Perceptual effects of daylight patterns in architecture

The profound impact of daylight on occupants is broadly recognized in the fields of architecture and lighting. In particular, the façade and its interplay with light is central design element, while the diversity of daylight in space is widely acknowledged as a source of interest and stimulation that enriches our spatial experience. However, little is known about how the façade geometry and the resulting daylight patterns affect occupants. Moreover, we have limited knowledge on the impact of space function and of regional differences on human perception.

This thesis investigates the effect of façade and daylight patterns on human responses, while simultaneously examining the impact of space function and regional differences on these responses. The literature suggests two important challenges in current experimental methods in lighting research that might be contributing to the aforementioned knowledge gaps: the changing daylight conditions, which create an unstable variable, and the use of rating scales as the sole method of data collection. To address these challenges, this work introduces two main methodological contributions: the use of immersive virtual reality (VR) as an experimental tool, and the collection of physiological data as a complementary measure to rating scales. Specifically, a novel experimental method that combines VR with physically-based scenes was developed and tested against real environments in experiments that examined its adequacy regarding the perception, presence, and physical symptoms of participants.

Following the positive findings for the adequacy of this method, VR was employed in a series of experimental studies that investigated human responses to façade and daylight patterns, and laid the foundation for a wider study that was replicated in Switzerland and Greece. In all studies, each participant was immersed in a daylit interior space with varying façade configurations of a constant aperture ratio, and the impact of façade geometry, sky type, and spatial context on participant responses was examined in different experimental designs.

The outcomes of this work revealed that the façade and daylight patterns impacted both the subjective and physiological responses of participants. In particular, façade and daylight patterns consistently influenced the spatial experience, such as how pleasant, interesting, exciting, calming, and complex the space was perceived. The façade geometry also impacted spatial attributes that are traditionally considered objective, such as the perceived brightness, spaciousness, and satisfaction with the amount of view in the space. Moreover, the presented façade and daylight patterns significantly affected the participants‘ heart rate, demonstrating in a VR setting that façade elements and their interaction with light can have quantifiable effects on occupants.

The perceptual effects of façade geometry were shown to be robust to changes in the sky type, as well as the function, type, and window size of the space. In addition, no differences were found between the responses of participants in Switzerland and Greece, revealing the generalizability of these design-driven perceptual effects across latitudes in Europe. The findings of this thesis demonstrate the importance of façade design as a powerful driver of the spatial experience, outlining new directions in the design of buildings that are not only comfortable and energy efficient, but also delightful for their occupants.

Ph.D. thesis can be accessed here

Nordic Light ‐ and its impact on the design of apertures in Nordic architecture

Living on the northern‐most part of the globe means we experience the Nordic light every day, and this dissertation is about this very special light.

Traditionally, the northern people have been very conscious of the Nordic daylight. They see the Nordic light as a distinctive feature of the northern countries as well as of great importance for the experience of Nordic architecture.

That is also the basis of this dissertation. But what are the characteristics of the Nordic light? Does it differ at all from other kinds of daylight? And does Nordic architecture in fact relate specifically to the Nordic light? Based on these questions, the dissertation will focus on the following issue: What are the characteristics of the Nordic light and how does it manifest itself in Nordic architecture?

The dissertation is organised in four main sections: Prologue, Light Characteristics, Light Modelling and Epilogue. The first main section makes use of many different statements in order to describe the understanding of the term Nordic. The second section on Light Characteristics makes use of meteorology as a method to identify the characteristics of the Nordic light. The meteorological studies document these characteristics through records of the frequency of clear blue sky and overcast sky, the character of the cloud cover and the sky luminance. The third section on Light Modelling uses phenomenology as a method to study the experience of the interaction between the Nordic light and architecture in three case studies. In the fourth and final main section, the dissertation juxtaposes the results of the previous studies and discusses how the architects work in relation to the Nordic light.

Clear sky		Intermediate sky		Overcast sky

Relationship between cloud cover and light intensity. The graphs illustrate how great intensity the sun and the sky lit up depending on the cloud cover extent specified in oktas. The graphs illustrate the lighting conditions of Copenhagen in June at 12 noon and a relatively thin cloud cover. The cloud cover thickness does not change from graph to graph; it is the fractional cloud cover that changes.

The architects in the case studies each express an eagerness to understand the characteristics of the Nordic light and to work in close relation to it. All three buildings are designed according to the specific local light characteristics, where large, bright and diffuse cloud cover is particularly dominant. The design of the light apertures and thereby the modelling of the light in the various rooms does not follow a particular standard or have a specific shape or size. The three examples illustrate how careful architectural modelling of the Nordic daylight can support a room’s function while also allowing the room to be perceived as atmospheric, intimate and inviting to its users.

This means that the best Nordic architect is often occupied with how to design the daylight apertures in a Nordic context. Therefore, this dissertation aims at pointing to the opportunities provided by daylight apertures to interact with the Nordic light. This means that the Nordic daylight aperture is not designed within a particular mode of expression or style, but rather it is designed in its own special way in order to relate to the light.

Link to Nanet Mathiasen’s Ph.D. thesis is available here

TOWARDS A NEUROAFFECTIVE APPROACH TO HEALING ARCHITECTURE

In recent years, there has been a growing conception that the architectural design of hospitals can help to promote healing processes among patients. These ideas have come from two relatively independent sources, namely Evidence Based Design (EBD) and the writings of individual medical researchers. However, as EBD tends as a methodological approach to keep the architectural framework e.g. patient bed rooms as a constant instead of a variable, very little information is gained about the possible effect of the architectural design itself. Furthermore, as EBD tends to concentrate on physical causes and physiological effects, while disregarding the physiological processes that mediate the demonstrated effects, it often becomes rather difficult to generalize from the results. On the other hand, a couple of medical researchers have presented ideas about how architecture might influence healing and promote health. In the case of these writers, the understanding of the physiological processes is very robust, but a systematic understanding of the link to architecture is missing. Thus, a consistent understanding of how the perception of architecture through physiological mechanisms might influence healing is missing. It is therefore defined as the aim of this thesis, to make a scientific contribution to the establishment of such an understanding.

It is established that the concept of the homeostatic balance is central to the concept of health and healing. Any living organism is faced with the challenge to keep its inner biochemical milieu stable within narrow bounds despite the relatively large fluctuations and physical threats that might occur in the outer environment. Compromised health can be understood as a state of homeostatic imbalance.

Research is then concentrated on finding mechanisms that tie together perception and homeostatic regulation. The stress systems is picked for further investigation, as stress basically can be defined as a state of threatened homeostasis, and a stress reaction as an adaptive behavior. Furthermore, there is a comprehensive interaction between the stress system and the immune system. The question is then, if an architectural context to a stressful event can influence the magnitude of the stress reaction. To investigate this, a stress experiment is carried out, using a virtual version of the so-called Trier Social Stress Test. Because the test is carried out in a virtual environment, the architecture can be systematically varied. Using a closed room versus a room with openings, it is shown that differences can be measured in secretion of the hormone cortisol, which is a stress hormone as well as an immune regulatory hormone, but no differences can be measured in the reaction of the other stress effector system, the sympathetic nervous system.

Thus, an understanding of how systematical variations in architecture through a welldefined physiological mechanism can influence health, healing and well-being is successfully established. However, the stress test only induces acute stress which has a different effect on the immune system compared to prolonged stress, and furthermore only young healthy males were tested due to age and gender differences in stress reactions. Thus, the experiment demonstrates that architecture can make a differences as far as cortisol is concerned, but that further research is needed to reach a comprehensive understanding of the interaction of the perception of architecture and physiology, along these lines.

However, the theory that the artificial environment that is constituted by architecture can influences physiological reactions such as stress reactions through their design is strengthened.

Lars Brorson Fich PhD Thesis is available here

HUMAN RESPONSIVE DAYLIGHTING IN OFFICES: a gaze-driven approach for dynamic discomfort glare assessment

This dissertation proposes a novel gaze-driven approach for dynamic discomfort glare assessments as a first step towards understanding human responsive comfort with respect to daylight. The objective was to observe the natural gaze behaviour in relation to glare for office spaces with the conditions implicitly constrained by real world luminous conditions. In the existing visual comfort models human behaviour is not sufficiently considered. These models employ only subjective assessments, which lack an objective understanding of the factors affecting the perceptual mechanism of light-induced visual discomfort. They so far have not integrated the inter-dependencies of visual discomfort perception and human gaze responses and have been limited to a fixed-gaze assumption directed towards the office task area.

In this dissertation, a gaze-driven approach is developed and adopted in the discomfort glare assessments. The assessments were done in a series of experiments in simulated office setting under different lighting conditions where participants gaze responses with means of mobile eye-tracking as well as their subjective assessments were recorded while monitoring photometric quantities relevant to visual comfort using high dynamic range luminance imaging. Integration of the luminance images coupled with eye tracking enabled us to obtain the gaze-centred luminance fields, which gives a better estimate of actual luminance values perceived by the eye, used as a basis to investigate the gaze direction dependencies of visual comfort.

This PhD dissertation describes different stages of conception of this novel dynamic discomfort glare assessment method. In the experimental phase, two pilot studies were made for proper integration of the adopted methods and techniques into discomfort glare assessments. Development of several routines, algorithms and tools to identify and translate the gaze directions in order to derive the actual luminance field perceived by the participants were needed to achieve this goal. A final comprehensive experimental phase was realised to investigate gaze behaviour in response to light. As a first validation step, the gaze-driven approach was compared to the fixed-gaze approach. Then the effects of different luminance levels as well as different view outside the window on the dynamic shifts of the gaze were investigated.The developed approach demonstrates the need to integrate gaze direction patterns into visual comfort assessments, which move us beyond the existing assumption of a fixed-gaze direction towards a gaze responsive comfort.

