Lighting accounts for approximately 15 % of the global electric energy consumption and 5 % of gre... more Lighting accounts for approximately 15 % of the global electric energy consumption and 5 % of greenhouse gas emissions. Growing economies, higher user demands for quality lighting and rebound effects as a result of low priced and more versatile electric lighting continuously still lead to an absolute increase of lighting energy consumption. More light is used, often less consciously.
The Gaze Visualizer tool is an implementation of eye-tracking (gaze) data and a preliminary gaze ... more The Gaze Visualizer tool is an implementation of eye-tracking (gaze) data and a preliminary gaze responsive light driven (GR<sub>L</sub>) model in Grasshopper3D. The workflow from obtaining the relevant photometric quantities, retrieving gaze data, introduction of the GR<sub>L</sub> model, which enables to visualize gaze behavior in a 3D space, and a simple data representation scheme are presented here. The final plugin is easy to use for Rhino/Grasshopper developers with only basic skills, and provides a quick estimations of the gaze responsive visual comfort in an illustrative way, that gives the user an adequate overview of the glare-free zones in the room. The new version includes LARK for spectral characterization of light at ocular level based on the gaze behavior.
Within the framework of a study investigating interactions among indoor environmental factors, tw... more Within the framework of a study investigating interactions among indoor environmental factors, two experiments were conducted on the effects of visual stimuli on thermal perception. Thermal responses were recorded with two methods, one quantitative via physiological measurements and a subjective one using a questionnaire. The questionnaire was developed on the basis of the standard EN ISO 10551 (2001-06-01) and recent publications on thermal comfort [1]–[3]. Two types of measurement scales were used, i.e., Likert-type and visual analogue. The first type was used for the questions about the thermal sensation, thermal comfort and thermal preference of the subjects and for the thermal sensation of their body parts (hands, feet and body). The only visual analogue scale in the questionnaire referred to the acceptability of the local climate in the room where the experiment was conducted. Different outcomes were recorded for the survey questions as they assess different aspects of thermal...
Zusammenfassung 2.1 Allgemeinverständliche Darstellung der wesentlichen Ergebnisse und der erziel... more Zusammenfassung 2.1 Allgemeinverständliche Darstellung der wesentlichen Ergebnisse und der erzielten Fortschritte gegenüber dem Stand des Wissens zum Zeitpunkt der Antragstellung. Fraunhofer ISE Im Rahmen der Testraumversuche konnten zahlreiche wissenschaftliche Fortschritte erzielt werden. Die durchgeführten Versuche bestätigen nicht nur die Blendungsbewertungskenngröße Daylight Glare Probability DGP, sondern ermöglichten auch, den DGP zu erweitern. Die Versuchsreihe mit streuenden Blendschutzsystemen zeigt, dass der DGP auch für diese Systeme ohne Modifikation anwendbar ist. Somit ist der DGP für alle marktrelevanten Blendschutzsysteme experimentell validiert. Der Einfluss des Alters auf die Blendungsbewertung konnte anhand der gewonnenen Versuchsdaten quantifiziert werden. Die Modifikation der DGP-Formel erfolgt durch einen Alterskorrekturfaktor. Für eine 60 jährige Person beträgt dieser Korrekturfaktor 1.25, für eine 20 jährige Person ist dieser 1.00. Ebenso konnte der Gültigkeitsbereich des DGP für Situationen mit geringer Blendungswahrscheinlichkeit erweitert werden. Der DGP war bislang für Werte < 0.2 nicht definiert. Auch hier erfolgt die Korrektur durch einen Faktor, der den DGP im Bereich zwischen 0.0 und 0.2 modifiziert.
In the field of lighting, luminance maps are often used to evaluate point-in-time lighting scenes... more In the field of lighting, luminance maps are often used to evaluate point-in-time lighting scenes from the occupant's vantage point. High Dynamic Range (HDR) photography can be used to generate such luminance maps. The aim of this tutorial is to present a comprehensive overview of a step-by-step procedure to generate a 180°luminance map of a daylit scene from a sequence of multiple exposures with semiprofessional equipment and the Radiance suite of programs. The procedure consists in capturing a sequence of multiple exposures of the visual scene; selecting the useful exposures; merging the exposures to generate the HDR image by using the predefined camera response function; nullifying the exposure value; resizing and cropping the HDR image by using the predefined fisheye view coordinates; adjusting the projection of the HDR image by using the predefined distortion function; correcting the vignetting of the HDR image by using the predefined vignetting curves; correcting the alterations of the HDR image due to the Neutral Density (ND) filter if one was used, by using the predefined ND correction function; adjusting the photometry of the HDR image by using the measured spot luminance value; editing the HDR image header by using the predefined projection type and real viewing angle; and checking the validity of the HDR image by using the measured vertical illuminance, and, if needed, the predefined luminous range. To conclude, an analysis of errors is made and attention points to adapt the procedure for electric or circadian lighting studies are discussed.
