Lighting Research and Technology

Published by SAGE Publications
Online ISSN: 1477-0938
Publications
Article
A field study was conducted with eighth-grade students to determine the impact of morning light on circadian timing, sleep duration and performance. Before and during school hours for a week in February 2009, half the students studied wore orange glasses that minimized short-wavelength light exposure needed for circadian system stimulation. A control group did not wear the orange glasses. The Daysimeter, a circadian light meter, measured light/dark exposures in both groups for seven days. Circadian timing was significantly delayed for those students who wore orange glasses compared to the control group. Sleep durations were slightly, but not significantly, curtailed in the orange-glasses group. Performance scores on a brief, standardized psychomotor vigilance test and self-reports of well-being were not significantly different between the two groups.
 
Article
Circadian rhythms are biological rhythms that repeat at approximately 24 hours. In humans, circadian rhythms have an average period of 24.2 hours. The 24-hour patterns of light and dark on the retina synchronize circadian rhythms to the local time on earth. Lighting characteristics affecting circadian rhythms are very different than those affecting visual responses. Lack of synchronization between the endogenous clock and the local time has been associated with a host of maladies. Therefore, it is important to measure circadian light exposures over the course of the 24-hour day and to be able to assess circadian entrainment and disruption in actual living environments. Presented is an overview of the recently developed Daysimeter, a personal measurement device for recording activity and circadian light-exposure. When the Daysimeter is worn on the head, two light sensors near the eye are used to estimate circadian light (CLA) exposures over extended periods of time. Phasor analysis combines the measured periodic activity-rest patterns with the measured periodic light-dark patterns to assess behavioural circadian entrainment/disruption. As shown, day-shift and rotating-shift nurses exhibit remarkably different levels of behavioural circadian entrainment/disruption. These new ecological measurement and analysis techniques may provide important insights into the relationship between circadian disruption and well-being.
 
Absolute response characteristics of the Daysimeter, both S and D versions, (a) and the Actiwatch Spectrum (b). Standard deviations are smaller than the size of the symbols in both graphs. 
Hourly geometric mean photopic illuminance levels (in lux) as measured by the Daysimeter-D (upper, shaded histogram bars) located on the wrist and by the Actiwatch Spectrum (lower histogram bars), located on the same wrist. The differences in geometric mean illuminance levels at each hourly time interval are also shown as a solid line; statistically significant differences from zero (p5.05) are indicated with asterisks. 
Hourly arithmetic mean activity levels as measured by the Daysimeter-D on the wrist (upper, shaded histogram bars) and by the Actiwatch Spectrum (lower histogram bars), located on the same wrist. The differences in activity levels at each hourly time interval are also shown as a solid line; statistically significant differences from zero (p5.05) are indicated with asterisks. 
Article
This paper documents the spectral and spatial performance characteristics of two new versions of the Daysimeter, devices developed and calibrated by the Lighting Research Center to measure and record personal circadian light exposure and activity levels, and compares them to those of the Actiwatch Spectrum (Philips Healthcare). Photometric errors from the Daysimeters and the Actiwatch Spectrum were also determined for various types of light sources. The Daysimeters had better photometric performance than the Actiwatch Spectrum. To assess differences associated with measuring light and activity levels at different locations on the body, older adults wore four Daysimeters and an Actiwatch Spectrum for five consecutive days. Wearing the Daysimeter or Actiwatch Spectrum on the wrist compromises accurate light measurements relative to locating a calibrated photosensor at the plane of the cornea.
 
Article
This paper examines whether the use of coloured light can influence aircraft passengers’ temperature sensations and can make the climate be perceived as cooler or warmer (‘hue-heat hypothesis’), a phenomenon shown in earlier light laboratory experiments. Experiments with 199 subjects were conducted under realistic conditions, a cabin of a single-aisle aircraft. Two lighting scenarios (yellow and blue) were combined with different temperatures. Results show an effect in the hypothesized direction. The impact of lighting colour on climate perception and evaluation can be observed in the whole sample and in certain subgroups of subjects. The size of the effect agrees with former studies. A largescale application of this effect in the aircraft/aviation industry could lead to energy savings and contribute to cost effectiveness.
 
Article
The aim of this paper is to present a complete analysis of the sky luminance distribution data measured with a sky scanner at the International Daylight Measurement Program station in Lyon. Besides presentation of the sky luminance distribution, we also derive the CIE sky type based on the CIE S 011/2003 standard. The CIE sky type is based on gradation and indicatrix functions. Determination of the gradation and indicatrix group is based on the calculation of luminance ratio between two elements on every almucantar. Since there are six gradation and six indicatrix groups, we have 36 combinations but only 15 of them are listed in the CIE standard. Since some of combinations are really rare, we provide a table to show how to allocate 36 combinations to 15 standard CIE sky types. At the end of the paper, we present frequencies of occurrence of CIE sky types in Lyon.
 