Mandana Sarey Khanie’s Ph.D. thesis is available at http://infoscience.epfl.ch/record/208929.

POWERED BY NATURE – The psychological benefits of natural views and daylight

For centuries nature has been our habitat. Many aspects of this natural habitat still have pronounced influence on our health and wellbeing. In this dissertation, two important aspects of nature have been studied; views to nature and exposure to daylight. The main focus has been on positive effects of these two phenomena as well as on the underlying psychological pathways of these beneficial effects.

The first chapter of this dissertation presented a review of the evidence for beneficial health effects of nature and daylight. The main conclusion of this chapter was that natural views and daylight exposure rendered very similar beneficial effects on a variety of health outcomes, but both phenomena have been studied in two separate research fields. Not only did this separation oftentimes result in ignorance with respect to contributions of one phenomenon while studying the other, but there were also substantial differences in the experimental paradigms used, the outcome variables, and the proposed underlying mechanism. Therefore, it was as of yet unclear whether natural elements and daylight exhibit similar beneficial effects and whether they share psychological underlying pathways. For these reasons, the aim of this dissertation was twofold. First, we wanted to test whether daylight and natural environments share underlying psychological mechanisms. Second, beneficial effects of nature and daylight were studied separately, but within uniform research paradigms to establish whether their health-benefits overlap.

A first series of experiments investigated possible underlying psychological pathways. The focus was on preference and associative pathways. Preference ratings are important in view of the adaptive function of preferences, guiding humans toward healthy -and away from unhealthy- environments. Chapter One reported a consistent preference for environments that are natural, bright, and sunny as opposed to urban, dark, and overcast environments. These findings were found for explicit preference, but not for implicit preferences. Two studies also investigating implicit preference for environments differing in naturalness, brightness, and weather type did not yield any evidence for implicit preferences. Importantly, we were also not able to replicate earlier findings concerning implicit preferences for natural environments. Preference for daylight over artificial light was further reported in Chapters Four and Six and higher preference ratings for natural as opposed to urban environments were reported in Chapters Three and Five. These higher preference ratings provided a first indication for possible restorative effects of daylight through psychological pathways.

Psychological mechanisms were further investigated in Chapters Three (for nature) and Four (for daylight). This time, the focus was on associative patterns, which are closely related to preference formation and have been previously theoretically linked to restorative potential. The series of experiments performed in these two Chapters aimed at testing whether and how associations differ between nature or daylight and their artificial counterparts. Results indicated that both daylight and natural environments generally evoked more positive associations than respectively electric light and urban environments. The valence of the associations generated with natural as opposed to urban environments mediated the preference ratings for these environments. The causal directionality of this relation was further investigated for natural environments by guiding the valence of associations. To this end, participants were instructed to generate either only positive or only negative associations and to suppress all oppositely valenced associations. The outcomes of these conditions rendered mixed results. Preference ratings for natural environments remained unaffected by the association instructions, whereas preference ratings for urban environments declined when generating only negative associations as compared to only positive associations.

Whereas natural environments and daylight both evoked more positive associations, the influence of these associations on preference formations differed between them. For natural environments, the valence of associations significantly mediated the effect of environment type on preference. However, for daylight the valence of associations did not mediate preference outcomes. Therefore, we did not guide the valence of associations with daylight versus electric light.

Not only did we investigate the relation between valence of associations and preference, we also studied the role of associations in restorative outcomes. For both natural environments (Chapter Three) and daylight (Chapter Four), little evidence for restorative effects of the manipulation was found. We hypothesized that the association generation task possibly interfered with the restoration process. On the other hand, in Chapter Three, we found that generating positive associations resulted in an improved restoration of positive affect. We postulated that natural environments generate more positive thoughts and that positive thoughts, in turn, can be restorative.

From the studies investigating psychological pathways for the effects of nature and daylight, we learned that they both generated more positive associations and higher preference ratings than electric light and urban environments. However, the relation between associations and preference ratings appeared to differ between the two phenomena, indicating that they could work through different psychological pathways.

These differences between daylight and nature proceeded when comparing the beneficial effects of nature and daylight on self-regulation, mood, and physiology. A uniform research paradigm was chosen to test these effects; ego-depletion. Chapter Five focused on the effects of nature, while controlling for daylight influences and Chapter Six investigated beneficial effects of daylight as compared to electric light while view content was kept constant.

In both chapters, the ego-depletion inductions were not always successful. Irrespective of this, Chapter Five reported consistent beneficial effects of natural environments on Heart Rate Variability and hedonic tone. By testing effects of nature after a depleting as well as a control task, we were further able to challenge the notion of restorative versus instorative effects. Contrary to the beneficial effects found for natural environments, no such effects were found for daylight. No difference in restoration outcomes were reported for daylight as compared to electric light in Chapter Six.

To conclude, we found that both daylight and nature generated higher preference ratings as well as more positive associations than their artificial counterparts. In a uniform research paradigm we established beneficial effects of nature, but not of daylight. In Chapter Seven, we postulated that the lack of evidence for beneficial effects of daylight could be due to the separation of daylight from view content. The psychological benefits of daylight may depend on exactly the factor we tried to single out; view content.

Femke Beute PhD Thesis is available at http://repository.tue.nl/780722

People have a deeply rooted need to experience control. Today we are surrounded by intelligent systems that take decisions and perform actions for us. This can make life easier, but there is a risk that users experience less control and reject the system. The central question in this thesis is whether we can design intelligent systems that have a degree of autonomy, while users maintain a sense of control. We try to achieve this by adding an ‘expressive interface’: the part of a system that provides information to the user about the internal state, intentions and actions of the system. We examine this question both in the home and the work environment.

In the workplace, we have focused on automated blinds systems. For 20 weeks, we have monitored the use of automated blinds in 40 offices and studied the user experience. Over 75% of users switched off the automatic mode permanently. This shows that users are not satisfied with the automatic behavior and want to operate the system themselves. However, this leads to less energy savings in a building than expected. Simulation results indicate that offices in which the automatic mode is deactivated consume on average about three times more energy for heating and cooling than offices in which the automatic mode is active. We therefore propose to improve the acceptance of automated blinds by making users aware of how the system works and how its use affects energy consumption. We designed an expressive interface for the automatic blinds consisting of a light feedback device that informs users about the current daylight conditions and the upcoming or recommended blinds adjustments. We have mounted the expressive interface to a virtual window with automatic blinds and tested the system in two user experiments. The results show that the addition of an expressive interface enhances the users’ satisfaction. Additionally, users made fewer corrections after an automatic adjustment of the blinds and they followed the suggestions of the system more often than with the system that had no expressive interface.

This thesis shows the potential of the expressive interface as an instrument to help users understand what is going on inside the system and to experience control. The expressive interface might be essential for the successful adoption of the intelligent systems of the future.

On July 5^th 2016, Bernt Meerbeek defended this thesis Cum Laude at the Eindhoven University of Technology. The thesis can be downloaded here

The distinctiveness of natural light in a built environment is a confluence of its physical feature––buildings, trees, and the ground––with its region-specific daylight source––the sun and the sky. The colours and patterns we see around us at different scales of cities, neighbourhoods or streets is the result of these complex interactions between the physical features and characteristics of its daylight. The current daylighting modelling workflows do not account for this distinct quality of light as the focus of performing a daylight simulation is to predict and plan for optimal quantities of light. Hence, surrounding buildings are usually modelled as ‘obstruction’ boxes with an assumed average reflectance of 30%; trees are modelled as spheres, cones or cylinders with assumed reflectance of 20%; and equal spectral energy sky models such as the CIE standard or all-weather Perez skies are used that lack spectral and colorimetric information. Two of the prime attributes of daylight in Singapore and an equatorial climate––patterns of light through trees and colour renditions of the built environment due to changing colours of the sky––are currently not represented in daylight prediction workflows. Therefore, the goal of this research is to first measure and model light through trees, and second measure and model interactions of Singapore’s built environment under various sky conditions typical of an equatorial climate. The first phase of the research presents the open-source program to generate a tree crown model that mimics the distribution of the measured leaves and gaps of a tree. This tree crown model, when used in daylight simulation workflows, helps predict their unique spatial and temporal transmittance and shadow patterns. In the second phase of the research, a detailed analysis of the spectral and colorimetric characteristics of the equatorial sky and its influence on Singapore’s built environment is presented. Two multi-spectral daylight rendering platforms are also compared for their visual, spectral and colorimetric representations of the equatorial light. This phase provides a framework for architects and designers to compute climate and context-specific daylight information and use an appropriate multi-spectral daylight rendering platform to compute colour-dependent visual perceptions.

The full Ph.D. thesis can be accessed here.

Contact Email: prijibalakrishnan@gmail.com

Additional Information: http://priji.com/

The objective of this thesis was to facilitate an integrated building design process applicable to office buildings in Nordic climate with respect to thermal comfort, daylighting and energy use. The thesis is divided into three main parts.

Part I contains a literature review carried out to investigate if the present thermal comfort and daylight design practices constitute any obstacle for conducting an integrated design. Based on findings in the literature it was suggested that modelling of mean radiant temperature (MRT) should be improved by considering the location in the room, accounting for both long-wave and short-wave radiation. With respect to daylight design it was suggested that static daylight calculations should be replaced by dynamic ones and that climate-based measures should be used in the evaluation of daylight supply and glare. Examples of measures for daylight supply are given in the literature (e.g. UDI and DA). Candidates for glare might be horizontal or vertical illuminance. Additionally, it was investigated how solar shading control should be modelled, since the fenestration system and its control is a crucial link between the thermal and daylighting performance. It was suggested that shading control strategies preferably should be multivariable and incorporate variables related to interior conditions. It was proposed that the tilt angle should be considered as a control variable for shading with blinds. Furthermore, it was found that more knowledge is needed regarding user acceptance of automatic solar shading controls.