Discomfort glare is a major challenge for the design of workplaces. The existing metrics for disc... more Discomfort glare is a major challenge for the design of workplaces. The existing metrics for discomfort glare prediction share the limitation that they do not take gaze direction into account. To overcome this limitation, we developed a ‘gaze-driven’ method for discomfort glare assessment. We conducted a series of experiments under simulated office conditions and recorded the participants’ gaze using mobile eye tracking and the luminance distributions using high dynamic range imaging methods. The two methods were then integrated to derive ‘gaze-centred’ luminance measurements in the field of view. The existing ‘fixed-gaze’ and the newly developed ‘gaze-driven’ measurement methods are compared. Our results show that there is a significant difference between the two methods. In this paper, the procedure for integrating the recorded luminance images with the recorded gaze dynamics for obtaining gaze-centred luminance data is described. This gaze-centred luminance data will be compared ...
This paper details the results of an experimental study investigating the combined effect of indo... more This paper details the results of an experimental study investigating the combined effect of indoor temperature (19 ℃, 23 ℃ and 27 ℃) and horizontal illuminances (∼140 lx, ∼610 lx and ∼1440 lx) on visual perception, with daylight as the only source of light. The goal is to evaluate the cross-modal effect of temperature and the unimodal effect of daylight illuminances on the visual perception of daylight. A 3 × 3 mixed-design experiment was conducted in an office-like test room with 84 participants. Results show that cross-modal effects of indoor temperature on visual perception occurred: Temperature influenced the perceived warmth of daylight, and temperature interacted with daylight illuminance as the high illuminance was considered more pleasant, was better evaluated and was more often chosen than the low one only in a thermally comfortable condition. In terms of unimodal effects, differences in visual comfort evaluations were substantial only between the low and the other two ill...
Because well-being is becoming a major challenge in construction alongside energy efficiency, the... more Because well-being is becoming a major challenge in construction alongside energy efficiency, there is an increasing need to be able to quantify discomfort in buildings. In the case of discomfort glare, the kind of glare provoking an irritating or distracting effect, no current indices can properly explain the high variability existing between individuals' discomfort glare perceptions. This is due to the fact that some of the factors influencing discomfort glare perception are still unknown and the mechanism behind the discomfort glare process is not well understood. Therefore, this article aims to review the factors potentially influencing discomfort glare perception from daylight. Every factor having been studied at least once for its potential influence on discomfort glare perception has been listed, described, and analyzed. Furthermore, this study categorizes the influence of these factors on discomfort glare by introducing an influence indicator based on the number of studies having investigated the factor, the sample size of these studies, and the agreement between them. The suggested categories rate a factor influence as "almost certain," "more likely," "somewhat likely," "inconclusive," "somewhat unlikely," "less likely," or "almost certainly null." Tables summarize the main information about the studies and the influencing factors. As expected, factors almost certainly influencing discomfort glare perception are the luminance of the glare source, adaptation level, contrast effect, and size and position of the glare source. In contrast, factors that almost certainly do not influence discomfort glare perception are the gender and optical correction of the observer. All other factors from the list of 30, such as the attractiveness of the view through the window or the culture of the observer, require additional studies to determine whether or not they influence discomfort glare perception.
Nowadays, discomfort glare indices are frequently calculated by using evalglare. Due to the lack ... more Nowadays, discomfort glare indices are frequently calculated by using evalglare. Due to the lack of knowledge on the implications of the methods and parameters of evalglare, the default settings are often used. But wrong parameter settings can lead to inappropriate glare source detection and therefore to invalid glare indices calculations and erroneous glare classifications. For that reason, this study aims to assess the influence of several glare source detection methods and parameters on the accuracy of discomfort glare prediction for daylight. This analysis uses two datasets, representative of the two types of discomfort glare: saturation and contrast glare. By computing three different statistical indicators to describe the accuracy of discomfort glare prediction, 63 different settings are compared. The results suggest that the choice of an evalglare method should be done when considering the type of glare that is most likely to occur in the visual scene: the task area method sh...
