Conference papers

LIPID publications

2017

Suitability of neighborhood-scale massing models for daylight performance evaluation.

M. Agarwal; L. Pastore; M. Andersen

2017. International Conference on Sustainable Design of the Built Environment (SDBE) 2017 , London, UK , December 20-21, 2017.

Access to daylight in buildings is the combined effect of a building’s own physical attributes along with its surrounding physical context. There is thus growing interest among researchers to extend the use of building performance simulation (BPS) tools for daylight performance evaluation, not just for an individual building, but to the neighborhood scale and beyond. In the design process of neighborhoods, massing models are often utilized and are a pivotal early design-stage work-product. These models are typically simple and delineate broad geometric dimensions of built enclosures. They are thus attractive for fast early design stage assessment using BPS tools and maybe used to determine daylight access potential. However, at this stage, the designer may have limited and imprecise information regarding the building façade, the vital element for daylight intake and distribution in the building interior. In this study, we assess the dependability of simple massing models for comparative indoor daylight assessments of neighborhood forms. Useful Daylight Illuminance (UDI) metric based performance values were calculated for five neighborhood design options using common practice for façade related inputs in early design stage simulation models and then ranked in decreasing order of performance. A virtual progression of the design-process was then carried out to develop multiple plausible façade design solutions for all proposed massing schemes. The main finding of this study is that significant changes can be observed in neighbourhood rankings when increasing the degree of detail in the façade design solutions. While the highest performing designs were found to maintain their ranks, the rankings of other projects shifted considerably when façade related information was supplied. This work informs on the possibility of erroneous design decisions resulting from simplified façade inputs in early design stage models and fosters the growing discussion on appropriate utilization of BPS tools for informing design decisions.

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Visualization techniques for heterogeneous and multidimensional simulated building performance data sets

T. Jusselme; R. Tuor; D. Lalanne; E. Rey; M. Andersen

Proceedings of the International Conference for Sustainable Design of the Built Environment. 2017. SDBE 2017 - International Conference for Sustainable Design of the Built Environment , London - UK , December 20-21, 2017. p. 971-982.

The architecture, environment and construction industry is facing, on the one hand, ambitious environmental regulations for low carbon and net zero energy buildings, and on the other hand, the emergence of new techniques such as parametric assessment and cloud computing. As a result, there is a dramatic increase of performance analysis and collected data during the building design phase. However, previous research highlighted major weaknesses of current building performance simulation -BPS- software regarding its ability to represent and explore input and output data, to interact with it, and to extract valuable data patterns and analyses. Therefore, this research aims to identify suitable visualization techniques that might increase the usability and the knowledge extracted from building simulation dataset. To that end, an interdisciplinary approach has been set up. First, a literature review allowed to characterize the specificities of BPS dataset, namely their heterogeneous nature -discrete, ordinal, categorical, and continuous-, their different correlation levels and their medium size. Second, key tasks that should be performed by BPS tools to support the design process are identified: exploration, solutions generation and evaluation. Then, two data visualization techniques that accept the BPS dataset specificities and that enable to perform these key tasks were selected within the information visualization research field: Decision Tree and Parallel Coordinates. Third, these techniques were applied to an extensive BPS dataset, generated from a series of parametric building simulations based on a high-performance building to be, called the smart living building. Finally, a qualitative comparison between the selected visualization techniques was conducted so as to reveal their strengths and weaknesses. This comparison highlights Parallel Coordinates as the most promising approach.

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COMPARISON OF LUMINANCE BASED METRICS IN DIFFERENT LIGHTING CONDITIONS

J. Wienold; T. E. Kuhn; J. Christoffersen; M. Sarey Khanie; M. Andersen

Proceedings of the CIE 2017, Midterm Meeting, Jeju Island, Korea. 2017. CIE 2017, Midterm Meeting , Jeju Island, Korea , October 20-28, 2017.

In this study, we evaluate established and newly developed metrics for predicting glare using data from three different research studies. The evaluation covers two different targets: 1. How well the user’s perception of glare magnitude correlates to the prediction of the glare metrics? 2. How well do the glare metrics describe the subjects’ disturbance by glare? We applied Spearman correlations, logistic regressions and an accuracy evaluation, based on an ROC- analysis. The results show that five of the twelve investigated metrics are failing at least one of the statistical tests. The other seven metrics CGI, modified DGI, DGP, Ev, average Luminance of the image Lavg, UGP and UGR are passing all statistical tests. DGP, CGI, DGI_mod and UGP have largest AUC and might be slightly more robust. The accuracy of the predictions of afore mentioned seven metrics for the disturbance by glare lies in the range of 75-83% and does not confirm findings from other studies stating a poor performance of existing glare metrics.

Annual glare evaluation for fabrics

J. Wienold; T. E. Kuhn; J. Christoffersen; M. Andersen

2017. PLEA 2017 , Edinburgh , July 3-5, 2017.

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 effect of short exposure to coloured light on thermal perception: a study using Virtual Reality

G. Chinazzo; K. Chamilothori; J. Wienold; M. Andersen

Proceedings of the Lux Europa 2017. 2017. Lux Europa 2017 , Ljubljana, Slovenia , September 18-20, 2017. p. 273-279.

