Article

Sensitive physiological indicators for human visual comfort evaluation

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Abstract

Three physiological factors (melatonin levels, tear mucus ferning quality and degree of asthenopia) were examined for their relationship to visual comfort. A lighting environment was created where the illuminance, illuminance uniformity and correlated colour temperature could be adjusted. A three-factor and three-level orthogonal experiment with 24 subjects was designed and carried out. The results indicated that the selected environmental factors had different impacts on the physiological factors. With the illuminance increasing, the melatonin level decreased significantly and the tear mucus ferning quality was improved. However, there is no general influence of illuminance uniformity and correlated colour temperature on the physiological parameters, only differential effects among the three levels were found.

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... CCT is also an influential factor that affects the visual perception, task performance, mood, and well-being of users; thus, several studies have conducted field lighting simulations considering CCT [8,13,25,35,50,[64][65][66]. For example, Viola et al. [13] conducted field lighting simulations in an office and identified lighting condition with 17000 K improves perceived mood, alertness, and task performance compared to lighting conditions at 4000 K. Hoffmann et al. [35] conducted field lighting simulations by using a survey and measuring sulfatoxymelatonin, which is linked to the circadian rhythm, and found that dynamic lighting conditions with varying CCT and illuminance levels during a day could improve users' subjective mood in an office. ...
... However, as mentioned above, the changes in the illuminance levels in the IVEs did not significantly affect the participants' visual comfort. However, some previous field lighting simulation studies [63,65,66] have reported results inconsistent with these findings. For example, Boyce et al. [63] observed that participants showed different levels of visual comfort based on illuminance levels in offices. ...
... For example, Boyce et al. [63] observed that participants showed different levels of visual comfort based on illuminance levels in offices. Similarly, Sun et al. [65] and Viitanen et al. [66] observed that participants indicated improvements in visual comfort as the illuminance increased. We believe that this inconsistency in our results is owed to the visual discomfort and mental workloads caused by using the HMD for IVE lighting simulations. ...
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In this study, the impact of two different types of window glazing using two identical rooms was studied. In one experiment both rooms were furnished as an office, in another experiment as a bedroom. The only other difference between the two rooms was the glazing of the window. In one room a standard three-pane window (2+1) with 4 mm clear glass was used, in the other a super-insulated four-pane window (3+1) with two silver-based low-emittance coatings. The results showed that people were clearly able to distinguish between the two windows. The room with the four-pane window felt more enclosed, and the daylight felt less strong and clear. The four-pane window also affected colour perception, making the colours of the room and of the view look more subdued or more drab. Spectral measurements revealed that the four-pane window transmitted a relatively higher percentage of the green part of the spectrum. The results agree with what might be expected given the lower transmittance and different spectral distribution of the four-pane window. It is questioned how far one should go in reducing the daylight transmittance of windows.
Article
A study is presented about the effects of three glazing colour types (blue, neutral, bronze) on daylight quality, arousal and switch-on patterns for electric lights. This study was carried out using a scale model (1:4) of an office room, where subjective evaluations of the luminous conditions were performed by 36 participants (mean age 23.8 years) with their upper bodies immersed in the model. The evaluations were achieved using questionnaires designed to assess five light quality factors: 1) visual comfort; 2) naturality; 3) pleasantness; 4) precision (of details and textures) and 5) light level. Mixed model analyses of the questions revealed significant higher scores for pleasantness (p = 0.003) comfort (p = 0.015) and light level (p = 0.044) for the bronze glazing type compared to the blue and neutral glazing, confirming results of earlier studies. Results from a paired t-test on the Karolinska Sleepiness Scale (KSS) scores indicated that the level of self-reported arousal decreased in presence of the blue glazing. However, the analysis did not reveal significant results regarding switch-on patterns of electric lights. Overall, the study shows that there is a preference for daylight filtered through bronze window glazing and that the glazing colour type may have a significant effect on arousal level of office workers.
Article
A pilot study for investigating the effect of six coated glazing materials on visual perception of the interior and of the view out in scaled rooms is presented. The study, which involved 18 subjects, is carried out in Hørsholm (Denmark, lat. 55.4°N), under overcast skies and a north orientation. The methodology involves subjective ratings using a questionnaire and seven grade bipolar scales. The results of the statistical analysis (ANOVA) show that despite significant amplitude in daylight transmittance (50%—79%), the glazing type did not have any statistically significant effect on the perception of the sharpness of shadows in the room. It is also found that higher transmittance glazing (77%—79%) resulted in views that are more glaring compared with the views obtained with the other glazing types. In terms of light level, the reference glazing (which contained an iron-free pane) results in statistically significant differences in the ratings (brighter room) compared with the ratings from all glazing types, including glazing types of similar transmittance. Finally, it is found that higher transmittance glazing types result in more positive ratings for factors, such as naturalness, beauty, and pleasantness and sharpness.