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
Advanced computer simulation tools for analyzing daylighting features and thermal performance of ... more Advanced computer simulation tools for analyzing daylighting features and thermal performance of buildings are improved at the Fraunhofer Institute for Solar Energy Systems.For an analysis of daylighting elements in lighting simulations, new light-deflecting structures and materials have been measured and modeled. In order to study the interaction between lighting and thermal behaviour of rooms, thermal and lighting simulation techniques are linked together. Thus, integrated energy concepts can be evaluated. Programs for handling parallel image generation in a network of high-performance Unix workstations have been developed.
In this paper, we present a physical validation of global illumination algorithms based on measur... more In this paper, we present a physical validation of global illumination algorithms based on measurements from a simple experimental setup. The validation methodology emphasizes tractability and error minimization. To this end, we discuss issues such as the acquisition and accurate simulation of material bidirectional reflection distribution functions (BRDFs) and the light source distribution, as well as error analysis. In addition, we present a nearestneighbor resampling technique for BRDFs and a simple method for extracting the light source distribution from digitized high dynamic range (HDR) images. Finally, we compare the measurements to a forward and backward raytracing solution (photon map and RADIANCE, respectively) in a set of case studies.
This paper presents a vision of how state-of-the-art computer-based analysis techniques can be ef... more This paper presents a vision of how state-of-the-art computer-based analysis techniques can be effectively used during the design of daylit spaces. Following a review of recent advances in dynamic daylight computation capabilities, climate-based daylighting metrics, occupant behavior and glare analysis, a fully integrated design analysis method is introduced that simultaneously considers annual daylight availability, visual comfort and energy use: Annual daylight glare probability profiles are combined with an occupant behavior model in order to determine annual shading profiles and visual comfort conditions throughout a space. The shading profiles are then used to calculate daylight autonomy plots, energy loads, operational energy costs and green house gas emissions. The paper then shows how simulation results for a sidelit space can be visually presented to simulation non-experts using the concept of a 'daylighting dashboard'. The paper ends with a discussion of how the daylighting dashboard could be practically implemented using technologies that are available today.
Daylighting and the impact of daylighting strategies on the visual environment continue to be a v... more Daylighting and the impact of daylighting strategies on the visual environment continue to be a vital issue for building occupants due to visual comfort and user acceptance of luminous indoor environments. Some of the critical factors affecting the level of visual comfort and quality in daylit office spaces include glare, window luminances, and luminance ratios within the field of view. One of the goals of this study was to provide new insight into the impact of luminance distributions on glare. The luminance distribution within the field of view was recorded using CCD camerabased luminance mapping technology. The technology provides a great potential for improved understandings of the relation between measured lighting conditions and user response. With the development of the RADIANCE based evaluation tool ''evalglare'', it became possible to analyse glare according to a number of daylight glare prediction models as well as contrast ratios in various daylit situations (workplace, VDU). User assessments at two locations (Copenhagen, Freiburg) with more than 70 subjects under various daylighting conditions were performed in order to assess existing glare models and to provide a reliable database for the development of a new glare prediction model. The comparison of the results of the user assessments with existing models clearly shows the great potential for improving glare prediction models. For the window luminance a squared correlation factor of only 0.12 and for the daylight glare index (DGI) of 0.56 were found. Due to the low predictive power of existing glare prediction models a new index, daylight glare probability (DGP), was developed and is presented in this paper. DGP is a function of the vertical eye illuminance as well as on the glare source luminance, its solid angle and its position index. The DGP showed a very strong correlation (squared correlation factor of 0.94) with the user's response regarding glare perception.
This report summarizes the evaluation of the calculation of illuminance in evalglare to prove the... more This report summarizes the evaluation of the calculation of illuminance in evalglare to prove the embedded algorithm. Evalglare-calculated illuminance values were compared with analytically-determined values as well as with values calculated from images by an alternative method that was provided by the author of RADIANCE. Only marginal differences between the two methods and analytical derived values were found. From the results, it can be concluded that the illuminance calculation in evalglare is reliable and delivers correct values.