This study investigates the effect of short exposure to coloured light on thermal perception. To give the impression of natural daylight passing through coloured filters, but avoiding the drawbacks of conducting an experiment with daylight, continuously changing due to daily and seasonal variations, and to weather conditions, we investigate the use of Virtual Reality as a means to control the visual conditions, creating a hybrid environment with thermal and visual stimuli from the real and virtual world, respectively. Two temperature levels (24 °C and 29 °C) are controlled in a climate chamber, while three visual conditions (orange, blue and neutral colour filters) are displayed in the Virtual Reality headset. Results of a between-subjects experiment show that the coloured light led to different thermal evaluations. In particular, under orange light conditions at 24 °C, subjects felt warmer, less comfortable and judged the thermal environment as less acceptable than under the other colours at the same temperature. The effect of short exposure to coloured light on thermal perception: a study using Virtual Reality. Available from: https://www.researchgate.net/publication/319963214_The_effect_of_short_exposure_to_coloured_light_on_thermal_perception_a_study_using_Virtual_Reality [accessed Sep 22, 2017].

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Sensitivity analysis of visual and thermal parameters for energy savings: combining illuminance and temperature set-points for possible trade-offs

G. Chinazzo; M. Plourde; J. Pereira; J. Wienold; M. Andersen

2017. Building Simulation 2017 , San Francisco, California, USA , August 7-9 2017.

This study presents a methodology for evaluating the effects of simultaneous temperature and illuminance set-point variations on energy consumption. Different illuminance levels are achieved with an innovative dynamic shading control algorithm that allows keeping constant values of maximum workplane illuminance. Findings from applying the methodology to a specific office-like workplace located in Switzerland show that the new shading control algorithm leads to lower cooling energy consumption in comparison with a standard shading control system (i.e., based on maximum irradiance) for constant 300 and 500 lux indoor illuminance thresholds. Moreover, multiple combinations of temperature and illuminance levels result in similar cooling consumption values, implying that trade-offs between those two parameters are possible to achieve energy savings.

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Exploring the influence of contemporary facade design on occupant satisfaction: a preliminary study in office buildings

L. Pastore; M. Andersen

2017. PLEA 2017 Edinburgh - Design to Thrive , Edinburgh , July 3-5, 2017.

This paper describes the preliminary findings of a post-occupancy evaluation campaign conducted on contemporary and energy-efficient office buildings with different façades treatments. The aim is to investigate occupants’ comfort and perceived productivity and to observe to what extent the space appearance and the façade design play a role in the ultimate user’s satisfaction and overall comfort. Two Swiss office buildings with different vertical enclosures are considered for this preliminary study: one has regular-shaped windows and regular blinds while the other presents a double-skin façade with a coloured silk-printed pattern partially covering the external pane and semi-transparent internal roller blinds. The results reported in this paper relate to an on-line extensive survey distributed among the buildings occupants to provide a global estimation of the comfort and perception they experience in their office. Findings suggest that in case of high dissatisfaction with some environmental factors, these influence strongly people’s overall comfort evaluation but not the self-rated productivity. However, when comfort ratings are less critical –though not optimal-, overall comfort as well as perceived productivity are more strongly correlated to the pleasantness of the space than to the environmental factors. Nevertheless, in the case of patterned glazing, the façade design has a low influence on comfort perception. The study suggests that further research should be conducted, especially to look at façade designs that play a greater role in determining the appearance and/or a certain level of personal environmental control in a workspace.

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Energy performance analysis in interdisciplinary education – Lessons learned from a simulation-based teaching approach

É. Nault; S. Aguacil Moreno; E. Rey; M. Andersen

2017. PLEA 2017 Edinburgh - Design to Thrive , Edinburgh, UK , July 3-5, 2017.

The education of building practitioners is challenged by the increasing need for interdisciplinary profiles in the professional practice. To progress toward the goal of a sustainable built environment, a common language must be shared among fields such as architecture and engineering, between which persisting barriers remain. This paper presents an interdisciplinary teaching approach that aimed at getting architecture and engineering students to develop – around a unique case study evolving in parallel to the course – an understanding of the relationships between architectural and constructive aspects, simulation parameters, and energy and thermal comfort performance. Lessons learned from this experience include: the (in)adequacy of using an advanced software (EnergyPlus) imposing a steep initial learning curve, the limitations of working on a case study whose scope extends beyond the context of the class, and the conflict between achieving pedagogical objectives and valuing ‘real-time consultancy’ work in an evolving project. These challenges however seem to have been key to enable students to develop a solid knowledge of the concepts and technical language, as well as strong simulation competences, pushing them to embrace the added value of interdisciplinarity possibly more effectively than if a theoretical exercise had been used.

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Integrating urban energy simulation in a parametric environment: a Grasshopper interface for CitySim

G. Peronato; J. H. Kämpf; E. Rey; M. Andersen

2017. PLEA 2017 Edinburgh - Design to Thrive , Edinburgh , July 3-5, 2017.

The increasing popularity of parametric design tools goes hand in hand with the use of building performance simulation (BPS) tools from the early design phase. However, current methods require a significant computational time and a high number of parameters as input, as they are based on traditional BPS tools conceived for detailed building design phase. Their application to the urban scale is hence difficult. As an alternative to the existing approaches, we developed an interface to CitySim, a validated building simulation tool adapted to urban scale assessments, bundled as a plug-in for Grasshopper, a popular parametric design platform. On the one hand, CitySim allows faster simulations and requires fewer parameters than traditional BPS tools, as it is based on algorithms providing a good trade-off between the simulations requirements and their accuracy at the urban scale; on the other hand, Grasshopper allows the easy manipulation of building masses and energy simulation parameters through semi-automated parametric workflows. In this paper, we present a preliminary version of the developed plug-in and a typical design workflow for the simulation and visualization of building performance at the neighbourhood scale. We conclude by discussing its scalability to larger urban areas using 3D geodata as input and the coupling with Computational Fluid Dynamics (CFD) simulations and optimization algorithms.