Article
Discomfort glare from daylight is a common problem in many office environments. It has been the subject of a significant body of research and many attempts have been made to develop reliable assessment and prediction models to address this problem. This paper reviews and discusses the advantages and limitations of using existing glare indices for daylighting conditions. It concludes that available assessment and prediction methods are of limited practical use in daylit situations and currently have no provision for integrated systems that combine daylighting and electric lighting. The paper also presents selected findings from a case study of daylit office environments which identify a number of important design considerations. On the basis of the discussion and the findings from the case study, additional research needs are identified to overcome current limitations. In the meantime, until results from such research are available and can be practically applied, this paper suggests ways to better integrate computer workstations in daylit offices.
Article
Lighting control integrated with daylighting is recognised as an important and useful strategy in energy-efficient building designs and operations. Prediction of the internal daylight levels is a key stage in daylighting designs. With the advances in computer technology, the computation of daylight illuminances can be conducted via lighting simulation program. This paper presents a study of the daylight coefficient (DC) approach using RADIANCE lighting software in simulating the indoor daylight illuminance of a corridor. The interior daylight illuminance data measured in the corridor were compared with the simulated results based on the computer software. It was found that the DC approach could give satisfactory results especially for the sun-shaded surface and sun-facing surface receiving a large amount of direct sunlight. Further, the daylight illuminance detected by the photosensor was also simulated in conjunction with measured daylight illuminance, dimming ratio and electric lighting power to predict the lighting energy savings. The findings suggested that the measured and predicted data showed a good agreement when large electric lighting savings resulted. The probable reasons causing the discrepancies were discussed.
Article
Using daylight as primary light source has been widely recognized as an important strategy to reduce building energy demand and enhance indoor environment quality. However, to design and operate a building to make full use of daylight, which is a dynamic light source, to meet diverse occupant needs remains a challenge. This paper reports a post-occupancy study of the visual environment in a laboratory building on a university campus, and puts a spotlight on the building occupants as it examines the effectiveness of the daylighting design and systems integration in creating a visual environment to support occupant comfort and satisfaction while reducing artificial lighting demand. Results show generally high satisfaction with daylit work environment and positive effect of the horizontal shading strategy. Issues about the integration between daylighting and electric lighting systems and level of occupant control are identified and discussed for improving the effectiveness of daylighting and enhancing the quality of the visual environment in the building of study. A multiple-tool methodology is developed and tested, which included occupant surveys, interviews, illuminance measurements, continuous data loggers, fisheye-lens camera and glare-identifying software, and documentation of spatial settings, systems features, and user behavior.
Article
Purpose: To investigate the effect of exposure to a low relative humidity (RH) environment on tear film physiology. Method: A controlled environment chamber was used to create 2 different environmental conditions. Ambient temperature was constant in both conditions (21°C) while the RH was set at 40% at the normal condition and at 5% in the desiccating environment. Tear evaporation, noninvasive tear break-up time, lipid layer thickness (LLT), osmolarity, ocular comfort, tear production, and ocular surface temperature were assessed in normal humidity and over a period of 60 minutes in the dry environment. Results: There was significant change in tear evaporation rate (P = 0.00), noninvasive tear break-up time (P = 0.00), LLT (P = 0.00), ocular comfort (P = 0.00), and tear production (P = 0.01) after exposure to the desiccating environment. No significant differences were observed between normal and dry environmental conditions in tear osmolarity (P = 0.09) and ocular surface temperature (P = 0.20). Conclusions: Evaporation rate, tear LLT, ocular comfort, tear stability, and production were adversely affected by low RH. The tear film parameters observed after exposure to a desiccating environment for 1 hour were similar to those of the dry eye patient. Therefore, to avoid tear film disruption and possible ocular surface damage, the environmental conditions of dry locations need to be improved or the tear film should be protected against adverse environmental conditions.
Article
Museums have the most complicated lighting criteria of common building types. A stable lighting environment for visitors and artworks should be guaranteed within the exhibition areas of museums. This paper presents a challenge to the application of daylighting simulation integrated into the architectural design process (DSADP). The scale model measurements and computer simulations were carried out to verify the computer program RADIANCE. A comparison between the measurement and simulation results showed that there was considerable relative error at measurement points. Therefore, a correction factor (CF) and corrected simulation (CS) were recalculated to correct the simulation results. The Seoul Museum of Art (SMOA) was selected to make an application of DSADP. The monitor and sawtooth-shaped toplights were chosen as attractive alternatives for the existing skylight of SMOA. The application of DSADP was carried out by changing the light transmission efficiency and opening size of the toplights. The RADIANCE results showed that computer simulation models can accurately represent the lighting environment under clear sky conditions, and more importantly, they can be used to propose an alternative toplight for SMOA. Therefore, the research results showed that DSADP technology would be very useful during the schematic design stage of the architectural design process. The findings of this research also suggested that there are large differences between the real sky conditions for scale model measurements and the CIE sky conditions for computer simulations. More studies are required to reduce the differences between real and simulated sky conditions.
