Should the Light be Static or Dynamic?

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ScienceDirect Procedia Manufacturing 3 (2015) 4635 – 4642

6th International Conference on Applied Human Factors and Ergonomics (AHFE 2015) and the Affiliated Conferences, AHFE 2015

Should the light be static or dynamic? Cristina Caramelo Gomesª, Sandra Pretob,* a

Faculdade de Arquitectura e Artes, Universidade Lusíada de Lisboa, Portugal b Faculdade de Arquitectura da Universidade de Lisboa, Portugal

Abstract The lighting design in workplaces environments involves/demands a multidisciplinary knowledge. Despite the several studies in this area of knowledge the reality shows that the lighting layout in indoor environments only considers the need for seeing. Nevertheless, the light is the basis of other needs of the human being, such as non-visual like the circadian rhythms. Both the visual and non-visual effects affect our wellbeing and health. To accomplish tasks without spending our energy in fighting the unfriendly environments we must achieve a well-designed indoor environ design that compensates our needs and fulfil our expectations. Besides the lighting codes, which are mostly related with lighting metrics, it is important to respond to our needs, both physical and psychological, and understand activities and individuals requirements. We spend more almost 90% of our life time in indoor environments without realising that we are putting our health in danger. Natural light provides us, not only the energy that allows us to see, but also the vitamin D that help maintain our health through our skin and eyes, moreover ultraviolet and infrared radiation also has an impact in our wellbeing. Artificial light should provide us the same composition and not withdraw of its spectral composition. The visible light, goes from the violet (short wavelength) to red (long wavelength) over the day and changes occur also along the year - on winter there is much less light available than in the summer. Meteorological conditions and geographic location (latitude) have impact on the light and how it affects our body and mind, in different ways. So, why is the indoor lighting static, once literature reveals the benefits of a dynamic light such as natural one? This paper aims to study the “do´s and don’ts” of a lighting design in a workplace. To achieve such goals the research will be conducted throughout literature review. © 2015 2015 The B.V. This is an open access article under the CC BY-NC-ND license © TheAuthors. Authors.Published PublishedbybyElsevier Elsevier B.V. ( Peer-review under responsibility of AHFE Conference. Peer-review under responsibility of AHFE Conference

Keywords: Daylight; Workplace; Artificial light; Wavelength/spectral; Circadian rhythm; Wellbeing

* Corresponding author. Tel.: +351 964113174. E-mail address: [email protected]

2351-9789 © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ( Peer-review under responsibility of AHFE Conference doi:10.1016/j.promfg.2015.07.550


Cristina Caramelo Gomes and Sandra Preto / Procedia Manufacturing 3 (2015) 4635 – 4642

1. Introduction We spend most of our lifetime indoors - some literature indicates 70% to 90% [1, 2, 3] - in places like our homes, workplaces, and even in environs dedicated to our leisure times. In many indoors environments daylight penetrates the building for less than a couple of hours, especially in winter time when the days are smaller and the sunlight weaker. Daylight has important benefits on human being, visual and non-visually, which affects our wellbeing and health, both psychological and biologically. Escape from decisions that compromise our mind and body is the premise of a good workplace, and to achieve this it is essential to have a deep understanding of all the implications and details that can help to maintain our balance. [4] Many of the designers and interior architects think that their profession is more closely related to art than to science. However we need to understand that the architectural environment in addition to aesthetic impressions influences the human psyche. Although the importance of the aesthetic value of a workplace, architects and designers have to have in mind that their interpretation produce an impact on the person who live and work in that particular spaces and their needs and expectations have to be considered when the project is conceived. The user is more concerned with their basic instincts that can be expressed in terms of comfort, while the architect, on the other hand, develops an aesthetic result of their academic experience, which later is present in their projects. [1] In order to achieve a well-designed workplace we must comprehend that it is necessary the knowledge of multidisciplinary teams collaborating and interacting together in a confluent way.[5] “The physical and psychological spaces of an organization work in tandem to define the effectiveness of the people within it.” [6] (…) “I´d suggest, is that we need to return human beings to the centre of the story. We need to learn to put people first.” [7] 2. Daylight Light exposure varies with the hour of the day: in the morning starts with a bright blue light, which declines at the end of the afternoon with reddish tints. Light and the radiation vary also along the year. These changes are important once they affect our wellbeing -as documented by literature the conditions like SAD (Seasonal Affective Disorder) occur mostly during the winter months, with remission in the summer. The effect on human wellbeing is because of the changes occurred on the light exposure and its spectral composition. [8, 9]. “Without water, one could survive for about a week. If one has sufficient air and water but no food, an average person could be expected to live for up to 30 days without serious complications developing. A lack of exposure to natural outdoor sunlight and exercise will contribute to a gradual degeneration of the body over a period of years, which will predictably result in disease, physical deformities and premature death.” [10] The light of the day, usually called as daylight, is necessary for seeing (visual functions) but also for resetting and shifting the circadian clock (non-visual functions). Every day the circadian (daily) and circannual (seasonal) rhythms regulates important physiological and behavioural rhythms, such as sleep-wake cycles, alertness and performance patterns, psychomotor vigilance, cognitive brain functions, attention, memory, CTB (core body temperature), heart rate, and hormone production such as melatonin, serotonin and cortisol but also have an impact on gene expression and pupil constriction. The absence of light affects us on mood in a negative way with SAD, and on neurocognitive processes. [4] Until recently the main drive of indoor lighting design was to illuminate when external natural light become insufficient. Now, we have the notion and begin to comprehend that the non-visual functions also depend on the brightness and wavelength of ambient light. [11, 12, 13]

