through
it, the mercury present in it, is vaporized, leading to the formation of ultraviolet light that then reacts with the
phosphor coating form the tube to radiate it as visible light (LRC, 2006). These are better than the incandescent
lamps as they are more energy efficient. The average luminous efficacy of fluorescent bulbs is around 50-100
lumens /watt (LRC, 2006). The life span of fluorescent lamps are generally more than the incandescent bulbs and
hence these are commonly used in houses (LRC, 2006). This is the second type of light source used in the design
strategies.
3.8.3 Incandescent bulb
In incandescent bulb, the tungsten filament present in it is heated at a very high temperature to give out light
(Aletheia, 2016). Incandescent light has different range of sizes and have low manufacturing costs (Keefe.T.J, 2012).
Hence, they are widely used in residential and commercial lighting. But they are not energy efficient and consume a
lot of energy. The luminous efficacy of typical incandescent bulb is 16 lumens/watt (Balzani et al., 2015) Because of
the increasing concern for sustainability, the use of incandescent bulbs is generally avoided. This is the third type of
fixture used in the design light (Aletheia, 2016).
3.8.4 Halogen Bulbs
A halogen lamp is generally an incandescent lamp. It has electronegative elements, including bromine, chlorine,
fluorine and iodine (Burtner, 2010). Luminous efficacy of halogens is low as compared to LED and fluorescent
lights, similar to incandescent bulbs (Sanford, 2014). Also, it heats up during its use and if it comes in contact with
the moisture it may explode (Halogen light bulbs- pros and cons, 2013). Hence, a lot of times halogen lights are
avoided in the smaller areas like residential and commercial places for the safety (Halogen light bulbs- pros and
cons, 2013). It is also not energy efficient fixture as compared to LED and fluorescent fixtures (Sanford, 2014). This
is the fourth type of fixture used in the design.
3.9 Three different lighting design test cases
The basic things to be considered while carrying out the simulations for the various designs were as follows:
 To calculate the illuminance data for the desk level and the eye level.

 To keep the horizontal illuminance at the desk level constant at 450lux for every design. This is the
required level of illuminance according to IESNA recommendations (Houser et.al, 2012).
3.9.1 Ceiling mounted luminaires (First design)
The fixtures used in the first deign were ceiling mounted fixtures. The fixtures were placed at a height of 4 meters
from the floor, and were mounted to the ceiling in the grid form with same distance between them. Ceiling mounted
fixtures are the typically used fixtures in the commercial offices and hence this concept was used in this design
(F.Carlessi et al., 2013). It was used to find the lighting values for a simple lighting design in an office. The above
mentioned light sources were used for the simulations. Different light sources of each type were selected on the
basis of different wattage and lumens. The horizontal illuminance value for the desk and the vertical illuminance
55

value at the eye were collected using the Grasshopper script. The elevation of ceiling mounted luminaires helped in
easy understanding of the design configuration (Figure 39).

Figure 39 Elevation of first design with ceiling mounted luminaires.
3.9.2 Hanging Pendant luminaires (Second design)
The concept used in the second design was to bring the fixtures close to the eye and the desk level. The fixtures
desired to used were decorative forms which are used in huge commercial offices to add aesthetics to the office
through lighting and through their design forms. The fixtures used were the hanging pendants. The pendants were
hanging from the ceiling at a height of 2.8 meters from the floor of the Test lab. Different types of light sources like
LED, fluorescent pendants, incandescent pendants and halogen pendants were used for collecting the data. Special
attention was paid at the illuminance levels of the desk and the eye, as the fixtures were closer than the first design. .
The elevation of hanging pendants helped in easy understanding of the design configuration (Figure 40).

Figure 40 Elevation of Second design method with hanging pendant luminaires.
3.9.3 Indirect lighting (Third design)
The above two designs were the examples of direct lighting with light focusing directly on the person and the desk.
The third design concept was to make a design using an indirect lighting, unlike the first two designs. In indirect
lighting, the light does not reach the object directly. Indirect lighting refers to fixtures that direct the light upward to
bounce off of the walls or ceiling to light the room’ (T.Larsen Design, 2013). The uplighting fixtures are placed in
the room at the height of 2.1 meters from the floor. The fixtures like uplighting floor lamps were used. Indirect
lighting was used in this design to analyze the impact of reflected lighting (T.Larsen Design, 2013) on the circadian
system and how the light levels of the desk and that reaching the eye point, match each other. The other reason to
use indirect lighting was to know the difference between the light levels used for direct and indirect lighting in the
56

Test lab. The elevation of indirect lighting fixtures helps in easy understanding of the design configuration (Figure
41). The above mentioned three lighting designs were used to run 60 different simulations.

Figure 41 Elevation of third design method with indirect lighting luminaires.
3.10 Summary.
The methodology section explained in detail the workflow used to find the EML and LPD values. The different
software programs were used in the workflow like Rhino, Grasshopper, Honeybee+ Ladybug and Circadian
Stimulus calculator. The different sections of the Grasshopper script were described along with its individual
functions. In addition, it also mentioned the context of the three different lighting test cases and four different types
of light sources that were used in the simulations. The data collected from the methodology section is arranged in
tabular and graphical form for the analysis. The next chapter was used to examine the working of the Grasshopper
script, the comparison of the three lighting design methods, judging the light sources on their working capabilities in
accordance with circadian system of humans and conceptualizing an easy way for the lighting designers to use all
these data during their design process.

57

CHAPTER 4
4 DATA COLLECTION
The three different lighting designs were tested in the test lab. This helped in finding the best design among them in
respect of their energy consumption and their effect on the circadian system. One of the central objectives of the
research was to test all the three lighting designs in a commercial office space and to analyze those deigns in
accordance with the circadian system of humans. This provides an overview for the types of lighting designs that
should be referred to lighting designers to use in their designs, which satisfy the required values of the circadian
system. The analysis begins by putting together all the collected data from the methodology section. In this chapter,
all the data from the methodology section is gathered and put together as a base for the next analysis step. The data
consists of the horizontal illuminance at the desk level, the vertical illuminance at the eye point and the EML
(Equivalent Melanopic Lux) at the eye point. The specifications of the light source were also provided in the data,
like the quantity of fixtures used in the room and the wattage of each fixture. This data was used to calculate the
LPD (Light Power density) for the test lab. The CS (Circadian stimulus) values were also considered in the table. CS
values were generated by using the ‘Circadian stimulus calculator’, generated by the Lighting Research Centre
(Figuerio, 2016). The whole data information was converted into the graphical form, for a better display of the
collected information. The data was arranged to assist in formulating the conclusions.
4.1 Ceiling mounted fixture design (1st Test case).
The first design as mentioned in the previous chapter was the ceiling mounted design. The data collected for the first
design method was described below in tabular (Table 3) and graphical form (Figure 42). The first column of the
table describes the type of fixture used for the simulation (Table 3). The ‘Illuminance in room’ was the average
horizontal illuminance for the room that was collected at the desk surface of the test lab. The ‘Illuminance at eye
point’ was the vertical illuminance collected at the eye point. ‘EML’ is the Equivalent Melanopic lux at the eye
point. This value describes the amount of light reaching the circadian system through eye (WELL, 2014). All the
three illuminances are measured in lux. These all columns were used to describe the effect of the fixture on the
circadian system of the humans. The LPD was used to determine the light power density of the room. It describes
the usage of electricity per area of room (Houser et.al, 2012). A lower value of LPD indicates that the fixture is
more energy efficient. The LPD collected from the grasshopper script has the units of square meters, and hence they
were converted to square inches by using the conversion factor. In order to get the values for LPD, the wattages,
quantity of fixtures and total wattages were mentioned in the table below (Table 3). The ‘CLA’ is circadian light and
‘CS’ is circadian stimulus. These both units are derived by LRC (Lighting research center) (Figuerio, 2016). CS is
used as unit by LRC to associate a particular design in relation with the circadian system (Figuerio, 2016). These
data were collected as an additional data from the available source of ‘Circadian stimulus calculator’ by LRC. The
data was collected for total of 20 different simulations.
The EML and LPD mentioned below (Figure 42) were the two main contents of the graph. The horizontal
illuminance at the desk level was kept constant to be 450lux. The EML and LPD data were represented in graphical
form (Figure 42). The graphs (Figure 42) show the LPD on the x-axis and the EML on the Y axis. These graphical
forms helped in determining the ‘Healthy and Energy Efficient’ zone for the fixtures. The ‘Healthy and Energy
Efficient’ zone is the zone in which the fixture will give an efficient amount of EML and is an energy efficient
fixture. The ‘Healthy and Energy Efficient’ zone fulfills both the purposes. The positions of the fixture also helped
to analyze the working and their effect on the circadian system.
58

Table 3 Descriptive Data for the first design method (Ceiling Mounted luminaires).

Figure 42 Left Figure- Values for the LPD and EML from the data of Figure 40. Right Figure- Graphical
representation of the values (shown in the left figure) with LPD as X-axis and EML as Y-axis for the first design
method. The horizontal illuminance at desk surface level is kept constant at approximately 450 lux for all the
simulations.
4.2 Pendant Design test case
The second design as mentioned in chapter 3.9.2, was with the hanging pendants in the test lab. The pendants were
used as decorative fixture and also as a fixture closer to the work surface. The data was collected in the same manner
as that for the first design with the same table format. The data collected for the second design method was
represented in the tabular form (Table 4) and in graphical form (Figure 43).
Light source
Horizontal
illuminance at
desk level (lux)
Vertical
illuminace at eye
(lux)
EML at eye (lux)
WATTAGE per
fixture at full
output
No. of lamps Total wattage LPD- (watts/sqm) LPD- (watts/sqft) CLA (lux) CS
LED-1 450 468.18 355.81 20 13 260 4.81 0.45 356 0.35
FLUORESCENT -1 450 476.22 276.21 32 12 384 7.11 0.66 378 0.362
HALOGEN-1 450 385.19 208.00 46.74 35 1635.9 30.29 2.81 470 0.404
INCANDESCENT-1 450 476.47 257.35 148.6 15 2229 41.28 3.83 534 0.427
LED -2 450 471.79 345.41 17 14 238 4.41 0.41 352 0.348
FLUORESCENT-2 450 477.16 271.95 26 14 364 6.74 0.63 362 0.353
HALOGEN-2 450 379.73 199.76 61 24 1464 27.11 2.52 455 0.397
INCANDESCENT-2 450 475.05 248.92 150 14 2100 38.89 3.61 524 0.424
LED -3 450 469.07 356.50 16 16 256 4.74 0.44 362 0.353
FLUORESCENT-3 450 475.09 275.55 31 12 372 6.89 0.64 374 0.36
HALOGEN-3 450 394.02 212.77 55 30 1650 30.56 2.84 483 0.409
INCANDESCENT-3 450 476.35 257.23 145 14 2030 37.59 3.49 533 0.427
LED-4 450 478.11 363.36 20 13 260 4.81 0.45 368 0.357
FLUORESCENT -4 450 476.23 276.21 34 11 374 6.93 0.64 381 0.363
HALOGEN-4 450 393.87 212.69 53 30 1590 29.44 2.74 483 0.409
INCANDESCENT-4 450 482.37 260.48 141 15 2115 39.17 3.64 549 0.432
LED -5 450 465.78 353.99 27 9 243 4.50 0.42 351 0.348
FLUORESCENT-5 450 475.82 275.98 27 14 378 7.00 0.65 390 0.368
HALOGEN-5 450 386.72 208.83 50 32 1600 29.63 2.75 466 0.402
INCANDESCENT-5 450 483.29 260.98 140 15 2100 38.89 3.61 557 0.435
LPD
(watss/sqft.)
EML (lux)
0.45 355.81
0.66 276.21
2.81 208.00
3.83 257.35
0.41 345.41
0.63 271.95
2.52 199.76
3.61 248.92
0.44 356.50
0.64 275.55
2.84 212.77
3.49 257.23
0.45 363.36
0.64 276.21
2.74 212.69
3.64 260.48
0.42 353.99
0.65 275.98
2.75 208.83
3.61 260.98
59

