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Residents of nursing homes often have a very limited access to natural daylight, which is the main environmental cue for circadian entrainment that usually cannot be compensated by standard indoor lighting. For the development of adequate modernization strategies with regard to a more human-centred lighting approach, reliable field measurements of the circadian effectiveness of the prevalent lighting conditions are required. To ease the task for the lighting practitioner, our lab recently developed a simplified method of estimating the biologically meaningful circadian stimulus (CS) metric using standard measurement equipment. In this work, the proposed method is applied for the first time in field measurements to assess the circadian effectiveness of the indoor light conditions including daylight entry of a nursing home in the Frankfurt Rhine-Main area. Reference thresholds for low, moderate and high circadian stimuli derived from the literature were used for subsequent data analysis. Mostly, moderate to rather low CS values were found. It is concluded that the amount of circadian-effective light is insufficient to provoke proper circadian stimulation, which may lead to progressive circadian disruptions manifesting in adverse effects on the residents’ health and well-being. Further evidence is provided that the insufficient-lighting-situation in nursing homes is a serious problem in long-term care and needs urgent consideration in health policy.

Electric lighting has decreased dependence on natural light to illuminate the workplace. Humans are genetically predisposed to be day-oriented (diurnal) and depend on daylight to regulate circadian rhythms. Shift work will force workers to sleep and work at non-biological times, inducing circadian disruption with implications for workers’ safety and health. The scientific literature may be used in practice in shift work settings to improve safety, performance and health in the workplace by reducing circadian misalignment. Alertness profiles at work and degree of melatonin suppression may indicate degree of circadian disruption among workers. However, when considering lighting solutions at night, there are several factors that need consideration. Light measures based on biological effectiveness should be used rather than room illuminance giving better predictions of performance and long-term health among workers. Also, large individual differences in light sensitivity and preferences suggest not only to rely on common lighting alone but also to implement complementary individual lighting solutions at work. Lighting advice should consider shift scheduling characteristics such as speed of turnover and shift timing to guide decisions of preferred circadian phase influence. Lighting should also include the flexibility to be fit for morning, afternoon and evening work.

Snow removal activities are performed by roadway agencies to enhance winter mobility and safety. Slower travel speeds during these operations, combined with low visibility and reduced pavement friction, mean that safety and collision avoidance remain a persistent concern. Many studies have implemented signing and lighting technologies to improve the visibility of snowplows. Although a few studies have evaluated the use of different colors on snowplows, there is no rigorous study that evaluates the potential impacts of using green warning lights for winter maintenance operations. This study, therefore, investigates the impacts of various warning light configurations on the visibility of snowplows, with the focus on green lights. To this end, 37 warning light configurations are designed using various color combinations (green and amber), and flashing patterns (single and quad) on the back (LED), the top (beacon), or both, of snowplows. These configurations are evaluated to identify the most effective configurations. Three sets of experiments are designed and implemented: static, dynamic, and weather to evaluate the visibility effectiveness in different contexts: day versus night, clear versus snowy weather, and static versus dynamic scenarios. Human subjects are employed to conduct the experiments and the test results are evaluated using statistical analyses. The conspicuity during the day time and glare during the night time are statistically different among various configurations. In addition, adding green lights with a single flash pattern to amber warning lights improves the conspicuity, while keeping the glare at an acceptable level relative to configurations using only amber.

The information contained in light from our surroundings is often taken for granted because of its ubiquity, and the subliminal nature of the way we normally use it. Revealing the richness and depth of our common human experience through the unexpected qualities of light is seen as an artistic opportunity. An architectural training enables the integration of a subjective and qualitative experience, with the ‘objective’ structures that we are surrounded by. The built space can act as a ‘neutral’ reference onto which the complexity of daylight is superimposed. The author, trained as an architect, has been involved for more than 30 years in the design and construction of non-gallery artworks that engage the experience of natural light in public and semi-public spaces. This practitioner reflection discusses the relation of the position of the observer and sources of light, and how the movement of the viewer acts as a catalyst for revealing their situation through six works of various scales that the author worked on in New York; Boston; Abu Dhabi; London; and Berlin.

In the past 30 years, tubular daylight guide systems (TDGSs) have become one of the most popular ways to transport outdoor natural light into the inner space in building design. However, tubular daylight guide systems are not widely used because of the lack of methods to evaluate methods on the suitability of the TDGSs. This study therefore summarizes the daylight performance metrics of TDGSs and presents the estimation methods in terms of field measurements, simulation and empirical formulae. This study focuses on the daylight performance and potential energy savings of TDGSs. Moreover, this study will be helpful for building designers to build healthy, comfortable and energy-saving indoor environment.

This paper analyses the forecast accuracy of current state-of-the-art, data-driven, spectral sky models. The aim is threefold: (i) to determine the forecast accuracy of existing spectral sky models based on a large dataset of spatially, spectrally and temporally resolved measurements, (ii) to investigate the practical implications of spectral forecast accuracies for the assessment of spectrally selective responses (here non-image-forming effects are expressed through melanopic irradiance) and (iii) to study if the use of spectral sky models is more appropriate to predict the non-image-forming effectiveness of daylight than the currently assumed CIE standard illuminant D65. The forecast analysis for CIE Standard Overcast Skies (CIE Sky Type 3) showed that the model published by Chain and colleagues in 1999 performed best, whereas the correlated colour temperature distribution can also be represented with the CIE standard illuminant D65. The analysis showed substantial discrepancies in the forecast for clear skies with low luminance turbidity (CIE Sky Type 12) depending on the correlated colour temperature range. Our findings suggest that for CIE 12 skies, even when simulating with the best performing spectral sky model, forecast inaccuracies affect the estimated non-image-forming effectiveness. Nonetheless, the assumption that the spectral distribution of daylight from a CIE 12 sky corresponds with the CIE standard illuminant D65 underestimates the non-image-forming effectiveness to a greater extent. The results advance the understanding of spectral characteristics of daylight and suggest that considering realistic spectral distributions instead of D65 will lead to a difference in the non-image-forming effectiveness assessment.