Article
Visual performance has been studied since the 1930s to help establish a foundation for recommended illuminances. Two approaches were taken to research visual performance, one by Weston in Great Britain and the other by Luckiesh in the United States, leading to different recommended illuminances in the two countries. Because of the energy crisis of the 1970s, applied research into visual performance was undertaken to resolve the discrepancy, resulting in a model of relative visual performance. More recently, a controversy has emerged regarding the value of illuminating roadways. Recent research shows that the incremental improvements in visual performance provided by roadway lighting are correlated with the incremental reductions in night-time crashes, demonstrating that an understanding of visual performance remains important for lighting practice.
 
Article
Daylighting and thermal loads are very important design issues for skylight design, especially in large spaces such as atria. However, the trade-off between daylighting and thermal performance of skylights has been difficult to solve, due to a lack of daylighting and thermal design tools. A mathematical model was developed to predict the visible/solar transmittance, absorptance and reflectance of multi-glazed domed skylights for both direct and diffuse radiation. The model is based on tracking the beam and diffuse radiation transmission through the dome surface. Since all building energy simulation and fenestration rating tools are limited to planar skylights, the model was translated into a simple method in which domed skylights were substituted by optically equivalent planar skylights. The results showed that domed skylights yield slightly lower visible/solar transmittance at low sun zenith angles, and substantially higher visible/solar transmittance at high sun zenith angles, or near the horizon, than do planar skylights having the same aperture. The absorptance of domed skylights is higher than that of planar skylights, particularly at high sun zenith angles, or near the horizon. The model was compared with the IESNA transmittance calculation procedure for domed skylights and with the Wilkinson model. The IESNA transmittance calculation procedure overestimates by 19% the transmittance of a dome at low sun zenith angles and significantly underestimates the transmittance of a dome at high sun zenith angles, or near the horizon. However, the Wilkinson model significantly underestimates the transmittance of a dome for both low and high sun zenith angles.
 
Demographics of survey respondents
Information about occupancy
Percentages of visited households that received their preferred durations of solar access during their preferred time of the day during summer. L ¼ living room, B ¼ bedroom, K ¼ kitchen
Percentages of visited households that received their preferred duration of solar access during their preferred time of the day during winter. L ¼ living room, B ¼ bedroom, K ¼ kitchen.
Article
Appropriate solar access is considered to be important to residents’ health, comfort and daily living. In the past few decades, guidelines and standards have been formulated for the provision of sunlight in low-density housing. However, in sub-tropical, high-density housing like that found in Hong Kong, relevant guidelines and standards are generally lacking. At the same time, better provision of sunlight to such housing has become a matter of concern. Residents’ preference for solar access is very important to the formulation of standards for solar access and daylighting, as well as urban planning and building design. This paper presents the results of questionnaire surveys regarding residents’ preferences for solar access in terms of timing, duration and location. Computer simulation provides information on the actual sunlight environment of the visited households. Policy-makers, as well as planners and architects, should take the findings into account when establishing appropriate guidelines and standards for high-density tropical cities like Hong Kong.
 
Article
This paper examines the role of assumptions commonly made in validation studies for lighting simulation programs and quantifies the sensitivity of results to uncertainties in key model parameters such as sky conditions and surface reflectivity. Actually occurring overcast skies are often taken to approximate the CIE standard overcast sky for the purpose of comparing predictions against measurements in real buildings. The validity of this assumption is tested against measurements of the sky luminance distribution for real skies. Illuminance predictions are particularly sensitive to the assigned reflectance of surfaces when the direct component of illumination is small. A number of confounding factors that can lead to imprecise estimates of surface reflectivity for building facades are identified and a methodology to minimize their effect is proposed. This study reveals that commonly made assumptions with respect to sky conditions and moderate imprecision in model parameters can lead to erroneous assessments of program accuracy. The degree to which existing validation findings can be extrapolated to very different application scenarios is discussed in the context of reported conflicting assessments of program accuracy. Dans ce mémoire, on étudie le rôle des hypothèses que l'on adopte souvent dans des études de validation des programmes de simulation de l'éclairage. Il s'agit de quantifier la sensibilité des résultats aux incertitudes que peuvent comporter certains paramètres de modèles clés, comme les états du ciel et la réflexivité des surfaces. Afin de comparer les prévisions avec les mesures dans des bâtiments réels, on tient souvent les ciels couverts réels pour une approximation du ciel couvert normalisé de la CIE. Les auteurs du mémoire ont mis cette hypothèse à l'étude en la confrontant à des mesures de la distribution de la luminance de ciels véritables. On a constaté dans les faits que les prévisions de l'éclairement lumineux sont particulièrement sensibles à la réflectance attribuée aux surfaces lorsque le composant direct de l'éclairement est faible. On a repéré plusieurs facteurs confusionnels qui peuvent entraîner des prévisions inexactes de la réflexivité superficielle des façades d'immeubles, et on propose une méthodologie pour réduire l'incidence de ces facteurs au minimum. Cette étude révèle que les hypothèses que l'on adopte souvent à l'égard des états du ciel, réuni à une imprécision modérée des paramètres du modèle, peuvent aboutir à des évaluations erronées de la précision d'un programme. L'examen des évaluations contradictoires que l'on a rapporté au sujet de la précision des programmes mène à une discussion de la mesure dans laquelle on peut extrapoler les constatations de validation actuelles à des scénarios d'application très différents. RES
 