Keywords: Glare ; Daylight Reference EPFL-TALK-208874 Record created on 2015-06-10, modified on 2... more Keywords: Glare ; Daylight Reference EPFL-TALK-208874 Record created on 2015-06-10, modified on 2016-08-09
Although fabrics are widely used as shading devices, reliable simulation models are rather rare a... more Although fabrics are widely used as shading devices, reliable simulation models are rather rare and therefore the choice of a fabric with appropriate material characteristics is difficult. This paper presents a simulation model, which can be applied to most of the common available fabric shading materials. Furthermore a comprehensive simulation study has been conducted in order to derive simple to use tables for the selection of appropriate shading properties for a designer. These tables enable the user to select the "right" fabric according to a combination of multiple boundary conditions (location, orientation, window sizes, user positions).
The evaluation of indoor comfort requires a thorough understanding of how human occupants perceiv... more The evaluation of indoor comfort requires a thorough understanding of how human occupants perceive four indoor environmental factors: visual conditions, air quality, acoustic ambience and thermal conditions. Recent studies have found that overall comfort is more than the average effects of these four parameters. Beside their main effects, their mutual interactions play an equally important role in the perception of comfort. Thus, to progress regarding our understanding of global comfort, more effort is needed to further investigate the interactions between indoor environmental factors. For this kind of perceptual evaluation, it is necessary to conduct user studies. In these, subjects’ evaluations need to be recorded in addition to the physical parameters that provoke them. Therefore, the sensitivity of people to their environment is the principal parameter around which the studies should be designed. This paper presents a first evaluation of the sensitivity of people to visual and t...
The presented study describes a method for evaluating control strategies for shading devices. The... more The presented study describes a method for evaluating control strategies for shading devices. The method is based on dynamic lighting simulations with RADIANCE and DAYSIM and explores energy, daylight supply and visual comfort parameters at the same time. In order to include the glare aspect more effectively in dynamic building simulations, a simplified glare measure “Daylight Glare Probability simplified (DGPs)” is presented and validated for situations when the sun does not hit the eye directly. For the evaluation of the solar thermal loads, a simplified method based on RADIANCE and DAYSIM is described to calculate dynamically the energy flux through facades for external mounted shading devices. The evaluation of different simulated shading control strategies show that the commonly used manual control strategies hardly activate the shading in summer. Therefore, the solar loads in summer for these strategies are very high and at the same time glare and low contrasts at the visual d...
Lighting accounts for approximately 15 % of the global electric energy consumption and 5 % of gre... more Lighting accounts for approximately 15 % of the global electric energy consumption and 5 % of greenhouse gas emissions. Growing economies, higher user demands for quality lighting and rebound effects as a result of low priced and more versatile electric lighting continuously still lead to an absolute increase of lighting energy consumption. More light is used, often less consciously.
The Gaze Visualizer tool is an implementation of eye-tracking (gaze) data and a preliminary gaze ... more The Gaze Visualizer tool is an implementation of eye-tracking (gaze) data and a preliminary gaze responsive light driven (GR<sub>L</sub>) model in Grasshopper3D. The workflow from obtaining the relevant photometric quantities, retrieving gaze data, introduction of the GR<sub>L</sub> model, which enables to visualize gaze behavior in a 3D space, and a simple data representation scheme are presented here. The final plugin is easy to use for Rhino/Grasshopper developers with only basic skills, and provides a quick estimations of the gaze responsive visual comfort in an illustrative way, that gives the user an adequate overview of the glare-free zones in the room. The new version includes LARK for spectral characterization of light at ocular level based on the gaze behavior.
Within the framework of a study investigating interactions among indoor environmental factors, tw... more Within the framework of a study investigating interactions among indoor environmental factors, two experiments were conducted on the effects of visual stimuli on thermal perception. Thermal responses were recorded with two methods, one quantitative via physiological measurements and a subjective one using a questionnaire. The questionnaire was developed on the basis of the standard EN ISO 10551 (2001-06-01) and recent publications on thermal comfort [1]–[3]. Two types of measurement scales were used, i.e., Likert-type and visual analogue. The first type was used for the questions about the thermal sensation, thermal comfort and thermal preference of the subjects and for the thermal sensation of their body parts (hands, feet and body). The only visual analogue scale in the questionnaire referred to the acceptability of the local climate in the room where the experiment was conducted. Different outcomes were recorded for the survey questions as they assess different aspects of thermal...