The present studies examined the feasibility and acute alerting effects of additional in-vehicle lighting within a passenger car. These factors were examined during morning driving (Study 1) and evening driving (Study 2). In a balanced within-subjects design, 37 participants drove a test car two times in the morning or in the evening. The test vehicle was equipped with either a daylight-supplementing interior lighting system or a placebo system, which participants were told would refresh the air. Both studies used identical protocols, and participants participated either in Study 1 ( n = 18) or Study 2 ( n = 19). In both studies, corneal illuminance levels were recorded while driving. Feasibility of the systems was assessed using subjective ratings. Efficacy outcomes were spindle rates in the alpha bandwidth of electroencephalogram recordings, performance on a psychomotor vigilance task and subjective sleepiness ratings. In both studies, daylight-supplementing significantly increased corneal illuminances while driving and did not cause any negative visual side-effects. Study 1 revealed lower spindle rates while driving under daylight-supplementing lighting, indicating that drivers had higher physiological alertness when exposed to additional light in the morning. This alerting effect of daylight-supplementing lighting, however, was not observed in Study 2. In both studies, performance on the psychomotor vigilance task as well as subjective sleepiness ratings did not significantly differ between the experimental conditions. The present studies provide novel evidence for the feasibility and positive impact of daylight-supplementing in-vehicle lighting systems on the physiological alertness of drivers under naturalistic driving conditions. Further studies are warranted to evaluate carry-over effects of increased alertness on road safety measures.

Exposure to daylight has much to offer and should be optimised to maximise its potential. In order to harvest its benefits, any visual discomfort from daylight should be anticipated and minimised. Hence, there is the need to predict discomfort from daylight glare. While more than 20 models for predicting discomfort from daylight glare have been developed, none accurately predict it. The inclusion of additional factors in the models may improve the predictions. One such factor is the socio-environmental context of the observer. This study compares the evaluations of discomfort glare from daylight for office buildings in four socio-environmental contexts: Chile, Belgium, Japan and Switzerland. The evaluations of discomfort glare, each consisting of subjective assessments and physical measurements of a view condition, were collected at the office desks of 401 participants, although only 211 responses were used in the analyses due to exclusion rules. The results do not suggest evidence of an influence of socio-environmental context on discomfort from daylight glare. In other words, the participants in this study perceived discomfort glare similarly, regardless of their socio-environmental context.

This paper presents an experimental research study intended to evaluate daylight perception in work environments. The current metrics for assessing daylight in work environments involve quantifying daylight and do not provide insight into the actual appearance of the space, thus overlooking the qualitative aspects of light and their effect on occupants. Conceptual content cognitive mapping (3CM), a mixed methodology, was used to obtain participants' hierarchical knowledge structure and mental model of daylight in work environments. This method was selected to understand the end users' perception of an environment rather than measuring the physical environment. A cognitive map of 50 participants, half architects and half non-architects, was created using 3CM. The results present a list of daylight lexicon and a vast selection of concepts related to physical and psychological comfort among all participants. This experiment reveals that connectivity and emotional reactions are the two dominant underlying dimensions describing daylight in work environments. The results illustrate both similarities and disjunctions between two groups of participants regarding the selected daylight terms and characterizations. The results also indicate the need to augment current planning practices with a qualitative multi-disciplinary approach to create more pleasant working environments.

A novel high-dynamic range camera-based approach to measure the cumulative daylight dose in historic/conservation spaces has been devised and tested in a real-world setting under normal viewing conditions. The technique derives illuminance from the high-dynamic range-acquired luminance at numerous patches of the wall surfaces visible in the high-dynamic range image. These patches serve as proxy illuminance meters, thereby allowing the prevailing illumination field across the entire visible wall to be derived using a Kriging algorithm. The technique was validated under both controlled and in-situ conditions over periods of several months and shown to have comparable accuracy to the illuminance logging devices commonly used in historic/conservation settings. The set-up comprising a consumer digital camera and tethered computer proved remarkably resilient and allowed for continuous monitoring periods of six months or more. Application in a real-world setting revealed operational practicalities that would not have been found in a controlled environment.

In building design, the decision-makers should not focus only on energy efficiency as a single objective but indoor environmental quality indicators, such as thermal comfort, daylight usage and so on, should also be considered as a part of building performance. The building performance can be ensured by determining the proper performance indicators and the variables during the design. In this context, a weighted (among the objectives) multi-objective cost function was proposed, for the optimisation of energy, thermal comfort and daylight usage of a case study archetype design, through the selected design variables, considering the base architectural design principles as well. A typical social housing archetype design was determined as the case study to apply the proposed approach. The window sizes are optimised for each orientation simultaneously, for a temperate-humid climatic region. The results were evaluated in terms of improvement potentials of energy, thermal comfort and daylight performances, and the dominant values for the window sizes for each facade. According to the results, the optimised scenario achieved an 11.42% reduction in primary energy use equivalent to 181.24 kWh/m2a, a 4.52% reduction in a predicted percentage of dissatisfied with 9.12%, and a reduction in lighting energy of 4.94% equivalent to 21.17 kWh/m2a. These reductions verify the possibility to achieve higher performances on each criterion.