Table 4 Descriptive Data for the Second Design method (Pendant luminaires).

Figure 43 Left figure- Values for the LPD and EML from the data of Figure 39. Right Figure- Graphical
representation of the values (shown in the left figure) with LPD as X-axis and EML as Y-axis for the second design
method. The horizontal illuminance at desk surface level is kept constant at approximately 450 lux for all the
simulations.
4.3 Indirect lighting design test case
The third design as mentioned in the methodology chapter 3.9.3, was with the indirect up lighting. The lights were
designed to throw the light in the upward direction toward the ceiling and the reflection of those lights illuminates
the room. The third design was purposely chosen to be indirect lighting to study the differences between the direct
and indirect lighting effects on the circadian system. The point of curiosity for the thesis was to check the difference
between the data values of the first two designs and the third design. The data was collected in same manner as that
for the first two designs. The data collected for the third design method was represented in the tabular form (Table 5)
and in graphical form (Figure 44).
Light source
Horizontal
illuminance at
desk level (lux)
Vertical
illuminace at eye
(lux)
EML at eye (lux)
WATTAGE per
fixture at full
output
No. of lamps Total wattage LPD- (watts/sqm) LPD- (watts/sqft) CLA (lux) CS
LED- 1 450 475.60 361.46 17 24 408 7.56 0.70 393 0.369
FLUORESCENT- 1 450 485.37 281.52 70 9 630 11.67 1.08 341 0.342
HALOGEN- 1 450 472.92 255.38 148 15 2220 41.11 3.82 570 0.439
INCANDESCENT- 1 450 538.80 290.95 96 6 576 10.67 0.99 641 0.46
LED- 2 450 477.51 362.91 19 22 418 7.74 0.72 397 0.371
FLUORESCENT- 2 450 485.30 281.47 62 9 558 10.33 0.96 540 0.342
HALOGEN- 2 450 469.54 253.55 130 15 1950 36.11 3.35 560 0.436
INCANDESCENT- 2 450 538.06 290.55 96 6 576 10.67 0.99 636 0.458
LED- 3 450 474.04 360.27 16 25 400 7.41 0.69 391 0.368
FLUORESCENT- 3 450 486.05 281.91 76 9 684 12.67 1.18 347 0.345
HALOGEN- 3 450 483.43 261.05 150 15 2250 41.67 3.87 597 0.447
INCANDESCENT- 3 450 541.42 292.37 88 6 528 9.78 0.91 656 0.464
LED- 4 450 482.28 366.53 17 24 408 7.56 0.70 392 0.368
FLUORESCENT- 4 450 487.83 282.94 65 10 650 12.04 1.12 338 0.34
HALOGEN- 4 450 468.51 253.00 135 16 2160 40.00 3.72 574 0.44
INCANDESCENT- 4 450 542.02 292.69 90 6 540 10.00 0.93 636 0.459
LED- 5 450 477.52 362.91 21 20 420 7.78 0.72 397 0.371
FLUORESCENT- 5 450 484.03 280.74 70 9 630 11.67 1.08 344 0.343
HALOGEN- 5 450 470.81 254.24 145 15 2175 40.28 3.74 566 0.438
INCANDESCENT- 5 450 533.06 287.85 98 6 588 10.89 1.01 647 0.461
LPD-
(watts/sqft)
EML (lux)
0.70 361.46
1.08 281.52
3.82 255.38
0.99 290.95
0.72 362.91
0.96 281.47
3.35 253.55
0.99 290.55
0.69 360.27
1.18 281.91
3.87 261.05
0.91 292.37
0.70 366.53
1.12 282.94
3.72 253.00
0.93 292.69
0.72 362.91
1.08 280.74
3.74 254.24
1.01 287.85
60

Table 5 Descriptive Data for the Third Design method (Indirect lighting method with luminaires uplighting on the
ceiling).

Figure 44 Left Figure- Values for the LPD and EML from the data of Figure 41. Right Figure- Graphical
representation of the values (shown in the left figure) with LPD as X-axis and EML as Y-axis for the third design
method. The horizontal illuminance at desk surface level is kept constant at approximately 450 lux for all the
simulations.
4.4 Summary
The data collected for all the three deigns was mentioned in the above chapter. These data were used as a source for
the comparison between the designs, based on its values for the EML and LPD. This resulted in studying the effects
of the three designs on the circadian system of humans in terms of EML values. The comparison of three designs
helped to understand the differences between the designs in terms of its circadian effects and energy efficiency. The
statistical differences between the values of the data helped in formulating new conclusions and new calculative
Light source
Horizontal
illuminance at
desk level (lux)
Vertical
illuminace at eye
(lux)
EML at eye (lux)
WATTAGE per
fixture at full
output
No. of lamps Total wattage LPD- (watts/sqm) LPD- (watts/sqft) CLA (lux) CS
LED-1 450 393.07 298.73 26 20 520 9.63 0.89 343 0.343
FLUORESCENT -1 450 457.66 265.45 62 24 1488 27.56 2.56 289 0.31
HALOGEN-1 450 421.69 227.71 88 24 2112 39.11 3.63 495 0.413
INCANDESCENT-1 450 422.92 228.38 124 18 2232 41.33 3.84 482 0.408
LED -2 450 400.32 304.25 20 25 500 9.26 0.86 334 0.338
FLUORESCENT-2 450 451.07 261.62 55 27 1485 27.50 2.55 292 0.312
HALOGEN-2 450 422.06 227.91 90 22 1980 36.67 3.41 502 0.416
INCANDESCENT-2 450 424.72 229.35 130 18 2340 43.33 4.03 499 0.414
LED -3 450 399.89 303.92 31 16 496 9.19 0.85 338 0.34
FLUORESCENT-3 450 448.93 260.38 64 24 1536 28.44 2.64 290 0.311
HALOGEN-3 450 421.17 227.43 83 25 2075 38.43 3.57 486 0.409
INCANDESCENT-3 450 422.06 227.91 114 18 2052 38.00 3.53 502 0.416
LED-4 450 395.92 300.90 27 18 486 9.00 0.84 333 0.337
FLUORESCENT -4 450 454.34 263.52 60 25 1500 27.78 2.58 290 0.311
HALOGEN-4 450 420.23 226.92 80 25 2000 37.04 3.44 499 0.415
INCANDESCENT-4 450 420.49 227.07 135 16 2160 40.00 3.72 496 0.413
LED -5 450 397.34 301.98 30 16 480 8.89 0.83 338 0.34
FLUORESCENT-5 450 458.78 266.09 58 26 1508 27.93 2.59 289 0.31
HALOGEN-5 450 423.35 228.61 95 22 2090 38.70 3.60 495 0.413
INCANDESCENT-5 450 421.60 227.67 121 18 2178 40.33 3.75 484 0.409
LPD-
(watts/sqft)
EML (lux)
0.89 298.73
2.56 265.45
3.63 227.71
3.84 228.38
0.86 304.25
2.55 261.62
3.41 227.91
4.03 229.35
0.85 303.92
2.64 260.38
3.57 227.43
3.53 227.91
0.84 300.90
2.58 263.52
3.44 226.92
3.72 227.07
0.83 301.98
2.59 266.09
3.60 228.61
3.75 227.67
61

templates that could be used by the lighting designers during the design process. This will eventually help the
lighting designers to design in a way suitable for the circadian system of the humans. At the end, the lighting for that
particular space should not have a negative impact on the circadian pattern of the body.

62

CHAPTER 5
5 ANALYSIS AND EVALUATION
If the circadian lighting design strategies are to be implemented for a design, it is important to examine the effects of
the design on the human body. Fixtures and their lighting performance in relation with its effect on the circadian
system of humans was assessed by studying three lighting design configurations in a virtual (i.e. simulation-based)
test space. The test model was designed as a commercial office space and was used as an experimental space for the
research. Hence, the outputs from the research were restricted for the commercial offices itself. Some of the
objectives were to provide lighting designers with useful data regarding the effects of lighting on the circadian
system of humans, and lighting design strategies that can help them during the design process. The main objective
was to build a workflow that helps the lighting designers to calculate the EML (Equivalent Melanopic Lux) values
easily and to try using it for different lighting designs.
In this chapter, the data collected from studying the three different lighting design conditions and various fixtures
types were analyzed through different perspectives. This chapter is divided into three sections. Section 1 gives an
overview on the comparison of all the three lighting test conditions. Also, it states the ‘Healthy and Energy
Efficient’ zone required for avoiding the disruption in the circadian system and required for energy efficiency.
Section 2 gives an overview of the difference between the types of light source in accordance with the EML and
LPD (lighting power density) values. Section 3 gives an overview of the relation between horizontal illuminance at
the desk work plane, vertical illuminance at the eye level and the EML at the eye. This concluded in formulating a
calculator, comfortable for the use of lighting designers in their initial stage of design process. The research
objectives were subdivided into individual sections, and each one of them was used to define the analysis of the
collected statistical data. The subdivided objectives are as follows:
 To develop a methodology that a lighting designer can use to easily find out the values of EML at eye point
for a design.