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Fig. 1. (a) Spectral Sensibility. [18]; (b) spectral absorption of cones and rods (R). And cones at Long- (L), Medium (M) and Short-(S) wavelengths. (adapted from Dartnall, Bowmaker & Mollon, 1983) [18]

The human retina has two types of visual photoreceptors, cones and rods which have different spectral sensitivities. The rods efficiency functions have a peak of sensitivity at 505 nm (Figure 1a, 1b). There is a large gap between photopic and scotopic vision, where both cones and rods provide an input to the visual system. These are the visual photoreceptors, but there are also the non-visual ones. And these biological or non-visual effects of light are mediated a photoreceptor that contains the photopigment melanopsin, the ipRGCs (intrinsically photopigment retinal ganglion cell). Melanopsin is more sensitive to short-wavelength light at 480 nm (blue wavelengths), while the cone’s peak sensitivity happens at 555 nm (Figure 1a). The sensibility of ipRGCs varies in the intensity, duration/pattern, and timing of light exposure as compared to vision. The long-duration blue-light exposure is more effective at enhancing alertness and performance [14]. Cones, combined with ipRGCs, also contribute to non-visual responses at the beginning of a light exposure and at low irradiance, even though they are slower and sluggish than cones and rods [15]. Melanopsin dominates the response to long duration light exposures and at high irradiances. During exposure to continuous light, ipRGCs drive sustained responses to light, but the contribution responses decrease over time [16]. Because of the difference in temporal properties between cone and ipRGCs, the magnitude of non-visual responses depend on both the spectral distribution and temporal characteristics of the light stimuli, and we must have in mind that different light sources have different SPD (spectral power distributions) (Figure 1b) [4, 17] Moreover, light exposure does not need to be continuous to have an effect on the non-visual system, since the ipRGCs do not respond to individual intermittent light exposures of low irradiance, but instead appear to integrate the light over time until reaching a steady response [16]. A single brief exposure to bright is highly effective for shifting the phase of the circadian clock, suppressing melatonin, and enhancing alertness [15]. [4] 3. Workplace The current recommendations for lighting in workplace’s design are based on visual criteria measured in photometric quantities, such as illuminance. [4] And as already stated, SAD improves when the exposure takes place under bright-light. Exposure to bright light in the morning and evening in the workplace also improve mood, energy, alertness and productivity in individuals with "sub-syndromal SAD"; the shortage of daylight exposure for office workers during daily life, and especially during winter, may compromise our health and wellbeing. [11] We are outdoor animals, and it is under the outdoor environments that we feel balanced -biological and psychologically. The differences between outdoor illuminance and indoor are huge, while outdoor typically ranges between 2000 and 100,000 lux, the indoor is considerably lower, with norms of approximately 500 lux and more often 200 lux. Over the past two decades, the nature of the work done in offices has changed, from the paper source, where the main work surface was horizontal and white, to the use of personal computer with vertical and black or coloured monitor’s image which also contributed to the change in the luminance in an office environs. [16]