Evaluation metrics using climate-based daylight modelling paradigms have become the de-facto standard in work environments but have only limited applicability in residential architecture. Qualities of daylight cited in the architectural design literature, such as daily and seasonal availability of daylight as well as access to direct sunlight, are simulated in detail but are usually overlooked in the commonly used evaluation metrics. In a recent paper, a new climate-based, annual daylight evaluation framework called the residential daylight score has been proposed for cold and temperate climates. It assesses daylight autonomy and access to direct light in 12 daily and seasonal bins and proposes targets for seasonal and diurnal daylight autonomy and duration of direct sunlight exposure. While the metric aims to capture essential characteristics of residential daylight, only a few reference cases exist in the literature to adequately judge its achievability and applicability. This paper aims to thoroughly test the residential daylight score and provide reference cases for 2444 apartments from a set of 18 multifamily buildings that compare the new metric with currently used climate-based metrics.

This article examines the association between daylight hours as a proxy for the seasonal affective disorder (SAD) and stock market return. Past studies have documented different decision-making mechanisms induced by investors’ cognition mainly influenced by greed and fear. However, this study appears to be different from evidence where investors’ mood is affected by seasonality, which plays a vital role in risk-taking propensity. Data have been taken from three indexes of Bombay Stock Exchange (BSE), for the period between April 2003 and December 2016. The impact of SAD on stock market return was examined by using naïve ordinary least square (OLS) model. This study reports a negative relationship between daylight hours and pattern of midcap as well as smallcap indexes, which are in alignment with mood maintenance hypothesis (MMH). The result of negative correlation suggests a summer-type SAD, which is an addition to the findings of the existing literature.

Calibration of an illuminance meter is indispensable for accurate measurement of the illuminance of indoor lighting and daylight. In recent years, because of the phasing-out of incandescent lamps and their replacement with LED lamps, it has become difficult to obtain an incandescent type standard lamp to calibrate an illuminance meter. To replace the standard lamp method, we constructed an illuminance meter calibration system based on an LED-based spectrally tunable light source. The approximate CIE Illuminant A spectrum realized by the LED-based spectrally tunable light source was controlled at various illuminance values (800–10,000 lx). A test illuminance meter was calibrated by comparison against a reference photometer with the realized approximate Illuminant A spectrum. The illuminance values measured using the reference photometer and using the test illuminance meter in the calibration system agreed within 2.5% without reference plane correction of the test illuminance meter, and within 1% with reference plane correction. Reference plane correction depends strongly on the measurement distance and the illuminance meter structure. This study demonstrated that it can be improved. Therefore, we infer that an illuminance meter calibration method using an LED-based spectrally tunable light source is a promising means of overcoming difficulties posed by the phasing-out of incandescent standard lamps.

Due to our social behaviours, people spend at least 80% of their time indoors, mostly under artificial light. In research and building design, daylight is considered a valuable asset because it is the primary source of free, good quality light and it is suggested that it has a positive influence on human performance, health and sleep quality. There is a tendency in the population for increasingly poor sleep quality with age, and this affects at least 50% of the elderly population. Research on sleep disruption has found that especially in the elderly population, interrupted sleep can affect alertness, cognitive performance and mood. This increases the risk of falls, increases fatigue and reduces some other mental functions. Exposure to daylight (indoors and outdoors) is expected to reduce sleep disruption. Physical activities and sleep quality were assessed using 32 participants living independently in the UK, aged between 65 and 95 years old. The study was divided into two seasons due to a considerable difference in daylight availability in summer and winter. In each season participants completed the Pittsburgh Sleep Quality Index (PSQI) questionnaire, Morningness–Eveningness Questionnaire (MEQ) and a seven-day sleep diary/log activity; where time spent outdoors was identified. It was expected that participants who reported less exposure to daylight during summer and winter would report worse sleep quality. However, this was not the case; subjective sleep quality did not differ greatly between summer and winter, even though exposure to daylight varies greatly between seasons. This study explores the relationship between exposure to daylight throughout two different seasons and people’s chronotypes, physical activities and sleep quality (between and within participants). This information is essential to find means of supporting an ageing population. Practical applications: In the built environment, daylight is an important feature to consider for the occupant’s health and wellbeing. This research provides real-world insight into the amount of daylight that active aged people are exposed to during two seasons in London, and how this could impact their overall sleep quality. The findings suggest that exposure to daylight could benefit people over 65 years old with poor sleep quality by reducing the number of awakenings during the night. This research provides a step towards understanding how daylight exposure effects people, and can be used to inform housing design for the ageing population.

This study explored the classroom luminous environment with prism daylight redirecting fenestrations. The differences between the International Commission on Illumination standard sky and the Perez all-weather sky models were analysed. The study described the method of generating a valid bi-directional scattering distribution functions .xml data for the prism daylight redirecting fenestrations. A new evaluation metric, daylight evenness, was proposed to describe indoor illuminance dispersion. Radiance simulation results indicate that at various solar altitude angles, compared with conventional glazing, the micro-prism film and micro-prism with an added diffuse layer on clerestories can improve the space average illuminance levels 23.2% and 18.7% under the International Commission on Illumination sky, as well as 15.4% and 10.6% under the Perez sky, respectively. The analysis results indicate that prism daylight redirecting fenestrations clerestories can improve indoor illuminance uniformity and daylight evenness when the solar altitudes range from 23.8° to 75°. A method combined field questionnaire and high dynamic range image analysis were conducted for discomfort glare study. Adding a diffused layer to the prism film clerestory is expected to alleviate discomfort glare for east- and west-facing prism daylight redirecting fenestrations clerestory with the daylight glare probability reduction of 3.8% to 21.7% at various solar altitudes. The research results present promising advantages of applying prism daylight redirecting fenestrations at classroom clerestories to improve the daylight luminous environment.