 To evaluate design outputs in terms of EML and LPD for three different lighting methods: ceiling mounted
design, pendant design and indirect lighting design.

 To examine the better type of light source in terms of EML and energy efficiency between the four: LED,
fluorescent, halogen, and incandescent for each type of design.

 To determine the zone required for the lighting fixture to be energy efficient and capable enough to avoid
disruption in circadian patterns of the occupants.

 To find the relation between the horizontal illuminance value at the desk level, the vertical illuminance
value at the eye level, and the EML at the eye
The analysis was mainly done of two important points of the research. The first was of the method created to define
the values of illuminance at eye and EML. Secondly, the analysis was mainly done of the data collected form the
simulations in the workflow.
5.1 To develop a methodology that a lighting designer can use to easily find out the values of EML at eye
point for a design.
The research began with a question to find a process that could help a lighting designer to verify his/her design to be
appropriate for the human circadian system. This meant that the EML values at the eye level should be easily
accessible to the lighting designers. The methodology mentioned in chapter 3 plays an important role to satisfy the
research purpose. A process was designed in such a way that the user would benefit with different values like the
illuminance of the room, illuminance at the eye level, EML at the eye point, and LPD for the design. The process
has some limitations like the use of grid point system in the whole design, which creates problems for the designs
with asymmetrical placement of fixtures. The scope was only limited to commercial offices. Hence, the data
collected cannot be used for any other type of space. But for commercial offices, this process proved useful for
fulfilling the requirements in accordance with the circadian lighting. Many other lighting software programs in the
63

market provide the horizontal illuminance at the surface and the vertical illuminance at the wall but fail to provide a
vertical illuminance at an eye point. This gap was filled by the thesis workflow. The methodology deals with the
combination of various software programs to give the final output. The negative aspect is that the software programs
used in this research, are not very well known in the lighting field, and the lighting designers should be made aware
of those software programs for using this methodology. A limitation was that only one type of light source was
considered for each simulation. For example, only LEDs were considered in the FLEX lab for a particular
simulation. The process was also flexible for the height of fixtures. Another limitation was that daylight was not
considered. The daylight can be considered in the process by attaching an ‘EPW (Energy Plus Weather)’ file in the
daylight component of grasshopper script (Subraminiam, 2016). But these will give results different than those of
the available data. The specifications of the walls, ceiling and the floor can vary with the design and are changeable.
The process designed is beneficial for the lighting designers. The lighting designers can use this methodology as a
positive step during their design process to get the values of their design in relation with the circadian system of the
occupants. The summary version of the workflow (as described in detailed in chapter 3) can be described as a
flowchart (Figure 45).

Figure 45 Flowchart of the workflow
5.2 To determine the zone required for the lighting fixture to be energy efficient and capable enough to
avoid the disruption in circadian patterns of the occupants?
The different zones used in the graphs for the following analysis chapter are described below (Figure 46). To
maintain the circadian cycle of the body, a person should receive minimum of 250 equivalent melanopic lux (EML)
at the eye (WELL, 2014). For the commercial offices, the Light Power Density (LPD) required is maximum
1.1watts/sqft as per the IESNA recommendations (Houser et.al, 2012). Hence, the zone that provides EML value
more than 250 and LPD value less than 1.1watts/sqft., was known as ‘Healthy and Energy Efficient’ zone’. The
design in this zone does not disturb the circadian system of the occupants and is an energy efficient design (Houser
et.al, 2012) (WELL, 2014). The other zones just suitable for EML and LPD are shown below (Figure 46). The
‘Unsuitable zone’ is the worst zone for the design as it will not only affect the circadian system of the person in such
lighting but also will consume a lot of energy design (Houser et.al, 2012) (WELL, 2014). The main zone to be
referred during the analysis process is the ‘Healthy and Energy Efficient’ zone’. The description of all zones in
graphical form makes this information easier to understand (Figure 46).
64

Figure 46 Zone description for the analysis process.
5.3 To evaluate design outputs in terms of EML and LPD for three different lighting methods- ceiling
mounted design, pendant design and indirect lighting design.
The data collected from the methodology was explained in chapter 4. This section helps to examine the data and
record the observations. One of the objectives of the thesis was to do a research on three different types of lighting
design methods, and to find their effects on the circadian system of humans in terms of EML values. In addition to
it, all the three designs were compared with each other to objectify the design recommendations for the enhancement
of the circadian system of the occupants. The data of all the three designs was combined for the easy comparison.
The LEDs, fluorescent lights, halogens and incandescent bulbs were compared from all the three designs with each
other (Figure 47).
In each design, the test lab was illuminated by multiple luminaires. Different design methods lead to different
exposure of light in the room. And difference in the exposure of light lead to different changes in the circadian
system (Figueiro et.al, 2016). Hence, it was essential to study the working of the design methods in relation with the
circadian system of the humans before using them in reality. Three different methods were studied: ceiling mounted
lighting, hanging pendants and indirect lighting method. The three designs were compared to each other based on
EML, the metric used to identify the effect of light on the circadian system (WELL, 2014), and LPD, the metric used
to find the energy efficiency of a fixture (Houser et.al, 2012). The graph describes the data for all the three designs
in the graphical manner (Figure 47). The values for the EML and the LPD for three different designs proved useful
in comparing them with each other to see the difference between the functioning of the fixtures and to analyze the
reasons for the change in their positions on the graph. A lot of variations was seen in the arrangements of the
fixtures of three different designs concluding that each design and fixture has a very different impact on the
circadian system of human body than the others (Figure 47). There were two red lines marked on the graph,
horizontally and vertically. The vertical line is marked at LPD 1.1 watts/sq ft which is the maximum LPD required
for a commercial space as per the IES recommendations (Houser et.al, 2012). The efficiency of the lighting for the
room depends on minimizing the LPD (Houser et.al, 2012). The horizontal line is marked at 250 EML. This is the
minimum EML value required to maintain the circadian rhythmic patterns according to the literature study in
chapter 2 (WELL, 2014). These basic values were used as markups to judge values of other light sources (Figure 47).
65

Figure 47 Comparsion of three lighting design methods- Ceiling mounted lighting, hanging pendants and indirect
lightigng. The horizontal illuminace at the desk surface is kept constant at 450 lux.
The comparison of all three lighting design methods in context of EML and LPD were represented in both the
textual and graphical form (Table 6 and Figure 48). Different aspects were considered for the comparison of design
methods in terms of EML and LPD (Table 6 and Figure 48). The aspects were used in such a way that the designs in
the ‘Healthy and Energy Efficient’ zone, the designs that are maintaining the circadian system and the designs that
are energy efficient, could be noted. Most of the sources of ceiling mounted design were available in the ‘Healthy
and Energy Efficient’ zone as compared to the other two designs (Figure 48). Its percentage is less than 50%. The
indirect lighting has less percentage of light sources in the ‘Healthy and Energy Efficient’ zone as compared to all
the three designs (Figure 48). The second aspect of comparison was in accordance with the required amount of
melanopic lux (Table 6). The design method providing EML more than 250 at the eye point, helped in maintaining
the circadian cycle in the human body (WELL, 2014). Such design methods are safer for the circadian system. The
pendant design luminaires used in this research reinforces the circadian cycle by 100%. The ceiling mounted design
has about 75% of light sources fulfilling the circadian system requirement and the indirect lighting design has less
than 50% (Table 6 and Figure 48). One of the reasons behind all the pendant luminaires providing more than 250
EML, was their distance from the eye point. The pendants were closer to the eye point, eventually leading to more
lux levels at the eye as compared to the light sources of the other two design luminaires. The next aspect was
comparison of the light sources that were below 250 EML. It’s the total opposite of the previous aspect. The
following aspect was in relation with the energy efficiency of light sources. It describes the fixtures that provide
LPD less than 1.1watts/sqft. The ceiling mounted was the most energy efficient design method among all the three
(Table 6 and Figure 48). About 50% of the light sources in ceiling mounted design has LPD values at least less than
1.1 watts/sqft. Less than 50% of the light sources in pendant design and indirect lighting does not fulfill the required
LPD values (Table 6 and Figure 48).
1.1 watts/sqft
250 EML
Healthy & Energy
Efficient zone
66

Table 6 Data describing the percentage levels of each lighting design method for each different aspect.

Figure 48 Graphical representation of Table 6
It was analyzed that the ceiling mounted design was a better design in respect of the energy efficiency and circadian
factor (Table 6 and Figure 48). The light provided by the pendant design for the person sitting in the room was
suitable for their circadian system and would not disturb their circadian pattern. The LPD for the designs, depend on
the selection of light sources (Houser et.al, 2012). The indirect lighting method was proved less useful in terms of
EML and LPD values as compared to other two designs. The same horizontal illuminance levels for the indirect
lighting and other designs, eventually lead the indirect lighting as non-energy efficient design. The lighting
designers can be recommended of using a ceiling mounted or pendant design in terms of the circadian effect on the
occupants.
5.4 To examine the better type of light source in terms of EML and energy efficiency between the four
different light sources.
The three lighting design test cases were compared with each other (Figure 49- 51). It was used to analyze the effect
of lighting design on the circadian system of the humans based on the values of EML. The overall comparison
helped to display the positive and negative aspects of each design; the light sources used in the design were
compared with each other. Such comparison helped in finding the effect of same light source on the circadian cycle
in three different designs. For example, comparing the LEDs used in all the three lighting configurations with each
other.
Design Method
Above 250 lux and less
than 1.1 watts/sqft.
(%)
Fixtures with EML
above 250 lux (%)
Fixtures with EML
below 250 lux (%)
Fixtures with LPD
less than
1.1watts/sq.ft
(%)
Fixtures with
LPD more than
1.1watts/sq.ft
(%)
Ceiling mounted 50 75 25 50 50
Pendants 40 100 0 40 60
Indirect lighting 25 50 50 25 75
67