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An Experiment in Virtual Reality to Measure Daylight-Driven Interest in Rendered Architectural Scenes

S. F. Rockcastle; K. Chamilothori; M. Andersen

Proceedings of Building Simulation 2017. 2017. Building Simulation 2017 , San Francisco, California, USA , August 7-9.

This paper introduces an experiment using a virtual reality headset to collect subjective evaluations of rendered daylit architectural scenes. By varying sky conditions and view directions from a fixed position in architectural renderings, the authors collected subjective perceptual ratings and compared them to image-based measures related to impressions of visual interest. The use of virtual reality allowed for the extraction of headtracking data, providing additional insight on how people perceived the immersive scenes. Findings reveal a dependency between visual interest impressions and quantitative predictors, both of which vary with sky conditions and view directions within the scene.

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A Simulation-Based Workflow to Assess Human-Centric Daylight Performance

S. F. Rockcastle; M. L. Amundadottir; M. Andersen

Proceedings of the 8th Symposium on Simulation for Architecture and Urban Design. 2017. 8th Symposium on Simulation for Architecture and Urban Design , Toronto, Canada , May 22-24.

This paper will present an annual simulation-based workflow for assessing human perceptual and non-visual responses to daylight across a series of view positions in an architectural case study. Through the integration of mathematical models used to predict visual interest and non-visual health potential, this paper will introduce an automated workflow to assess an array of view positions (located at eye level) under varied sky conditions and across multiple view directions to analyze the predicted impacts of daylight on perception and health in architecture. This approach allows for a spatial and occupant centric analysis of daylight using an integrated simulation-based approach.

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2016

A preliminary study on the sensitivity of people to visual and thermal parameters in office environments

G. Chinazzo; J. Wienold; M. Andersen

Proceedings of the 9th Windsor Conference: Making Comfort Relevant. 2016. 9th Windsor Conference: Making Comfort Relevant , Cumberland Lodge, Windsor, UK , 7-10 April 2016.

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 thermal parameters in real office environments to establish a groundwork for future investigations. From this cross-sectional observational study, we concluded that possible effects of interactions between factors are difficult to see when the conditions are more or less comfortable. In that case people are not enough sensitive to environmental changes.

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Examining Building Design Decisions Under Long Term Weather Variability and Microclimatic Effects: A case-based exploratory study

M. Agarwal; P. Rastogi; M. M. V. Peltier; L. Pastore; M. Andersen

Proceedings of the 32nd International Conference on Passive and Low Energy Architecture. 2016. PLEA , Los Angeles, USA , July 11-13, 2016. p. 1504.

Thermal building simulation currently uses Typical Meteorological Year (TMY) data to guide the design decision-making process or for compliance with energy standards. TMY data usually excludes extremes and in many cases are gathered from microclimatic contexts that are not sufficiently representative of the project sites (e.g., airports), adding uncertainty in the analyses. To enable a quantification of uncertainty due to weather by exploring a wide variety of atypical weather conditions, the authors have previously proposed synthetic weather data for building simulation. This is a suite of weather time series, generated from typical weather data that includes heat waves and atypical peak temperatures. In this paper, we used this synthetic weather to examine the effect of considering atypical conditions on design decisions. We also compared the impact of including ‘city-modified’ weather data on retrofit decisions using urban microclimate simulation. We found that it may not be viable to pre-select a subset of weather data for all buildings at a given location. Rather, multiple weather data sets may be simulated based on the design strategies and performance criteria of importance. In other words, an extreme condition/year for one building isn’t necessarily the same for another. For example, in the case study presented, heat island effect was found to be a likely hindrance to night time cooling. This paper informs the debate on the necessity of expanding the current energy building analyses to a broader consideration of weather variability and more realistic urban microclimate characterization.

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Design of a light confining concentrator for a solar photochemical reactor and upper bound to the method

B. Karamata; M. Andersen

Nonimaging Optics: Efficient Design For Illumination And Solar Concentration Xiii-Commemorating The 50Th Anniversary Of Nonimaging Optics. 2016. Conference on Nonimaging Optics - Efficient Design for Illumination and Solar Concentration XIII -Commemorating the 50th Anniversary of Nonimaging Optics , San Diego, CA , AUG 28-29, 2016. p. 99550A.

DOI : 10.1117/12.2238313.

Optical concentration obtained by light confinement bears unique features that can increase the efficiency of a photochemical reactor. A suitable implementation of this method for a solar reactor is a series of parallel tubular receivers sealed in a slab-shape reflective cavity, in which light is trapped thanks to a self-adaptive optical filtering mechanism. To predict the concentration in such a generic configuration, we had previously established an analytical model based on idealistic assumptions, which are not valid in our real configuration. Here, we use analytical calculations and numerical ray-trace simulations to investigate how the finite size of the latter impacts the prediction of our model and extrapolate design guidelines for minimal departure from ideality. We apply these guidelines to design an optical concentrator maximizing flux density on tubular receivers and discuss the upper bound to the method, as well as the benefits from its unique features. Accounting for practical and technological limitations, this method can provide optical concentration in the order of ten suns in our generic configuration.