Article
The paper examines the influence of source, receiver and sample dimensions on the accuracy of measurement of the coefficient of luminous intensity of retroreflectors and retroreflective materials. Expressions are developed from which requirements for an acceptable accuracy can be derived. The error caused by a wrong adjustment of the observation angle is also discussed.
 
Article
This study investigated the impact of well geometry and surface reflectance on the vertical daylight factors of walls in atria with square plan forms under a CIE standard overcast sky. Artificial sky scale model measurements were used to validate predicted values of vertical daylight factors using the software package Radiance. More simulated vertical daylight factors data for a much wider range of square atrium geometries and surface reflectances were then produced. From the results the variations of the vertical daylight factor on the walls of square atria were assessed and explained and some empirical functions derived. Some guidelines for supporting design are presented.
 
Article
This study investigated the impact of well geometry and surface reflectance on vertical daylight factors on the walls of rectangular atria under a CIE standard overcast sky. The vertical daylight factors predicted using the modelling software Radiance were validated by artificial sky scale model measurements. More simulated data of vertical daylight factors for a very wide range of rectangular atrium geometries and surface reflectances are presented. From the results the variations of the vertical daylight factor on the walls of rectangular atria were assessed and some empirical functions were derived. Initial guidelines for supporting design are presented.
 
Article
Glare models were reviewed with an eye for missing conditions or inconsistencies. Ambiguities were found relating to when to use small source versus large source models and as to what constitutes a glare source in a complex scene. Also, there was surprisingly little information validating the assumed independence of the factors driving glare. A barrier to progress in glare research is the lack of a standardized dependent measure of glare. The glare models were inverted so as to predict luminance and to compare model predictions against the 1949 Luckiesh and Guth data that form the basis of many of them. The models performed surprisingly poorly, particularly with regards to the luminance-size relationship and additivity. Evaluating glare in complex scenes may require fundamental changes to the form of the glare models.
 
Article
Laboratory tests were carried out to investigate lighting for pedestrians at mesopic levels under lamps of different spectral power distribution. This paper reports an evaluation of lamp spectrum effects on visual acuity, using Landolt ring charts of high and low luminance contrast, and forced choice judgements of the preferred appearance of human hands, a colour array and an illuminated space. These were carried out alongside judgements of brightness reported in a previous paper. Five types of lamp were used, including standard high pressure sodium, two metal halide and a fluorescent lamp of broader spectral distribution and a two-colour solid state device (LED). It was found that lamp spectrum affected judgements of preferred appearance, with the high pressure sodium and LED lamps being considered poor compared with the two metal halide lamps; these results correlated better with the CIE General Colour Rendering Index than other metrics of lamp spectral characteristics. It was also found that acuity was affected by lamp spectral power distribution, with the high pressure sodium (HPS) lamp enabling more Landolt rings to be correctly read than lamps of higher S/P ratio.
 
Article
Daylight–electric light integrated schemes encompassing soft computing models have been perceived as a lucrative option for lighting energy conservation. This paper exploits the quintessence of design and real-time implementation of an adaptive predictive control strategy for robust control of a daylight–electric light integrated scheme. To elicit daylight variations, occupancy detection and user preferences an online self-adaptive, predictive control algorithm is structured for real-time control of electric lights and window blinds. The adaptive, predictive model entails integration of an online, adaptive daylight illuminance predictor in conjunction with an electric light intensity control algorithm for interior illuminance regulation and a fuzzy-logic based window blind control algorithm to eliminate glare and solar heat gain. The control algorithm modelled with real-time sensor information administers an online process of identification, prediction and parameter adaptation. The prototype controller is successfully implemented in a test chamber. A real-time user-friendly simulator provides an online visualisation of illuminance performance indicators and control of the process. The anticipated synergetic effects of the online control algorithm validated in the test chamber highlights the benefits of the scheme in terms of glare control, illuminance uniformity and energy efficiency.
 