Zusammenfassung 2.1 Allgemeinverständliche Darstellung der wesentlichen Ergebnisse und der erziel... more Zusammenfassung 2.1 Allgemeinverständliche Darstellung der wesentlichen Ergebnisse und der erzielten Fortschritte gegenüber dem Stand des Wissens zum Zeitpunkt der Antragstellung. Fraunhofer ISE Im Rahmen der Testraumversuche konnten zahlreiche wissenschaftliche Fortschritte erzielt werden. Die durchgeführten Versuche bestätigen nicht nur die Blendungsbewertungskenngröße Daylight Glare Probability DGP, sondern ermöglichten auch, den DGP zu erweitern. Die Versuchsreihe mit streuenden Blendschutzsystemen zeigt, dass der DGP auch für diese Systeme ohne Modifikation anwendbar ist. Somit ist der DGP für alle marktrelevanten Blendschutzsysteme experimentell validiert. Der Einfluss des Alters auf die Blendungsbewertung konnte anhand der gewonnenen Versuchsdaten quantifiziert werden. Die Modifikation der DGP-Formel erfolgt durch einen Alterskorrekturfaktor. Für eine 60 jährige Person beträgt dieser Korrekturfaktor 1.25, für eine 20 jährige Person ist dieser 1.00. Ebenso konnte der Gültigkeitsbereich des DGP für Situationen mit geringer Blendungswahrscheinlichkeit erweitert werden. Der DGP war bislang für Werte < 0.2 nicht definiert. Auch hier erfolgt die Korrektur durch einen Faktor, der den DGP im Bereich zwischen 0.0 und 0.2 modifiziert.
In the field of lighting, luminance maps are often used to evaluate point-in-time lighting scenes... more In the field of lighting, luminance maps are often used to evaluate point-in-time lighting scenes from the occupant's vantage point. High Dynamic Range (HDR) photography can be used to generate such luminance maps. The aim of this tutorial is to present a comprehensive overview of a step-by-step procedure to generate a 180°luminance map of a daylit scene from a sequence of multiple exposures with semiprofessional equipment and the Radiance suite of programs. The procedure consists in capturing a sequence of multiple exposures of the visual scene; selecting the useful exposures; merging the exposures to generate the HDR image by using the predefined camera response function; nullifying the exposure value; resizing and cropping the HDR image by using the predefined fisheye view coordinates; adjusting the projection of the HDR image by using the predefined distortion function; correcting the vignetting of the HDR image by using the predefined vignetting curves; correcting the alterations of the HDR image due to the Neutral Density (ND) filter if one was used, by using the predefined ND correction function; adjusting the photometry of the HDR image by using the measured spot luminance value; editing the HDR image header by using the predefined projection type and real viewing angle; and checking the validity of the HDR image by using the measured vertical illuminance, and, if needed, the predefined luminous range. To conclude, an analysis of errors is made and attention points to adapt the procedure for electric or circadian lighting studies are discussed.
Discomfort glare is a major challenge for the design of workplaces. The existing metrics for disc... more Discomfort glare is a major challenge for the design of workplaces. The existing metrics for discomfort glare prediction share the limitation that they do not take gaze direction into account. To overcome this limitation, we developed a ‘gaze-driven’ method for discomfort glare assessment. We conducted a series of experiments under simulated office conditions and recorded the participants’ gaze using mobile eye tracking and the luminance distributions using high dynamic range imaging methods. The two methods were then integrated to derive ‘gaze-centred’ luminance measurements in the field of view. The existing ‘fixed-gaze’ and the newly developed ‘gaze-driven’ measurement methods are compared. Our results show that there is a significant difference between the two methods. In this paper, the procedure for integrating the recorded luminance images with the recorded gaze dynamics for obtaining gaze-centred luminance data is described. This gaze-centred luminance data will be compared ...
This paper details the results of an experimental study investigating the combined effect of indo... more This paper details the results of an experimental study investigating the combined effect of indoor temperature (19 ℃, 23 ℃ and 27 ℃) and horizontal illuminances (∼140 lx, ∼610 lx and ∼1440 lx) on visual perception, with daylight as the only source of light. The goal is to evaluate the cross-modal effect of temperature and the unimodal effect of daylight illuminances on the visual perception of daylight. A 3 × 3 mixed-design experiment was conducted in an office-like test room with 84 participants. Results show that cross-modal effects of indoor temperature on visual perception occurred: Temperature influenced the perceived warmth of daylight, and temperature interacted with daylight illuminance as the high illuminance was considered more pleasant, was better evaluated and was more often chosen than the low one only in a thermally comfortable condition. In terms of unimodal effects, differences in visual comfort evaluations were substantial only between the low and the other two ill...