Salvadori, Giacomo/0000-0002-0720-2380; LECCESE, FRANCESCO/0000-0002-2256-7943; Oner, Merve/0000-0001-5551-068X, WOS: 000501954100001, This study explored the impact of daylight illuminance on cognitive load during visual display terminal use by means of various physiological, performance and subjective measures. Repeated-measures design was adopted to identify the impact of variations in daylight levels that were manipulated through the shading system configurations (shading-on; shading-off). A total of 30 subjects performed visual and cognitive demanding tests. Performance measures were supported by subjective data and eye-related measures during the experimental analysis. Results revealed that the use of a shading system had positive impact on sustained attention. Concerning ocular measures, percentage of eye closure values showed opposite tendencies among vigilance and sustained attention demanding tests. Eye aspect ratio-max and blink duration were significantly correlated with reported glare sensation. In all tests, eye aspect ratio-max was found significantly higher in lower illuminances. Search velocity was significantly correlated with ocular variables in higher illuminances whereas sustained attention showed an opposite trend. This, initially, explains that even slight differences in daylight illuminance might have distinctive effects on the relationship between different groups of assessment variables while measuring cognitive load. Secondly, it proves the significance of carrying out sensitive experiments in terms of both light levels and test characteristics.

Various metaheuristic optimization methods have been applied in high-performance glazing and shading system design due to the complexity and nonlinear impact of the fenestration characteristics on the daylighting performance. However, the optimal solutions found by different optimization methods may vary because of the stochastic nature and the configurations of the optimization methods. This paper studied the improvements in the reliability, consistency and robustness of the genetic algorithm (GA) using hybridization with simulated annealing (SA) considering different cooling strategies in the SA, including the initial temperature and state transitions for each temperature, which controls the comprehensiveness and the convergence acceleration of the search by SA. Analysis of the reliability, consistency and robustness of the optimization methods based on the mean values and the variances of the objective function values of the best cases found in different methods revealed that there is a significant difference between the hybrid GA/SA with higher temperature and GA, where hybrid algorithm performed better than the GA.

A new set of CIBSE weather files for building performance simulation was recently developed to address the need for better quality solar data. These are essential for most building performance simulation applications, particularly for daylighting studies and low-energy building design, which requires detailed irradiation data for passive solar design and overheating risk analysis. The reliability of weather data becomes paramount when building performance is pushed to its limits. Findings illustrate how principles of good window design can be applied to a case study building, built to the Passivhaus standard, and how its expected performance is affected by the quality of solar irradiation data. Analyses using test reference years were most affected by changes in the solar radiation model (up to 8.3% points), whereas for design summer years the maximum difference was 1.7% points. Adopting the new model caused overheating risk to be classified as more severe using test reference years than design summer years, prompting a discussion on the design summer year selection method. Irradiance data measured on-site were used as a benchmark to evaluate the new solar radiation model, which was found to significantly improve the accuracy of irradiance data within weather files and so the reliability of overheating assessments. Practical application: CIBSE weather files are widely used for compliance verification of building performance in the UK context. This paper tests how the introduction of a new solar radiation model in weather files will affect daylighting and overheating simulation results. Examples are given on how low-energy building design considerations driven by advanced simulation techniques can help reaching indoor visual and thermal comfort requirements.

When looking out of a window, natural views are usually associated with restorative qualities and are given a higher preference than urban scenes. Previous research has shown that gaze behaviour might differ based on the natural or urban content of views. A lower number of fixations has been associated with the aesthetic evaluation of natural scenes while, when looking at an urban environment, a high preference has been correlated with more exploratory gaze behaviours. To characterise gaze correlates of view preference across natural and urban scenes, we collected and analysed experimental data featuring subjective preference ratings, eye-tracking measures, verbal reasoning associated with preference and nature relatedness scores. Consistent with the literature, our results confirm that natural scenes are more preferred than urban views and that gaze behaviours depend on view type and preference. Observing natural scenes was characterised by lower numbers of fixations and saccades, and longer fixation durations, compared to urban views. However, for both view types, most preferred scenes led to more fixations and saccades. Our findings also showed that nature relatedness may be correlated with visual exploration of scenes. Individual preferences and personality attributes, therefore, should be accounted for in studies on view preference and gaze behaviour.

A recent paper proposed a more precise approach for investigating the impact of ambient light (daylight versus after dark) on road traffic collisions. The present paper first repeated that analysis of road traffic collisions in the UK to test reproducibility; it then extended the analysis to determine whether the greater precision affected the outcome of road traffic collision analyses. Results of the previous analysis were reproduced in terms of the direction of the effect, but the repeated analysis found greater differences between daylight and darkness. The odds ratio determined using the new method led to higher odds ratios than the analyses used in some past studies, suggesting that past studies may have underestimated the detrimental effect of darkness on road traffic collision risk.

The paper reports a study that examines how to determine if a road traffic collision took place in daylight or in the dark. An innovative method was developed, based on solar altitude, to establish cut-off points of daylight and darkness determined from a study of daylight availability in England, Scotland and Wales. This approach provides a rigorous method to differentiate daytime and night-time collisions. The criteria were used in a study of the collisions reported in the STATS19 data set for the weeks either side of the clock changes that are necessary between Greenwich Mean Time and British Summer Time. By comparing periods with the same clock time either side of the time change, using the aforementioned method, it was possible to isolate collisions within the same time period that during one week occurred in darkness and in the other week in daylight. The initial finding was that there are 19.3% more collisions in the dark periods and there is an even greater increase (31.7%) in pedestrian injuries.