Article
Discomfort glare is an underutilized parameter in contemporary architectural design due to uncertainties about the meaning of existing metrics, how they should be applied and what the benefits of such analysis are. Glare is position and view direction-dependent within a space, rendering it difficult to assess compared to conventional illuminance-based metrics. This paper compares simulation results for five glare metrics under 144 clear sky conditions in three spaces in order to investigate the ability of these metrics to predict the occurrence of discomfort glare and to hence support the design of comfortable spaces. The metrics analyzed areDaylight Glare Index, CIE Glare Index, Visual Comfort Probability, Unified Glare Rating and Daylight Glare Probability. It is found that Daylight Glare Probability yields the most plausible results. In an attempt to deal with multiple positions and view directions simultaneously, the concept of an ‘adaptive zone’ is introduced within which building occupants may freely adjust their position and view in order to minimise the effect of glare. The spatial and directional extents of the adaptive zone depend on furniture layout and the freedom of occupants’ tasks. It is found that applying the adaptive zone concept to a sidelit office with manually operated venetian blinds reduces the predicted hours of intolerable discomfort glare from 735 to 18 occupied hours per year and increases the annual mean daylight availability from 40% to 72%.
 
Article
An experiment was carried out to examine user preferences for light level using the method of adjustment. The study sought preferred illuminances under lighting from fluorescent lamps of different correlated colour temperature. It was hypothesised that the preferred illuminance would be influenced by variables inherent in the experimental design including the available stimulus range, the anchor (initial setting before adjustment) and adaptation time before onset of adjustment action. The experiment included three different stimulus ranges (21–482 lux, 38–906 lux and 72–1307 lux) and these lead to significantly different preferred illuminances (337 lux, 523 lux and 645 lux, respectively). The experimental results confirmed that stimulus range and anchor have significant effects on the outcome of the adjustment task, confirming the importance of considering and reporting these variables when determining user preference with this method.
 
Article
An increased illuminance at the workplace is often said to be linked to an increase in productivity. We investigated this relationship in 23 workers on a production line in a car factory. Measurements of visual performance (visual acuity, colour vision and contrast sensitivity), a physiological assessment of alertness and subjective assessments of four parameters of well-being were made during the daytime shift under three illuminances (500 lux, 1500 lux and 2500 lux). The physiological alertness results and all but one of the subjective parameters showed no significant differences between the three illuminance conditions. Subjective alertness was the only parameter that was rated to be significantly greater at 2500 lux than at 500 lux. The utilisation of higher illuminances in the workplace should be carefully considered before being implemented.
 
Article
Road lighting practice in Europe is currently under change, the changes being induced by the European Union Ecodesign regulations, the rapid development of LEDs and the new CIE system of mesopic photometry. This makes it a good time to listen to the opinions of the end users of road lighting. What are the aspects of road lighting that the drivers value? What are the most difficult visual tasks faced by drivers at night? Are drivers willing to reduce the amount and quality of lighting to save energy? All these questions and more were presented to over 100 drivers aged 20–79 years in a questionnaire in Finland during the autumn of 2010. This paper summarises the results and discusses the expectations of drivers that should be considered when preparing future guidelines for road lighting.
 
Measured environmental conditions in the experimental classroom (Study 2)
Average scores and standard deviations of concentration performance for three measurement times (Study 2)
Average scores and standard deviations of number of errors made for three measurement times (Study 2)
Article
The importance of lighting for performance in human adults is well established. However, evidence on the extent to which lighting affects the school performance of young children is sparse. This paper evaluates the effect of lighting conditions (with vertical illuminances between 350 lux and 1000 lux and correlated colour temperatures between 3000 and 12 000 K) on the concentration of elementary school children in three experiments. In the first two experiments, a flexible and dynamic lighting system is used in quasi-experimental field studies using data from 89 pupils from two schools (Study 1) and 37 pupils from two classrooms (Study 2). The third experiment evaluated two lighting settings within a school-simulating, windowless laboratory setting (n = 55). The results indicate a positive influence of the lighting system on pupils’ concentration. The findings underline the importance of lighting for learning. Several suggestions are made for further research.
 
Article
This paper describes a rapid and reliable method of measuring the spectral power distribution of a lamp. The computer program which calculates the colour rendering index and the correlated colour temperature from this s.p,d, is used to study the influence on colour rendering and correlated colour temperature of adding a line to the spectrum of a metal halide (HPI) lamp. Another application of the computer program shows that with spectra consisting of only three spectral lines it is possible to achieve a general colour rendering index Ra~80. It appears that the three lines have to be chosen in three different wavelength regions, namely a blue line in the region 455-485 nm, a green line in the region 525-560 nm and a red line in the region 595-620 nm. With decreasing colour temperature the optimal wavelengths shift slightly to longer wavelengths whilst the general colour rendering index slightly increases.
 
Article
The paper introduces a method which allows the consideration of the curvature and stratification of the atmosphere when determining relative optical air mass. Formulae for relative optical air mass determination for places at sea level, at higher altitudes and for cloud formations are presented. These formulae were derived to promote further sky model development.
 
Article
The effects of light on alertness have been shown several times and the proposed cause has been suppressed melatonin levels. The relation of melatonin and alertness applies at night but not by day when there is hardly any melatonin. Still, light can be used to improve daytime alertness, but how? This paper describes the brain mechanisms involved in light-induced daytime alertness and proposes a novel model of two parallel mechanisms. In addition to the well-established circadian pathway, it is suggested that light can use the amygdala in the limbic system to send signals to the cerebral cortex. The participation of the amygdala in light-induced alertness means that light is provoking and modulating emotions that induce alerting responses. The model is assembled from known relations but has not yet been verified as a functional system. The paper proposes methods to test the model.
 
