| 1. |
- Adamsson, Mathias, et al.
(author)
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Comparison of Static and Ambulatory Measurements of Illuminance and Spectral Composition That Can Be Used for Assessing Light Exposure in Real Working Environments
- 2019
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - : Taylor & Francis. - 1550-2724 .- 1550-2716. ; 15:2-3, s. 181-194
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Journal article (peer-reviewed)abstract
- Reliable measurements are of utmost importance when investigating the relationship between light and human reactions. The aim of the present study was to compare two methods for measuring light exposure in real working environments. Ambulatory recordings of illuminance and irradiance were compared with static field measurements of horizontal illuminance at the normal working position, average horizontal illuminance in the room, vertical illuminance at the position of the eye in the normal angle of gaze, and spectral composition of the light radiation at the normal working position and at the position of the eye in the normal angle of gaze. The ambulatory measurements were carried out during a 3-day experimental period and were repeated monthly throughout the year. The static field measurements in the subjects’ offices were conducted five times during the year, in the morning and afternoon during one day. The relationship between the illuminances and irradiances measured with the portable instruments and the static measurements was statistically analyzed. Results from the analyses revealed that more than one third of the static measurements of vertical illuminances recorded were below 200 lx, and only 7% of the measurements exceeded 1000 lx. Measurements of the spectral composition of the light radiation in the rooms suggested that the light, although at a fairly low intensity, included relatively much radiation that can have a non-image forming effect. Furthermore, only a small number of significant correlations between the ambulatory and static measurements were found. Results from the t-tests showed that there were no differences between ambulatory measurements, and static measurements of horizontal illuminance at the normal position, average illuminance in the room and vertical illuminance at the position of the eye during three, five, and seven of the 10 measurements, respectively. There is a need to define appropriate parameters in order to describe the quality of a lit environment with respect to the non-image-forming effects of light radiation.
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| 2. |
- Boork, Magdalena, et al.
(author)
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Sensory evaluation of lighting : a methodological pilot
- 2020
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - 1550-2724 .- 1550-2716. ; , s. 1-17
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Journal article (peer-reviewed)abstract
- Current standards for light environments are based on technical requirements, e.g. luminance, uniformity, and illuminance, and do not necessarily describe all parts of the light experience to ensure visual comfort from a user perspective. Including experience-related requirements would most likely yield better lighting comfort. To do that, new methods for specifying and measuring the user experience are needed. This paper describes a pilot study exploring a new method to analytically assess perceived lighting properties by using a trained human panel and thus make human assessments more objective. The methodology is built on established sensory methods, where the human senses are used in product assessments, traditionally applied within e.g. the food, packaging, and car industries. An analytical panel comprising eight persons fulfilling specific selection criteria were recruited and trained to assess lighting products in a multi-sensory laboratory. The results show that the panelists were able to assess lighting by distinguishing between attributes and products. Significant differences were identified between the different luminaires, both in terms of sensory and physical properties, e.g. read ability and glare. Conclusively, analytical sensory methods can be applied to lighting to assess luminaires in a non-subjective way. Physical and sensory attributes do not, however, always co-vary, which shows that data from physical and sensory measuring methods provide complementary information about light quality. This knowledge may in turn be applied in tools supporting the communication between different professions in lighting design and procurement to promote light environments that are both energy efficient and desirable from an end-user perspective.
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| 3. |
- Boork, Magdalena, et al.
(author)
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Sensory Evaluation of Lighting : A Methodological Pilot
- 2022
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - : Taylor and Francis Ltd.. - 1550-2724 .- 1550-2716. ; 18:1, s. 66-82
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Journal article (peer-reviewed)abstract
- Current standards for light environments are based on technical requirements, e.g. luminance, uniformity, and illuminance, and do not necessarily describe all parts of the light experience to ensure visual comfort from a user perspective. Including experience-related requirements would most likely yield better lighting comfort. To do that, new methods for specifying and measuring the user experience are needed. This paper describes a pilot study exploring a new method to analytically assess perceived lighting properties by using a trained human panel and thus make human assessments more objective. The methodology is built on established sensory methods, where the human senses are used in product assessments, traditionally applied within e.g. the food, packaging, and car industries. An analytical panel comprising eight persons fulfilling specific selection criteria were recruited and trained to assess lighting products in a multi-sensory laboratory. The results show that the panelists were able to assess lighting by distinguishing between attributes and products. Significant differences were identified between the different luminaires, both in terms of sensory and physical properties, e.g. readability and glare. Conclusively, analytical sensory methods can be applied to lighting to assess luminaires in a non-subjective way. Physical and sensory attributes do not, however, always co-vary, which shows that data from physical and sensory measuring methods provide complementary information about light quality. This knowledge may in turn be applied in tools supporting the communication between different professions in lighting design and procurement to promote light environments that are both energy efficient and desirable from an end-user perspective.