5.4.1 LED light source
The comparison of all LEDs used in all the three lighting design methods were represented (Figure 49). The ‘LEDs
comparison’ demonstrates the position of all LEDs in regards of its EML and LPD values. All the LEDs from three-
different designs, lie in the ‘Healthy and Energy Efficient’ zone. There was difference amongst the LEDs, in their
EML values and LPD values. The two bar charts, explain the comparison of all LEDs used in this research based on
EML and LPD values (Figure 50 and 51). The ‘LEDs comparison (LPD)’ graph, shows the light power density
consumed by each LED light source in a lighting design method (Figure 50). The LEDs used in the ceiling mounted
design were more energy efficient than those in pendant and indirect lighting design. The graph (Figure 50) shows
an increasing trend line of LPD values form the ceiling mounted design towards the indirect lighting design. This
shows that the energy efficiency of LEDs changed in a negative manner during the pendant and indirect lighting
design as compared to the ceiling mounted light sources. Even though the LPD was changing in a negative manner,
all the LPD values of LEDs were satisfying the required energy efficiency limit of 1.1 watts/sqft. Indirect lighting
design has the most LPD value in comparison of all three. The reason was that it needs more number of light sources
to satisfy the requirements of the visual lux. The indirect lighting is based on the concept of reflection of light
through the ceiling (T.Larsen Design, 2013). Hence it loses some of light in the process, leading to the use of light
sources with more intensity or with increase in its quantities. The light sources should provide the horizontal
illuminance of 450lux at the desk surface level (Houser et.al, 2012). As per the collected data through this research,
the uplighting luminaires consumed more amount of energy than the pendant luminaires and recessed ceiling
fixtures. It also depends on the type of light fixtures chosen for the designs.
The ‘LEDs comparison (EML)’ depicts the comparison of all LEDs from three designs in accordance with the EML
values at the eye point. The EML values of the ceiling mounted and pendant design are slightly different form each
other. One of the reasons for the difference is their dissimilar distance from the eye point. Pendant design light
sources were closer to the eye point as compared to ceiling mounted light sources. Hence the eye receives more lux
through pendant luminaires, eventually leading to more EML in comparison to ceiling mounted design. The indirect
lighting fulfills the requirement of minimum 250 EML value but provides less melanopic lux than the other two
designs.
From the graphs, it was analyzed that LEDs were recommendable light sources for enhancing and maintaining the
circadian cycle of humans, irrespective of its design method. In case of comparison, LEDs in ceiling mounted design
was preferable more than the uplighting LED luminaires (Figure 49-51).

68

Figure 49 Comparison of all LED light sources for the three different lighting methods. The maximum dotted line
for LPD is at 1.1watts/sqft. The minimum dotted line for EML is at 250lux.

Figure 50 Comparison of LPD values of all LED light sources for three different lighting methods. The maximum
dotted line for LPD is at 1.1watts/sqft.

Figure 51 Comparison of EML values of all LED light sources for three different lighting methods. The minimum
dotted line for EML is at 250lux.
69

5.4.2 Fluorescent light source
The graphs (Figure 52) show the comparison of all the fluorescent lamps used in three design test cases based on
LPD and EML. The fluorescent light sources used in the ceiling mounted design were in the ‘Healthy and Energy
Efficient’ zone. 40% of the fluorescent lamps from the pendant design satisfied the requirement of energy efficiency
and melanopic lux. None of the fluorescent lamps from the indirect lighting method were present in the ‘Healthy and
Energy Efficient’ zone. In scope of comparison of LPD (Figure 53), only the ceiling mounted fluorescent light
sources satisfy the requirements. The LPD of indirect lighting design was a lot more than the other two used lighting
design configurations. In case of EML values (Figure 54), all fluorescent sources were eligible to be used for
effective circadian lighting. The fluorescent bulbs from the pendant design have the peak point in EML values. One
of the reasons for this, was the distance between the light source and eye point.
From the graphs, it was concluded that fluorescent light sources are recommended for the ceiling mounted design
for energy efficiency and for the enhancement of the circadian system of humans. The fluorescent pendant and
uplight luminaires are to be avoided in terms of energy efficiency. In short, all the fixtures can use fluorescent light
source in their design, and the occupants will be receiving the required amount of melanopic lux that would not
disturb their circadian patterns (Figure 52-54).
70

Figure 52 Comparison of all fluorescent lamps for the three different lighting methods. The maximum dotted line
for LPD is at 1.1watts/sqft. The minimum dotted line for EML is at 250lux.

Figure 53 Comparison of LPD values of all fluorescent lamps for three different lighting methods. The maximum
dotted line for LPD is at 1.1watts/sqft.

Figure 54 Comparison of EML values of all fluorescent lamps for three different lighting methods. The minimum
dotted line for EML is at 250lux.
71

5.4.3 Halogen light source
The graph (Figure 55) shows the comparison of all halogens used in three design methods of the research, based on
LPD and EML. None of the design with halogen light source fall in the ‘Healthy and Energy Efficient’ zone. All the
sources are at a far distance from the required zone. They are either in the ‘Suitable for EML’ zone or in the
‘Unsuitable zone’. In terms of LPD (Figure 56), all the halogen sources are above the maximum requirements of
LPD, hence not considered to be energy efficient. Halogens intensity of emitting lumens was very less, hence it
needed a lot of fixtures to satisfy the 450lux requirement of horizontal illuminance in the test lab. As the number of
fixtures increases, the LPD automatically increases (Houser et.al, 2012). Halogens consume a lot of energy as
compared to LEDs and fluorescent lamps (Ireland, 2012). The ceiling mounted halogens and uplighting halogens in
indirect lighting designs have values less than 250 EML, and that type of light is considered as insufficient light for
the maintenance of circadian cycle (Figure 57). A person sitting in this amount of light will have effects on his/her
circadian system (Figueiro et.al, 2016). Halogen is having a less value of ratio (to the visual lux) in the ‘Circadian
ratio’ chart (WELL, 2014). The light output noted at different wavelengths selected for the formation of ‘Circadian
ratio’ chart in WELL Building Standard guidelines, shows less values, leading to a less ratio with visual lux (WELL,
2014). The ‘Circadian ratio’ chart shows the ratio value for halogens as 0.54. The horizontal illuminance at the desk
level was considered to be 450 lux according to the IESNA recommendations (Houser et.al, 2012). The use of this
illuminance value with the given ratio does not fulfill the requirement of 250 EML. Hence, the visual lux provided at
the Test model should be increased to get EML more than 250. From the graphs (Figure 55- 57), it was analyzed that
the halogens lamps are not appropriate for the circadian cycle. It cannot provide the enough light required to
maintain the circadian patterns. The IESNA (Illuminating Engineering Society of North America) recommends the
value of 450lux for the commercial offices (Houser et.al, 2012). The EML value produced by halogens using this
horizontal illuminance was not satisfying the requirements. Halogens were not found to be energy efficient by the
analysis of the data. Hence, the use of halogens should be avoided in respect of energy efficiency and circadian
system maintenance. Among the three, a halogen in pendant design is recommendable, as it provides EML values
very close to the required value (Figure 55-57).
72

Figure 55 Comparison of all halogens for the three different lighting methods. The maximum dotted line for LPD is
at 1.1watts/sqft. The minimum dotted line for EML is at 250lux.

Figure 56 Comparison of LPD values of halogens for three different lighting methods. The maximum dotted line for
LPD is at 1.1watts/sqft.

Figure 57 Comparison of EML values of all halogens for three different lighting methods. The minimum dotted line
for EML is at 250lux.

73

5.4.4 Incandescent light source
The graph (Figure 58) shows the comparison of all incandescent bulbs used in three different designs based on LPD
and EML. The incandescent bulbs were not in the ‘Healthy and Energy Efficient’ zone in any of the designs. In
accordance with the LPD (Figure 59), the incandescent bulbs in all the designs were above the required maximum
level of 1.1 watts/sqft. The EML values (figure 60) for incandescent fixture in all the designs were on the edge of the
minimum requirement of 250. The indirect lighting design does not satisfy this requirement. Incandescent light
source in the pendant lighting has the maximum EML value as compared to all three designs.
It was concluded from the data (Figure 58-60) that incandescent bulbs cannot be recommended as energy efficient
for any of the designs. The same condition is with the EML values and hence they cannot be used for the
enhancement of the circadian cycle.
74

Figure 58 Comparison of all incandescent bulbs for the three different lighting methods. The maximum dotted line
for LPD is at 1.1watts/sqft. The minimum dotted line for EML is at 250lux.

Figure 59 Comparison of LPD values of halogens for three different lighting methods. The maximum dotted line for
LPD is at 1.1watts/sqft.

Figure 60 Comparison of EML values of all halogens for three different lighting methods. The minimum dotted line
for EML is at 250lux.
75

5.5 Comparison between four light sources in each design
All the light sources were different from each other. After comparing the same type of light source, the next step
was to compare different types of light source for a design method. The fixtures have different wattage, lumen level,
and spectral power distribution. The comparison of different light sources like LED, fluorescent lamps, halogens and
incandescent bulbs helped in observing different effects on the circadian system even though all light sources were
in the same design test case. The comparison was done based on EML and LPD values. In each design, a total 5
light sources were used of each type. The percentage (Figure 61) depicts that how many light sources (for a
particular type) fulfill the required given conditions. For example, 80% of the incandescent bulbs are having values
more than 250 EML (Figure 61). This means that 4 out of 5 incandescent bulbs used in the design fulfilled the
condition of 250 EML value. Hence, the displayed value in graphs is 80%.

Figure 61 Comparison of all light sources used in celling mounted lighting design in percentage for different
aspects.
The graph (Figure 61) explained the differences between the light sources like LED, fluorescent, halogen and
incandescent for the ceiling mounted lighting. The first context for the comparison was of the ‘Healthy and Energy
Efficient’ zone. All the LEDs and fluorescent light sources were found in the ‘Healthy and Energy Efficient’ zone.
The LEDs, fluorescent lights and 80% of the incandescent light source bulbs used in the research, proved efficient
for sustaining the circadian patterns in the human body. The LEDs and fluorescent are the only energy efficient light
sources used in the ceiling mounted lighting design.
This graph (Figure 61) showed that LEDs and fluorescent bulbs satisfy the requirements of both the EML and LPD
values. There is a difference between their LPD and EML values but all LEDs and fluorescent light sources provide
100% satisfaction for the requirements of energy efficiency and enhancement of circadian system. All the light
sources have different spectral power distribution (Padfield, n.d). Hence, the spectral power varies at wavelengths of
different fixtures. This leads to the difference in their light outputs, making them different form each other (Padfield,
n.d). The incandescent fixture was suitable for circadian patterns but was not energy efficient. Even though the
design method was same for all the light sources, the results shown by them were different. LEDs and fluorescent
lamps were recommended in the ceiling mounting design.
In the pendant design (Figure 62), the LEDs and 20% of the fluorescent fixtures sources were in the ‘Healthy and
Energy Efficient’ zone. The fluorescent pendant luminaires were found to be helpful in setting and maintaining the
circadian cycle of the humans. All the four light sources were fulfilling the requirements of enhancing the circadian
cycle. Only the EML values were different from each other. In energy efficiency, the LEDs and 20% of fluorescent
fixtures were having values less than 1.1watts/sqft. The difference between the light sources was seen because of
76

their wattage requirements. The energy consumption and the quantities of light sources were different for each of
them. Hence, the LPD values vary for all. The pendant design proved to be very helpful in maintaining the circadian
pattern of the occupants based on the EML values.