Comparison of the luminance distribution of the CIE overcast sky with the luminance of the uniform sky of unit luminance, both giving equal illuminance on the horizontal plane.
Variation of the vertical sky component for uniform sky, and CIE overcast sky.  
Article
This paper presents algorithms for calculation of sky components and daylight factors in linear building structures using the solid angle projection method. In order to estimate the precision of calculations two sky models; the uniform sky and CIE overcast sky, both giving equal illuminance on the horizontal plane, are used. Daylight factors calculated for CIE overcast sky are also compared to daylight factors measured in a physical scale model of a linear atrium in an artificial sky of the mirror-box type.
 
Article
Due to new European standards and requirements for energy performance in non-residential buildings, it is important to explore and quantify the benefits of intelligent (automated) energy-efficient operating systems relative to conventional (manual) systems. This paper explores the energy performance of an automated lighting control system under realistic conditions in two groups of lecture rooms that have the same shape, dimensions and exposure. The results demonstrate that the use of automated systems for electric lighting control can improve the energy performance of the system between 40% and 65% depending on the complexity of the system and the parameters under control.
 
Article
Although time-lapse photography offers great potential for providing information on lighting energy conservation, it has been undeveloped because the quantity and detail of the data demand a great deal of time for analysis. Two simple analytic procedures are described to make time-lapse photography more useful: (1) a sampling procedure for data reduction, and (2) a formula for computing wasted lighting energy based upon occupancy and light usage. It is argued that poor utilisation of lighting energy can be addressed with these procedures. Bien que la photographie en pause permette d'obtenir des renseignements sur la consommation d'énergie pour l'éclairage, cette technique n'a pas été très développée car la quantité et les détails des résultats nécessitent une longue analyse. Deux méthodes analytiques simples sont décrites pour interpréter la photograhie en pause de facon pratique: 1) une méthode pour obtenir des échantillons et réduire le nombre des données, et 2) une formule pour calculer les pertes d'énergie pour l'éclairage basées sur l'occupation des bâtiments et l'utilisation de l'éclairage. Grâce à ces deux méthodes, on peut se rendre compte du gaspillage d'énergie pour l'éclairage. RES
 
Article
An algorithm is introduced to minimise the beam angle of compound parabolic concentrators (CPCs) with LED sources under the condition of a fixed exit aperture, as a big beam angle will cause large off-axis aberration and low efficiency for a projection system. According to the edge-ray principle and coordinates transform, the formula for the algorithm is derived with LED sources considered as extended sources. In this paper, an example is given to prove the algorithm. Not only the minimum beam angle but also the specific parameters of CPCs can be obtained by this algorithm.
 
Article
This paper describes research on forward and backward light reflection of road surfaces for typical vehicle-related illumination and observation conditions. The aim is to improve luminance simulation in order to include quality criteria of headlamp light distributions that correspond to visual perception under night driving conditions. Measurements were performed under full scale conditions instead of the usual laboratory tests. Traffic safety requires tests under dry and wet conditions. The experimental data can be described by luminance coefficient-based models. Due to its fixed geometry, backward reflection can be covered with a single luminance coefficient. For forward reflection an angular dependent reflection model is described with which headlamp light distributions can be improved for their impact on automatically detected oncoming traffic even under wet conditions.
 
Article
Zenithal openings are attractive because they provide a high illuminance level. Nevertheless, this type of opening may create glare or overheating due to the penetration of direct sunlight. Conventional protective systems, north oriented sheds, unfortunately reduce the daylighting performance when the sky is overcast On the other hand, movable blinds give a good compromise but introduce reliability and maintenance problems. In the present paper, a new concept of a top opening without moving parts is developed and analysed. Based on anidolic optics (non-imaging optics), this device gives efficient solar protection and reflects inside the building a large part of the diffuse natural light. In the present situation, the numerical simulations show that, in overcast conditions, this system is equivalent to horizontal glazing with a transmittance of 58%. Compared to sheds, this device increases significantly the building lighting autonomy and the visual comfort.
 
Normalised spectral power distributions for the LEDs based on as-grown n-ZnO nanorods and after annealing in air, oxygen and nitrogen ambient atmospheres.
Photoresist p-GaN A / 2 0 3
Article
The effect of post-growth annealing on the colour properties of the light emitted by n-ZnO nanorods/p-GaN white LEDs has been investigated. The as-grown ZnO nanorods were annealed in nitrogen, oxygen, argon and air atmospheres at 600°C for 30 minutes. The colour rendering indices and correlated colour temperatures were calculated from the spectra emitted by the LEDs. It was observed that the ambient atmosphere used for annealing is very effective for altering the colour properties of the fabricated LEDs. The LEDs annealed in nitrogen have excellent colour rendering properties with a colour rendering index and a correlated colour temperature of 97 and 2363 K, respectively, in the forward bias and 98 and 3157 K in the reverse bias.
 