Gaze Responsive Visual Comfort: New Findings On Gaze Behaviour In A Daylit Office Space In Relation To Glare

M. Sarey Khanie; J. Stoll; W. Einhaeuser; J. Wienold; M. Andersen

Proceedings Of Cie 2016 Lighting Quality And Energy Efficiency. 2016. CIE Conference on Lighting Quality and Energy Efficiency , Melbourne, AUSTRALIA , MAR 03-05, 2016. p. 373-384.

Using a newly developed gaze-driven methodology for discomfort glare assessments, we studied gaze behaviour in different glare conditions. The study was done in a series of experiments where gaze behaviour of the participants were recorded using eye-tracking techniques and the daylight dynamics were measured using high dynamic range (HDR) imaging techniques. In these experiments 5 daylit and one artificial lighting condition were considered to further our understanding of gaze behaviour in relation to light. Here we present the findings on how gaze behaves in different lighting conditions in relation to glare and task.

Glare Caused By Contrast Between Task And Immediate Surround: An Evaluation Of Luminance Distribution In The Field Of View

P. Hansen; M. Sarey Khanie; T. E. Kuhn; J. Christoffersen; J. Wienold et al.

Proceedings Of Cie 2016 Lighting Quality And Energy Efficiency. 2016. CIE Conference on Lighting Quality and Energy Efficiency , Melbourne, AUSTRALIA , MAR 03-05, 2016. p. 132-141.

Luminance ratios have historically been used to assess glare. Using data from a previous experiment, this exploratory study investigates the relationship between luminance variations in the field of view (FOV), measured as luminance ratios, and glare sensation in daylit office-like settings. Correlations between glare sensation assessments and luminance ratios between task area, its immediate surround and far surround were calculated. The results indicate that there are certain definitions of contrast ratio which have better correlations with subjective assessments. The inclusion of this type of glare will enhance the existing glare models for better prediction of glare in a wider set of situations.

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3D-modeling of vegetation from LiDAR point clouds and assessment of its impact on façade solar irradiation

G. Peronato; E. Rey; M. Andersen

The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 2016. 11th 3D Geoinfo Conference , Athens , October 20-21, 2016. p. 67-70.

DOI : 10.5194/isprs-archives-XLII-2-W2-67-2016.

The presence of vegetation can significantly affect the solar irradiation received on building surfaces. Due to the complex shape and seasonal variability of vegetation geometry, this topic has gained much attention from researchers. However, existing methods are limited to rooftops as they are based on 2.5D geometry and use simplified radiation algorithms based on view-sheds. This work contributes to overcoming some of these limitations, providing support for 3D geometry to include facades. Thanks to the use of ray-tracing-based simulations and detailed characterization of the 3D surfaces, we can also account for inter-reflections, which might have a significant impact on fac¸ade irradiation. In order to construct confidence intervals on our results, we modeled vegetation from LiDAR point clouds as 3D convex hulls, which provide the biggest volume and hence the most conservative obstruction scenario. The limits of the confidence intervals were characterized with some extreme scenarios (e.g. opaque trees and absence of trees). Results show that uncertainty can vary significantly depending on the characteristics of the urban area and the granularity of the analysis (sensor, building and group of buildings). We argue that this method can give us a better understanding of the uncertainties due to vegetation in the assessment of solar irradiation in urban environments, and therefore, the potential for the installation of solar energy systems.

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A Multi-Criteria Decision-Support Workflow for Early-Stage Neighborhood Design based on Predicted Solar Performance

É. Nault; E. Rey; M. Andersen

Proceedings of PLEA 2016, 32nd international Conference on Passive and Low Energy Architecture. 2016. PLEA - 32nd International Conference on Passive and Low Energy Architecture. Cities, Buildings, People: Towards Regenerative Environments , Los Angeles, USA , July 11-13, 2016.

Despite recent developments, the need for adequate guidance and support in the early decision-making process of urban planners, designers, and architects has recurrently been recognized. Traditional performance assessment methods, which are often based on partial and independent dynamic simulations evaluating individual metrics, are better suited for detailed design and are particularly complex and time-consuming at the urban scale. They typically follow a linear design-and-test approach, limiting the user-guidance features. Taking a different approach, this paper proposes a multi-criteria decision-support workflow that evaluates the daylight and passive and active solar potential of early-stage neighborhood designs. The performance evaluation is done through a predictive mathematical function for the passive solar and daylight potential, requiring little information from the user. The implemented workflow is introduced, and the development of the underlying performance assessment engine is summarized, along with the results from a proof-of-concept study to probe the validity boundaries of the predictive functions. Results show the proposed workflow to be promising as an interactive and real-time performance-based design support.

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Urban planning and solar potential: Assessing users' interaction with a novel decision-support workflow for early-stage design

É. Nault; L. Pastore; E. Rey; M. Andersen

Proceedings of Sustainable Built Environment (SBE) Conference. 2016. Sustainable Built Environment (SBE) , Zurich, Switzerland , June 13-17.