Because well-being is becoming a major challenge in construction alongside energy efficiency, the... more Because well-being is becoming a major challenge in construction alongside energy efficiency, there is an increasing need to be able to quantify discomfort in buildings. In the case of discomfort glare, the kind of glare provoking an irritating or distracting effect, no current indices can properly explain the high variability existing between individuals' discomfort glare perceptions. This is due to the fact that some of the factors influencing discomfort glare perception are still unknown and the mechanism behind the discomfort glare process is not well understood. Therefore, this article aims to review the factors potentially influencing discomfort glare perception from daylight. Every factor having been studied at least once for its potential influence on discomfort glare perception has been listed, described, and analyzed. Furthermore, this study categorizes the influence of these factors on discomfort glare by introducing an influence indicator based on the number of studies having investigated the factor, the sample size of these studies, and the agreement between them. The suggested categories rate a factor influence as "almost certain," "more likely," "somewhat likely," "inconclusive," "somewhat unlikely," "less likely," or "almost certainly null." Tables summarize the main information about the studies and the influencing factors. As expected, factors almost certainly influencing discomfort glare perception are the luminance of the glare source, adaptation level, contrast effect, and size and position of the glare source. In contrast, factors that almost certainly do not influence discomfort glare perception are the gender and optical correction of the observer. All other factors from the list of 30, such as the attractiveness of the view through the window or the culture of the observer, require additional studies to determine whether or not they influence discomfort glare perception.
Nowadays, discomfort glare indices are frequently calculated by using evalglare. Due to the lack ... more Nowadays, discomfort glare indices are frequently calculated by using evalglare. Due to the lack of knowledge on the implications of the methods and parameters of evalglare, the default settings are often used. But wrong parameter settings can lead to inappropriate glare source detection and therefore to invalid glare indices calculations and erroneous glare classifications. For that reason, this study aims to assess the influence of several glare source detection methods and parameters on the accuracy of discomfort glare prediction for daylight. This analysis uses two datasets, representative of the two types of discomfort glare: saturation and contrast glare. By computing three different statistical indicators to describe the accuracy of discomfort glare prediction, 63 different settings are compared. The results suggest that the choice of an evalglare method should be done when considering the type of glare that is most likely to occur in the visual scene: the task area method sh...
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand-outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
Advanced computer simulation tools for analyzing daylighting features and thermal performance of ... more Advanced computer simulation tools for analyzing daylighting features and thermal performance of buildings are improved at the Fraunhofer Institute for Solar Energy Systems.For an analysis of daylighting elements in lighting simulations, new light-deflecting structures and materials have been measured and modeled. In order to study the interaction between lighting and thermal behaviour of rooms, thermal and lighting simulation techniques are linked together. Thus, integrated energy concepts can be evaluated. Programs for handling parallel image generation in a network of high-performance Unix workstations have been developed.
In this paper, we present a physical validation of global illumination algorithms based on measur... more In this paper, we present a physical validation of global illumination algorithms based on measurements from a simple experimental setup. The validation methodology emphasizes tractability and error minimization. To this end, we discuss issues such as the acquisition and accurate simulation of material bidirectional reflection distribution functions (BRDFs) and the light source distribution, as well as error analysis. In addition, we present a nearestneighbor resampling technique for BRDFs and a simple method for extracting the light source distribution from digitized high dynamic range (HDR) images. Finally, we compare the measurements to a forward and backward raytracing solution (photon map and RADIANCE, respectively) in a set of case studies.
This paper presents a vision of how state-of-the-art computer-based analysis techniques can be ef... more This paper presents a vision of how state-of-the-art computer-based analysis techniques can be effectively used during the design of daylit spaces. Following a review of recent advances in dynamic daylight computation capabilities, climate-based daylighting metrics, occupant behavior and glare analysis, a fully integrated design analysis method is introduced that simultaneously considers annual daylight availability, visual comfort and energy use: Annual daylight glare probability profiles are combined with an occupant behavior model in order to determine annual shading profiles and visual comfort conditions throughout a space. The shading profiles are then used to calculate daylight autonomy plots, energy loads, operational energy costs and green house gas emissions. The paper then shows how simulation results for a sidelit space can be visually presented to simulation non-experts using the concept of a 'daylighting dashboard'. The paper ends with a discussion of how the daylighting dashboard could be practically implemented using technologies that are available today.