Article
Dr. Mardaljevic's recent paper on his implementation of the concept of daylight coefficients into the RADIANCE simulation environment is a well-written and a logical extension of his previous work on the validation of RADIANCE daylight simulations under real sky conditions. The interested reader might further want to learn, that the computational efficiency of Tregenza's concept of daylight coefficients has been recognized by a number of researchers, and the calculation approach has been implemented into RADIANCE by at least two other groups; one version has been implemented into the building simulation program ESP-R by Janak and Macdonald at the University of Strathclyde in Glasgow, Scotland and another version has been developed by Reinhart and Herkel at the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany. Both approaches also distinguish between direct and diffuse daylight coefficients although some differences exist in how direct sunlight is treated. Le récent article du Dr Mardaljevic sur la mise en application du concept de coefficients de lumière du jour dans l'environnement de simulation RADIANCE est un prolongement bien écrit et logique de ses travaux antérieurs sur la validation des simulations de la lumière du jour dans RADIANCE dans des conditions réelles d'éclairement provenant du ciel. Le lecteur intéressé aimerait peut-être savoir qu'un certain nombre de chercheurs ont reconnu l'efficacité du concept de calcul des coefficients de lumière du jour de Tregenza et qu'au moins deux autres groupes ont appliqué cette méthode de calcul dans RADIANCE. Le premier, soit celui de Janak et Macdonald de l'Université de Strathclyde, à Glasgow (Écosse), l'a appliqué au programme de simulation d'immeubles ESP-R, tandis qu'une autre version a été élaborée par Reinhart et Herkel de l'Institut Fraunhofer pour les systèmes à énergie solaire, à Fribourg (Allemagne). Les deux méthodes font une distinction entre les coefficients de lumière du jour directe et diffuse, bien qu'elles ne traitent pas tout à fait de la même façon l'éclairage direct par le soleil. RES
 
Article
This paper describes an investigation of the effect on electric lighting demand of applying occupancy models of various resolution to climate-based daylight modelling. The lighting demand was evaluated for a building zone with the occupant always present, with occupancy corresponding to absence factors, based on an estimated annual mean occupancy, based on estimated 1-hour mean occupancy, and based on 2-min occupancy intervals. The results showed little difference in the annual electric lighting demand when the same occupancy profile was used every day, as opposed to when profiles were used where occupancy varied every day. Furthermore, the results showed that annual electric lighting demand was evaluated slightly conservatively when a mean absence factor was applied as opposed to using dynamic occupancy profiles.
 
Article
The use of the new ISO/CIE Standard General Sky offers some new challenges for lighting designers. The MAMmodeller package described in this study provides a user-friendly tool for visualizing each of the SSLD 15 models in simple design contexts. The method of aperture meridians (MAM) provides a relatively simple geometric framework to estimate the appearance of the sky as a luminance map in the window opening, as seen from a point of interest inside the room. In addition, the total horizontal illuminance at the same point is estimated. This provides the user or designer with a quick tool for undertaking preliminary design investigations. MAMmodeller is not a complete lighting design tool, it considers only sunlight and the diffuse light component from the sky entering through the window opening. It does not account for internal reflections, artificial lighting, or external reflections.
 
Article
Colour selection is an important aspect in the design process of any building; to be purposeful, selection must take into account several aspects of colour. The investigation reported in this paper was concerned with the influence of colour on perception of the spatial form of the environment. The apparent 'nearness' of colours of different Munsell hue, value and chroma, selected according to a factorial design, was studied using thirty observers drawn from the general population ; samples subtended an area 12°×10° at the eye. The effects of hue, value and chroma on apparent distance of the test surfaces were all highly significant and some two-factor interactions were also significant. The implications of the results for the use of colour in interiors are discussed.
 
Article
The basic subjective attributes of colour perception are brightness, hue, and colourfulness; but, for coloured objects, the derived attributes of saturation, lightness, and perceived chroma, can also be important. Objective measures that correlate approximately with some of these subjective attributes are luminance, dominant wavelength, purity, and luminance factor. These psychophysical measures, however, are related to the subjective attributes in very non-uniform ways, and, to avoid this disadvantage, psychometric measures have been devised that have a more uniform correlation
 