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Fig. 2. (a) Biologically effective lighting. Biologically effective lighting should mimic daylight: natural light spectrum: the biologically effective range is the blue spectrum around 460 nm [24]; (b) Spectral distribution of different light sources. [25]

The companies begin to worry about employees’ wellbeing due to the employees’ sense of safety and comfort since wellbeing reduces absenteeism. The companies’ investment in more qualified workplace environments can be reimbursed by the employees’ efficiency and insurance premiums. The comfort conditions and better ergonomic solutions must contribute to the idea that users should leave the workplace at the end of the day healthier than when they start working (in the morning). [20] Office work requires mental resources - stress and attention are common issues on office surroundings - so any environmental feature that help users to minimise the stress or fatigue throughout the day deserves our attention. [21] Nevertheless, brightness can also result from poor ergonomic solutions. It is important to remember that older eyes need more time to adapt to brightness differences because of the reduced elasticity of the iris and the speed of the photochemical process that is the constant accommodation, which occurs when we need to change jobs between the far and the near, cause eyestrain. [22] Adaptive lighting could help to prevent diseases, disorders, physiological deregulation and enhance employees’ productivity and performance while reducing accidents, and decreased health related costs. [10] The advantages of better health and wellbeing are important for the workers, and might also lead to better work performance, fewer errors, more safety, and lower absenteeism. Although poor lighting has been associated repeatedly with mental health problems, the direct effect of lighting on psychological wellbeing and mental stress is not yet fully understood. [23] 4. Artificial light Regarding lighting design, one of the reasons that led to the illuminance levels recommended between 1930 and 1970 was the introduction and development of the fluorescent and high-intensity discharge, since they have higher luminous efficacies once compared with the incandescent lights (Figure 2a, 2b). Nevertheless, illuminance is the main design criterion because it is easier to measure and can be easily connected to the cost of the lighting installation. [19] Colour appearance of the light itself is not specified in the European Norm because so far the colour appearance was associated with psychology and aesthetics subjects and it is considered to be natural. [13] Nevertheless, the quality of lighting should be considered in terms of visual comfort, safety, and of health and wellbeing [26]. [27]. [23] Artificial light is able to affect the circadian system. [8] Nowadays, two electric light source systems are able to influence the human circadian system: LED and fluorescent lamps which indicates that we need to combine both visual acuity lighting solutions with wavelength since they affect the circadian system [8]. The fluorescent indoor

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lighting contains considerably less blue light than natural daylight, which is precisely the component of the spectrum thought to be highly relevant for achieving non-visual, biological effects. [11] The extent of blue light in the spectrum of light sources proportionally increases with colour temperature. The higher colour temperatures have a significant impact on human being once activate the mental activity level [28], and enhance the parasympathetic and sympathetic nervous systems; [29] moreover, sleepiness is higher under lower colour temperature lighting [30]. [11] Epigenetic Design is an emerging design practice which bridges the gap between scientific discovery and energy efficient design. This branch of Design aims to promote healthier environments while integrating natural and artificial light which are controlled by a lighting control system. [8] Dynamic light emerges as an innovative lighting solution to control the effects of lighting properties such as colour temperature and illuminance. Artificial office lighting is typically constant/static in both illuminance and colour temperature, whereas natural light ranges throughout the day as a result of weather conditions and the position of the sun. Daylight has a positive influence on mood and stimulation which justifies people preference for artificial light in addition with day lighting in indoor environments. [4] With dynamic lighting, colour temperature and illuminance ranges during the day according to a pre-set protocol, aiming to support or even enhance the natural rhythm of employees’ alertness. This could be achieved with higher illuminance and colour temperature since morning to lunchtime with lower and warmer white light during the late morning and afternoon. [21] 5. Circadian Light influences the regulation of the circadian rhythm and the secretion of the hormones cortisol (“stress hormone”) and melatonin (“sleep hormone”), which influences alertness and sleep. Cortisol increases blood sugar to give the body energy and enhances the immune system. When cortisol levels are too high over an extended period, the system becomes exhausted and inefficient. Cortisol levels increase in the morning and prepare the body for the coming day’s activity, and will remain at a sufficiently high level over the course of the bright day, decreasing finally to a minimum at midnight. The melatonin makes the same sequence but it drops in the morning, thus reducing sleepiness, and rises again when it becomes dark, offering healthy sleep. For good health, it is important that these rhythms are not disrupted too much. In case of rhythm disruption, bright light in the morning helps to restore normality [13]. These biological effects are dependent on the colour temperature, light level, duration and timing of exposure as well as on the size and position of the light source and have a crucial influence on individuals’ well-being, health and performance. [21] A healthy level of serotonin (mood hormone), which regulate mood, appetite, sleep, as well as muscle contraction, throughout our lifetime decreases by 10% per decade, drawing attention to circadian system neurodegenerative disorders. [29, 31] We must have in mind that the length of the clock‘s period is an individual characteristic, it does not vary in adults, but it is flexible during childhood and youth, and serotonin secretion only happens with luminance levels greater than 1,000 lux[32]. Artificial light, typically used in workspaces, does not touch these values. [33, 34] Although there are situations where there is no need for high illuminance values it is important that we do not ignore the fact that exposure to bright light during the day (over 1400 lux) can advance the phase of circadian cycles. [35, 36] Bright light increased heart rate and CBT during the night-time exposure but not during daytime exposure to the high light level. Exposure to 1000 lx had a significant effect on subjective sleepiness, performance, slow and fewer eye movements, shorter reaction times on vigilance test, we feel more alert, less fatigued and more energetic but not on melatonin level. Melatonin levels were low as expected during daytime. Research in psychological effects of light suggests that both high illuminance and high colour temperature can have positive effects on people’s well-being, health and performance. Exposition to higher colour temperature lighting (5600 K) is more stimulating than warm white lighting (3000 K) which is usually experienced as more pleasant. [37] High colour temperature (17000 K) [38] improves the workers’ ability to concentrate, level of fatigue, alertness, daytime sleepiness and subjective performance compared to a lower colour temperature (2900 K). [21] Again, the variable lighting pattern, consisting of relatively short peaks in lighting level in the morning and early afternoon, has positive effects on self-reported activity, while under static lighting, subjective ratings of deactivation