Part II describes verification of improved models of MRT and daylighting implemented into the simulation tool IDA ICE, which is one of the steps to make the integrated design method practically applicable for building designers. The new MRT model takes short-wave radiation hitting the occupant into account. The new daylight feature utilises the Radiance engine and the climate-based three-phase method, which arranges for daylight calculations to be conducted based on the same underlying boundary conditions as used in thermal comfort and energy calculations. Further, Part II describes the results from an occupant survey carried out to investigate occupants preferences with respect to use of automatically controlled venetian blinds and their sensation of glare in an office work environment. The results from the occupant survey indicated that views to the outside were an important factor for the occupants and it confirmed that the tilt angle should be incorporated as a control variable in the shading strategy. The results further indicated that there was a statistically significant correlation between both vertical eye illuminance and horizontal illuminance at the desk and the occupants’ perception of glare. Based on this study, threshold of 1700 lux vertical eye illuminance at the occupant position and 1900-2100 lux horizontal at the desk was found to be reasonable for avoiding excess glare perceptions in perimeter zones. Part II is ended with a proposal for a solar shading strategy suitable for office buildings in cold climates. The proposed strategy is based on a modified version of a control algorithm developed within the Norwegian R&D project “Glazed facades keeping what we promise”. The strategy is improved with findings from the literature and results from the occupant survey by utilising tilt angle as a control variable as well as applying vertical illuminance of 1700 lux as activation criterion. Full-scale measurements during both winter and summer conditions along with annual simulations verified high energy, thermal comfort and visual performance; resulting in better performance than with the use of a conventional strategy where the shading is activated according to external irradiance with closed slats in activated position.

Photo of the south façade of the Cube and section and plan view of the experimental room and placement of sensors in the experimental room.

Studies show that shading devices have a positive impact on the energy performance of buildings and in the visual and thermal comfort of their interior spaces. However, such systems are classified as Complex Fenestration Systems (CFS), which usually present very complex optical properties, making them very hart to model within energy performance and lighting simulations. In the last few years, using the concept of Bidirectional Scattering Distribution Function (BSDF), different software have been provided with modules that allow modeling them more accurately, taking into account their complex optical behavior.

Since CFS are installed for providing simultaneous enhanced lighting and thermal environments, performing integrated simulations between those two domains is a necessity. Also, since shades and luminaires of the building will be handled by occupants and/or automatic systems, simulation not only has to be integrated, but also has to involve control. The purpose of this thesis is to advance in the development of a tool that allows performing integrated lighting/thermal analysis of spaces with controlled CFS and artificial lighting. According to this, it was concluded from the literature review that the assessment of the solar BSDFs of CFS, and the implementation of a methodology for performing integrated analysis are crucial steps in the process, and required simplification.

This thesis shows, comparing results with analytical solutions, that genBSDF tool is capable of assessing solar BSDFs of CFS. Also, the development of a new program, mkSchedule, is explained. This program intends to simplify and improve the integration of lighting and thermal software. Finally, a design methodology is proposed. This methodology allows performing integrated lighting and thermal analysis of spaces with controlled artificial lighting and CFS. Even more, it allows designing not only the building itself, but also the CFS, the artificial lighting and the control algorithms. The thesis is closed with an analysis of a simple case study.

The full thesis is available here.

“Space and light and order. Those are the things that men need just as much as they need bread or a place to sleep.”
[Le Corbusier]

Exposure to light, and especially to daylight, has much to offer. Regarding buildings’ occupants, daylight has been shown to boost performance, improve sleep, provide a connection to the outside, increase comfort, lessen agitation, and reduce depression. Regarding buildings, daylight enhances the aesthetics of a space and improves its energy efficiency. On one condition, though: that it does not produce visual discomfort. In order to harvest the benefits of daylight, visual discomfort has to be minimized. Hence, discomfort glare from daylight should be predictable.

To date, more than twenty daylight discomfort glare models have been developed. However, none of them can consistently and accurately explain the large variation between subjects’ discomfort glare perception. Improving current models predicting discomfort glare perception remains a crucial step to move towards optimal daylighting design in buildings.

In this context, it is hypothesized that the prediction of discomfort glare perception can be improved by including relevant additional factors related to the context or to the subject in the models. The main research question that this study aims to answer is to determine whether one of these factors, namely the socio-environmental context of the subject, influences discomfort glare perception from daylight in office buildings. The socio-environmental context is defined here as the climate and habitat, including indoors and outdoors, to which a subject has been acclimatized, her/his behavior toward these elements, and her/his expectations about them. Two additional research questions aim at investigating other potentially influencing factors and potential experimental biases in order to guide further research in the field.

For this purpose, a field study was conducted in real office buildings located in four socio-environmental contexts, i.e., Chile, Belgium, Japan, and Switzerland. Discomfort glare perception evaluations, each consisting of a subjective assessment of discomfort glare from daylight and the measurement of the visual stimulus, were collected at the office desk of the 401 subjects who took part in the study. The raw data was processed to derive useful information, and cleansed according to specific rules to ensure data quality.

Different statistical analyses were conducted on the processed and cleansed data to answer the main research question. No statistically significant differences in the sensitivity to discomfort glare from daylight could be observed between the subjects acclimatized to the Chilean, Belgian, Japanese, and Swiss contexts. The results show therefore no evidence of an influence of the socio-environmental context of a subject on discomfort glare perception from daylight in office buildings.

Furthermore, the influence of several other factors on discomfort glare perception from daylight in office buildings was tested and the data was further analyzed regarding potential experimental biases in order to answer the two additional research questions.

A statistically significant effect was found for three factors, namely the self-assessed glare sensitivity, the attractiveness of the view through the window, and the indoor air temperature. From this result, it can be hypothesized that these factors could influence discomfort glare perception. Moreover, further analyses suggest that two experimental biases, namely the glare rating scales and the study type, could be influencing the results of studies on discomfort glare perception. However, since the study was not specifically designed to answer these two additional research questions, and in view of its limitations, no conclusion can be drawn on these last observations. They can, however, be used to guide the development of future studies.

In conclusion, this research provides no evidence that discomfort glare from daylight is perceived differently in different socio-environmental contexts. Research efforts in discomfort glare perception from daylight should therefore aim at improving prediction models by looking at other potential factors, such as physiological and environmental ones. Finally, future studies should also aim for the validation of reliable methods to study discomfort glare, and for the development of a unified methodological framework to promote the reproducibility of studies and the comparability of results.

This thesis introduces a new approach to characterize and evaluate ocular light exposure based on the discovery of novel blue light-sensitive photoreceptors in the human eye. These photoreceptors are the primary mediators of ‘non-visual’ responses impacting human health, from resetting the circadian clock to directly alerting the brain. In recent years, studies have found that light at short-wavelengths is more effective than light at longer wavelengths at inducing and suppressing a range of ‘non-visual’ responses. Although it has been recommended that we approximate the spectral sensitivity of these novel photoreceptors with an action spectra peaking near λmax = 490 nm, the optimal approach for quantifying non-visual spectral effectiveness is yet unknown. These novel photoreceptors, in addition being photoreceptors themselves, receive inputs from the classical photoreceptors (rods and cones) that in return affect the overall spectral sensitivity of the non-visual system as it changes with lighting conditions. Due to this time-varying spectral sensitivity and the relatively slow temporal processing, the relation between dynamic external light stimuli and the magnitude of non-visual responses cannot be explained with a single function or a simple threshold value.

To better understand these non-linear and unknown relations, this thesis aims to develop a novel computational method, based on recent findings about the ‘non-visual’ — also called non-image-forming—effects of light on human health. A dynamic wavelength-dependent model framework is proposed to evaluate the non-visual health potential of light. This novel approach integrates the spectral effectiveness of irradiation and accommodates time-varying spectral sensitivity functions. These time series of light quantities serve as inputs for the light-driven model, which accounts for light intensity, duration, history, and timing of light exposure. By quantifying light in terms of spectral effectiveness and temporal dynamics, different light exposure patterns can be ranked in terms of its potential to have an impact on human health.

The final objective of this thesis is to support the design of healthier buildings by applying evidence-based lighting criteria, which can then inform architectural design through a simulation-based approach. Incorporating non-visual effects into a building simulation workflow requires a good approximation of daylight spectra as it varies with sun position and sky type. Performance predictions must also account for occupant behavior and scheduling, which brings us to the question: How can we apply such a method to make informed decisions about our built environment? The integration of the proposed model into a functional simulation workflow is demonstrated using an architectural case study but first the non-visual spectral effectiveness of light will be evaluated under varying sky conditions to analyze the model output sensitivity to input accuracy. The model and its application to the built environment will then be investigated using multiple view directions and by considering occupant behavior and scheduling to make an immersive prediction within a space.

This novel computational approach can be seen as a first step towards human-centric lighting application, simulating an occupant’s light consumption to evaluate non-visual health potential that can support decision-making in the built environment.

The thesis can be accessed here.