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| 4. |
- Bournas, Iason
(author)
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Association between Perceived Daylit Area and Self-reported Frequency of Electric Lighting Use in Multi-dwelling Buildings
- 2022
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In: LEUKOS - Journal of Illuminating Engineering Society of North America. - : Informa UK Limited. - 1550-2724. ; 18:1, s. 83-102
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Journal article (peer-reviewed)abstract
- This paper examines the association between daytime electric lighting use and perceived indoor daylight availability in residential spaces. In addition, occupant preferences were evaluated, in particular which rooms are prioritized in terms of daylight availability. The study deployed a questionnaire survey that was carried out in typical multi-dwelling apartment blocks in Malmö, Sweden (Latitude: 55.6 °N). Occupants were asked to report how often they use electric lighting during daylight hours (EL) in their kitchen, living room and main bedroom, and how much of the floor area they perceive as adequately daylit (DA) throughout the year. Responses EL and DA were measured in seven-point semantic differential scales, and were correlated (Spearman) to evaluate their association for different room groups. Groups were based on age, room function, façade orientation, balcony obstruction and fenestration geometry. In addition, occupants were asked which room they would choose if there had to be one underlit room. Results indicate that EL is strongly associated with DA in the overall room sample (rS = −0.588, p <.01, n = 225). The association is persistent across room groups of different characteristics, with the Spearman rank correlation coefficient ranging between −0.4 and −0.8, and not differing significantly between groups. In terms of preferences, a significantly high proportion of participants would choose the bedroom if there had to be one underlit room (62%, p <.05), while the kitchen was selected by only 5 out of 108 respondents.
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| 5. |
- Bullough, J. D., et al.
(author)
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Influence of spectral power distribution on scene brightness at different light levels
- 2014
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - : Taylor and Francis Inc.. - 1550-2724 .- 1550-2716. ; 10:1, s. 3-9
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Journal article (peer-reviewed)abstract
- Exterior lighting has multiple objectives. Brightness perception is a relevant parameter for outdoor lighting because it is correlated with perceptions of safety and security. Understanding the influence of the spectral characteristics of lighting to scene brightness perception is important in order to devise exterior lighting specifications that support perceptions of safety and security in exterior lighted environments, as well as to optimize light source technologies to account for these factors. A study of scene brightness perception under different light levels and spectral power distributions was conducted to assess whether scene brightness perception exhibited increased short-wavelength spectral sensitivity as a function of increasing light level. The results confirm that a successful model of spectral sensitivity for scene brightness perception should incorporate a shift in short-wavelength sensitivity like the one investigated in the present study.
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| 6. |
- Dervishaj, Arlind, et al.
(author)
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Sunlight Autonomy for Buildings: A New Methodology for Evaluating Sunlight Performance in Urban and Architectural Design
- 2024
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - : Informa UK Limited. - 1550-2724 .- 1550-2716. ; , s. 1-31
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Journal article (peer-reviewed)abstract
- Due to urbanization and growing density in cities in the past century, metrics were introduced to assess daylight performance such as minimum sunlight hours and the daylight factor. The paper initially explores the shortcomings of early-stage daylight and sunlight evaluation methods. A novel methodology called Sunlight Autonomy (SA) is proposed for evaluating sunlight performance in buildings. The SA is based on the “Exposure to sunlight” criteria in EN 170307 “Daylight in Buildings,” where a computational method is used for the evaluation on a specified day. The SA concept expands the analysis temporally over the entire year, and spatially on building facades, leading to new metrics for a point of evaluation, and spatial metrics for buildings. The SA methodology is analyzed in a case study across four European cities. The SA metrics on facades between February 1st and March 21st, days in EN 17037, led to differences up to 63%. This revealed a significant shortcoming in EN 17037, relevant for Nordic regions. The differences of spatial metrics between March 21st and 50% of the year were within 5%, and up to 33% between February 1st and 75% of the year. The timestep affects the metrics and a window evaluation showed that the error of a 10-minute analysis was within 5% of daily insolation and 5 days for the annual SA. The potential of these metrics for urban planning and the architectural design process is examined. The interaction between SA and EN 17037, as well as other ongoing research developments, is discussed.
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| 7. |
- Hammad, Grégory, et al.
(author)
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Open-source python module for the analysis of personalized light exposure data from wearable light loggers and dosimeters
- 2024
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - : Taylor & Francis. - 1550-2724 .- 1550-2716.
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Journal article (peer-reviewed)abstract
- Light exposure fundamentally influences human physiology and behavior, with light being the most important zeitgeber of the circadian system. Throughout the day, people are exposed to various scenes differing in light level, spectral composition and spatio-temporal properties. Personalized light exposure can be measured through wearable light loggers and dosimeters, including wrist-worn actimeters containing light sensors, yielding time series of an individual’s light exposure. There is growing interest in relating light exposure patterns to health outcomes, requiring analytic techniques to summarize light exposure properties. Building on the previously published Python-based pyActigraphy module, here we introduce the module pyLight. This module allows users to extract light exposure data recordings from a wide range of devices. It also includes software tools to clean and filter the data, and to compute common metrics for quantifying and visualizing light exposure data. For this tutorial, we demonstrate the use of pyLight in one example dataset with the following processing steps: (1) loading, accessing and visual inspection of a publicly available dataset, (2) truncation, masking, filtering and binarization of the dataset, (3) calculation of summary metrics, including time above threshold (TAT) and mean light timing above threshold (MLiT). The pyLight module paves the way for open-source, large-scale automated analyses of light-exposure data.