Proposed linked mechanisms map.  
Final linked mechanisms map, showing lighting condition test results with dotted lines, and mediated regression test results with solid lines. Heavy solid lines show the Appraisal path, and black solid lines with double-headed arrows show the Vision path. The light grey solid lines show extra links, with small effect sizes, added to the model on the basis of the mediated regression results.  
Article
In two experiments in a simulated office space, temporary office personnel worked under one of six lighting conditions for a day. A previous paper reported the results of statistical tests for lighting conditions effects on perceptions, feelings, and task performance. This paper reports mediated regression analyses testing the linked mechanisms by which lighting conditions affect health, well-being, and task performance. Combined results from the two statistical approaches show that people who perceived their office lighting as being of higher quality rated the space as more attractive, reported more pleasant mood, and showed greater well-being at the end of the day. Direct-indirect lighting and personal control were favoured. Lighting conditions that improved visibility also improved task performance. Dans le cadre de deux (2) expériences réalisées dans un espace de bureau simulé, des membres de personnel de bureau temporaires ont travaillé pendant une journée sous l'une de six (6) conditions d'éclairage différentes. Un document antérieur a fait état des résultats d'essais statistiques quant aux incidences des conditions d'éclairage en matière de perceptions, de sensations et de performance dans l'exécution de tâches. Ce document fait le compte-rendu des analyses de régression raisonnées testant les mécanismes liés par lesquels les conditions d'éclairage influent sur la santé, le sentiment de bien-être et l'exécution des tâches. Selon les résultats regroupés des deux approches statistiques, les personnes qui perçoivent l'éclairage de leur bureau comme étant de meilleure qualité notaient l'espace comme étant plus attrayant, une ambiance plus agréable ainsi qu'un sentiment de bien-être supérieur à la fin de leur journée de travail. On a indiqué préférer le système d'éclairage direct-indirect et les commandes personnelles. Les conditions d'éclairage qui amélioraient la visibilité amélioraient également la performance dans l'exécution des tâches. RES
 
Article
This paper discusses some of the theoretical problems of the use of scale models. Findings from a number of experiments on the validity of models are discussed. Generally, these experiments show a degree of similarity of observer responses to full-size mock-ups and scale models. However such similarities do not dispel the possibility that scale models and indeed full-size mock-ups are not true facsimiles of the real world because of the artificiality of many experimental set-ups; there is always a need for some field validation work. With the tendency towards using 'subtle' psychological measures for environmental evaluation rather than explicit criteria as in psychophysical experiments, further studies are urgently required.
 
Article
This paper uses data regarding detection of pavement obstacles to explore two approaches to establishing an appropriate illuminance for road lighting designed to meet the needs of pedestrians. A previous obstacle detection experiment was repeated using young observers under high pressure sodium (HPS) lighting. One approach was to identify whether there is a plateau-escarpment relationship between obstacle detection ability and illuminance – better detection with increasing light level until further increases bring little improvement: This suggested an appropriate illuminance of 5.7 lux. The second approach was to identify the size of an obstacle that a pedestrian should expect to be able to detect and the associated probability of detection: An obstacle of height 25 mm located 6 m ahead may require 1.8 lux to be detected with 95% probability.
 
Article
The Waymouth model, which describes the glow-to-thermionic arc transition in qualitative terms, has been extended. To get a quantitative description of the glow-to-arc transition phenomena in metal halide lamps (with their emitterless electrodes) it is essential to include in the model a current dependent glow voltage. When this is done, the model calculations of the glow time and ignition time are found to agree well with experimental results. The influences of a number of lamp parameters on glow time and ignition time have been investigated in the light of this improved model.
 
Article
In this research, a field investigation was done with 263 coronary artery bypass graft (CABG) surgery patients to identify the impact of daylight exposure on patient length of stay (LoS) in hospital. Lighting data were collected by installing sensors inside in-patient rooms, and were used to develop a multiple linear regression (MLR) model to explore the relationship between daylight intensity and patient LoS in the presence of other environmental (i.e. provision of outdoor view and room status) and clinical (i.e. mean arterial pressure, heart rate and diabetes mellitus) variables. The coefficient estimates of the developed MLR model suggest that while holding the other explanatory variables constant, the patient LoS reduced by 7.3 hours per 100 lx increase of daylight inside in-patient rooms.
 
Article
A method is outlined for predicting the likely use of manually operated lighting. The method is based upon patterns of switching behaviour observed in field studies. A series of worked examples are given which demonstrate application of the method to multi-person offices and open-plan teaching spaces. Two points of interest revealed by the examples are the considerable effect that a midday switch-off has on the predicted overall time that lights are on in a space; and the comparatively small effect that gradual afternoon switch-on of lights has on overall use.
 
Article
The availability and present use of photo-electric continuous dimming or simple switching lighting controls are described and the cost effectiveness of using such systems is investigated. Although data on use of lighting are lacking, necessitating some assumptions, it is concluded that at present costs automatic dimming systems are likely to be cost effective in new buildings. Fitting existing lighting installations with automatic dimming control is not usually cost effective although an increase in electricity cost of about 4% per annum in real terms could change this. Despite smaller potential savings automatic switching can often be cost effective since initial costs are significantly lower. The maximum conservation potential of automatic controls is between 0.2 and 0.4% of UK primary energy use.
 