In our experience of daylit architecture, our visual perception is greatly impacted by the ephemeral and inherently dynamic conditions of the surrounding environment. Driven by changes in sky type, time-of-day, and time-of-year, these variable conditions can alter our impressions and appraisal of indoor space. Daylight, including both direct sunlight and indirect skylight, drives a powerful range of perceptual phenomena, which transform structured geometry into a time lapse of slow and smooth or fast and harsh ethereal effects.  Between the disciplines of architectural design and building engineering, there are many approaches to evaluating daylight performance, from qualitative considerations such as texture, color, spatial depth, and ambiance to compliancy targets regarding task performance, energy, and visual discomfort.  While some of these considerations, like visual discomfort, are both quantitative in prediction method and qualitative in subjective evaluation, there are few quantitative measurements developed to predict the positive perceptual impacts of light on human perception. Unlike other environmental factors like temperature, air quality, and sound, daylight creates direct impacts on the appearance of a space and cannot be divorced from the simultaneously aesthetic implications it has on architectural design.  Research in daylight is therefore necessarily interdisciplinary, as it integrates physics, with the psychology of emotion, the bio-mechanics of perception, and the aesthetics of architectural design.

To integrate perceptual, aesthetic, and emotional considerations into lighting performance evaluation, the aim of this thesis is to determine whether objective, quantifiable characteristics of luminous composition within an architectural scene can be linked to subjective evaluations of visual interest (like contrast, excitement, pleasantness, etc) and whether these characteristics are sensitive to temporal dynamics. This thesis begins with a review of existing quantitative measures for predicting contrast perception in daylit scenes (both real and digital) and presents a comparison of these measures using a catalogue of rendered scenes.

Through a pair of experiments designed to induce visual effects and record subjective responses – an online survey using 2D renderings and an immersive 3D study done in Virtual Reality -, this doctoral thesis introduces a method for predicting those perceptual responses using image-based algorithms and a proportional odds model. Using the algorithms and model developed from experimental data, a visually immersive, simulation-based approach is adopted for evaluating and visualizing predictions of visual interest and excitement through space and over time.  By selecting a series of architectural spaces to exemplify this approach, dynamic predictions of daylight-induced excitement across an array of eye-level view positions show the highly variable nature of perceptual performance and its capacity to impact occupant appraisals of space.

The novelty of proposed measures, prediction model, and simulation-based approach provides an exciting new frontier in daylight performance evaluation, giving rise to the importance of occupant perception alongside existing task, energy, and comfort considerations.

The thesis can be accessed here.

Discomfort glare is considered to be an annoyance or distraction caused by sources of non-uniform or high luminance within the field of view of an observer. There are still significant gaps in our understanding of the conditions that characterise the magnitude and occurrence of discomfort glare, this being especially evident in the presence of large sources of luminance such as windows. The large degree of scatter that is observed when subjective evaluations of glare sensation are compared against calculated glare indices suggests that discomfort glare may be dependent on other variables beyond the physical and photometric parameters that are commonly embedded in glare formulae (e.g., source luminance, source size, background luminance, and position index). There are strong reasons to believe that some of these variables might be linked to the time of day when the observer is exposed to the glare source. In response, this thesis investigated the research hypothesis that subjective glare sensation is associated with temporal variability. This hypothesis was tested in two stages. The first stage was conducted within a laboratory setting, and sought to examine temporal effects under controlled artificial lighting conditions. The collection of temporal variables and personal factors – thereby examining the scatter in glare responses across the independent variable (time of day) and isolating potential confounding variables – enabled to identify factors that could influence the subjective evaluation of glare sensation along the day. Having established the presence of a temporal effect on glare response, the influences detected were further explored within a test room with direct access to daylight, whereby temporal variables and personal factors were measured in conjunction to glare sensation for them to be statistically masked from the analysis. The results confirmed the hypothesis of an increased tolerance to glare as the day progresses. This supported the conclusion that physical and photometric parameters alone are not sufficient for a robust prediction of discomfort glare.

The thesis can be accessed here

The objective of this thesis is to provide a decision tool to evaluate the daylighting potential of a space considering also its thermal component in order to balance the presence of daylight illuminances and solar heat gains to provide enough daylight for visual tasks avoiding situations of discomfort, such as glare or overheating.

This research is based on the evidence that the amount of daylight that enters into space has, at the same time, luminous (solar radiation in the visible spectrum) and thermal effects (solar radiation in the infrared spectrum). Nevertheless, both aspects are studied nowadays separately, so this research proposes an integrated study.

In addition, the Climate-based Daylight Modelling allows to obtain illuminance values with the same time-step resolution and climatic dependence that the values of solar heat gains obtained by means of thermal simulation.

Once the differences in the calculation methods of the daylighting and insolation metrics are highlighted, this thesis establishes a common calculation frame which allows to obtain the illuminances that simultaneously are reached in the work plane and compare them with the solar heat gains in the space.

In order to evaluate the daylighting potential of a space and limit the solar heat gains that provoke discomfort, 5 metrics have been defined on the basis of the Daylight Sufficiency criterion (300 lux, 50 % time, 50 % workplane), the illuminance ranges recommended for the development of visual tasks and the irradiance upon which user close blinds due to glare or overheating.

In addition, by means of a parametric analysis, this research applies the methodology developed to analyse the influence of different architectural design parameters in the daylighting and insolation potential.

The results have allowed to obtain the behaviour or trend of each one of the parameters, the capacity of every parameter to modify each of the metrics and a certain classification of the influence of these parameters on daylighting and insolation.

These results allow to establish design recommendations and to prioritize those parameters of architectural design that must be considered in order to provide a daylighting that balances daylight illuminances for visual task and avoids excessive illuminances and/or solar heat gains that produce glare and/or overheating.

This approach, therefore, supposes a first step in combining daylighting potential of a space and its correlated heat gains.

The thesis can be accessed here

Dr. Paula M. Esquivias Fernández can be contacted: paula.esquivias@gmail.com

Daylighting in offices creates a comfortable and healthy working environment for its users. Additionally, it can decrease the electricity consumption for artificial lighting. However, maximizing the amount of daylight can cause some issues. In Northern European climates, visual discomfort is the most negative side effect from windows. Also, excessive short-wave directly-transmitted solar radiation and long-wave indirectly-transmitted energy can cause thermal discomfort and an increased energy demand for cooling. To counterbalance these problems, designers implement shading systems, which control the transmitted solar and visual radiation. Different control strategies exist, but researchers evaluate their performance merely by checking the impact on the energy need, without considering the visual comfort of the user. Furthermore, the acceptance and satisfaction of the user regarding these strategies remains low.

Therefore, we developed a control strategy that is based on the comfort requirements of the users. The control strategy aims at avoiding visual discomfort for the user, while optimizing for daylight availability and improving user satisfaction. This is the first study where a shading device is controlled by a controller system with a low-resolution camera. The controller system captures luminance maps and evaluates a visual comfort parameter, namely the ’Daylight Glare Probability’. The system controls the actuator of the shading device based on the assessed level of comfort. The user can override the automated control and the controller system will adapt itself to the preferred user set-point.

This thesis uses numerical simulations of an indoor environment to check the performance of the control strategy in terms of the impact on the energy consumption and the visual and thermal comfort. Next, the thesis demonstrates two experimental case studies where the low-cost controller system and the control strategy are implemented. The controller system keeps the discomfort glare below the predefined limit and reduces the cooling demand, while sufficient daylight can still enter the office room.

Full thesis can be accessed here, under the Files

Climate-Based Daylight Modelling (CBDM) can be defined as the assessment of the luminous conditions within the built environment that makes use of representative climate data to recreate realistic sky luminance distributions, at hourly or sub-hourly consecutive steps, by means of physically accurate lighting simulation tools. CBDM made its appearance among other Building Performance Simulation disciplines relatively recently, marking a profound change from the previously established daylighting analyses, such as the Daylight Factor and Sun Path diagrams. Daylight metrics derived from CBDM now appear in building guidelines, and CBDM evaluations are becoming widespread in design practices since they have proven to be a powerful tool to extract a wealth of information on the daylighting annual performance of buildings. However, despite the now widespread use of CBDM, the findings of this thesis showed that the accurate representation of direct sunlight still poses significant challenges for current simulation tools, due to its high intensity, variability and directionality. This has important consequences for any evaluation that depends on the effects of sunlight and indicates that further research in the field is required.

The objectives stated in the thesis aimed at broadly assessing the applicability of CBDM by looking at multiple aspects: (i) the way CBDM is used by expert researchers and practitioners; (ii) how multiple state-of-the-art simulation techniques compare to each other and how they are affected by uncertainty in input factors; (iii) how the simulated results compare with data measured in real occupied spaces.

The answers obtained from a web-based questionnaire portrayed a variety of workflows used by different people to perform similar – if not the same – evaluations. At the same time, the inter-model comparison performed to compare the existing simulation techniques revealed significant differences in the way the sky and the sun are recreated in each technique. The results also demonstrated that some of the annual daylight metrics commonly required in building guidelines are sensitive to the choice of simulation tool, as well as other input parameters, such as climate data, orientation and material optical properties. All the analyses were carried out on four case study spaces, modelled on existing classrooms that were the subject of a concurrent research study that monitored their interior luminous conditions. A large database of High Dynamic Range images was collected for that study, and the luminance data derived from those images could be used to extend this work to explore a new methodology to calibrate climate-based daylight models.

The results collected and presented in this dissertation illustrate how, at the time of writing, there is not a single established common framework to follow when performing CBDM evaluations. Several different techniques coexist but each of them is characterised by a specific domain of applicability.

The thesis can be accessed here

It is already challenging to make small changes to buildings – painting the window panels, upgrading the kitchen, or even (as many Copenhageners are familiar with) installing a shower. But there is a pressing need for more extensive change – we need to learn how to build again and build more sustainably. As part of the EU Marie Curie project “Innovation for Sustainability (I4S)”, my PhD dissertation investigates how the Active House Alliance and their co-founder, VELUX, experiment with demonstration houses in order to develop a sustainable building standard for a trifecta: environment, energy, and comfort. In other words, it examines how they use experiments (building, then building again) to best synergize the three and holistically improve building practice.

