Sensitivity Analysis of Glare Rating Metrics

Ashdown, Ian

doi:10.1582/leukos.2005.02.02.003

Cited by 13 publications

(12 citation statements)

References 8 publications

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“…A drawback of this method is that the resulting UGR value is very sensitive to observer position and cannot be directly linked to the limiting values of the workplace standards, which are related to the averaged UGR values. This sensitivity of the UGR calculation at a single point was already observed by Ashdown (2005), who recommends a calculation of glare ratings from various viewpoints on a dense grid, rather than at a single point.…”

Section: Introduction: Ugr Formula and Tabular Methodssupporting

confidence: 54%

“…When the UGR formula (1) is directly applied to any realistic lighting installation, the UGR value may be highly sensitive to the exact observer position: we have simulated huge variations with values between UGR 10 and UGR 20 using only a 200 mm displacement of the observer. We have demonstrated that a large portion of this sensitivity can be explained by the fact that the UGR contribution of each luminaire is evaluated only at the center point of the luminaire (in agreement with Ashdown, 2005). Such variations are not related to the variation in glare perception of real observers in the real world.…”

Section: Resultsmentioning

confidence: 63%

“…It should be noted that the wild variations of the UGR value (between 1 and 10 UGR points for a small observer displacement of 200-300 mm) cannot be physically correct as the displacement is much smaller than the luminaire size. This error is caused by the fact that (in the used software) the contribution to UGR of a luminaire is evaluated only at the center point of the luminaire (see also Ashdown, 2005). This can be demonstrated by the following example.…”

Section: Single Point Calculationmentioning

confidence: 99%

See 2 more Smart Citations

Robust Unified Glare Rating Evaluation for Real Lighting Installations

Vissenberg

Vries

Wouters

et al. 2019

PROCEEDINGS OF the 29th Quadrennial Session of the CIE

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The unified glare rating (UGR) is a widely accepted measure for discomfort glare of indoor lighting installations. Standards for the lighting of workplaces provide limiting values for the UGR based on the so-called tabular method, like the well-known limit of UGR 19 for office lighting applications. These limiting values are averaged values based on a standardised room layout (rectangular space with rectangular grid of luminaires), indicative of the average discomfort glare to be expected in an actual installation. A direct application of the UGR formula (e.g. using point calculations) to real lighting installations is known to lead to unreliable UGR values that are very sensitive to observer and luminaire positions. These UGR values cannot be directly verified against the limiting values of workplace standards due to the nature of the original determination of the limiting values. An averaging method is proposed that enables a robust UGR calculation for any real indoor lighting installation, i.e. much more flexible than the tabular method that is limited to rectangular spaces with rectangular luminaire layouts of a single type. The method provides UGR values that may be compared to the limiting values of workplace lighting standards.

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Section: Introduction: Ugr Formula and Tabular Methodssupporting

confidence: 54%

Section: Resultsmentioning

confidence: 63%

Section: Single Point Calculationmentioning

confidence: 99%

See 1 more Smart Citation

Robust Unified Glare Rating Evaluation for Real Lighting Installations

Vissenberg

Vries

Wouters

et al. 2019

PROCEEDINGS OF the 29th Quadrennial Session of the CIE

View full text Add to dashboard Cite

show abstract

“…[2][3][4][5][6][7] Unfortunately, the physiological and psychophysical mechanisms of discomfort glare are not yet well understood. 8 As a result, different glare indices have been individually developed in four fields to evaluate interior electric lighting, [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] daylighting (windows), [28][29][30][31][32][33][34][35][36][37] exterior area lighting, [38][39][40] and roadway and traffic lighting. [41][42][43][44][45] In particular, for evaluating interior electric lighting, Guth 9 developed an index called visual comfort probability (VCP), based on the borderline between comfort and discomfort brightness (BCD), 10 (Equation ( 1)).…”

Section: Introductionmentioning

confidence: 99%

“…VCP is calculated using Equations (2)- (5) for single or multiple light sources. 8,[11][12][13]16 Note that in Equation (2), a glare source needs a solid angle subtense, ! of at least 0.0000002924 sr, otherwise, the calculated glare sensation value M could be negative.…”

Section: Introductionmentioning

confidence: 99%

Evaluating discomfort glare from non-uniform electric light sources

Cai

Chung

2012

Lighting Research & Technology

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This study tested the appropriateness of unified glare rating (UGR), CIE glare index (CGI), British glare index (BGI), and visual comfort probability (VCP) for evaluating discomfort glare from common non-uniform electric light sources. An experiment was conducted in a windowless room. High dynamic range photogrammetry was used for measuring three non-uniform fluorescent glare sources. The luminance and geometry data were acquired to calculate the glare ratings. The sub-divisibility and additivity of UGR, CGI, BGI, and VCP were tested via numerical method. Their predictability was evaluated using 67 subjects in two sessions. It was found that UGR, CGI, BGI, and VCP all have valid additivity, but only UGR and CGI have valid sub-divisibility. Current formulae of UGR, CGI, BGI and VCP all overestimate the glare sensation from non-uniform sources that young people may feel.

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Unweaving the human response in daylighting design

Andersen

2015

Building and Environment

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Daylighting as a research topic situates itself at the interface between psycho-physiological and environmental factors, bringing together questions relevant to architectural design and building engineering, but also to human physiology and behaviour. While daylighting has a strong impact on human health and well-being, and an undeniable association with (subjective) emotional delight and perceived quality of a space, it is also highly dynamic and variable in nature, based on a combination of predictable (sun course) and stochastic (weather) patterns. This makes it both a challenging and essential aspect of how "performative" a space can be considered.This paper aims to discuss selected research developments regarding how architectural engineering and other domains of science could be more strongly bridged to address the need for meaningful decision support in daylighting design: how can we better integrate the complexity of human needs in buildings into effective design strategies for daylit spaces? As a basis for discussion and to illustrate this overview, it describes a unified goal-based approach in an attempt to address the multiplicity of perspectives from which daylighting performance can -and should -be evaluated in building design. Through five very different perspectives ranging from task-driven illumination or comfort to human-driven health and perception, it proposes a simulation and visualization framework in which one can start approaching these from an integrated approach.

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Sensitivity Analysis of Glare Rating Metrics

Cited by 13 publications

References 8 publications

Robust Unified Glare Rating Evaluation for Real Lighting Installations

Robust Unified Glare Rating Evaluation for Real Lighting Installations

Evaluating discomfort glare from non-uniform electric light sources

Unweaving the human response in daylighting design

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