Article
A very high optical performance can be achieved by enclosing a metal halide lamp, suitably doped for the printing and reprographics industry, in a sealed beam reflector and refractor enclosure. The period of exposure needed under this very actinic light source is considerably shorter than that required by pulsed xenon, mercury vapour or the carbon arc and its enclosed optics ensure an excellent u.v. maintenance throughout a long life. Designed to be used on a 240 V a.c. supply the lamp consumes 400 watts and operates with a choke ballast and starter unit.
 
Article
Through the influence on circadian rhythms, natural and artificial lighting, as well as lifestyle and architecture, affect health and performance. Epidemiological and interventional studies of light-initiated circadian biological outcomes require robust 24‐hour data on personal light exposures, including blue light weighted irradiance data. The performance of the detection systems used is a key factor. We assessed the performance of 16 Actiwatch Spectrum™ devices for spectral response, directional response and dynamic range and propose techniques for calibration, deployment and data analysis for use of the watches in circadian studies. The results are presented, followed by a discussion of applicability focussing on spectral response for circadian studies.
 
Article
Sky luminance models are important tools for daylighting planning. In this paper some selected overcast sky models have been evaluated and compared with measured data from the Building Research Establishment, Garston, UK. Against the fully overcast sky data used, the CIE standard overcast sky performed best.
 
Article
The lamp industry has always played a leading role in the field of standardization and quality assurance. Lamp Standards were in existence before World War I and the industry was among the first to introduce statistics in its quality control. The use of the manufacturers' own test results for official approvals is explained together with a description of how the present IEC Publication 64 is used for an internal quality assurance system.
 
Article
A detailed study is presented of the relationship between the luminous efficacy of the three components of solar radiation (direct, global and diffuse) for a cloudless sky, and solar zenith angle, ozone content, water vapour content and turbidity. Aerosols and water vapour are found to be the most important factors. Other factors such as ozone or the aerosol downward scattered fraction are generally of secondary importance. Calculated luminous efficacies are based on a simple transmittance parameterization of the spectral irradiance model.
 
Article
Atrium and skylight shapes are important architectural design elements that influence daylight availability within the space and, therefore, lighting energy consumption. There is a lack of prediction models for skylight transmittance and daylight availability in atria. A new concept was developed to predict the diffuse transmittance of skylights. A skylight shape is converted into a representative shape through a shape parameter. Generic formulae for the skylight diffuse transmittance were developed under different sky conditions. A zonal model combined with the flux transfer method was developed to predict daylight availability in top-lit atria through the prediction of the average daylight factor (DF) at the atrium floor and ceiling (non-glazed portion of the roof), and the local DF normal to walls. The developed DF model was compared with currently available models derived from theory and experiments under artificial skies. The results showed that the computed diffuse transmittance for translucent skylights under real partly cloudy or clear skies may reach up to 33% in summer and 56% in winter higher than that under CIE overcast skies. The developed zonal model yielded very close results to the models based on the finite-element method. However, models based on physical scale measurements lack general consensus among themselves, and may produce average DF values at floor level up to 45% higher than those produced by the zonal model. Physical scale models may also yield local DF values normal to walls up to 50% lower than those predicted by the zonal model.
 
Article
An atrium creates indoor conditions mimicing outdoor space. One effective method for creating outdoor-like conditions is landscaping using various plants. This study aims to provide building designers with daylight availability data for plants in atria. With the Daysim program, which uses weather data for Incheon, Korea, the daylight autonomies (DAs) of four-sided open-top atria for 112 cases were determined according to the geometry and orientation. The main geometric indices adopted were the aspect ratio (AR) and the plan aspect ratio (PAR). The results show that the DAs for 750 lx and 1000 lx were negligibly affected by the atrium shape, while the DA for 2000 lx was notably affected by the AR. The impacts of the PAR and orientation on the DA for 2000 lx were prominent in atrium wells with ARs of 0.36.
 
Experimental design and time schedule of the study Note: BL (Bright light) group (n ¼ 16) and RL (Room light) group (n ¼ 16) worked under standardised conditions over three consecutive simulated night shifts. RL group worked at 300 lux all night, BL group was exposed to a 4-hr moving light at 3000 lux and at 300 lux 
Results from an analysis of covariance for repeated measures for light-and time-independent variables F-value
Article
Night work is associated with reduced levels of performance. Due to demographic change, the ability of over 50-year-olds to work at night is important for the employment market. Ageing is associated with decrements in both cognitive abilities and the capabilities of the visual system. This study focuses on the effects of exposure to bright light at night on selective and divided attention in elderly persons during three consecutive night shifts. After statistical control for neuroticism and intelligence as covariates, the results demonstrate that exposure to bright light at night reduced error rates for a divided attention task but performance on a selective attention task was unaffected.
 
Top-cited authors
Edward Ng
  • The Chinese University of Hong Kong
Roland Brémond
  • Université Gustave Eiffel
Arnold J Wilkins
  • University of Essex
Eric Dumont
  • Université Gustave Eiffel
Siegmund Staggl