Figure 62 Comparison of all light sources used in pendant design in percentage for different aspects.
The comparison of four light sources in the indirect lighting design is explained in the below graph (Figure 63). The
LEDs were found in the ‘Healthy and Energy Efficient’ zone in this design. LEDs and fluorescent lamps have the
EML values of above 250 lux and LEDs has the LPD below 1.1watts/sqft. The indirect lighting design did not
provide a lot of options for the use of light sources in accordance with EML and LPD through their results. The
halogens and the incandescent bulbs failed to satisfy the circadian system and LPD requirements. The values of
EML for halogens and incandescent fixtures can be increased by increasing the value of vertical illuminance at eye
point. The constant factor of horizontal illuminance at desk level in this research will be disturbed. In general, the
indirect lighting method was not showing the results that were beneficial for either the circadian system of the
occupants or for the energy efficiency of the space.
77

Figure 63 Comparison of all light sources used in indirect lighting design in percentage for different aspects.
5.6 What is the percentage increase or decrease in the values of EML and LPD between the four light
sources for each design?
The comparison of light sources based on LPD and EML were explained in the previous graphs (Figure 61-63). By
comparing the light sources, it is must to know the numerical difference between them in context of LPD and EML.
The percentage difference between the light sources were described (Table 7). The objective of this analysis was to
know a range of percentage difference between the available data. The values of light sources were compared within
the same design method. The amount of increase or decrease in the EML and LPD of fixture in accordance with the
best values of EML and LPD amongst the collected data gave the understanding that how much the light source
should have a percent decrease or increase, to reach the best values.

78

Table 7 Percentage decrease and increase in EML and LPD values between four light sources for each lighting
design method. The values highlighted in the blue color are the best values for EML and LPD as compared to others
in every design, and the percentage of increase and decrease was calculated by using those values as reference.

The chart (Table 7) described the percentage decrease and increase in the LPD and EML values for each design. The
LEDs were the light sources having the least LPD and the highest EML value among all the light sources. This chart
described the percentage difference between the lowest value of LPD and other LPD values and between the highest
value of EML and other EML values of light sources. For example, consider the chart of ceiling mounted lighting
fixtures. It shows that for a LPD of fluorescent, a percentage decrease of 34.9% will lead to the LPD value of LED.
In the other column, it shows that for an EML value of fluorescent fixture, a percentage increase of 31.55% in the
EML value will lead to the EML value of LED. Earlier, in this chapter, the comparison between the light sources of
every design was explained in detailed. This was used to determine which light source is better among all. This chart
(Table 7) exhibited the same difference but in numerical form. Hence, the chart (Table 7) provided the range of
percentage differences between the values of LEDs, fluorescent bulbs, halogens and incandescent bulbs in terms of
EML and LPD.
5.7 (EML + LPD) Calculator - Coefficients
One of the objectives was to find an effective tool which can be easily used by the lighting designers to find the
value of EML for their lighting design. The alternative way for the methodology was to create a calculator using the
calculated data. The main aim was to make an easily accessible tool that can be used by the lighting designers to
determine the EML and LPD values in graphical and numerical form. This provided the lighting designers with an
easy tool to evaluate their design on the basis of its effect on the circadian system of the occupants in terms of EML
values and the energy efficiency of the design in terms of LPD values. The calculator completely depends on the
workflow with simulations. The information and the analysis done up to this part of the research is combined and
converted to create a calculator.
Ceiling Mounted Design
LPD
(watts/sqft.)
EML (lux)
Percent
decrease-
LPD (%)
Percent
increase-
EML (%)
LED 0.41 363.36 0 0
Fluorescent 0.63 276.21 34.9 31.55
Halogen 2.52 212.77 83.7 70.77
Incandescent 3.49 260.98 88.25 39.22
Hanging Pendant Design
LPD
(watts/sqft.)
EML (lux)
Percent
decrease-
LPD (%)
Percent
increase-
EML (%)
LED 0.69 366.53 0 0
Fluorescent 0.96 282.94 28.12 29.54
Halogen 3.35 261.05 79.4 40.4
Incandescent 0.91 292.69 24.17 25.22
Indirect lighting
LPD
(watts/sqft.)
EML (lux)
Percent
decrease-
LPD (%)
Percent
increase-
EML (%)
LED 0.83 304.25 0 0
Fluorescent 2.55 266.09 67.45 14.34
Halogen 2.58 228.61 67.82 33
Incandescent 3.72 229.35 77.68 32.65
79

The working of the calculator is explained in Chapter 3.7. The concept of the calculator was to input the basic things
required and allow the calculator to work on its own to provide the results. The inputs include, type of design
configuration, the horizontal illuminance of the room, and the light source. In order to get the value for EML, the
vertical illuminance at eye point must be known. The vertical illuminance for eye point was available in the data. A
relation was found between the horizontal illuminance at desk surface and the vertical illuminance at the eye level
(Table 8). The vertical illuminance of eye was divided with the constant horizontal illuminance at the desk to get a
coefficient between them. Table 5 explains the co-efficient for the horizontal and vertical illuminance. The co-
efficient is for each light source of each design. This played an important role in the proper functioning of the
calculator.
Table 8 Co-efficient values for all three lighting designs. These are the co-efficient between the horizontal
illuminance at the desk and the vertical illuminance at the eye point.
`

For example, a lighting designer is using hanging pendants in the commercial office area (Figure 64). The lighting
designer creates a model of the commercial office in AGi32 and carries out the calculations to get the value of
horizontal illuminance in the room. The horizontal illuminance for room is 450lux. This value of horizontal
illuminance is inserted in the first column of calculator. In the second column, the ‘pendant design’ type is selected.
This displays the options of the light sources used in the pendant design in the research. The light source used by the
lighting designer was ‘fluorescent -2’. Selecting this light source, displays co-efficient value ‘1.08’ in the next
column. Automatically, the vertical illuminance at the eye level is calculated using the co-efficient. The value of
vertical illuminance at eye level is 485lux. In the next column, the lighting designer selects the ‘4000k fluorescent
‘from ‘Circadian ratio’ chart of WELL Building Standard guide. This automatically displays the co-efficient for it
and calculates the EML value in the next column. The final EML value is 281. On the other side, the area of the
room (580 sqft.), the number of fixtures used (9) and watts per fixture (62watts) is inserted to get the LPD of the
room (0.96watts/sqft.). The point with LPD and EML value is directly displayed in the graph (Figure 64). The
lighting designer does not have to go through the whole complicated process of simulation if the light source
selected by them is from the research or closer to it. This makes the whole long process, short and easy. Hence, the
lighting designer can verify that his/her deign does not provide disturbance to the circadian system of the occupants
based on the EML value and is an energy efficient design based on the LPD value.
Ceiling mounted lighting
Light Source Co-efficient
LED- 1 1.06
FLUORESCENT- 1 1.08
HALOGEN- 1 1.05
INCANDESCENT- 1 1.20
LED- 2 1.06
FLUORESCENT- 2 1.08
HALOGEN- 2 1.04
INCANDESCENT- 2 1.20
LED- 3 1.05
FLUORESCENT- 3 1.08
HALOGEN- 3 1.07
INCANDESCENT- 3 1.20
LED- 4 1.07
FLUORESCENT- 4 1.08
HALOGEN- 4 1.04
INCANDESCENT- 4 1.20
LED- 5 1.06
FLUORESCENT- 5 1.08
HALOGEN- 5 1.05
INCANDESCENT- 5 1.18
Pendant lighting
Light Source Co-efficient
LED- 1 1.04
FLUORESCENT- 1 1.06
HALOGEN- 1 0.86
INCANDESCENT- 1 1.06
LED- 2 1.05
FLUORESCENT- 2 1.06
HALOGEN- 2 0.84
INCANDESCENT- 2 1.06
LED- 3 1.04
FLUORESCENT- 3 1.06
HALOGEN- 3 0.88
INCANDESCENT- 3 1.06
LED- 4 1.06
FLUORESCENT- 4 1.06
HALOGEN- 4 0.88
INCANDESCENT- 4 1.07
LED- 5 1.04
FLUORESCENT- 5 1.06
HALOGEN- 5 0.86
INCANDESCENT- 5 1.07
Indirect lighting
Light Source Co-efficient
LED- 1 0.87
FLUORESCENT- 1 1.02
HALOGEN- 1 0.94
INCANDESCENT- 1 0.94
LED- 2 0.89
FLUORESCENT- 2 1.00
HALOGEN- 2 0.94
INCANDESCENT- 2 0.94
LED- 3 0.89
FLUORESCENT- 3 1.00
HALOGEN- 3 0.94
INCANDESCENT- 3 0.94
LED- 4 0.88
FLUORESCENT- 4 1.01
HALOGEN- 4 0.93
INCANDESCENT- 4 0.93
LED- 5 0.88
FLUORESCENT- 5 1.02
HALOGEN- 5 0.94
INCANDESCENT- 5 0.94
80

Figure 64 Example of EML +LPD calculator.
The main aim of the development of such calculator was to give an easy access to the lighting designers to verify
their designs based on LPD and EML. Also, they can judge their design on any one of the aspect as the minimum
and maximum lines were marked on the graphs. In terms of circadian system, the lighting designer will get the idea
whether the design is suitable for the circadian system of the occupants. The calculator can be used in the initial
stages of design process as it will provide rough values. There are several limitations to the calculator. This
calculator is at the conceptual stage and needs to be refined. One of the limitations of the calculator at this
conceptual stage is that the lighting designer can use only the light sources which were used in this research or the
light sources which are closer to those values available in the data. All the light sources mentioned in the calculator
had run simulations to give the values, collected in data. So, at this stage, when a lighting designer wants to use a
light source other than those available in the data, it must run though the whole simulation method to get the values.
The ‘(EML+LPD) calculator’ was an advance version of the initial workflow mentioned in chapter 3. The
development of this tool was for the easy accessibility by lighting designers. The initial workflow used to simulate
the design through software programs like Rhino, Grasshopper and Ladybug +Honeybee. The new calculator only
deals with ‘Microsoft Excel’. The ‘(EML +LPD) calculator’ is the next link of the workflow with simulations. It is
of prime importance to consider that the new calculator is not the substitution of method for the workflow because
the data available in the calculator was achieved form the workflow with simulations. It is the other version of the
complex workflow in terms of accessibility and use. The main function for this creation of other version is to make
it easy for the lighting designers to understand and access it without any difficulty. It is easy to understand when a
comparison between both the versions are displayed (Figure 65).
81