This paper presents a data analytics model-based predictive control approach for a daylight–artificial light integrated scheme. The essential data are collected from an automated test room with dimmable LED luminaires and motorized Venetian blinds. This study considered machine learning techniques to develop a novel control strategy for all the four-window orientations for maintaining comfort and energy conservation. The shades are operated one at a time, and the annual data collected were used to develop the predictive models. The irradiance, altitude, temperature and daylight on the window are the predictors, and the blind position is the response variable to establish the models for the windows on all four sides of the test room. The standard support vector regression, Bayesian support vector regression and Gaussian process regression models are analysed in comparison with the baseline model. The luminaire dimming control signals generated using the predicted optimum blind position and exterior illuminance based on a building information illuminance model is commissioned for a given room. This approach mainly concentrated on the implementation of an industrial-level product by reducing the computational complexity of the rule-based blind positioning system. At present, the models are in a reconfigurable embedded WiFi-enabled operating system.

In this paper an iterative, closed-loop light control scheme is proposed and evaluated by a white light emitting diode-based, daylight-responsive luminaire to follow the time-varying pattern of correlated colour temperature and illuminance of a daylight scene. The proposed control scheme functions primarily with the response signals of two RGB colour sensors, viz., a daylight sensor to monitor the daylight scene at the window plane and an internal light sensor to monitor the light scene created by the test white light emitting diode luminaire. The control scheme controls the lumen delivery of individual light emitting diode arrays of the test luminaire by adjusting the duty cycles to follow the instantaneous correlated colour temperature of daylight and at the same time to respond to the variation of window plane illuminance in the reverse pattern. Evaluation is conducted by laboratory testing and in situ testing. The maximum deviations in correlated colour temperature, illuminance and chromaticity from the required values under laboratory testing and in situ testing are found to be [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text], [Formula: see text] respectively, which establish the acceptable performance of the proposed iterative light control scheme.

The amount of received sunlight and radiant energy could affect the energy consumption in heating, cooling and lighting systems. Utilization of natural daylight in architecture, in addition to fulf...

Though numerous daylight studies have been conducted worldwide, works for the daylight climate and/or the daylight variations/trends are rare. This gap is treated here. Therefore, the innovative trend analysis and the month–hour diagrams are applied to the illuminance time series at Athens over the period of 1992–2017 under all-/clear-sky conditions. For all skies, the global illuminance shows a broad maximum at summer noon, while the diffuse counterpart is in spring. Under clear skies, the global illuminance maximum becomes broader, covering spring/summer. However, the diffuse illuminance maximum splits into minor ones in April and June. The innovative trend analysis method finds that the identified trends are + 2.83%/decade (−1.89%/decade) for the global (diffuse) illuminance, under all skies. In clear skies, the above values are modified to +2.66%/decade (−2.00%/decade). These results confirm a recovery in the Athens daylight levels as in the solar radiation ones found by many researchers. Another outcome of the study concerns the observed decline in diffuse illuminance levels in the examined period, which may be attributed to a decline in cloudiness and an increase of sunshine over the area. Also, the variation of the global and diffuse illuminance efficacies on a month–hour basis is examined using the month–hour diagram method.

LED *Shared senior authors. light sources have a discontinuous light spectrum with a prominent ‘blue’ peak between 450 and 470 nm that influences non-image forming responses in humans. We tested an LED lighting solution mimicking a daylight spectrum on visual comfort, circadian physiology, daytime alertness, mood, cognitive performance and sleep. Fifteen young males twice spent 49 hours in the laboratory under a conventional-LED and under a daylight-LED condition in a balanced cross over design flanked by a baseline and a post-light exposure night. Despite different light spectra, the photopic lux and the correlated colour temperature of the lighting were the same for both LEDs. The colour rendering index and the melanopic strength were 25.3% and 21%, respectively, higher for the daylight LED than the conventional LED. The volunteers had better visual comfort, felt more alert and happier in the morning and evening under daylight LED than conventional LED, while the diurnal melatonin profile, psychomotor vigilance and working memory performance were not significantly different. Delta EEG activity (0.75–4.5 Hz) was significantly higher after daylight-LED than conventional-LED exposure during the post-light exposure night. We have evidence that a daylight-LED solution has beneficial effects on visual comfort, daytime alertness, mood and sleep intensity in healthy volunteers.

In urban areas in Texas and the rest of the United States, roadway work zone and construction activities are often conducted at night to reduce disruption to traffic and to prevent congestion caused by lane closures during peak hours. The reduced traffic delays due to nighttime construction have the potential to reduce traffic emissions. However, the air quality impacts associated with moving these activities from daytime to nighttime have not been studied in detail. Air quality impacts depend on two major factors: the traffic emissions and meteorological conditions. While the impact of traffic emissions between time periods has been studied in the literature, there is limited knowledge on understanding the impact of meteorological conditions on the dispersion of mobile source pollutants. This study specifically addresses this gap by evaluating the impact of the meteorological conditions on pollutant concentrations under different input settings related to the region, land use, distance from roadways, and averaging periods. The assessment of the impact of metrological conditions indicated that for the same amount of emissions, the nighttime period could result in higher pollutant concentration levels. However, given that traffic congestion and overall traffic volumes are generally substantially lower in the nighttime period, the findings do not imply that nighttime construction activities result in worse air quality in terms of pollutant concentrations. Thus, the relative difference in pollutant concentrations obtained from shifting construction activities from daytime to nighttime periods should be assessed based on a combination of meteorological and traffic conditions.

Occupant surveys were conducted in 4 office buildings, 2 with traditional non-tinted low-e glass (LeG) and 2 with electrochromic glass (EC). 106 employees working in these buildings volunteered to participate in the study. Results showed that subjective reports of overall ambient lighting conditions were comparable in the buildings. However, EC optimizes daylight and reduces sunlight glare, and significantly more workers sat close to the windows in the EC buildings compared to the LeG buildings. Workers in the EC office buildings reported significantly better daylight, significantly less adverse glare, and significantly fewer symptoms of computer vision syndrome than those in the LeG buildings.