The need for sustainable architecture and urban design and planning has long been acknowledged, along with the necessity for adequate, early-phase guiding instruments. This paper aims at exploring the effectiveness and usability of a novel decision-support workflow for neighbourhood-scale projects, developed to provide practitioners with early-stage design alternatives in an interactive and iterative sequence. The prototype includes a performance assessment engine, which quickly computes an estimate of the daylight and passive and active solar potential for each design alternative. To assess the added value for design and the educational features offered by the workflow, workshops were organized with architects and urban planners. Participants were asked to work on a realistic micro-urban design project by means of two different approaches: making use of their conventional tools and methods, and then using the prototype. In addition to these design phases, the workshop included ranking design alternatives with respect to their performance before and after using the prototype, and filling pre- and post-workshop questionnaires to gather the participants’ level of experience and their feedback. The main outcomes from these tasks show that the prototype yields a strong potential in terms of design guidance, despite mixed results in the level of success in the before and after ranking phases. Results also highlight the necessity to pursue the development and adoption of energy-oriented early-stage design instruments.

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Assessing the impact of contemporary urbanization on bioclimatic features of historic architecture through a two-step simulation process

L. Pastore; P. Rastogi; S. F. Rockcastle; H. Y. C. Monari; G. Rueff et al.

Proceedings of PLEA 2016. 2016. Passive and Low-Energy Architecture , Los Angeles, CA, USA , July 11-13, 2016.

The aim of this paper is to provide a systematic understanding, through simulation-based assessment, of how contemporary urban planning affects the bioclimatic features of existing historic architecture. An emblematic early 20th century Brazilian building, the Casa das Rosas in São Paulo, has been chosen as a case study to see how the deep transformation of its surroundings has altered its indoor conditions. Taking into account both the original and the current urban and environmental conditions, a two-step assessment is conducted by moving between two levels of simulation: the urban- and building-scales. The urban-scale simulations characterize the microclimate parameters (temperature, humidity, and wind speed) that will represent the boundary conditions for the building-scale simulation. EnergyPlus and DIVA-for-Rhino were used to assess the bioclimatic features in terms of indoor thermal and visual comfort levels respectively. Despite the revival of passive design solutions derived from historic architecture, studies of the influence of contemporary urban settlements on their comfort behavior are still quite limited. Outcomes from our simulations show that urban planning can have a significant impact on the indoor light levels of historic buildings, but that the average temperature conditions are not significantly affected. We expect that the results would show a bigger difference if anthropogenic heat sources were taken into account, especially for outdoor comfort conditions.

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Incorporating Climate Change Predictions in the Analysis of Weather-based Uncertainty

P. Rastogi; M. Andersen

2016. ASHRAE and IBPSA-USA SimBuild 2016 -- Building Performance Modeling Conference , Salt Lake City, UT, USA , August 8-12, 2016.

This paper proposes randomly-generated synthetic time series incorporating climate change forecasts to quantify the variation in energy simulation due to weather inputs, i.e., Monte Carlo analysis for uncertainty and sensitivity quantification. The method is based on the use of a small sample (e.g., a typical year) and can generate any numbers of years rapidly. Our work builds on previous work that has raised the need for viable complements to the currently-standard typical or reference years for simulation, and which identified the chief components of weather time series. While we make no special efforts to reproduce either extreme or average temperature, the sheer number of draws ensures both are seen with either the same or higher probability as recent recorded data.

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Daylight patterns as a means to influence the spatial ambiance: a preliminary study

K. Chamilothori; J. Wienold; M. Andersen

Proceedings of the 3rd International Congress on Ambiances. 2016. 3rd International Congress on Ambiances , Volos, Greece , September 21-24, 2016.

This contribution focuses on perforated façades, investigating the effect of the façade and the resulting daylight pattern on the perceived spatial ambiance. The daylight conditions, as well as the geometry and regularity of the façade pattern are manipulated in an immersive virtual space, producing different conditions. A preliminary study was conducted, where subjective evaluations of the virtual space were recorded across six variations of façade pattern and sky type. The results indicate that the façade pattern characteristics have an impact on the perceived spatial ambiance, underlining the need to investigate further the perceptual aspect of the spatial and temporal diversity of light in space through experimental studies.

Sensitivity of calculated solar irradiation to the level of detail: insights from the simulation of four sample buildings in urban areas

G. Peronato; S. Bonjour; J. Stoeckli; E. Rey; M. Andersen

Proceedings of PLEA 2016, 32th international Conference on Passive and Low Energy Architecture. 2016. PLEA2016 Los Angeles - Cities, Buildings, People: Towards Regenerative Environments , Los Angeles, California, USA , July 11-13, 2016.

The assessment of the solar potential in urban areas relies on a geometrical model that can be defined at different levels of detail (LOD). In this work we compare the solar irradiation simulated on the surfaces of four sample buildings, which were modeled at three different LODs as defined by the CityGML standard. Results indicate a general overestimation of the solar irradiation when using LOD1 and LOD2 models, if we consider LOD3 (i.e. the finer model) as the ground truth. However, results show also that the error varies significantly between the analyzed buildings and the considered minimum irradiation thresholds and, if we take into account only rooftops, the effect of added elements might result either in an overestimation or an underestimation of the annual total irradiation. We conclude by discussing how such findings should influence current practices in the assessment of the solar potential at the urban scale.

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Towards a novel prediction model for visual interest in daylit renderings

S. F. Rockcastle; M. L. Ámundadóttir; M. Andersen

Proceedings of the 7th Symposium on Simulation for Architecture and Urban Design (SimAUD). 2016. 7th Symposium on Simulation for Architecture and Urban Design (SimAUD) , London, UK , May 16 - 18, 2016.

