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About this book

This book explores how lighting systems based on LED sources have the ability to positively influence the human circadian system, with benefits for health and well-being. The opening chapters examine the functioning of the human circadian system, its response to artificial lighting, potential health impacts of different types of light exposure, and current researches in circadian photometry. A first case study analyzes the natural lighting available in an urban interior, concluding that it is unable to activate the human circadian system over the entire year. Important original research is then described in which systems suitable for artificial circadian lighting in residential interiors and offices were developed after testing of new design paradigms based on LED sources. Readers will also find a detailed analysis of the LED products available or under development globally that may contribute to optimal artificial circadian lighting, as well as the environmental sensors, control interfaces, and monitoring systems suitable for integration with new LED lighting systems. Finally, guidelines for circadian lighting design are proposed, with identification of key requirements.

Table of Contents

Frontmatter

Chapter 1. Introduction: From Chronobiology to Lighting

Abstract
The 2017 Nobel Prize in Medicine and Physiology, awarded on the topic of circadian research, has reawakened the attention of researchers, designers and stakeholders to the theme of the relationship between lighting design and the human circadian cycle. In this introductory chapter we lay the foundations necessary for understanding the following chapters, also regarding the non-image forming (NIF) effects of light. We introduce the science known as chronobiology and the important impact that the research of the three 2017 Nobel prizes has had in this context. We introduce the historical development of the philosophical and scientific definition of light, up to the description used today in lighting design. Continuing the historical analysis, we introduce the theme of the impact of artificial lighting on human society and how electric light sources have evolved over the past 150 years. The theme of the relationship between artificial and natural light is introduced in relation to the profound change in the lifestyles of the last five generations following the industrial revolution. Finally, we follow the position of legislative bodies, regulators and international trade associations, with regard to the NIF effects and the environmental sustainability of the lighting systems.
Maurizio Rossi

Chapter 2. The Human Circadian System

Abstract
This chapter analyses the human circadian system in detail, with particular attention to the effects of light. From a lighting design-oriented perspective, it presents the results of the main research, applied to lighting or developed in the physiological medical field, with reference to the non-image forming (NIF) effects produced by artificial lighting on the human organism. These effects primarily affect the regulation of melatonin production, which is the main marker of the state of the human circadian cycle, but also the central nervous system, with effects on neurophysiological parameters such as cognitive performance, attention level and alertness level. The existing positive and negative relationships between light and some diseases such as seasonal depression, Alzheimer’s syndrome, sleep disorders and premature birth are also examined. Furthermore, this chapter provides a general description of the functioning of the human circadian system, the factors that regulate it and its effects on the organism. Finally, it analyses the possible relationships between the circadian cycle and the modern environment, with particular reference to the human interior spaces.
Maurizio Rossi

Chapter 3. Evaluation of Artificial Light with Respect to Human Health

Abstract
After having illustrated in the second chapter the various relationships existing between light and human physiology, the focus here is on the quantitative aspects of light, which can be used as part of the requirements of the lighting design methodology, which may have NIF effects on the organism. The emphasis is placed on the dose-effect relationships that can come into play in human centric lighting, as positive or negative elements, and on possible sources of risks, with particular reference to LED light. These elements include consolidated requirements of lighting design, such as the control of glare and of the temporal modulation of light, which are now applied to LED lighting. A further topic of reflection, which has seen a lot of interest by the press, concerns the presumed photobiological hazard related to LED lighting. Finally, starting from the assumption that melatonin is the main marker able to detect the state of the human circadian cycle, this chapter introduces the basic elements for the possibility of defining a circadian photometry that can support the activity of the lighting designer, evaluating the current state of the research in this regard.
Maurizio Rossi

Chapter 4. Case Studies: Natural Light in Interior Spaces

Abstract
After having discussed in the previous chapters the non-image forming (NIF) effects of light and the methods currently available to evaluate these effects, this chapter deals with a topic of central importance for the book. Having established that natural light is the best light for a correct timing of the human circadian cycle, with all the benefits that derive from it, this chapter explores the question if the real availability of natural light, for people who live and work in interior spaces, is adequate for a correct timing of the circadian cycle as it happens outside. This topic is developed in three contexts of interior design: office spaces, residential areas and training facilities. The question is analysed based on studies conducted at the Politecnico di Milano, placing them in relation with those carried out by other research groups. We also present the survey methods used, to then conclude that only in particular cases, unfortunately limited, the natural light present in interior spaces is able to correctly stimulate the human circadian system. This therefore leads to the consideration that artificial lighting in interior spaces could have NIF effects in the daylight hours, compensating for the lack of natural light.
Maurizio Rossi

Chapter 5. LEDs and New Technologies for Circadian Lighting

Abstract
In order to implement artificial circadian lighting in interior spaces, to compensate for the lack of natural light, one must take into account the light requirements of human beings and therefore the technologies that makes it possible to meet them. In this chapter, we present the latest lighting technologies that can facilitate the circadian lighting design. A first part introduces the types of LEDs currently available on the market, analysing the main positive and negative aspects of the different technological solutions. The following part focuses on sensors and light management systems that make it possible to receive information on the amount of light and the presence and position of people in interiors. This information must be managed by smart lighting control systems, which are presented both from a theoretical and an applicative standpoint. The study also focuses on the regulatory aspects of lighting products, with reference to energy saving. Lastly, we introduce some smart lighting solutions aimed at integrating into the new “smart home” concept.
Maurizio Rossi

Chapter 6. Case Study: An Applied Research for Circadian Lighting Design

Abstract
This chapter presents a research conducted at the Laboratorio Luce of the Politecnico di Milano as part of an industrial research project. Research has focused on the creation of a human centric lighting for residential spaces of the elderly, focusing on both the lighting design and the lighting product design based on the new LED technologies. This study has started with a detailed analysis of the needs and problems of the elderly in relation to artificial lighting. With reference to this aspect, the characteristics of a correct lighting for the elderly have been outlined, and then translated into requirements to be applied to lighting design and lighting product design, eventually identifying technological solutions and defining guidelines, lighting programs and concepts.
Maurizio Rossi

Chapter 7. Conclusions and Possible Guidelines for Circadian Lighting Design

Abstract
Today there is no internationally accepted standard that establishes rules for designing a circadian lighting system for interior spaces. For several years, in many different contexts, we have been talking about human centric lighting, although both the definition and the practical application of this discipline are controversial and debated. In this concluding chapter, through the analysis of the original research results presented in this book and of other sectoral research, we propose a framework of possible guidelines for circadian lighting. The elements that come into play in this framework are the natural light present in interior spaces, but also lighting design and lighting product design achievable currently thanks to the availability of LED light sources and the new lighting management systems.
Maurizio Rossi
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