Energy efficiency strategies based on daylight-artificial light integration have grown exponentially in recent years. Taking into account the dynamics to be considered for control and the dependence on natural and occupancy factors, it is better to use a test workbench prior to setting up the final control scheme. This work describes a climate model based test workbench for the real time testing of the control of luminaires and window blinds in a daylight-artificial light integrated scheme. The established climate model based control scheme suitable for the optimum integration of visual comfort, thermal comfort, and energy consumption can be tested for any ecological conditions. The input irradiance from a BF5 sensor, the internal temperature from a Micro DAQ logger, the occupancy and photo sensors associated with the luminaire all provide input data for the test workbench. A fuzzy logic based motorized window blind controller and look-up table based dimming of LED luminaires are used to set the required illuminance with reduced load on the heating, ventilation, and air conditioning system. The anticipated synergetic effects of the test workbench have been validated using real time climate data. The test work bench is established on a Labview platform and developed as a standalone system using myRIO.

This work concerns the subjective impression of perceived illumination. The purpose of the study is to test attributes expressing qualitative experiences referring to ambient lighting that can be applied as descriptors. Seventy participants viewed an actual model room, with the fourth wall removed (viewing booth). Walls, floor, and ceiling were achromatic. Two achromatic cubes were placed inside the room: One was a reflectance increment to the walls, the other a decrement. The room was illuminated by two different light sources, Artificial Daylight (D65) or Tungsten Filament (F), the order of which was randomized across participants. The participants’ task was to evaluate ambient illumination for each light source. A semantic differential method was employed with 27 pairs of adjectives on 1 to 7 rating scales, categorized in three groups: characteristics of atmosphere, time, and cross-modal. Only the ratings of nine pairs of adjectives were not influenced by the type of illumination. The most differentiated couples under different illuminants were hot/cold and modern/old, but large differences also appeared with the following couples: hard/soft, technological/primitive, summery/wintry, warm/cool, sensual/frigid, natural/artificial, and hospitable/inhospitable. The hypothesis that there would be consistency among the subjects in evaluations of the characteristics tested and that these would be differently perceived under different illuminants was confirmed. The results show that it is possible to identify subjective perceived illumination as a phenomenon endowed with specific filling-in qualities and that as a perceptual experience it can be categorized, with implications for application in architecture and design.

Throughout history, the spaces of sacred buildings have benefited from inspiring patterns of light. In this context, the present study aims to analyze how daylight pervades the sequential spaces of Sheikh Lotfollah Mosque, Isfahan, Iran, one of the most well-known mosques, during the day. The spaces of the mosque present several appearances of daylight, controlled during different time intervals. Photographs of the spaces taken with the help of a camera depict the different daylight penetrations from outside to inside the mosque, categorized into different episodes. The observation of daylight penetrations in each episode reveals that building orientation, fenestration, reflection, and daylight variability are the major factors to analyze daylight in sequential spaces. Based on the analyses, the results of the current article present the major findings to establish a framework that can help design other mosques and buildings with similar spaces.

Residential architecture constitutes one of the largest market segments in the construction sector. However, the attention that it is given in the field of daylight performance simulation is surprisingly low. This poses the question of whether existing daylighting metrics are well suited for residential design. Findings from 79 references are summarized, and a critical review of current climate-based daylighting metrics in the context of residential architecture is provided. It is found that existing workflows often overlook relevant aspects of daylight in residential spaces, such as diurnal and seasonal availability of daylight and access to direct sunlight. Hence, a concept for a new climate-based, annual evaluation framework that overcomes these shortcomings, called the residential daylight score, is introduced.

The aim of the study was to investigate whether indoor lighting quality would have any systematic impact on psychological well-being of people working in café environments. Earlier studies have mostly focused on the impact of lighting in typical workspace environments through laboratory settings. The present study was conducted under two different real café environments; one with daylight, another without daylight, with a total of 66 customers’ participation. Two psychological pathway models that linked customers’ self-reported lighting quality, pleasantness, aesthetic judgement of space appearance, environmental satisfaction and feelings of eye discomfort were developed. Application of structural equation modelling produced strong fits to these two models, one with daylight, another without daylight, in which quality of lighting was linked with environmental satisfaction and feelings of eye discomfort in both cafés. The results suggest that under a non-daylit café environment, providing good quality lighting can both directly and indirectly promote environmental satisfaction and decrease negative feelings of eye discomfort, while under a daylit café environment, perceived lighting quality was only indirectly linked.

Residential and commercial buildings together account for one-third of world’s final energy consumption, thus making energy management in buildings of considerable significance. Passive design concept that depends on climate and location can be used as an effective and economical method to reduce the energy consumption in buildings. Seven cities in India, each representative of different geographic and climatic conditions, were selected for analysis. This article studies how the peak cooling and heating load are affected by varying some of the passive design parameters for each of the seven cities. The parameters varied are wall insulation thickness, roof insulation thickness, overhang depth, window orientation, and window-to-wall ratio. Results show that optimized passive design could reduce the peak cooling and heating loads by about 50%. Shading reduces cooling loads but is found to increase heating loads. In some of the locations, both heating in winter and cooling in summer are needed and designers should adopt appropriate passive measures depending on the location. Also for the same building, evaluation of shading is done in the context of lighting energy savings. An algorithm has been developed to iteratively alter and analyze set of roller blind positions to maintain visual comfort; as a result, the corresponding potential annual energy savings due to lighting were estimated. It was also observed that even after providing visual comfort to the occupants, energy savings only reduced by approximately 1% as compared to the case when visual comfort was overlooked.