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and fatigue increased in the afternoon. Unfortunately, the findings did not point in the same direction unequivocally and although sulphatoxymelatonin levels decreased during the day, this pattern did not differ between static and dynamic light. It appears that melatonin levels were already low in the early morning and quickly decreased to their natural daytime minimum. [21] The use of strategically placed spikes of alerting blue-rich light together with alternating cycles of shifting dynamic lighting with appropriate shading controls throughout the day and night are particularly well suited for industries where employee alertness is paramount during all phases of 24 / 7 / 365 operation. [8] In spite of the European standard limiting indoor light levels to 200 LUX (during the work day) to decrease energy costs policies are being taken to consider and establish a unified circadian standard of acceptable light levels to provide sufficient light to suppress daytime circulating melatonin, and a maximum dim light threshold for LAN (light at night) in order to promote inherent sleep and health benefits. Currently the debate focuses on establishing 1000 lux as a base line lighting level necessary for daytime melatonin suppression (however the exact timing and duration for the application of this light is still being questioned). [8] We must consider that numerous luminous codes and recommendations fail in their qualitative component because they are based on quantitative measures. The visual system needs dynamic patterns. Indexes and numbers do not take into account the aesthetic and emotional needs of the human being. There is little understanding of the relationship between the amount of light and the perception of brightness. [35] 6. Wavelength/spectral Light exposure, particularly at the short-wavelength range, triggers several non-visual responses in humanbeings. However, the extent to which the melatonin-suppressing and alerting effect of light differs among individuals remains unknown. [39] Presently, there exists no accepted methodology to evaluate different lighting conditions based on the spectral and temporal characteristics of the light source. [4] 7. Wellbeing The idea of health (wellbeing) is no longer recognized only by the absence of disease, since it has acquired a broader scope that includes the physical, biological, social and cultural wellbeing. [40, 41] Psychosomatic studies showed that the mind and body affect each other, which means that the physical condition can be of psychological origin and vice-versa. Emotions influence the body, stress can cause headaches, fear can increase the heart rate, and anger can affect the stomach and increase blood pressure. PNI (Psychoneuroimmunology) assumes that emotions can even influence our immune system. Biochemical, immunologists discovered nerve fibre networks and "bridges" molecular who maintain a permanent connection between the body and the mind. It is increasingly clear that emotions play an influence that often extend to the last cell of our body and thus strengthens or weakens our body defences. From a psychotherapeutic point of view, the architectural space may have meant as a framework, i.e. the architectural space features, layout and ambience are considered as important factors that support the therapeutic process, the reconstruction of self-acceptance and selfesteem and social relationships. Research in PNI area indicates that positive emotions strengthen defences against disease and illness, while negative emotions weaken our body. [42, 43] The physiological and psychological comfort is positively stimulated by light sources, material and colour selections that have an energizing effect and architecture may have a placebo effect. [42, 44] 8. Conclusions It is important that the companies and the governments acknowledge that the actual guidelines have an impact in all aspects of business expense and profitability due to the interconnection between human health and the built environment which entrains, align and influence the human biological clock. [8] Dynamic lighting is designed to have positive effects on well-being and performance, [18] if we have higher colour temperatures and illuminances in the morning period we would perform better. It seems that the shortwavelengths affect our visual and non-visual functions as well, although there are studies that state that blue light on