In spaces where daylight is a primary source of illumination, our visual perception of architecture is largely influenced by the ephemeral composition of sunlight and shadow. To evaluate these perceptual effects, the authors will apply quantitative contrast measures to HDR renderings for a series of existing contemporary architectural spaces under variable sunlight conditions. These measures will then be compared to subjective ratings of visual interest, collected through an online survey designed to test the influence of spatial and temporal parameters. The objectives of this study assess the impact of sunlight dynamics on subjective ratings of daylit architectural renderings and compare the relationship between these subjective ratings and existing quantitative measures. The results show that one modified local measures can be used to predict factors of visual interest in daylit renderings. When applied through an annual simulation-based approach, this novel metric reveals human perceptual responses to dynamic daylight conditions.

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LCA as key factor for implementation of inertia in a low carbon performance driven design: the case of the smart living building in Fribourg, Switzerland

A. Brambilla; E. Hoxha; T. Jusselme; M. Andersen; E. Rey

Proceedings of Sustainable Built Environment (SBE) Conference. 2016. Sustainable Built Environment (SBE) Conference , Zurich, Switzerland , June 15-17, 2016.

The building sector is known as a major contributor to greenhouse gas (GHG) emissions and energy consumption. These impacts are commonly evaluated by life cycle assessment (LCA), which assess the potential impacts of a building from the construction to the end of life. LCA considers: the operating impacts (OI) occurring during the service life of buildings, and the embodied impacts (EI) occurring during the other lifecycle. Materials usually increase EI, but some of them, such the ones used for thermal inertia (TI), concur to energy efficiency and can reduce OI. This makes it difficult to understand the role of such materials in low carbon building strategies. The aim of this study is to understand how to weigh the overall environmental benefits of TI. Four building models were used to assess LCA with either low, medium, high or very high levels of TI. These are reached using materials characterized by different embodied impacts, such as concrete and earth. The difference with the low inertia case, taken as the base case, is evaluated for each model regarding OI and EI. The comparison between OI and EI determines which scenario brings the lowest impacts on LCA. To evaluate how the results are influenced by climate change, the analysis is made with two different scenarios: one with the typical meteorological year (TMY, Meteonorm) and the other with the weather conditions for 2050 (IPCC, International Panel on Climate Change). The paper shows a methodology to evaluate the effects of a design strategy on the LCA, applied to the case of TI. It demonstrates that TI is not very relevant in the frame of this case study because the EI related to the added materials is higher than the induced operating savings. Furthermore, it has been demonstrate that in the future when the carbon content of the energy may be lower, TI can change its effects and influence negatively the lifecycle environmental impacts.

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Impact targets as guidelines towards low carbon buildings: Preliminary concept

E. Hoxha; T. Jusselme; A. Brambilla; S. Cozza; M. Andersen et al.

2016. PLEA , Los Angeles, USA , July 11-13, 2016.

Developing building projects with low environmental impacts is a real challenge, yet a problem faced every day by designers. To that end, in the design process, iteration between propositions and objectives have been used that are complex and time consumption. The impact targets leading to low-carbon buildings have the potential to simplify this complexity and saving time in the building design process. This study introduces a methodology for the definition of impact targets for components and systems of buildings. The definition of impact targets has been envisaged as a two-step process combining top-down and bottom-up approaches. The desired impact target of building is defined by a top-down approach and the targets for components and systems by a bottom-up approach. Impact targets for the Swiss context are defined applying the methodology to the smart living building that aim at reaching the 2050 goals of the 2000-watt society vision. Through this approach, we were able to set up impact targets on the components and systems level for global warming potential indicator. Impact targets can be used as guidelines in the design process for developing component or system one by one without analysing the whole building, which is guided toward low carbon objectives.

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Introduction of a dynamic interpretation of building LCA results: the case of the smart living (lab) building in Fribourg, Switzerland

E. Hoxha; T. Jusselme; M. Andersen; E. Rey

Proceedings of Sustainable Built Environment (SBE) Conference. 2016. Sustainable Built Environment (SBE) Conference , Zurich , June 15-17, 2016.

Although a building lifetime is not predictable, it is an essential data in the yearly impact calculation. Yet, in the assessment of the environmental impacts of building the lifetime is considered as a fixed value. The purpose of this study is to introduce a new dynamic interpretation of LCA results, which aims at improving the reliability of assessment of buildings’ environmental impacts. To that end, are compared: - the environmental impacts assessed for 50, 70 and then 100 years of the building’s lifetime; - and environmental impacts assessed for anytime during the first 100 years of building’s lifetime. Since the impacts depend on the type of the building’s components and their quantity, in this study two scenarios have been applied: one compares two building projects that differ from each other on the shape and functionality; the other compares two projects that differ only on components and systems employed in the building. Possible projects of the smart living building have been selected as case studies. This building aims at reaching the goals of the 2000-watt society vision and will be built by 2020 in Fribourg, Switzerland. The dynamic interpretation of building’s impacts shows that the LCA results could vary up to 20%, according to the assumed building’s lifetime and thus, completely change the conclusion in the comparison of the impacts of different building projects when the projects differ from the components and systems. The dynamic interpretation assessed more reliable LCA-results, that are useful for strengthen comparisons in the decision making process.