Article
Visual requirements are high when sorting mail. The purpose of this visual ergonomics intervention study was to evaluate the visual environment in mail sorting facilities and to explore opportunities for improving the work situation by reducing visual strain, improving the visual work environment and reducing mail sorting time. Twenty-seven postmen/women participated in a pre-intervention study, which included questionnaires on their experiences of light, visual ergonomics, health, and musculoskeletal symptoms. Measurements of lighting conditions and productivity were also performed along with eye examinations of the postmen/women. The results from the pre-intervention study showed that the postmen/women who suffered from eyestrain had a higher prevalence of musculoskeletal disorders (MSD) and sorted slower, than those without eyestrain. Illuminance and illuminance uniformity improved as a result of the intervention. The two post-intervention follow-ups showed a higher prevalence of MSD among the postmen/women with eyestrain than among those without. The previous differences in sorting time for employees with and without eyestrain disappeared. After the intervention, the postmen/women felt better in general, experienced less work induced stress, and considered that the total general lighting had improved. The most pronounced decreases in eyestrain, MSD, and mail sorting time were seen among the younger participants of the group.
Article
The objective of this work is to investigate the accuracy of the Adeline lighting software in simulating the illuminance distribution from daylighting and the electrical lighting consumption of an existing atrium building. The case study is an enclosed atrium space equipped with an automatic on/off lighting control system and roofed by a skylight made of several.-lazing systems. Field monitoring of the atrium space was conducted during summer and winter and included measurements of horizontal indoor and outdoor illuminance, solar radiation and electrical lighting system time-of-use. The computer simulation included the creation of one simple and one complex computer model used to simulate the daylighting performance of the atrium space. The software accuracy was evaluated based on comparisons between the predicted and the on-site measured illuminance distribution and lighting energy consumption.
Article
This paper presents findings from a web-based survey on the current use of daylight simulations in building design. The survey was administered from December 2nd 2003 to January 19th 2004. One hundred and eighty five individuals from 27 countries completed the survey. The majority of respondents worked in Canada (20%), the United States (20%), and Germany (12%). Most participants were recruited through building simulation mailing lists. Their self-reported professions ranged from energy consultants and engineers (38%) to architects and lighting designers (31%) as well as researchers (23%). They worked predominantly on large and small offices and schools. Ce document présente les conclusions d'une enquête Web sur l'utilisation actuelle de lumière du jour simulée dans la conception des bâtiments. L'enquête a été menée du 2 décembre 2003 au 19 janvier 2004 auprès de 185 personnes dans 27 pays. La majorité des participants travaillait au Canada (20 %), aux États-Unis (20 %) et en Allemagne (12 %). La plupart des participants ont été sollicités par l'intermédiaire de listes distribution touchant la simulation dans les bâtiments. Ils ont déclaré exercer des professions dans les domaines de l'énergie et de l'ingénierie (38 %), de l'architecture et de la conception d'éclairage (31 %) et de la recherche (23 %). Ils travaillaient principalement dans des bureaux et des écoles de dimensions diverses. RES
Article
The integration of daylighting and electric lighting systems within buildings (also designated by "Green lighting") is a recent issue for the lighting research community: it allows achieving better lighting conditions for building occupants in particular within office rooms. Besides the substitution of electric light, daylighting can contribute in a significant way to improve the users' visual comfort and performance, a large variety of novel daylighting systems and components having been developed during the last years. In order to demonstrate this, an anidolic daylighting system combined with several electric lighting fixtures was set-up in an office room of the LESO solar experimental building located on the EPFL campus in Lausanne (Switzerland). Three different electric lighting modes, involving recessed luminaries (direct lighting), floor lamps (indirect lighting) and desk lamps (task lighting), were considered for that purpose.
Article
The endogenous circadian rhythm of melatonin in humans provides information regarding the resetting response of the human circadian timing system to changes in the light-dark (LD) cycle. Alterations in the LD cycle have both acute and chronic effects on the observed melatonin rhythm. Investigations to date have firmly established that the melatonin rhythm can be reentrained following an inversion of the LD cycle. Exposure to bright light and darkness given over a series of days can rapidly induce large-magnitude phase shifts of the melatonin rhythm. Even single pulses of bright light can shift the timing of the melatonin rhythm. Recent data have demonstrated that lower light intensities than originally believed are capable of resetting the melatonin rhythm and that stimulation of photopically sensitive photoreceptors (i.e., cones) is sufficient to reset the endogenous circadian melatonin rhythm. In addition to phase resetting, exposure to light of critical timing, strength, and duration can attenuate the amplitude of the endogenous circadian rhythm of melatonin. Measurement of melatonin throughout resetting trials provides a dynamic view of the resetting response of the human circadian pacemaker to light. Future studies of the melatonin rhythm in humans may further characterize the resetting response of the human circadian timing system to light.
Article
Melatonin, acting through melatonin receptors, is involved in numerous physiological processes including circadian entrainment, blood pressure regulation, oncogenesis, retinal physiology, seasonal reproduction, ovarian physiology, immune function and most recently in inducing osteoblast differentiation. Moreover, melatonin was proved to be a potent-free radical scavenger and a broad-spectrum antioxidant. More research is required into the effects of therapeutically modulating the melatoninergic system on circadian haemodynamics and rhythm under varying physiopathological conditions and the possible impact on morbidity and mortality in humans.