Daylighting and the impact of daylighting strategies on the visual environment continue to be a v... more Daylighting and the impact of daylighting strategies on the visual environment continue to be a vital issue for building occupants due to visual comfort and user acceptance of luminous indoor environments. Some of the critical factors affecting the level of visual comfort and quality in daylit office spaces include glare, window luminances, and luminance ratios within the field of view. One of the goals of this study was to provide new insight into the impact of luminance distributions on glare. The luminance distribution within the field of view was recorded using CCD camerabased luminance mapping technology. The technology provides a great potential for improved understandings of the relation between measured lighting conditions and user response. With the development of the RADIANCE based evaluation tool ''evalglare'', it became possible to analyse glare according to a number of daylight glare prediction models as well as contrast ratios in various daylit situations (workplace, VDU). User assessments at two locations (Copenhagen, Freiburg) with more than 70 subjects under various daylighting conditions were performed in order to assess existing glare models and to provide a reliable database for the development of a new glare prediction model. The comparison of the results of the user assessments with existing models clearly shows the great potential for improving glare prediction models. For the window luminance a squared correlation factor of only 0.12 and for the daylight glare index (DGI) of 0.56 were found. Due to the low predictive power of existing glare prediction models a new index, daylight glare probability (DGP), was developed and is presented in this paper. DGP is a function of the vertical eye illuminance as well as on the glare source luminance, its solid angle and its position index. The DGP showed a very strong correlation (squared correlation factor of 0.94) with the user's response regarding glare perception.
This report summarizes the evaluation of the calculation of illuminance in evalglare to prove the... more This report summarizes the evaluation of the calculation of illuminance in evalglare to prove the embedded algorithm. Evalglare-calculated illuminance values were compared with analytically-determined values as well as with values calculated from images by an alternative method that was provided by the author of RADIANCE. Only marginal differences between the two methods and analytical derived values were found. From the results, it can be concluded that the illuminance calculation in evalglare is reliable and delivers correct values.
Keywords: Glare ; Daylight Reference EPFL-TALK-208874 Record created on 2015-06-10, modified on 2... more Keywords: Glare ; Daylight Reference EPFL-TALK-208874 Record created on 2015-06-10, modified on 2016-08-09
Although fabrics are widely used as shading devices, reliable simulation models are rather rare a... more Although fabrics are widely used as shading devices, reliable simulation models are rather rare and therefore the choice of a fabric with appropriate material characteristics is difficult. This paper presents a simulation model, which can be applied to most of the common available fabric shading materials. Furthermore a comprehensive simulation study has been conducted in order to derive simple to use tables for the selection of appropriate shading properties for a designer. These tables enable the user to select the "right" fabric according to a combination of multiple boundary conditions (location, orientation, window sizes, user positions).
The evaluation of indoor comfort requires a thorough understanding of how human occupants perceiv... more The evaluation of indoor comfort requires a thorough understanding of how human occupants perceive four indoor environmental factors: visual conditions, air quality, acoustic ambience and thermal conditions. Recent studies have found that overall comfort is more than the average effects of these four parameters. Beside their main effects, their mutual interactions play an equally important role in the perception of comfort. Thus, to progress regarding our understanding of global comfort, more effort is needed to further investigate the interactions between indoor environmental factors. For this kind of perceptual evaluation, it is necessary to conduct user studies. In these, subjects’ evaluations need to be recorded in addition to the physical parameters that provoke them. Therefore, the sensitivity of people to their environment is the principal parameter around which the studies should be designed. This paper presents a first evaluation of the sensitivity of people to visual and t...
The presented study describes a method for evaluating control strategies for shading devices. The... more The presented study describes a method for evaluating control strategies for shading devices. The method is based on dynamic lighting simulations with RADIANCE and DAYSIM and explores energy, daylight supply and visual comfort parameters at the same time. In order to include the glare aspect more effectively in dynamic building simulations, a simplified glare measure “Daylight Glare Probability simplified (DGPs)” is presented and validated for situations when the sun does not hit the eye directly. For the evaluation of the solar thermal loads, a simplified method based on RADIANCE and DAYSIM is described to calculate dynamically the energy flux through facades for external mounted shading devices. The evaluation of different simulated shading control strategies show that the commonly used manual control strategies hardly activate the shading in summer. Therefore, the solar loads in summer for these strategies are very high and at the same time glare and low contrasts at the visual d...
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Papers by Jan Wienold