Bicyclists risk being involved in collisions with motor vehicles, even during daytime. Thus, bicyclists who ride in daylight must enhance their conspicuity. This study assessed the daytime conspicuity benefits of bicycle taillights using eye tracking technology. Participants were driven along an open-road route while wearing an eye tracker and pressed buttons when they detected and recognized a test bicyclist. Participants encountered the bicyclist displaying one of four taillight configurations, and the distances from which they responded to the test bicyclist were recorded. The results revealed that, after participants first glanced at the bicyclist, a significant amount of time was needed to detect and recognize the bicyclist. Further, seat post-mounted lights displayed with or without lights mounted to the heels of the rider’s shoes provided the greatest conspicuity advantage in terms of recognition. This experiment offers useful insights into the optimal light placement options for bicyclists to enhance their daytime conspicuity.

The development of an accurate control system for shading devices, essentially motorised Venetian blinds, relies on the rational use of daylight in buildings. This study proposes a control strategy for building lighting components, both daylighting and artificial lighting, to automatically adjust the light level in an office building as required and to block direct sunlight from entering the office, when necessary. The proposed control strategy is based on a hybrid statecharts model mainly consisting of a supervisory control system that chooses appropriate control actions for a current sky condition depending on the sky ratio and clearness index. These control actions are implemented to automatically adjust the blind height and slat angle, and turn on the artificial lighting only when needed. Real experiments in a test-cell demonstrate the effectiveness and flexibility of the proposed control strategy.

Developed in 2006, the veil of darkness approach is one of the most widely accepted methods for assessing the impact of driver race on traffic stops. Building on the original methodology, we innovate in three important ways to enhance the veil of darkness approach: (a) invoke generalized linear mixed models to account for the lack of independence among observations in traffic stop data sets, (b) decompose the relationship between daylight and driver race to consider the role of driver sex, and (c) assess variability in racial disproportionality across law enforcement units. Nearly 20,000 traffic stops are analyzed for the Durham (NC) Police Department. Results indicate that more than 10% of the variability in the rate of Black drivers stopped is accounted for by officer-level factors, racial disproportionality was only for male drivers, and evidence of disproportionality was found among some units, but no evidence was found among others.

Chronic sun-induced dysplastic skin changes (actinic keratoses) are extremely common in fair-skinned people in Scotland. These changes are a major cause of morbidity and may develop into skin cancer. Actinic keratoses are often extensive and pose a therapeutic challenge as field-directed treatment is required for chronic disease management. One such treatment approach is hospital-based photodynamic therapy, which is a well-established treatment in Scotland for actinic keratoses, using a photosensitiser pro-drug and red LED light irradiation. However, photodynamic therapy using daylight as the activating light source is increasingly and effectively used in continental Europe, but had not been explored in Scotland until we initiated this in 2013. We report our experience of daylight photodynamic therapy in 64 patient-treatment courses and demonstrate that this can be an effective, well-tolerated treatment, which is liked by patients. Our most recent data show that most patients (73%) achieved clearance or at least a good response to treatment and had high levels of satisfaction with daylight photodynamic therapy. Daylight exposure measurements indicated that treatment is feasible in Scotland between April to September. Daylight photodynamic therapy is an important advancement in treatment options for Scottish patients with extensive pre-cancerous field changes and provides opportunities for home-based treatment and increased efficiency of photodynamic therapy services.

Light is the most potent time cue that synchronizes (entrains) the circadian pacemaker to the 24-h solar cycle. This entrainment process is an interplay between an individual's daily light perception and intrinsic pacemaker period under free-running conditions. Establishing individual estimates of circadian phase and period can be time-consuming. We show that circadian phase can be accurately predicted (SD = 1.1 h for dim light melatonin onset, DLMO) using 9 days of ambulatory light and activity data as an input to Kronauer's limit-cycle model for the human circadian system. This approach also yields an estimated circadian period of 24.2 h (SD = 0.2 h), with longer periods resulting in later DLMOs. A larger amount of daylight exposure resulted in an earlier DLMO. Individuals with a long circadian period also showed shorter intervals between DLMO and sleep timing. When a field-based estimation of tau can be validated under laboratory studies in a wide variety of individuals, the proposed methods may prove to be essential tools for individualized chronotherapy and light treatment for shift work and jetlag applications. These methods may improve our understanding of fundamental properties of human circadian rhythms under daily living conditions.

This study evaluates daylight performance in an art museum in İstanbul, Turkey to analyse the effects of daylight design features on visitors’ satisfaction in art museums. The study is based on users’ data obtained through a survey and daylight simulation achieved by Autodesk 3D’s Max 2014. A three-part questionnaire was conducted with 100 participants in overcast- and clear-sky conditions to rate visitors’ satisfaction with the museum and their importance level of daylight design issues in museums. The museum’s daylight illuminance data were measured on a scaled model by a computer simulation program. The statistical results and simulation renderings show that daylight design is a multi-parameter task. There are statistically significant correlations between visual comfort and visitor satisfaction. The study finds two essential daylight considerations for a practical guide to promote healthy and effective daylight use in museums: (i) that certain design aspects in a museum, such as location, window size and window distance from partitions or displays, are important regardless of weather conditions and that (ii) glare prevention from openings such as windows and skylights is also a crucial aspect in visual comfort. © 2017, The Author(s) 2017.

Objective: This article reports summer verses winter seasonal variations across a suite of blue light, illuminance levels and health and well-being indicators. Background: The quality of lighting in care homes has been assessed previously, yet seasonal comparisons and the associations with sleep quality are limited. This exploratory study investigates light exposure in two seasons to determine the changes over time and the associations with health and well-being. Methods: In a repeated measures design, 16 older people (aged 72–99 years) living in a care home had their personal light exposure and sleep/wake patterns monitored for 4 days. Cognitive ability, mental well-being, daytime physical activity, and visual function were assessed. Mean light levels at preset times across the day, duration in light exposure over 1,000 lux, and sleep parameters were computed. Statistical investigations included correlations exploring associations and paired means tests to detect the changes between seasons. Results: The mean morning illuminance level in summer was 466 lux and 65 lux in winter. Duration in bright light over 1,000 lux was 46 min in summer and 3 min in winter. Light measures were significantly higher in summer. There was no statistical difference in sleep quality parameters between seasons, but there were significant difference in daytime physical activity level (i.e., this was higher in summer). Conclusion: The findings indicate low level of light exposures experienced in both seasons, with exposure levels being particularly low in winter. This provides new insights into the limited amount of light older people receive independent of season and the possible impacts on sleep and daytime physical activity level.