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Towards a pre-design method for low carbon architectural strategies

T. Jusselme; S. Cozza; E. Hoxha; A. Brambilla; F. Evequoz et al.

Proceedings of PLEA 2016, 32th international Conference on Passive and Low Energy Architecture. 2016. PLEA2016 , Los Angeles, USA , July 11-13, 2016.

To face climate change, Switzerland proposes the 2050 energy strategy by fixing greenhouse gas (GHG) emission targets for the built environment. Designers will then have to increase operating performances while inimizing embodied impacts. This represents an issue for the building design process. In addition, there is a relationship between the design efficiency and the early integration of the knowledge about design. The purpose of this paper is to highlight the potential of a pre-design method to identify the building design parameters that reach the 2050 climate change objectives. To that end, four major steps are developed in this project. First, design parameters (e.g. wall thermal transmittance) which influence the building GHG emissions the most, are identified thanks to a literature review. Morris method (Saltelli et al, 2004) is used to create combinations of design parameters changing their values one by one. Secondly, these combinations are attributed to architectural feasibility studies (Sinclair, 2013) developed in the brief design phase to perform lifecycle analysis. Thirdly, KBOB database (KBOB et al., 2014) and lifetime of components proposed by PI-BAT were used for assessing GHG emissions. Lesosai software was used for primary energy assessment. Lastly, the combinations of design parameters and their relative GHG emissions are interpreted with data mining and visualization techniques. The smart living lab building has been chosen as a case study: this building aims at achieving the 2050 goals of the 2000-watt society vision and will be built by 2020 in Fribourg, Switzerland. Thanks to the preliminary results it is possible to rank the design parameters according to their GHG contribution, in order to highlight them during the early building design stage. The method offers combinations of design parameters allowing to reach the 2050 climate change objectives. Data mining and visualization enable designers to easily find the values of these parameters to fit into the architectural strategy. In order to offer a wider range of design parameter values, techniques to enhance the database should be further investigated.

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Studying the Dynamic Relationship between Energy Supply Carbon Content and Building Energy Demand

D. Vuarnoz; T. Jusselme; S. Cozza; E. Rey; M. Andersen

2016. PLEA 2016 Los Angeles - 36th International Conference on Passive and Low Energy Architecture. Cities, Buildings, People: Towards Regenerative Environments , Los Angeles, California, USA , July 11-13, 2016.

Due to different temporal combinations of energy generation processes, the global warming potential (GWP) of energy supply evolves constantly. Despite this, the greenhouse gas (GHG) emissions related to the energy consumption in buildings are commonly assessed with yearly averaged carbon content of the energy supply. The knowledge of the hourly carbon content of the energy supply, would allow a more realistic assessment of the GHG emissions. Moreover, a temporal relationship between the GWP energy supply and building energy demand for reducing carbon footprint could be addressed. In this study, different methods to evaluate the hourly carbon contents of the on-site available energies are presented. The potential of load shifting for GHG emission mitigation is also investigated. To test the methodology, an application to a case study where the energy is supplied from the electrical grid and on-site renewables is proposed. The chosen case study is the smart living building, currently being designed and expected to be built by 2020 in Fribourg, Switzerland. This study points out significant differences between a yearly average and an hourly dynamic carbon emission assessment. Carbon footprint benefits by load shifting at day scale are found to be very limited in the context of the smart living building.

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2015

Benefits of a translucent building envelope made of DSC-integrated glass blocks

R. Corrao; G. Milia; M. Morini; L. Pastore; C. Tutone

Proceedings of 10th Energy Forum on Advanced Building Skins. 2015. 10th Energy Forum on Advanced Building Skins , Bern, Switzerland , November 3-4, 2015. p. 18-27.

The aim of this paper is to analyse the benefits deriving from the replacement of the glazed façades of an office building located in Palermo (Sicily) with a new translucent BIPV envelope made of multifunctional glass block panels integrated with Dye-sensitized Solar Cells (DSCs). The analysed 11-storey building is cladded by a curtain wall determining high management costs, especially during summer, in order to maintain indoor comfort. After the design of the building envelope and of the components for the connection of the glass block panels with existing load bearing structure, the energy performance of the building, before and after the replacement of its envelope, were analysed with the support of Design Builder software. Other software tools – like Therm, Window and Optics – were used to calculate more in detail the thermal properties of the building envelope. The results of the energy performance simulations on the current state were compared with those deriving from the installation of the new envelope made of BIPV glass block panels. Besides the clean electricity production, a significant reduction in building energy consumption related to air conditioning systems was registered, due to the shading effect and solar gain reduction provided by the DSC-integrated glass blocks.