Figure 65 Comparison of flowcharts between the 'workflow with simulations' and '(EML +LPD) calculator.'
5.8 Summary
This chapter gives an overview of the analysis of the collected data through different perspectives. The workflow for
calculating the EML and LPD values proved useful. But an easy accessible tool by name ‘EML + LPD calculator’,
was created in Excel as an advance version of the workflow with simulations. The entire process from the
methodology to the creation of calculator was for the refinement of the topic of circadian lighting. The EML values
of pendant design was found to be stable as compared to other two design test cases. By comparing the design test
cases, it was concluded that the direct lighting methods was more beneficial than indirect lighting method in
consideration with EML values. LED light source satisfied the requirements of EML and LPD in all the design test
cases. Hence, it is one of the recommended light source for circadian effect and energy efficiency. The next chapter
explains in details the conclusions finalized from the analysis process.
82

CHAPTER 6
6 CONCLUSION
The research involved the development of a method for the calculation of equivalent melanopic lux (EML) at eye
point and lighting power density (LPD) for electric lighting in a test lab. Three different lighting configurations and
four different light sources were used to collect the data for analyzing the difference between each of them in terms
of energy efficiency (based on LPD) and their effect on the circadian system (based on EML). A commercial space
model was formed in the software programs (Rhino, Grasshopper, Ladybug, and Honeybee), to be used as the test
model for the study. Three lighting design test cases were incorporated in test case study. Daylighting was not
incorporated. The horizontal illuminance at the desk level for three different configurations were kept constant at a
value close to 450 lux. The values closer to 450lux were converted to constant 450 lux, converting the values of
vertical illuminance by maintaining the same ratio between the horizontal illuminance at desk and the vertical
illuminance at the eye level. The three test cases were compared on the basis on two aspects: EML (equivalent
melanopic lux) at the eye and LPD (light power density) of the room. The research study had two objectives:
1. To develop a method that could be easily accessed by the lighting designers to record the EML values
produced at the occupants’ eye by a particular lighting design. The method should help lighting
designers to determine whether their design is enhancing and maintaining the circadian cycle of the
occupants or its affecting their circadian system. It should also examine the energy efficiency of the
lighting design along with the effect on the circadian system helping the lighting designers to create an
energy efficient circadian positive lighting design.

2. To evaluate three light design test cases with four different types of light sources per design with the
help of the developed methodology in terms of energy efficiency and circadian effect.
The two objectives were interrelated with each other as both of them depends on one another and were responsible
for the completion of each other. Several research questions were formed to address the objectives. To answer the
questions related to the development of new methodology for the calculation of EML and for examining different
lighting designs and light sources, a test model of commercial office was created with the help of software programs
like Rhino, Grasshopper, Ladybug, and Honeybee. Lighting fixtures, light collecting sensors and the eye point were
introduced into the model to calculate the values for EML and LPD. Three different lighting test cases and four
different types of light sources were included in it. A variety of data was created from the simulations and was
analyzed. The analysis lead to the formation of a new conceptual method which was the next step of the initially
(above) mentioned workflow. Hence, the two methodologies and the analysis of the data from the methodology
were the final product.
There are two notable outcomes. The first outcome is divided into two parts. The first part was the detailed
description of the workflow developed using the software programs. The workflow assisted in creating models in
Rhino and adding different light fixtures. The simulations resulted in the values for the horizontal illuminance at the
desk surface, vertical illuminance at the eye level and EML value at the eye. The workflow benefits right from the
design stage up to the determination of EML values. The lighting designer can use this workflow to simulate their
design and to find the energy efficiency and the efficiency of their design in terms of the circadian effect. It is
important to note that the study was conducted with the help of the grid based design of lighting fixtures, and the
performance outcomes should be considered in terms of the grid based design. The second part of this outcome is
the development of a new calculator based on the data collected from different simulation of different designs. The
calculator was the next step of the initial workflow. The necessity of the lighting designer to learn new software
programs like Grasshopper and Rhino was substituted by this calculator. Inputting the value of the horizontal
illuminance in the room at desk level into the calculator will give the output of the EML at the person’s eye sitting in
that room. It calculates the LPD of the room by inputting the area of the room, wattage of light source, and the
number of light sources used. The final graphical output shows the location of the design on the graph of EML and
LPD. This gives a very easy understanding of the complicated circadian lighting theory about the design. The
objective was to make a simple understanding of the complex process. The calculator is at the concept stage of
formation. It is very important to note that the calculator has the values based on the design data and the simulations
collected from this research.
83

The second outcome was an examination of three lighting design test cases along with four different light sources
like LED, fluorescent lamps, halogens, and incandescent bulbs in the test lab. The simulations with the software
programs (Rhino, Grasshopper, Ladybug, and Honeybee) helped in collecting the data for all the test cases. This
data helped in the comparison of three lighting design configurations, four type of light sources with each other and
the same type of light source from all three lighting design test cases with each other. The analysis showed that the
pendant design is more useful for the circadian system of the body as compared to the other two designs. The
distance of the fixture from the eye point matters in the effects on the circadian system. The indirect lighting strategy
failed to provide the required values in terms of EML and LPD. Hence, a less suggestion for the use of this method
and more recommendation of refining the method for the circadian lighting. The LEDs are the common light sources
that should be used in the circadian lighting design strategies based on the data of this thesis. In the cases of the
halogens, the constant horizontal illuminance as recommended by IES leads to the failure of design in terms of the
circadian effect for commercial lighting. At 450lux the halogen was not able to provide 250 EML. The IES
recommendations values and the minimum values provided by WELL Building Standard does not match in some
situations like that of the halogens. The circadian ratio provided by WELL Building Standard does not allows the
required IES light levels to reach the required EML values. A change in some of the recommendations was required
based on this conclusion. These steps assisted in learning about the chosen design strategies and the chosen light
sources.
The topic of circadian lighting is huge and was not totally covered in this research. There were some limitations, for
example, this study was conducted for commercial office space. The methodology formed is useful for just the
commercial office type spaces. The test lab considered was a single room without any doors and windows.
Daylighting was not included in the calculations One type of fixture was used in each simulation and not
combinations of 2 or more light sources in a design. During the whole process, grid-based lighting was used and this
method may not prove useful for asymmetrical lighting design. Some of the IES files from manufacturers were not
able to pair up with the workflow in the software programs. A limited quantity of design strategies and light sources
were considered during this research. The conclusions of this research are very specific to the three mentioned
design cases. None of the practical experiments were conducted using the subjects, to show the effect of circadian
lighting on humans. The values were just calculated using the software programs. No specification of the eye in the
room were provided in the research like its ability for visualization as per the age. The position of the person in the
room was kept constant for the whole research. The factors like the age and health of the person were not considered
during research. The variables like the glare caused by lighting on the computer screens in offices, different
reflectance values of walls, ceiling and floor, and wavelength of paint were not included in the research. The focus
of the research was just on the relation of light and circadian system. Therefore, performance outcomes should be
considered in context of the scope of thesis.
The research provided with the workflow for calculating the circadian effect on the health of humans in terms of
EML values due to various design test cases. It also leads to the creation of EML + LPD calculator, an easy
accessible tool for the lighting designers to find the circadian effect and energy efficiency of the design. The
comparison of different lighting design test cases and light sources assisted in knowing that how each type of design
and light source affects the values of melanopic lux.

84

CHAPTER 7
7 FUTURE WORK
This study introduces several possible areas for future research including: using daylight, circadian lighting for a
variety of spaces and for a variety of occupants, examining different configurations and different type of light
sources, examining practical experiments on occupants, asymmetrical pattern of lighting, redefining EML + LPD
calculator, false color rendering image and lighting pattern scheduled and circadian lighting sensors.
7.1 Future works for methodology
Daylighting - Including daylight in this research will change a lot of values in the data. The combination of daylight
and electrical lighting should be studied because a lot of spaces have the capability of incorporating a huge amount
of daylight in the office through the large glass facades. The effect of the daylight + electric lighting on the circadian
system will be the appropriate next step for discussion.
Circadian lighting for a variety of spaces and for a variety of occupants- The circadian lighting is an emerging topic
and steps should be taken for the methodologies in other types of spaces like the residential, schools and industrial.
The required EML values and the IES recommended illuminance values will differ from place to place (Houser
et.al, 2012) (Figuerio, 2016). Also, the occupants will change as the place changes. For example, the type of
circadian lighting designed for the adults in commercial places cannot be the same for the children in the schools.
The occupants are important for lighting (Figuerio, 2016). Hence the requirements of circadian lighting will change
from place to place. The circadian lighting depends on a lot of different factors. In reality, the requirement for
circadian lighting changes from person to person. The age, health, resistance power, eye power, occupants body
condition and the most important – individual’s circadian system, are the factors which affects the requirements of
circadian lighting (Figuerio, 2016). A study of such factors should be taken into consideration. The topic of
circadian lighting is very vast with a lot of affecting factors under it.
Examining different lighting configurations and light sources to make a solid data collection – Three different
lighting test configurations were used. A variety of lighting strategies should be run through the simulations, to
collect more data. The strategies like the task lighting and the panel lighting should also be tried. Likewise, only
four different light sources were used. More different types of light sources should be tried in the variety of spaces.
More the data available, more specific the conclusions.
Examining practical experiments on the occupants in terms of the lighting (Daylight + electric) effect on their
circadian system- All the data collected was based on the simulations in the software programs (Rhino, Grasshopper,
Ladybug, and Honeybee). No practical data of melanopic illuminance was collected by studying the biological
behavior of the occupants, sitting inside the office. The practical readings of the circadian effect on the occupants’
body should be collected. This will help in verifying the data collected by the practical study with the data from this
research and will tell how much of both the data match with each other. It will give the relation between the data
collected through simulations and through practical testing.
Asymmetrical pattern of lighting – The lighting was grid-based lighting. Hence, this methodology would not be
useful for the lighting with asymmetrical designs. A continuation of this methodology will provide a chance to
advance the work in the asymmetrical design EML calculations. The asymmetrical design will affect the EML
values as the position of the eye changes.
7.2 Future works for EML + LPD calculator.
(EML + LPD) calculator- The calculator created in the research have several limitations. One of the limitations of
the calculator at this conceptual stage is that the lighting designer can use only the light sources which were used in
this research or the light sources which are closer to those values available in the data. All the light sources
mentioned in the calculator had run simulations to give the values, collected in data. So, at this stage, when a
lighting designer wants to use a light source other than those available in the data, it must run though the whole
simulation method to get the values. The calculator should be refined and new solutions should be targeted so that ir
can be used for any type of design and any type of light source. An effort should be made to omit the need of
lighting designer to go back to the simulation methodology.
85