The third dimension “comfort” has been particularly challenging to develop in that there has not historically been a formal definition or measurement of comfort in buildings. The PhD’s first article delves into how Active House goes about legitimating technical specifications (i.e. measurable parameters) for comfort in buildings. Not least of all, this has involved revisiting basic elements like light exposure, air exchange, and indoor human health (see for example the Circadian House Report). The research finds a reciprocal relationship between commensuration (conversion of qualities into comparable quantities, see Espeland & Stevens, 1998 and 2008) processes and legitimacy building – both among other professionals internationally and locally in the context of the projects.

The second article addresses structurally influencing the building users towards sustainable consumption – so that by design, people may behave more sustainably in buildings. Buildings are made with default rules: the rules for which infrastructural set-ups come ready-made. We know that default rules can affect sustainability-related behaviors (Mont et al., 2014; Sunstein & Reisch, 2013; Dolan et al., 2011; Brown et al., 2013). For example, the space orientation determines how much light a living room receives, and thus when and how for how long one uses lights. The literature holds that default rules work, in part, because they do not engage people’s awareness. However, this research finds that, in relation to sustainable consumption, that there are further nuances. Where at first people are unaware of how the defaults are affecting their behavior, after they leave the experimental buildings and live in their former, non-sustainably designed structures, the contrast makes them aware. It is this change that gears them towards making more sustainability-oriented consumption choices in the future.

Lastly, the third paper delves into the development of sensor-based building technology systems, such as WindowMaster, NetAtmo, Nest, and so forth. In an era of pressure for technologies that can decide for or replace the actions of people (McIntyre-Mills, 2013), building systems can manage entire households – from running grocery lists and scheduling exercise to adjusting electricity usage and changing temperature. At the same time, the building industry grapples with the performance gap, wherein the planned energy performance of buildings does not match reality, largely explained by failures to grasp how people will behave (Frankel et al., 2015). Rather design needs both technical and social considerations (Maguire, 2014). This article uses the Active House building demonstrations to show how these experiments have helped standards makers to learn from too much focus on technological automation – as it leads to an overshoot, wherein people feel too controlled by technology and either submit or tamper with it, akin to technological interaction highlights in the works of Rip and Kemp (1998) and Shove (2003). The paper argues that the pendulum can swing too far towards technological reliance, and that co-design, a balance between human and technological development is needed – especially under seeking sustainable solutions to societal challenges.

Altogether, the idea is: that which is built can be rebuilt, our norms and practices are fluid and constantly under development. In the case of sustainable building, governance projects and experiments must tackle challenges of measurement, consumer base, and rapidly evolving technologies. It is an era of uncertainty, wherein there are no clear trajectories for sustainability transitions; but when experimenting within the frame of learning and adapting for the next steps, we can lay the first building blocks.

The thesis can be accessed here

Development of a simple framework to evaluate the daylight conditions in urban buildings in the early stages of design

The thesis proposes a simple method to aid urban designers in the daylighting aspect of the decision-making process in the early stages of design when the outline of the city is defined. As input to this simple method, complex simulations of the urban canyon structure were made. Paper I reports on a study on the simplified representation of the structure of the streets and buildings in cities. From the results in this study, a simple 4-step method was developed to evaluate facades in an urban context based on daylight simulations in which the densities of the urban building layout, external surface reflectances, and facade window areas were varied. The method developed was based on a CIE overcast sky, so it did not consider the effect of building orientation, geographical location, changes of sky distribution, or the time of day on its results. In Paper II, climate-based daylight simulations of the urban structure were introduced. The climate-based simulations consisted of annual simulations of the daylight conditions. These simulations took into account the enormous variations in daylight illuminances during the year as well as geographical location, facade orientation and user occupancy patterns. For these simulations, the luminance distribution of the sky was described by the Perez all-weather sky-model, based on hour-by-hour input of direct and diffuse irradiance from weather data files.  This meant that the weather data files used had an important impact on the simulations. In Paper III, the impact of different weather data sets for a given location and of the time-steps applied was therefore investigated. Occupancy patterns also have an important impact on climate-based daylight simulations. The effect of applying occupancy profiles of varying complexity was investigated in Paper IV. In the urban planning stage of design, you usually know very little, or nothing, about the future occupants of the building, so it is useful to know whether detailed simulations of occupancy profiles, as opposed to using simplified assumptions, would increase the value of the simulation.

The general hypothesis to be evaluated in this thesis was that: Simple models for the early stages in the design of urban building structures can represent the complexities of daylighting without loss of important characteristics.

This hypothesis was investigated through the work reported in the four papers appended. The research showed that the simple method can be expanded to include more complex aspects if the simplifications include the important parameters. To transform complex urban simulations into the simple 4-step representation, it was necessary to include simulations with i) various facade reflectances, ii) rooms located on different floors, iii) buildings with different orientations, and iv) buildings in different geographical locations. So when the right framework is set-up, the general hypothesis was confirmed. The more complex model of the urban structure used weather and occupancy data. The research showed that it made very little difference to the simulation outcome if different weather data files were applied for a given location. Furthermore, simulation with hourly mean irradiance values, as opposed to 1-min resolution, also made little difference to the simulation outcome. This means that simulating the urban structure based on hourly-mean values is sufficient. From the investigations made on the impact of occupancy profiles, it was found that applying an absence factor, as opposed to simulating the dynamic presence of occupants, also made little difference to the simulation outcome. In other words, the complex input in terms of the presence of occupants can be reduced to an absence factor.

Anne Iversen’s thesis can be downloaded at http://www.byg.dtu.dk/~/media/Institutter/Byg/publikationer/PhD/byg-r256.ashx

ARCHITECTURAL EXPERIMENTS. Design with Knowledge

The vision of creating balance between the consumption and production of energy in our build environment has created ambitious energy targets and requirements in the building regulations, which has accelerated the development of new energy optimized technologies and components. This has increased the focus on quantitative values in the process of designing energy optimized buildings. There is a need to focus on user aspects and qualitative values by retaining architectural qualities through transdisciplinary design processes: processes where scientific and technical knowledge is mixed with cultural awareness in a “hybrid imagination”, processes where scientific and creative methods are united through designing with several criteria. In the thesis it will be discussed, how this can be done using light as a multidimensional design element in architectural experiments.

The thesis is motivated by my experience from a number of interdisciplinary architectural experiments, which I have realized in the period 2001-2011 as a researcher and teacher at schools of architecture and as a project manager in the construction industry. Through these I have developed methods, concepts for collaboration, cross-disciplinary research, education, industry, technology, developmental environments and practice in the process of developing energy producing technologies, components and buildings with architectural potentials.

Three experiments from my previous work are used as the empirical material in the thesis to demonstrate: a model to collaborate and incorporate knowledge from a diversity of fields by defining criteria and visions, constructions and various methods for compiling and synthesizing the values. In all three experiments light is central as a multidimensional design element, both to produce energy and add architectural values.

The theory in the thesis is drawn from knowledge from different fields such as architecture, innovation, design and anthropology to form a multidisciplinary theoretical platform discussing how to mix and transform knowledge through experiments.The thesis thus addresses the question, how can knowledge of light from different disciplines support a creative design process and generate new knowledge, which supports a sustainable development?

To approach the problem area of the development of knowledge through design in a transdisciplinary environment, the three experiments and the supporting theories demonstrate that research from different traditions can be integrated with distinct criteria in the projects. It is thus possible, in the same process, to work with hypotheses that are tested in parallel with the three criteria on the basis of technical/scientific, social science and art/humanities traditions.

It is intended that the outcome takes the form of generalized discussions, principals and concepts that can be adapted to individual development and educational progress and thereby create added value in sustainable living environments with focus on the natural resource of daylight – an energy source and an architectural potential.

This is a PhD thesis ‘without previous studies’, which means that publications from previous work are part of the thesis and will be included in the assessment.

The thesis can de downloaded from this link: http://www.create.aau.dk/images/Design_med_viden_Phd_indhold.pdf

DAYTIME LIGHT EXPOSURE – EFFECTS AND PREFERENCES

Light enables us to see the world around us, but is also important for our physiological and psychological functioning. During the last decades, light has become an important research topic for engineers, chronobiologists and neuroscientists. Developments in lighting technologies (e.g., LED) are offering new possibilities for flexible, dynamic and personalized lighting applications. Moreover, the discovery of a third (non-rod, non-cone) photoreceptor in the human retina has significantly advanced our knowledge about the role of light in human behavior and physiology. A substantial body of research has demonstrated the relevance of light exposure for circadian regulation. In addition, research has shown acute activating effects of bright light exposure on subjective and objective indicators of alertness and arousal. These studies have revealed robust effects in the late evening and at night. Yet, to what extent and under what conditions such effects exist during daytime for healthy day-active persons is largely unknown.

In the current thesis, we studied the relation between diurnal light exposure and human functioning during daytime, from a more psychological perspective. Complementing earlier studies performed in domains of chronobiology and neuroscience, we explored the role of daytime light exposure in human mental wellbeing, health and performance, focusing on individuals’ behavior, experiences and preferences during regular daytime hours. To this end, a series of studies were performed to investigate potential alerting and vitalizing effects of bright light exposure during daytime on subjective experiences, task performance and physiology and to explore whether individuals’ appraisals and light preferences reflected these effects. A field study was performed to investigate daily light exposure patterns and explore the relationship between light exposure and feelings of vitality during daytime. Moreover, a series of laboratory studies was performed to explore effects of bright light exposure during regular daytime hours on self-report, task performance and physiological arousal measures. In addition, we investigated preferred light intensity as a function of alertness, vitality and performance, to explore whether persons would prefer a higher illuminance level, i.e., seek more light, when they felt mentally fatigued and depleted than when feeling more alert and vital.