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our visual system is a bad influence since it destroys our retina. Even though, if the lighting system is a dynamic one our circadian system is ensured since the lighting will move from short to long-wavelengths, like daylight, which in turn will enhances our health and wellbeing. We must evaluate and re-draw the actual guidelines since they are based in metrics, in quantity of lux according the task developed rather than in a qualitative, in tandem of quantitative. 9. Discussion So, lighting system should help us to achieve our goals, in our professional and personal life. The lighting system of daylight is a variable one, and the artificial should be guided by the same course. Perhaps we need more studies in order to better understand which values, which spectral, which luminances and which color temperature will enhance our circadian (non-visual) and visual system. But, at least, we could start to make some changes and perceive that, in the end, we will all gain, in health, wellbeing, performance and economically. The companies will realize that they will have the returning of the investments in the conversion of the static lighting systems into dynamics ones at medium term. References [1] F. Mahnke, Color, Environment & Human Response. Wiley. 1996. [2] R. Hobday, Healing Sun: Sunshine and Health in the 21st Century. Findhorn Press Ltd. 1999. [3] R. Kuller, Physiological and Psychological Effects of Illumination and Colour in the Interior Environment. 1986. [Online]. Available in: <>. [4] M. L. Ámundadottir, M. A. St. Hilaire, S. W. Lockley, M. Andersen, Modelling Non-Visual Responses to Light: Unifying Spectral and Temporal Characteristics in a Single Model Structure. 2013. [Online]. Available in: . [5] T. Brown, Change by Design: How Design Thinking transforms Organizations Inspires Innovation. 2009. Harper Collins Publishers. [6] T. Brown, Change by Design: How Design Thinking transforms Organizations Inspires Innovation. 2009. Harper Collins Publishers, pp. 32. [7] T. Brown, Change by Design: How Design Thinking transforms Organizations Inspires Innovation. 2009. Harper Collins Publishers, pp. 39. [8] D. Burnett, Circadian Adaptive Lighting: A Landmark Paradigm Shift with Unprecedented ROI Potential. (2012) [Online]. Available in: . [9] H. Thorne, K. Jones, S. Peters, S. Archer & D. J. Djik, Daily and Seasonal Variation in the Spectral Composition of Light Exposure in Humans. [Online]. Available in: . [10] H. Braun, Photobiology: The Biological Impact of Sunlight on Health & Infection Control. 2008. [Online]. Available in: , pp. 1. [11] P. R Mills, S. C. Tomkins & L. J. M. Schlangen, The Effect of High Correlated Colour Temperature Office Lighting on Employee Wellbeing and Work Performance. (2007) [Online]. Available in: . [12] M. Smith, V. Revell & I. E. Charmane, Phase Advancing the Human Circadian Clock with Blue-Enriched Polychromatic Light. (2009) [Online]. Available in: . [13] W. Bommel, Lighting for Work: Visual and Biological Effects. 2004. [Online]. Available in: . [14] S- W. Lockley et al., Short-Wavelength Sensitivity for the Direct Effects of Light on Alertness, Vigilance, and the Waking Electroencephalogram in Humans. Sleep, 29(2) (2006) 161-168. [15] A.-M. M. Chang et al., Human Responses to Bright Light of Different Durations. J Physiol, 590(13) (2012) 3103-3112. [16] J. J. Gooley et al. Melanopsin and Rod-Cone Photoreceptors Play Different Roles in Mediating Pupillary Light Responses During Exposure to Continuous Light in Humans. J Neurosci, 32(41) (2012.) 4242-14253. [17] E. Chen, Seeing Blue. 2010. [Online]. Available in: . [18] E. B. Goldstein, Sensation and Perception (8 th edition). Wadsworth, Cengage Learning. 2007, pp 57. [19] P. Boyce, Human Factors in Lighting. CRC. 2003. [20] Steelcase, Inc., Series 7. [2014] [Online]. Available in: . [21] Y. de Kort & K.C. H. J. Smolders, Effects of Dynamic Lighting on Office Workers: First Results of a Field Study with Monthly Alternating Settings. 2010. [Online]. Available in: . [22] G. Stefy, Architectural Lighting Design. Wiley. 2008.