7.3 Future works for outputs.
False color rendering image- The output at the end of the methodology of this research is in numerical values. The
next step will be to get the output in the form of false color rendering images. The image showing the lighting of the
space in the false colour will help the lighting designer and especially the client to understand the effect of the light
on the circadian system in the room. The image can display what part of the rooms receive how much equivalent
melanopic lux (EML)in the form of RGB colours. Some of the examples are given below:

Figure 66 Examples of false colour rendering images of lighting. (Left figure- Light+Architecture, New DIALux
EVO, April 2012, http://blog.lightingvanguard.com/2012/04/new-dialux-evo-review-with-screenshoots.html )(Right
figure- Lighting as a service, Designed solution, http://www.lightingasaservice.com/design-solution/ )
Lighting patterns and circadian lighting sensors for commercial spaces- The Lighting Research Centre has worked
on the colour tuning pattern 24 hour scheduled for different projects (Figuerio, 2016). This research can be carried
out in future on the light level tuning patterns for the commercial offices, as colour temperatures were not
considered in this research. Dimming the lights when an unrequired EML values are being produced (Brodrick,
2016). Daylighting should be included in this process. The EML values for various timings of the day should be
collected. This EML values can be arranged in the chart form as per the timings of the day and night and should
produce a 24hour timetable for tuning the light levels in the office space. Automatic tuning can be done by setting
up the algorithms to dim the lights in order to reduce the light levels according to the timetable (Brodrick, 2016).
The other option is the use of sensors. Like the occupancy and daylight sensors, circadian lighting sensors should be
created. The maximum and minimum level can be set in the sensor. The sensor can detect the light levels in the
room and can have more light levels if it does not fulfill the minimum required light levels for maintaining the
circadian cycle of the occupants. The sensors can dim the lights if the light levels are passing the maximum light
levels for circadian lighting.
7.4 Summary
Circadian lighting is a huge topic and there are various sections in this field in which research can be conducted in
future. Some of the aspects for the future works were mentioned in this chapter. The scope of circadian lighting can
be increased by adding and redefining different topics related to this concept (as mentioned in this chapter). The
workflow and the calculator generated in the research will benefit the lighting designers to evaluate different types
of designs and light sources that will prove useful for the health of the occupants. It will enhance and maintain their
circadian patterns, keeping them healthy. Circadian lighting is an important topic which the lighting designer should
consider during the design process and should never be neglected.
86

8 REFERENCES
Abrahamson EE and Moore RY, 2001, ‘Suprachiasmatic nucleus in the mouse: Retinal innervation, intrinsic
organization, and efferent projections’, Brain Res 916: 172-91
Aletheia Cyr , June 2016, ‘What is an incandescent light bulb and how does it work?’, Lighting insights blog,
Regency Lighting.
Ander Gregg D., September 2016, FAIA, Daylighting, U.S Department of Energy Federal Energy Management
Program (FEMP), Whole Building Design Guide (WBDG).
Ashdown Ian, P.Eng.,FIES, April 2016, ‘Sports Lighting Regulations’, All Things Lighting – Relevance in
Illumination Engineering (Blog).
Balzani Vincenzo, Giacomo Bergamini, Ceroni Paola, 2015, Light: A Very Peculiar Reactant and Product’, In:
Angewandte Chemie International Edition 54, Issue 39.
Bloom Susan, January 2014, ‘Lighting Design software unwrapped’, Electrical contractor magazine,
http://www.ecmag.com/section/lighting/lighting-design-software-unwrapped
Brodrick James, 2016, ‘Tuning the light in a senior-care facility’, Vol. 46. New York: Illuminating Engineering
Society.
Burtner Dave, October 2010, ‘What’s the difference between a halogen and incandescent bulb?’, Top bulb (blog),
http://www.topbulb.com/blog/whats-difference-halogen-incandescent-bulb/.
Carlessi, F., Oliveira MO, HO Ando Junior, Neto J. M., Spacek A. D., Coelho V. L., Schaeffer L., Bordon H.,
Perrone O. E., and Bretas A. S., 2013, "Evaluation of Alternative Disposal and Replacement of Fluorescent Lamps",
International Conference on Renewable Energies and Power Quality (ICREPQ’13).
Cooper lighting design guide, 2015, Technical Lighting design guide, pg. 514 and 515, Cooper lighting and safety,
http://www.cooper-ls.com/sites/cooper-ls.com/files/design_guides/downloads/cc2715-lighting-solutions-2015-
11technical-and-index-lighting-design-guide.pdf
Crystallinks.com, ‘Circadian Rhythms- Biological clock’ (webpage), accessed on October 7, 2016,
http://www.crystalinks.com/biologicalclock.html
Echarri, V., August 2016, ‘Eco-Architecture VI: Harmonization between Architecture and Nature’, WIT Press.
ISBN 1784661112.
Edgar, Rachel S., Green Edward W., Zhao Yuwei, van Ooijen, Gerben, Olmedo Maria, Qin Ximing, Xu, Yao, Pan
Min, Valekunja Utham K., May 24, 2012, ‘Peroxiredoxins are conserved markers of circadian rhythms’, Nature 485,
pg 459-464 ,
Eugenia Victoria Ellis, PhD, Elizabeth W. Gonzalez, PhD, APRN-BC, and Donald L. McEachron, PhD, ‘Chrono
bioengineering Indoor Lighting to Enhance Facilities for Aging and Alzheimer's Disorder’, BAU Architecture,
accessed on August 27, 2016, http://www.bauarchitecture.com/research.chronobioengineering.shtml
Figueiro Mariana, PhD, Lighting Research Centre, Troy, NY, USA, 2013, ‘Non-visual Lighting effects and their
impact on health and well being’, Springer science+ Business Media New York, 2013.
87

Figueiro, Mariana G., Kassandra Gonzales, and David Pedler, 2016, ‘Designing with circadian stimulus’, Vol. 46.
New York: Illuminating Engineering Society.
Figueiro, MG, 2008, ‘A proposed 24 h lighting scheme for older adults’, Lighting Research & Technology 40 (2):
153-60.
Fisher Tim, June 30, 2016, ‘What is an IES file? (How to open, edit and convert IES files)’, Lifewire,
https://www.lifewire.com/ies-file-2621816
Hagen Emilie & Richardson Henry, 2016, ‘Circadian daylight in practice’, Façade Tectonics World Congress,
Volume 2.
Halogen light bulbs- pros and cons, Hub pages, 22nd April, 2013, http://hubpages.com/living/Halogen-light-bulbs-
pros-and-cons.
Healthy living (Image 7), October 18, 2013, ‘Even Some shift work may raise diabetes risk’, The Huffington Post,
http://www.huffingtonpost.com/2013/10/18/shift-work-diabetes-_n_4109956.html
Houser Kevin, Misrick Richard, Dilaura David and Stelly Gary, 2012, The Lighting Handbook, 10
th
Edition,
Reference and Application, Illuminating Engineering Society of North America. http://research.ng-
london.org.uk/scientific/spd/?page=info
Iglesia Horacio de la, Department of Biology, University of Washington, Seattle, EEUU, September 2007,
‘Circadian Desynchronization as a Possible Cause of Cardiovascular Disease’, Published at 5
th
Virtual Congress of
Cardiology- QVC.
Inanici Mehlika, Brennan Martin, Clark Edward, University of Washington, Department of Architecture, Seattle,
WA, USA, ZGF Architects, Seattle, WA, USA, 2015, Spectral Daylighting Simulations: computing Circadian Light.
Institute of Lighting Professionals, Feb 2015, ‘The circadian system and lighting’, Slideshare,
https://www.slideshare.net/theilp/ilp-presentation-the-circadian-system-and-lighting
Ireland Beck, 2012, ‘What lamps will be phased out?’, EC & M2012.
Jet-lag hacks (Image 7), July 8, 2016, ‘The Backpacking mama’, https://thebackpackingmama.com/2016/07/08/jet-
lag-hacks/
Keefe, T.J., 2007, "The Nature of Light", Archived from the original on 2012-04-23. Retrieved 2007-11-05.
Lam, Raymond W., 1998, ‘Seasonal affective disorder and beyond: Light treatment for SAD and non-SAD
conditions ‘, edited by Raymond W. lam., 1st;CSZA; ed. Washington, D.C: American Psychiatric Press.
Leslie, RP, LC Radetsky, and AM Smith, 2012, ‘Conceptual design metrics for daylighting’, Lighting Research &
Technology 44 (3): 277-90.
Lighting Research Centre, 2016, Circadian Stimulus Calculator, Light and Health Alliance, Rensselaer polytechnic
institute, Lighting Patterns for Healthy Buildings, http://www.lrc.rpi.edu/programs/lightHealth/
Loomis Mark, December 23, 2010, About Generative Design platforms by Mark Loomis (Blog), Design
Playgrounds.
LRC (Lighting Research Centre), 2006, Fluorescent, LRC publications,
http://www.lrc.rpi.edu/resources/publications/lpbh/062Fluorescent.pdf
88