Wood is a material often used by architects to enhance the overall ambience of a space, but few researches have been reported to discuss its actual impact on visual impression and luminous effects. This research studies the influence of wood materiality in relation to creating specific lighting ambiances in architecture. In particular, it focuses on the impact of decorative wood indoor panels on the creation of daylighting diversity in interior space and the potential to improve daylighting quality and energy efficiency. The research uses scaled models for their accuracy in rendering complex daylighting ambiances. The photo-luminance meter enables the comparison between different settings of interior spaces created by a selection of wood type materiality: ratio (percentage), colour (Oak, Cape Cod Grey and Dark Walnut coatings) and gloss concerning illuminance patterns obtained from Ecotect software. The CIE L*a*b* colour space is used to classify luminous ambiances. Results indicate that bright colour Oak favours a deeper daylighting penetration and increases the colour temperature of the space by about 300% when applied on the floor. Cape Cod Grey coating provided a neutral colour balance even under sunlighting. High gloss Dark Walnut located on the ceiling produces the highest luminance values, enlarging the window-lighting pattern. The research underlines the role of wood materiality in achieving luminous diversity and creating visually comfortable interior ambiances.

Cycling with motor vehicle traffic on roadways is inherently risky for bicyclists, and it is important for bicyclists to make themselves conspicuous to drivers. This experiment used a closed-road method to test the daytime conspicuity of rear-facing bike lights. Participants provided subjective ratings of conspicuity from a test vehicle parked at two different distances from a bicyclist pedaling on a stationary bicycle with one of 16 configurations of bike lights. Some configurations featured lights on the bicyclist’s ankles to highlight the bicyclist’s biological motion. The results of this experiment provide a better understanding of the relative conspicuity benefits of bike lights in daylight as a function of light intensity, light placement, and viewing distance. The findings offer useful insights on the optimal intensity and placement of bike lights to enhance their own conspicuity during daylight.

The importance of daylight in homes is widely understood Site Layout Planning for Daylight and Sunlight: A Guide to Good Practice (BR209), Bracknell: BRE Press, 2011 [Extracted from the article] Copyright of Lighting Research & Technology is the property of Sage Publications, Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission However, users may print, download, or email articles for individual use This abstract may be abridged No warranty is given about the accuracy of the copy Users should refer to the original published version of the material for the full abstract (Copyright applies to all Abstracts )

Various emerging technologies encourage the embedding of intelligent and climate responsive behaviour into architectural elements. Light-shelves have been used for decades to enhance natural light in spaces, however, their static nature is limiting their overall performance potential. This paper explores the convergence of rapid prototyping, parametric design and environmental modelling software to create a dynamic and direct-reflection daylight redirection system that significantly enhances daylight availability. A Radiance-based simulation workflow to optimise and study the system is used and a 1:1 mock-up is developed. The mock-up is based on a horizontal-light shelf with an array of mirror tiles that can tilt in two axes based on sun position. The potential impact of such a system is then evaluated for a side lit office space in multiple climates in the northern hemisphere. Results show that daylight can be redirected deep into the building more effectively and therefore improve daylight availability for otherwise underlit floor plan regions. Projected savings for electric lighting range from 17% to 35% compared with a static redirection system.

Innovative daylighting systems (IDS) are used to deliver daylight into windowless spaces and building cores. Cleaning the exposed surfaces is essential for maintaining their efficiency because the accumulation of dirt inhibits their effectiveness. However, a review of the literature has indicated that this issue has not received the attention it deserves. This study reviews the cleaning methods currently used for solar devices and conventional daylighting systems. It also presents the technologies that can currently be employed to produce an IDS cleaning system, and suggests six cleaning mechanisms and 12 cleaning systems that suit different types of IDS in various operating circumstances. These include air-blowing, water-jetting, dragging-contact, rotary-contact and certain aid treatments. Air-cleaning and washing with water can both be used to restore functionality. Wiping and scrubbing are effective for increasing efficiency. Further productivity can be obtained by drying solar collectors after they have been washed. The systems suggested herein can be developed using already available technologies in order to achieve the ultimate in IDS efficiency restoration. However, before this can be done, the economic, environmental and operational aspects, in addition to potential levels of efficacy and applicability, must be assessed.

Daylighting integrated with artificial lighting control is recognized as an important and useful strategy in energy-efficient building designs. The prediction of the internal daylight levels is a key stage in daylighting designs. For this research, the ‘type design’ residential quarters building as a case has been selected from Nagpur region in central India having a hot and dry climate. These ‘type design’ have the major issues related to the performance of daylight and thermal comfort due to lack of some rules related to sizes of fenestrations in the development control regulation. The aim of this research is to evaluate the most critical liveable area of a dwelling unit of ‘type design’ for daylight and thermal comfort. This research includes evaluation of the selected parameters by comparative analysis of useful daylight illuminance (UDI), daylight autonomy (DA), thermal comfort hours and carpet area to window ratio (CAWR) with the help of dynamic simulation by using ‘Daysim’, ‘radiance analysis tool’ and ‘temperature distribution tool’ of Ecotect 2011 software. The findings of this research arrive to derive the CAWR with respect to orientation (four cardinal directions) of the building without compromising the thermal comfort with respect to the temperature of a dwelling unit of ‘type design’.