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| 8. |
- Mangkuto, R. A., et al.
(author)
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Analysis of various opening configurations of a second-generation virtual natural lighting solutions prototype
- 2014
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - : Informa UK Limited. - 1550-2724 .- 1550-2716. ; 10:4, s. 223-236
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Journal article (peer-reviewed)abstract
- To address the absence of natural light in working spaces, virtual natural lighting solutions (VNLS) can be promising. VNLS are systems that artificially provide lighting as well as a realistic outside view with properties comparable to those of real windows and skylights. This article discusses the evaluation and analysis of various opening configurations of a second-generation VNLS prototype, which features an array of light emitting diode (LED) tiles coupled with a line of linear LED fixtures with adjustable color temperatures that provide direct light. Simulation using Radiance was performed and validated with the measurement results. Various possibilities of placing the prototypes inside the test room were investigated in Radiance to determine the effect on space availability and visual comfort. Based on the comparison of seven configurations of two prototypes with equal total opening size, it was found that nearly all configurations tested yielded a space availability of 100% with a criterion of 200 lx and where space availability is defined as the percentage of points on a horizontal grid that meet or exceed the target illuminance. Taking 300 lx as the criterion, two openings on each short wall facing each other (configuration 2) and four openings on a long wall (configuration 5) yielded space availabilities of more than 90%. Taking 500 lx as the criterion, configurations 2 and 5 yielded space availabilities between 25% and 50%. The highest uniformity (Emin/Eavg) was achieved under configuration 2 (0.59), whereas the maximum daylight glare probability (DGP) values under all configurations were between 0.25 and 0.30. Our simulation results suggest that the space availability in a private office can be optimized by placing a VNLS prototype on each short wall facing each other or by placing two on a long wall.
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| 9. |
- Sithravel, RatnaKala, et al.
(author)
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Optimizing presence sensing lighting for energy efficiency and user behavioral needs in small Swedish homes
- 2024
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In: LEUKOS The Journal of the Illuminating Engineering Society of North America. - : Taylor & Francis. - 1550-2724 .- 1550-2716. ; 20:1, s. 107-125
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Journal article (peer-reviewed)abstract
- A hybrid workstyle is becoming more common post-COVID-19, and longer occupancy hours at home are increasing household electricity consumption. Small homes are regarded as a potential for improving energy efficiency in the residential sector, and a home consists of mixed-function spaces with dynamic occupancy behaviors. These underpin the opportunity to optimize presence sensing lighting in small homes for energy efficiency and user-behavioral needs. A comprehensive overview of presence sensing approaches, comparing four types of non-wearable sensors connected to home lighting is made. A bibliometric mapping of the reviewed literature visually reinforces a significant research gap that presence sensing studies were not connected to home lighting but inclined toward the commercial and institutional context. Next, a non-exhaustive example of commercially available presence sensing products applicable to residential lighting for small homes is analyzed, and their general characteristics and technologies are synthesized. The literature and product overview identified five significant product knowledge gaps. Incorporating the gathered information leads to the proposal of a conceptual flexible radar-based sensor (prototype design), addressing a wish list with three important criteria to optimize future presence sensing lighting in a mixed-function small home. Future radar sensing studies are expected to develop an anticipatory lighting system that processes real-time multi-user vital signals for smarter localized and personalized lighting options for (small) living environments.
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| 10. |
- Mattsson, Pimkamol, et al.
(author)
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Self-Report Diary: A Method to Measure Use of Office Lighting
- 2013
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In: LEUKOS - Journal of Illuminating Engineering Society of North America. - 1550-2724. ; 9:4, s. 291-306
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Journal article (peer-reviewed)abstract
- This methodological study was conducted to examine the suitability and reliability of the diary form to measure lighting use in work places. The occupants of 18 single-occupant offices were asked to report in diary form on their lighting-use-related activities and times present in their offices for one workday every two months from June 2009 through May 2010. Electronic measurement of the occupants' time in their offices and use of ceiling luminaires was recorded by data logger during the same period. The self-reported data correlated significantly with the logged data for the occupants' for the two variables investigated: (i) regulating of ceiling luminaires, and (ii) occupancy of their offices. The correlation was strongly significant between self-reported-and logged data with regard to light-on time, while a weak relationship was identified between the self-reported-and logged data regarding occupancy time. Considering the relationship between light-on time and occupancy time, a significant relationship from the self-reported data was found, but, unlike the logged data, these two variables did not seem to relate to each other. The results suggest that the diary form is suitable to measure office occupants' use of general lighting (ceiling luminaires), particularly for a short-term use, whereas the suitability to measure presence in offices is questionable. The diary form was also able to characterize the amount of energy used for lighting. However, the form should be improved to obtain more accurate responses and to indicate the lighting levels provided by dimming controls.
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