Schematic overview different routes for potential effect of light on human functioning.

Together, these studies demonstrated the relevance of light exposure for mental wellbeing and performance, even during daytime and in everyday life. Results of the field study showed that hourly light exposure was significantly related to feelings of vitality, indicating that persons who had been exposed to more light felt more energetic immediately afterwards. In line with these results, our laboratory studies showed that more intense light induces alertness, assessed with self-reports and some indicators for task performance and physiology, even during regular daytime hours (i.e., in the absence of sleep and light deprivation). More specifically, bright light exposure induced higher feelings of alertness and vitality, resulted in faster responses in sustained attention tasks and higher physiological arousal (measured with EEG power density in the theta range, heart rate and skin conductance level). Yet, effects on subjective alertness and vitality as well as on sustained attention were more consistent than the effects on the measures for cognitive performance and physiology. Moreover, results indicated that the effects on human experiences may depend on persons’ prior mental state (i.e., mentally fatigued vs. rested), and effects on task performance and physiology may depend on time of day, duration of exposure and type of indicator, motivating the use of person-centered and dynamic lighting scenarios for day-active persons.

Results of the studies investigating light preferences suggested that preferred light settings to perform an attention task are probably only modestly affected by a person’s experienced mental state. Overall, preferred illuminance levels showed substantial inter- and intra-individual variations and the alerting effects of bright light were only subtly reflected in individuals’ light preferences. This suggests that although participants may benefit from bright light exposure during regular daytime hours, persons may not consciously adjust the light to increase their level of alertness and vitality.

Up to now, research to the non-image forming effects of light had rendered convincing evidence for alerting and vitalizing effect of bright light exposure during persons’ biological night or on certain subgroups (such as persons suffering from seasonal affective disorder or dementia). Although those earlier findings mainly had practical implications for shift workers and particular clinical subgroups, the current research suggests the potential for the application of bright light (natural or electric) to benefit the population at large. Our results provide valuable insights for engineers and lighting designers in the development of person-centered lighting solutions, but also propose new research directions for scientists. Moreover, the results shed light on potential underlying mechanism during daytime.

Karin Smolders thesis can be downloaded at http://repository.tue.nl/762825

The Impact of Light Including Non-Image Forming Effects on Visual Comfort

Visual comfort at workplaces has often been considered in terms of discomfort glare, luminance distribution and task visibility. Besides visual effects, the lighting environment has also impact on human physiology and behaviour. These effects of light are transmitted via a novel class of photoreceptors in the mammalian retina, which was discovered only a decade ago. Since then, it has become evident that light also plays an important role in regulating Non‐Image Forming (NIF) functions such as circadian rhythms, alertness, well‐being and mood. In lighting design it is accordingly necessary to take into account not only luminous intensity, but also light’s spectral composition, since the novel class of photoreceptors is more maximally sensitive to different luminous wavelengths than the classical photoreceptors (e.g. rods and cones).

The main focus of this doctoral thesis is on visual comfort assessment at workplaces. It was hypothesized that the impact of light on visual comfort comprises not only luminance distribution and/or luminous intensity, but also other qualitative aspects of the lighting environment. Office lighting influences building occupants in terms of visual task performance, alertness, health and well‐being. The aim of this thesis was to assess the impact of office lighting on visual comfort including NIF effects.

Firstly, in order to monitor the luminance distribution within a scene, a new photometric device based on a high dynamic range logarithmic visual sensor (IcyCAMTM) was set up. After calibrations and validations, the photometric device was used to assess luminance distribution of office spaces in a very efficient way. Secondly, two experimental studies were performed with human subjects, aiming to test the acute effects of light on visual comfort variables, subjective alertness, mood and well‐being. Lastly, the novel device was also used during one of the studies to monitor the impacts of luminous distribution over time and under various lighting conditions.

The novel photometric device enables to assess luminous distribution also in circadian metrics with respect to NIF effects of light. The results from the two studies showed the effects of office lighting including different sky conditions and time‐of‐day changes on visual comfort and NIF functions. Inter‐individual differences, as assessed in extreme chronotypes, also had an influence on visual comfort. Interestingly, luminance distribution was not only found to impact on visual comfort but also on subjective alertness, mood and well‐being. To conclude, the results obtained with the new device provide a more comprehensive scientific framework and practical basis for indoor lighting design at workplaces.

Apiparn Borisuit defended her PhD thesis in December 2013. The entire dissertation can be downloaded at http://infoscience.epfl.ch/record/190815

Influence of Presentation Modes on Visual Perceptions of Daylit Spaces

Virtual renderings are increasingly used in the architectural design process and in lighting quality research to assess the visual appearance of indoor environments. Thanks to imaging technologies continuously in development to improve the “realism” of these images, pictures can nowadays be presented in various ways. Regrettably, to date, few studies assert that such images replicate the visual appearance perceived in actual daylit environments.

The present research investigated the perceptual equivalence between actual daylit environments and images. Two types of images – photographs and virtual renderings – were studied as well as four modes of presentation – QuickTime virtual reality (QTVR) panoramas, 2D display, 3D display, and high dynamic range (HDR) display.

ight groups of 40 students viewed four daylit corridors and filled in a questionnaire about the appearance of lighting and space elaborated for the study. The corridors were presented in several ways: a first group of participants visited the actual rooms while the other groups visualized, in a lab context, their reproduction in sketches, photographs or virtual renderings.

This research provides some proofs that images can reasonably be used as a surrogate for the real world when studying the appearance of lighting (characterized by the perceived brightness, coloration, contrast, distribution, directivity and glare). On the other hand, the study suggests that images poorly reproduce the appearance of space (pleasantness and enclosedness were studied). As a result of the research, we determined precisely the media to use for studying each dimension characterizing the appearance of lighting and space.

Coralie Cauwerts graduated from the Louvain School of Engineering (EPL) at the Université catholique de Louvain (UCL) with a Master in Architecture and Engineering in 2007. She conducted her thesis between 2009 and 2013 as a research fellow of the Fonds de la Recherche Scientifique (FNRS) and she successfully defended her PhD thesis in November 2013.

The entire dissertation can be downloaded at http://hdl.handle.net/2078.1/135934.

Daylight and View

A window doesn’t only allow daylight to come inside, but also offers a view of the outside environment. View has a much bigger influence on the overall appearance of indoor spaces than people are generally aware of. Glare by daylight, for instance, is experienced as less disturbing when the outside view is of a high quality.

Aim of my PhD research was to develop a method for the analysis of the daylight and view quality of windows, the D&V analysis method. Initially, office workers in eight different buildings in the Netherlands were questioned on the quality of their workplace concerning the office, the lighting and the view. Subsequently, the D&V analysis method was developed based on scientific literature and the results of the questionnaire study.

The analysis method includes a rating system for view quality. It grants points for several aspects of the view. If you’re looking at nature, it’s plus four points, if your view is human-built there are no points to start with. This basis is refined by points for the amount of visual layers (depth of view), presence of water, vegetation, the amount of diversity etcetera.

In another set-up was studied how the appreciation of the daylight access and the outside view varied with different window size, shape and position. Participants in this study were asked to look outside through a miniaturised (1:5) office room. By varying the façade of the scale model, the influence of different windows and views was studied on the visual quality of the office room.

This latter study made clear that people wanted a window at least a quarter the size of the wall, but not a fully glass wall. The shape of the window was of secondary importance, but panorama was favoured above portrait. The sky component (what part of the view is sky) was a pretty good indicator for the amount of incident daylight.

I hope that my study will contribute in putting the view on the architect’s agenda. A proper placement of a building on the lot, respecting lines of sight and making the best of adjacent green can – for the same price – improve people’s appreciation of their views and thus of the spaces they occupy.

The dissertation can be downloaded from the website of the university library: http://repository.tudelft.nl/view/ir/uuid:2daeb534-9572-4c85-bf8f-308f3f6825fd/

Integrated Energy Design in Masterplanning

This PhD thesis considers urban structure and buildings in an energy correlation and use the knowledge to design energy- and comfort-optimized cities and buildings. The parameters are: the structure of nature, the city and the landscape, both in terms of geometry and interrelationships and in terms of opportunities and limitations with regard to light, shade, sun and wind.

The aim is threefold: (1) to unfold the link between building energy use and urban density, typology and fabric; (2) to analyse how technical scientific knowledge can be integrated in early urban planning and design decisions (IED); and (3) to show the architect’s responsibility and opportunities to rethink their architectural role based on new goals and knowledge.

The research results show an impact from urban form on building energy consumption which is much greater than previously thought, more precisely described, and more dynamic in character as daylight is taken into account. Furthermore the results suggest that there are limits to urban densification (200–300%) as an energy optimization strategy. The solar energy and daylight potential should be considered, and indeed protected, as a common resource in urban design.

The most important observation for qualitative design research is that the first step to improving energy performance must be taken with the architect’s first sketch on paper. It is here that the framework and preconditions for the city and the building’s performance will be set. Argued this way, optimization of the special properties of urban density, typology and fabric takes priority over the optimization of technical service systems. This means that in the design process the architect’s responsibilities outweigh those of the engineers. The research is reported in the main body of this thesis and in the papers for scientific journals.

Jakob Strømann-Andersen, Henning Larsen Architects, successfully defended his PhD thesis titled ’Integrated Energy Design in Masterplanning’ at the Technical University of Denmark. The research is based on a close collaboration between the Technical University and Henning Larsen Architects – with support from Realdania.