LRC (Lighting Research Centre), 2016, ‘Circadian Stimulus Calculator’, Lighting Research Centre (LRC), NY,
2016 - http://www.lrc.rpi.edu/programs/lightHealth/
Lucas Robert J., Peirson Stuart N., Berson David M., Brown Timothy M., Cooper Howard M., Czeisler Charles A.,
Figueiro Mariana G., Gamlin Paul D., Lockley Steven W., O’Hagan John B., Price Luke L.A., Provencio Ignacio,
Skene Debra J., Brainard George C., ‘Measuring and using light in the melanopsin age’, Trend in Neurosciences,
Volume 37, Issue 1, January 2014 , pages 1-9,
http://www.sciencedirect.com/science/article/pii/S0166223613001975 - ‘ A method for quantifying light – presented
that accounts for complex photoreceptive inputs.’
Mastin Luke, 2013, ‘How sleep works (circadian rhythms)?’, SLEEP.
McNeil Andrew, Kohler Christian, Lee Elanor S. and Selkowitz Stephen, December 2014, ‘High Performance
Building Mockup in FLEXLAB’, Ernest Orlando Lawrence Berkeley National Laboratory, Energy Technologies
area, Page 1- 11.
Murgia Madhumaita (Image 7), January 12, 2016, ‘IPhone will get ‘Night mode’ to improve sleep’, The Telegraph,
http://www.telegraph.co.uk/technology/apple/iphone/12094488/iPhones-will-get-night-mode-to-improve-sleep.html
Mostapha Sadeghipour Roudasri, 2016, Ladybug & Honeybee, Parametric Monkey, Posted by Paulwintour,
https://parametricmonkey.com/2016/03/13/ladybug-honeybee/
Novakovic, Vojislav, and Thor Endre Lexow, 2007, ISO/TC 163 ‘Thermal performance and energy use in the built
environment’, SC 2: Calculation methods.
Padfield Joseph, ‘Measuring and working with different light sources: Spectral power distribution curves’, The
National Gallery, accessed on March 10, 2017,
Pedersen Bell, Deborah, Vincent M. Cassone, David J. Earnest, Terry L. Thomas, Paul E. Hardin, Susan S. Golden,
and Mark J. Zoran., 2005, ‘Circadian rhythms from multiple oscillators: Lessons from diverse organisms’. Nature
Reviews Genetics 6 (7): 544-56.
Plug-in (computing), Wikipedia, the free Encyclopedia, accessed on January 14, 2017,
https://en.wikipedia.org/wiki/Plug-in_(computing)
Ramin Martin F., April 18, 2013, ‘Learn how much energy your light bulbs help you save’, How to, Tips and
Advice, Homedit (Interior design and architecture).
Ransen Owen F., Candelas, Lumens and Lux, Second Edition, Chapter 3, Published on January 17, 2017.
Rea M., 2000, IESNA Lighting Handbook: Reference and Application. 9th ed. New York, NY: Illuminating
Engineering Society of North America.
Robert McNeel & Associates, Rhino 4.0, accessed on February 5, 2017, https://www.mcneel.com/
Rutten David, November 2013, Back home, ‘I Eat Bugs for Breakfast’.
Sanford Scott, July 2014, ‘Lighting Technology: LED lamps for home, farm and small business’, Energy Efficiency
series, A4050 l-07-2014.
Savov Vlad, February 2017, ‘LED light bulbs are a smart upgrade whether or not they’re ‘smart’’, Circuit breaker-
The Verge (Blog).
89

Siminovitcch Michael and Graeber Nicole, August 2016, ‘Research: Next Generation Healthcare Lighting’, Lighting
Design + Application magazine, pg 60-63.
Subraminiam Sarith, January 13, 2016, ‘Indoor IES Electric Lighting Grid base calculations’, Ladybug Analysis
tools (Discussions), Grasshopper- Algorithmic modelling for rhino,
http://hydrashare.github.io/hydra/viewer?owner=sariths&fork=hydra&id=IES_Electric_Lighting_Grid-
based_calculations&slide=0&scale=5.278031643091583&offset=-2081.262394364055,-1587.550805053517
T.Larsen Design .LLC, 2013, ‘What is Indirect lighting?’, A Little Design help (discover the designer in you),
http://alittledesignhelp.com/what-is-indirect-lighting/
Tedeschi Arturo, "Intervista a David Rutten", January 2011, ‘Mix Experience Tools1 (in Italian and English).
Naples, Italy: Mix Experience. pp. 28–29, Retrieved February 8, 2011.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin
Company, ‘Circadian Rhythm in medicine’, Published by Houghton Mifflin Company-
http://www.dictionary.com/browse/circadian-rhythm
Tharp Margaret Elizabeth (Image 7), January 14, 2017, ‘Me, The 33 year old woman’, Write Now- An Etcetera
Blog, https://erinwritesnow.com/2017/01/14/me-the-33-year-old-old-woman/
Tuunainen, A., D. F. Kripke, and T. Endo., 2004, ‘Light therapy for non-seasonal depression’, Cochrane Database of
Systematic Reviews (Online)(2): CD004050.
‘Talking Photometry: Understanding Photometric Data Formats’, Pro Lite Technology. Accessed February 21,
2017.
USGBC, "About LEED | U.S. Green Building Council", http://www.usgbc.org/leed, Retrieved 2015-11-21
WELL Building Standard guide, Oct. 2014, Version 1.0, INTERNATIONAL WELL BUILDING INSTITUTE,
Delos Living LLC, pg 1-15, 90-104, 189 and 190.
Wetterberg, Lennart, 1993, ‘Light and biological rhythms in man’, 1st ed. Vol. 63;63, Oxford ;New York: Pergamon
Press.
Wolken, Jerome J.,1969, Photobiology, New York: Reinhold Book Corp.
Yanko Design- Form Beyond Function (Image 7), Pinterest, Accessed on August 15, 2016,
https://www.pinterest.com/pin/522206519262749184/?lp=true
Zatz, M. (ed.), 2005, ‘Human circadian rhythms: regulation and impact [special issue]’, J. Biol. Rhythms 20, 279–
386.
Zofchak Jessica, ‘Circadian daylight in practice’, pg.8, 2016, Atelierten, Environmental design consultants+
Lighting designers.

Abstract (if available)

Abstract Humans need to be exposed to a certain amount of light, and overexposure to light may lead to various disorders in bodies. The human circadian system is considered rarely in designing the lighting for a place. Usually the main issues of vision, glare, illuminance and luminance are considered. Whether the provided lighting system is useful for the human bodies using them or not is also one of the most important points that every lighting designer should consider. Every single space is different than another, and hence every space should have its unique lighting. The research was helpful to the lighting designers in determining whether the lighting designed by them for a place is going to help the humans using that space or its going to affect them in an opposite negative manner. The main objective was to design an easily accessible workflow for the lighting designers to evaluate their design in terms of circadian system. Using this workflow, three different configurations of lighting design with four different light sources were evaluated and compared with each other to give outputs in relation with the circadian system. There is currently limited guidance to help the lighting designers to judge their design and find its suitable level for the humans in that space. So, the thesis was like a stepping stone in this positive direction. ❧ A test model was created as a replica of commercial office for the research. The test model was linked with various software programs like Rhino, Grasshopper and Ladybug + Honeybee to carry out different simulations. Three different lighting design test cases and four different types of light sources were considered during the research. The EML (Equivalent Melanopic Lux) and LPD (Lighting Power Density) values were collected for each type of design test case and each type of lighting source. Workflow was developed for the lighting designers to evaluate their design in relation to its effect on the circadian system of the occupants in terms of the EML values. The comparison between the design configurations and light sources, helped to determine the better among them for the circadian system and for the energy consumption. The workflow and data collected, led in the formation of an easy accessible tool for the lighting designers. The newly created calculator could evaluate a particular design to verify whether the design would disturb the circadian pattern or would enhance and maintain the circadian cycle along with its energy efficiency.

Linked assets

University of Southern California Dissertations and Theses

Conceptually similar

PDF

Evaluation of daylighting circadian effects: Integrating non-visual effects of lighting in the evaluation of daylighting designs

PDF

Daylight and health: exploring the relationship between established daylighting metrics for green building compliance and new metrics for human health

PDF

Visualizing architectural lighting: creating and reviewing workflows based on virtual reality platforms

PDF

Simulation-based electric lighting control algorithm: integrating daylight simulation with daylight-linked lighting control

PDF

Development of circadian-effective toplighting strategies: using multiple daylighting performance goals for dementia care communities

PDF

Streamlining sustainable design in building information modeling: BIM-based PV design and analysis tools

PDF

Blind to light loss: evaluating light loss through commercial building facades as a contribution to urban light pollution

PDF

Exploring the influence of scheduling on daylighting performance evaluation in assisted living: testing two new metrics based on sDA and ASE

PDF

Lateral design with mass timber: examination of structural wood in high-rise timber construction

PDF

Double skin façades performance: effects on daylight and visual comfort in office spaces

PDF

Net zero energy building: the integration of design strategies and PVs for zero-energy consumption

PDF

Effective light shelf and form finding: development of a light shelf design assistant tool using parametric methods

PDF

Comparative evaluation of lighting design software programs for daylighting in buildings

PDF

The intelligent control strategy of kinetic façades for daylight and energy performance: evaluating the daylight effect of adaptive systems based on parametric workflow

PDF

MM Electrical Tool: a tool for generating electrical single line diagrams in BIM

PDF

Visualizing thermal data in a building information model

PDF

CFD visualization: a case study for using a building information modeling with virtual reality

PDF

Multi-domain assessment of a kinetic facade: determining the control strategy of a kinetic façade using BIM based on energy performance, daylighting, and occupants’ preferences; Multi-domain asse...

PDF

Daylight prediction: an evaluation of daylighting simulation software for four cases

PDF

Adaptive façade controls: A methodology based on occupant visual comfort preferences and cluster analysis

Asset Metadata

Creator Sardeshpande, Amol (author)

Core Title Integrating non-visual effects of lighting in the evaluation of electrical lighting designs for commercial offices

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Publication Date 04/24/2017

Defense Date 03/22/2017

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag circadian system,Equivalent Melanopic Lux,horizontal illuminance,lighting power density,melatonin,OAI-PMH Harvest,vertical illuminance

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Konis, Kyle (committee chair), Kensek, Karen (committee member), Schiler, Marc (committee member)

Creator Email amol_vks@yahoo.com,sardeshp@usc.edu

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c40-365756

Unique identifier UC11258121

Identifier etd-Sardeshpan-5268.pdf (filename),usctheses-c40-365756 (legacy record id)

Legacy Identifier etd-Sardeshpan-5268.pdf

Dmrecord 365756

Document Type Thesis

Rights Sardeshpande, Amol

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the a...

Repository Name University of Southern California Digital Library

Repository Location USC Digital Library, University of Southern California, University Park Campus MC 2810, 3434 South Grand Avenue, 2nd Floor, Los Angeles, California 90089-2810, USA