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[23] M. Varkevisser, R. J. E. M. Raymann, D. V. Keyson, Nonvisual Effects of Led Coloured Ambient Lighting on Well-Being and Cardiac +Reactivity: Preliminary Findings . (2011) [Online]. Available in: . [24] G. Bizjak, Nonvisual Effects of Light. (2013) [Online]. Available in: . [25] Essilor Inc., Blue Light Hazard: New Knowledge, New Approaches to Maintaining Ocular Health. (2013) [Online]. Available in: . [26] M. B. C. Aries, J. A. Veitch, G. R. Newsham, Windows, View, and Office Characteristics Predict Physical and Psychological Discomfort. Journal of Environmental Psychology (2010), doi:10.1016/j.jenvp.2009.12.004. [27] J. A. Veitch, Principles of Healthy Lighting: Highlights of IE TC6-11’s Forthcoming Report. In: Proceedings of the International LRO Lighting Research Symposium – Light and Human Health 2002 (Report No.1009370). Electric Power Research Institute, Palo Alto (2002). [28] T. Deguchi, M. Sato, The Effect of Color Temperature of Lighting on Mental Activity Level. Ann Physiol Anthropol 1992, 11:37-43. [29] H. Mukae, M. Sato, The Effect of Color Temperature of Lighting Sources on the Autonomic Nervous Functions. Ann Physiol Anthropol 1992, 11:533-538. [30] H. Noguchi, T. Sakaguchi, Effect of Illuminance and Color Temperature on Lowering of Physiological Activity. Appl Human Sci 1999, 18:117-123. [31] D. Burnett, Circadian Adaptive Lighting: A Landmark Paradigm Shift with Unprecedented ROI Potential. (2012[Online]. Available in: . [32] C. Gronfier, The Good Blue and Chronobiology: Light and Non-Visual Functions. (2013) [Online]. Available in: . [33] M. Boubekri, Daylight Design: Planning Strategies and Best Practices Solutions. Birkauser. 2014. [34] C. Cajochen, Alerting Effects of Light. 2007. [Online]. Available in: . [35] K. Parpairi, Daylight Perception. In “Environmental Diversity and Architecture”. Spon Press. 2004. [36] D. Avery et al., Dawn Simulation and Bright Light in the Treatment of SAD: A Controlled Study. 2001. [Online]. Available in: . [37] S. Fleischer, H. Krueger, C. Schierz, Effect of Brightness Distribution and Light Colours on Office Staff, Results of the ‘Lighting Harmony’ Project: Proceedings of Lux Europa 2001, Reykjavik, Iceland, 2001. [38] A. U. Viola, L. M. James, L. J. M. Schlangen, D.-J. Dijk , Blue-Enriched White Light in the Workplace Improves Self-Reported Alertness, Performance and Sleep Quality. Scandinavian Journal of Work, Environment and Health 2008; 34(4): 297–306. [39] S. Chellappa, et al., Human Melatonin and Alerting Response to Blue-Enriched Light Depend on a Polymorphism in the Clock Gene PER3. 2011. [Online]. Available in: . [40] G.. Borasi & M. Zardini, Demedicalize Architecture. In “Imperfect Health”. Lars Muller Publishers. 2012. [41] E. Huisman et al., Healing Environment: A Review of the Impact of Physical Environmental Factors on Users. 2012. [Online]. Available in: . [42] G. Meerwein, B. Rodeck & F. Mahnke, Color: Communication in Architectural Space. Birkhauser Verlag. 2007. [43] F. Birren, Color Psychology and Color Therapy. [1st edition 1950] 2nd edition. Martino Fine Books. [44] M. Campbell, Strange Bedfellows: Modernism and Tuberculosis. In “Imperfect Health: The Medicalization of Architecture”. Lars Muller Publishers. 2012.