The PhD Thesis can be downloaded at http://www.byg.dtu.dk/english/~/media/Institutter/Byg/publikationer/PhD/byg-r254.ashx

Design Parameters of Pleasurable Light Atmosphere

At the moment, the future of hospital design is a subject of interest and thereby also a subject of discussion. It is a fact that new hospitals have an increased focus on user perspectives and an interest for improving the physical environment in such a way it supports the user needs and preferences and thereby the experience of an admission to the hospital. Recent literature such as “Hospitals of the senses” and “Healing Architecture” presents research and design solutions focused on senses and experience of the design. The Danish Regions ask for Evidence Based Design to future prove the hospitals by research base the design of the buildings. The present PhD project expands the existing knowledge of lighting research by focussing on the experienced light atmosphere. The project uses multi strategies of methodology based on a flexible design to elaborate on the socio-cultural aspect of light and the sensory impact of light. To frame the work, the “Model of Light Atmosphere” is created and improved throughout the study, first as an abstract model and then it is exposed for detailed study. The detailed study first of all creates a theoretical and visual context. Then explorative studies seek to investigate unknown or tacit knowledge on how light is used in a Danish context, preferences for light in different situations and investigating the hospital ward as frame for a lighting concept. The concept is installed in a hospital ward at Odense University Hospital as a “real world” study and evaluated by the patients in the ward.

The project is based on the Danish Regulation for light in hospitals (DS703), which is a supplement to the regulation of artificial lighting in workplaces (DS700). The kick-off to the project was reading the DS703, second paragraph, chapter 2 about general requirements for lighting.

In general, measurable parameters such as the amount of Lux, the composition of CRI and degree of Kelvin is described precisely in a way so the designer can handle the requirements. But what does it mean to create a “home-like” and “pleasant or appealing” light in this context? Does the composition of CRI and degree of Kelvin tell it all? Is it enough information to provide an illumination, which the patient can experience as homely and pleasant?

This project seeks to highlight the design process of lighting a hospital ward and articulate visual as well as written what a homely and pleasant light atmosphere could be in a Danish context. Therefore, the study investigates the socio-cultural understanding and the geographical impact of the understanding of light atmosphere. “Model of Light Atmosphere” Ill: 12 describes four key aspects of light atmosphere and displays what is important when a light atmosphere is qualified. The four key aspects are: “Light”, “Space”, “Users” and “Time”.

The “Light” aspect describes, as shown in the figure below, the character of the light, light information and light effect i.e. function, aesthetics or symbolism. The “Space” aspect looks into the dimension of the space, geographical orientation, interior design, composition of the space, materials, surfaces and objects. The parameter “Time” elaborates on the time one is present in the space, the season and time of day. The “Users” aspect is split up into categories such as characteristics exploring the user group’s preferences and needs. The user group has quite diverse needs and preferences, while the staff needs task lighting and the patient a space experienced as homely and pleasant.

“Model of Light Atmosphere”

Categories such as “pleasure” and “activities” are also a part of the user aspect. The space is divided into subcategories as ”location of the space” and “geographical orientation”. The interior design, surface and spatial composition of the space are also parameters of importance.

The model “Light Atmosphere” is the focal point of the project through iterative process and also developed through the study. First the model frames the study and later serves as a design tool for creating light atmosphere in hospital wards.

The project is performed through four cycles of iterations. The first cycle describes the “State of the art” in the research field “Atmosphere”. Here the study find its theoretical foundation based on Gernot Böhmes’ concept of atmosphere. It also finds its visual understanding by studying the architects’ way to design atmosphere. The second cycle explores the users’ preferences and trends of light atmosphere in four exploratory studies. First presented is a study of light preferences in Danish homes. Then, the trends of light atmosphere in Denmark are investigated and light zones at the hospital ward defined in order to optimize the illumination. Lastly, an observation of ward atmosphere is presented. The third cycle of iteration is an experimental study testing a lighting concept developed and grounded in the knowledge gained through the first and second cycle. The fourth cycle evaluates the effect of the light atmosphere at the ward. Here the patients are admitted to two similar wards not including the artificial illumination. The evaluation uses Semantic Environmental Description developed by environmental psychiatrist Rikard Küller, in order to evaluate the light atmosphere.

The thesis can be downloaded from http://riverpublishers.com/book_details.php?book_id=246

Further information at www.lostdesign.dk

Spectral Modulation of Melanopsin Response – Role of Melanopsin Bistability in Pupillary Light Reflex

In addition to the canonical photoreceptors, rods and cones, a novel melanopsin-expressing retinal ganglion cell (mRGC) was recently discovered. The novel photopigment melanopsin in the human retina has been shown to express invertebrate-like bistable properties both in vitro and in vivo. In bistable photopigment systems, light elicits photosensory responses and drives photoregeneration of the chromophore to restore photic responsiveness. These studies have shown that prior light exposure can modulate the amplitude of subsequent photic responses of melanopsin.

In this thesis, the putative bistability of melanopin in humans is examined. The bistability was studied using 1) pupillary light reflex (PLR) as a tool, 2) developing a method for quantifying the effects of lens density for melanopsin-mediated photoreception, and 3) providing a quantitative mathematical framework for modeling bistable pigment systems and non-image forming (NIF) visual system.

Exploiting the bistable properties of melanopsin could allow for optimization of spectral light distribution in experimental, industrial, domestic and clinical phototherapy applications by appropriate use of the photoregenerative effects of long wavelength light.

Further information at http://www.petteri-teikari.com/

Parametri i Praksis – Generative Performance i Arkitektur

This PhD project examines the development of parametric sketch tools that integrate multidisciplinary knowledge into the creative architectural design process. Done in collaboration with the Danish architecture office 3XN and Centre for IT and Architecture (CITA) at The Royal Danish Academy of Fine Arts, School of Architecture, Design and Conservation. The project investigates how daylight quality, solar radiation control, and visual and thermal control can be design parameters in the initial design phase. The research is based on practical experiments performed in the competition department at the architecture office 3XN. These experiments are carried out in close collaboration with daylight consultants at Esbensen Engineers, DTU, and the Danish Technological Institute.

Today 80 % of vital design decisions are made during the first 20 % of the design process [Theßeling et al. 2008]. These early decisions concern the work of architects involved in the initial design phase. Today the architecture profession is facing increasing demands for sustainable solutions and so, daylight conditions and indoor comfort have come into focus as never before. The design processes and creative work methods of architects are challenged by the technical processes involved in calculating daylight. The digital toolsets for analysis and simulation have for years been used primarily by engineers and have been applied very late in the design process. At this stage it is costly and often too late to change the overall building design [Liebchen 2002]. Developments in recent years have made analysis and simulation tools for daylight available for architects. In spite of this, these tools are rarely being used in the early design phases, where decisions mainly rely on “rule-of-thumb” methods and past experience.

In recent years programs like Grasshopperand Generative Components2 have made parametric tools with visual programming interfaces accessible to architects at low cost. This gives the opportunity to produce customised toolsets where simulation and architectural design can happen simultaneously. This research project investigates if parametric tools can be used to simulate daylight thereby increasing communication between members of the design team and improving early design decisions.

The entire dissertation can be read at http://issuu.com/parametri/docs/afhandling_tore_banke_web (Thesis in Danish, English Summary)

Light Shapes Spaces: Experience of Distribution of Light and Visual Spatial Boundaries

Light enables us to experience space. The distribution of light is vital for spatial experience but has not been the main focus of previous research on lighting. The lighting designer’s professional knowledge is to a great extent experience-based and tacit. With design practice as the point of departure, this thesis aims to explore spatiality and enclosure in relation to the distribution of light – with the intention of increasing subjects’ understanding of what can be regarded as a space, and to show how spaces can be shaped by the distribution of light. By focusing on users’ experiences and interpretations, relationships between the distribution of light and perceived spatial dimensions and experienced spatial atmosphere have been investigated. The main contribution of this thesis is to widen the base of knowledge that lighting designers, architects and customers can use as a common reference.

This thesis is based on three studies: the Scale Model Study, the Auditorium Study and the Church Park Study. The thesis includes concept- and method development. The mixed methodologies comprise a range from introspective phenomenological observations to deep interviews and questionnaires. The experimental setups have also shifted from scale models to real-life interior and exterior settings. Consequently, a quantitative approach has complemented the mainly qualitative approach. Through artistically based research, patterns and relationships are dealt with in complex real spaces. The findings of these studies lead to a discussion of when, why and how patterns of brightness and darkness influence spatial perceptions of dimensions.

The findings also show that brightness not only contributes to our experiencing a space as more spacious than it really is, but in certain situations brightness can actually have the reverse effect. Furthermore, darkness can contribute to a spacious impression, which has hardly been discussed in previous research. What subjects regard as a space may shift between the clearly defined physical space and the perceived space, which include light zones. Light zones can create a sense of inclusion or exclusion for subjects, which affects their sense of community and their feeling of safety. Light topography, e.g. the height of luminaire positions, as well as light direction influence the way we experience the private and the public. Enclosure can, if related to visible spatial boundaries, facilitate reassurance and safety.

The entire dissertation can be downloaded at https://gupea.ub.gu.se/handle/2077/31448 or order the dissertation at http://www.konst.gu.se/artmonitor/avhandlingar/ulrika-wanstrom-lindh/

Sustainability – Energy Optimization – Daylight and Solar Gains

This thesis discusses how energy optimization focused on daylight and solar gains may be qualified as an architectural design method, which does not just increase the energy efficiency of the built environment, but may potentially increase its overall qualities by offering new insights into the complex interrelationships between urban and building design, environmental performance, human needs and behaviour, technology and energy use.

The main hypothesis is that a hierarchy of scales related to energy optimization and environmental performance may be used to guide and support architectural design decisions in the earliest design stages. The hypothesis is examined through literature studies, empirical observations, interviews with practitioners, a series of simulation studies focused on energy optimization, solar gains and daylight, and a final case study applying derived design principles in an architectural design competition.

The aims are:

1. To situate energy optimization and environmental performance as qualitative architectural design issues which should also be understood in quantitative terms, by discussing these in a wider cultural and social context of sustainability.
2. To investigate the impact of basic urban and building design decisions on energy use and environmental performance in Northern Europe, using the central city districts of Copenhagen as references.
3. To combine the insights gained into a theoretical framework, relating the various aspects of energy optimization focused on daylight and solar gains into a coherent methodology.

The thesis demonstrates that not just one, but several functional and cultural hierarchies of scales can be found from practical and theoretical studies and combined into a coherent theoretical framework. It confirms that the most basic architectural design decisions – urban density and pattern, building form and material choice, window to wall ratio, colour and insulation properties of facades, have great impacts on energy use and environmental performance, which is described with more detail and greater precision than previous studies, by adding climate based daylight analysis to thermal and energy simulations.

Design issues related to urban density receives particular attention as the bottom level of a hierarchy of scales, in addition to addressing the trend of increased urbanization and urban densification which is seen internationally as well as in Denmark. It is found that an optimal range of urban densities can be defined balancing building energy efficiency with access to sun and daylight depending on regional climate. In Northern Europe this density can be described as plot ratios between 100 – 300%. But great environmental performance differences among building typologies within this range indicates that there is plenty of design opportunity to improve environmental performance of buildings by working with urban design, building form and orientation and the geometry and properties of the building skin.

It is argued that it is more important to see energy optimization as a creative opportunity to create better, diverse and stimulating environments using urban and building design as the key instruments, rather than focusing on narrow optimization of technical subsystems. The results demonstrate that daylight and solar access is more dependent on urban scale design decisions than energy use, and should therefore be considered primary design objectives in the very beginning of the design process in the context of Northern Europe.

The thesis can be downloaded at http://orbit.dtu.dk/en/publications/sustainability–energy-optimization–daylight-and-solar-gains(8f401bbe-2f4d-4602-81f3-a7b85a106c03).html

It is desirable to design buildings with natural daylight and views to the outside, which can maximize passive solar heating, minimize electric lighting use and contribute to feelings of well-being and awareness. Unfortunately, the presence of daylight is not always a positive one. Excessive brightness, strong contrast or intense reflections from daylight can cause visual discomfort or the inability to perform tasks. Typically, the total amount of luminous flux incident upon a surface per unit area–illuminance–present is used to predict visual discomfort due to questions about the benefit and validity of luminance-based analysis measures that are more related to the way the human visual system perceives light. This thesis aims to advance the understanding and usefulness of visual comfort prediction to the point that it can become commonly used in architectural design processes.

One method through which this is achieved is by testing the ability of visual comfort analysis to resolve subjective occupant comfort. It was found that of existing discomfort glare metrics, daylight glare probability (DGP) was the most likely to perform well in a variety of daylight conditions and space types. Furthermore, a long-term simulation and survey study found that between 53.7% and 70.1% of an occupant’s visual satisfaction could be resolved by analyzing DGP, the presence of direct sunlight and predicted monitor contrast ratio. This choice of metrics was reinforced by a separate laboratory study, which found that 74.4% of subjective comfort could be resolved and identified new subjective luminance thresholds that identify likely discomfort. A new adaptive visual comfort model, the ‘adaptive zone,’ is proposed in this thesis to deal with spatiality and view in visual discomfort analysis. Finally, ways of applying these verified and new measures in design processes are tackled in this work by producing new temporal maps, spatial discomfort analysis, and plan-based mappings of long-term visual comfort.

J. Alstan Jakubiec’s Ph.D. thesis can be downloaded at http://dspace.mit.edu/handle/1721.1/91295#files-area

The thesis is a result of an Industrial PhD work carried out in collaboration between Department of Architecture, Design & Media Technology and Department of Civil Engineering, Aalborg University, Investment and Holding Company VKR Holding A/S and roof window producer and Green Growth Thought Leader VELUX A/S. The work was carried out from winter 2009 til winter 2014.

The aim of the work is to develop a Model for Enquiry of Sustainable Homes through exploration of built, in-use, sustainable homes; three Model Home 2020 houses (LichtAktiv Haus, Sunlighthouse and Maison Air et Lumiére) and families living in them. Aiming at complying with the complexity of the world of sustainable architecture, the model employs methods of enquiry through four different perspectives; namely in-situ research, blog research, questionnaire survey and technical measurements. Thereby several aspects of the built environment come together in creating a more complete understanding of what sustainability actually entails.

Future sustainable buildings are not merely optimized mechanical constructions with intelligent adjustment systems but houses that imply and require quality in their environments to support and embrace life displayed in and around them. Therefore, it is becoming increasingly central to develop more holistic approach to enquiry and thereby the understanding of sustainable environments is viewed in balance between perceptual qualities as well as technical abilities. Summary of this thesis are thus:

i. A model for enquiry of sustainable homes that include occupant perspectives, perceptual quality and technical ability. The developed and tested Model for Enquiry of Sustainable Homes offers a more complete illustration of the sustainability of a house than either of the tested methods are able to do on its own.

ii. Occupant perspectives of perceived everyday encounters with automated homes through a combination of questionnaire and blog enquiry.

iii. Knowledge from in-situ research, blogs and questionnaire can provide valuable arguments for sustainability on a level somewhat comparable to technical measurements.

iv. Enclosure of perceived quality in enquiry of sustainable architecture and a more tangible approach to collect, treat and explore aspects of perceptual nature.

v. Focus on aspects of variability in enquiry of sustainable architecture. Research in sustainable buildings should focus more on perceptual, social and everyday perspectives – here lie answers to how future sustainable environments can be solved to give more than they take.

The Model for Enquiry is specified through testing the theme of Perceived Indoor Environment. The diagram illustrate the four methods In-situ research, Blog research, Questionnaire and Technical measurements and their processing though I) Identification, II) Design, III) Collection, IV) Treatment, and V) Dissemination.

Gitte Gylling Hammershøj Olesen’s Ph.D. thesis is available at https://vbn.aau.dk/ws/portalfiles/portal/316447625/PhDThesis_GitteGyllingHammersh_jOlesen.pdf

Daylight Glare in Offices

The influence of discomfort glare is often underestimated in daylighting design and in the use of buildings. Many façade solutions are intended to increase the amount of daylight penetrating the room and creating a glare free environment at the same time. But as soon as a planning process comes to the point to quantify the glare freeness of a solution, the question of suitable glare measure arises.

To analyze the reliability of existing glare rating methods, user assessments under real daylight conditions in office like test rooms are designed and carried out at two sites using different Venetian blinds and a foil system. For the evaluation of high dynamic digital images, a new tool “evalglare” is developed.

The existing glare rating models show moderate or poor correlations with the user’s perception of glare. The window luminance as single glare descriptor exhibits no correlation at all. On the basis of the user assessments a new daylight glare rating – the daylight glare probability DGP – is developed and validated. The DGP describes the probability that a person is disturbed by daylight glare. The DGP is also used as a basic glare descriptor for new climate based glare evaluation methods, which enables an assessment of daylight glare for a full year data set within a design process. For the evaluation, a glare rating classification based on simulations and frequency distributions is proposed.

Jan Wienold PhD Thesis is available to order at https://www.verlag.fraunhofer.de/bookshop/buch/Daylight-Glare-in-Offices/234308

Daylight Simulation: Validation, Sky Models and Daylight Coefficients

The application of lighting simulation techniques for daylight illuminance modelling in architectural spaces is described in this thesis. The prediction tool used for all the work described here is the Radiance lighting simulation system. An overview of the features and capabilities of the Radiance system is presented. Daylight simulation using the Radiance system is described in some detail. The relation between physical quantities and the lighting simulation parameters is made clear in a series of progressively more complex examples. Effective use of the inter-reflection calculation is described.

The illuminance calculation is validated under real sky conditions for a full-size office space. The simulation model used sky luminance patterns that were based directly on measurements. Internal illuminance predictions are compared with measurements for 754 skies that cover a wide range of naturally occurring conditions. The processing of the sky luminance measurements for the lighting simulation is described. The accuracy of the illuminance predictions is shown to be, in the main, comparable with the accuracy of the model input data. There were a number of predictions with low accuracy. Evidence is presented to show that these result from imprecision in the model specification – such as, uncertainty of the circumsolar luminance – rather than the prediction algorithms themselves. Procedures to visualise and reduce illuminance and lighting-related data are presented.

The ability of sky models to reproduce measured sky luminance patterns for the purpose of predicting internal illuminance is investigated. Four sky models and two sky models blends are assessed. Predictions of internal illuminance using sky models/blends are compared against those using measured sky luminance patterns. The sky model blends and the Perez All-weather model are shown to perform comparably well. Illuminance predictions using measured skies however were invariably better than those using sky models/blends.

Several formulations of the daylight coefficient approach for predicting time varying illuminances are presented. Radiance is used to predict the daylight coefficients from which internal illuminances are derived. The form and magnitude of the daylight coefficients are related to the scene geometry and the discretisation scheme. Internal illuminances are derived for four daylight coefficient formulations based on the measured luminance patterns for the 754 skies. For the best of the formulations, the accuracy of the daylight coefficient derived illuminances is shown to be comparable to that using the standard Radiance calculation method.

The use of the daylight coefficient approach to both accurately and efficiently predict hourly internal daylight illuminance levels for an entire year is described. Daylight coefficients are invariant to building orientation for a fixed building configuration. This property of daylight coefficients is exploited to yield hourly internal illuminances for a full year as a function of building orientation. Visual data analysis techniques are used to display and process the massive number of derived illuminances.

John Mardaljevic PhD Thesis is available at http://climate-based-daylighting.com/doku.php?id=resources:thesis