The sensitivity of predicted energy use to urban geometrical factors in various climates

É. Nault; P. Rastogi; E. Rey; M. Andersen

2015. Passive and Low Energy Architecture (PLEA) , Bologna, Italy , September 9-11, 2015.

Urban morphology, including building typology and layout, has a significant influence on the built environment’s access to the sun, which impacts its energy exchange with the environment. This energy exchange is a strong factor in determining the comfort levels of occupants in buildings and the energy consumed to reach comfort. The influence of urban form has been quantified in previous studies for certain building typologies and programs for specific climates (i.e. location-specific case studies). We are interested in taking this further to assess the variation, due to climate, of the influence of different urban forms on the urban energy balance. This is part of a larger project to study the interaction between form and climate vis-à-vis energy and comfort in buildings. In this paper, we explore this issue through simulation, in various climates, of 3D neighbourhood models. These models consist of a series of parametrically generated variations on building typologies like block, L-shaped, and courtyard block. Each neighbourhood alternative is described through a set of geometrical parameters including the form factor, window-to-floor and plot ratio. We used an extensive database of heating and cooling uses generated by simulating each variant in a representative set of climates to assess the sensitivity of energy use to the geometrical descriptors and climate types. This is done using a regression equation whose input parameters are easily calculable, e.g. form factor, and whose output is an estimate of simulated energy use. The aim of exploring this relationship is to use it to assess the suitability of different urban forms in a given climatic context. Moreover, it provides a promising route to avoid the necessity of detailed energy simulations in comparing the performance of different early urban design alternatives.

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Robustness Assessment Methodology for the Evaluation of Building Performance with a view to Climate Uncertainties

G. Chinazzo; P. Rastogi; M. Andersen

Proceedings of BS 2015. 2015. 14th International Conference of the International Building Performance Simulation Association , Hyderabad , December 2015.

This paper describes a new methodology to assess the robustness of building performance in the long term with a probabilistic approach. The aim is to include uncertainties related to climate change predictions as well as the intrinsic uncertainties in weather files describing them. A case study focussing on refurbishment strategies of a realistic building in Turin is presented to demonstrate the methodological steps. The main outcome is that it is advisable to have outcomes in terms of ranges of energy consumption instead of single output values to evaluate energy efficient design solutions in both present and future years.

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Sampling of building surfaces towards an early assessment of BIPV potential in urban contexts

G. Peronato; E. Rey; M. Andersen

2015. 31st International PLEA Conference , Bologna, Italy , September 9-11, 2015.

Although the integration of PV systems in the building envelope (BIPV) is an important factor for the acceptability of such installations, current urban-scale solar potential metrics only partially consider this aspect. As part of the definition of BIPV-suitable surfaces, we argue that a geometric-regularity criterion can help predict the possible disposition of solar panels already in the early assessment of BIPV potential in urban contexts. To address this need, we developed an algorithm for the geometric sampling of the parts of the building envelope achieving a minimum irradiation threshold, with the aim of defining uniformly-covered active solar surfaces. The proposed methodology is implemented in a flexible parametric design platform and tested in a case study in Neuchâtel (Switzerland). We show that integrating geometric regularity in the assessment of BIPV potential can have a significant influence in the calculation of the solar energy production and discuss the value of such information in urban planning practices.

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Human perceptions of daylight composition in architecture: a preliminary study to compare quantitative contrast measures with subjective user assessments in HDR renderings

S. F. Rockcastle; M. Andersen

Proceedings of the 14th International Conference of the International Building Performance Simulation Association. 2015. International Conference of the International Building Performance Simulation Association , Hyderabad , December 7 - 9.

Humans perceive daylight as a rich and dynamic luminous composition and yet existing performance metrics most often evaluate natural illumination for its ability to adequately illuminate a two-dimensional task surface while avoiding glare-based visual discomfort. This rather limited task-driven approach places a disproportionate emphasis on surface illumination and glare-based discomfort and ignores the likelihood that contrast can provide a positive visual impact on our impression of space. Existing studies on perceptual daylight performance have linked subjective ratings to digital images, yet they have relied on simple global contrast measures without reaching a robust consensus. These ‘global’ measures do not account for the composition of luminance values within a scene and while more robust methods have been developed in computational graphics, vision research, and psychology, they have not been applied to studies in qualitative lighting research. As daylight-driven visual effects in daylit space are heavily influenced by dynamic sky conditions, this paper will introduce an experimental method for comparing subjective ratings of daylight composition in architecture against existing global and local contrast metrics under a range of annual moments. The goal of this paper is to identify which quantitative measures (local and/or global contrast metrics), if any, correlate to subjective responses for contrast, uniformity, complexity, variation, stimulation, and excitement. This preliminary study will test which factors: sky type, spatial composition, or subject, shows a significant effect on these ratings.

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Gaze-Driven approach for estimating luminance values in the field of view for discomfort assessments

M. Sarey Khanie; J. Stoll; W. Einhäuser; J. Wienold; M. Andersen

2015. 28th CIE Session, , Manchester, UK , June 29 - 4 July, 2015.

A gaze-driven methodology for discomfort glare was developed and applied for glare evaluation. A series of user assessments were performed in an office-like test laboratory under various lighting conditions. The participants’ gaze responses were recorded by means of mobile eye tracking while monitoring photometric quantities relevant to visual comfort using HDR luminance imaging. The integration of the luminance images coupled with eye-tracking methods enabled us to use gaze-centred luminance distribution to have an accurate estimate of the light received at the eye. Using a novel gaze-driven approach, a unique database was created as a basis to investigate the gaze direction dependencies of visual comfort. Here we compare the proposed gaze-driven approach with two other approaches based on fixed-gaze assumptions: gaze fixating on the task area, and gaze shifted 45 ° towards the window area. The results show that there is a significant difference between luminance distributions driven by gaze and those based on fixed-gaze assumptions, indicating a potentially important impact on glare assessment results as well.

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Performance of the Glass Block in Photovoltaic Generation

F. Viola; P. Romano; R. Miceli; E. Riva Sanseverino; G. Perrone et al.

Proceedings of 2015 Tenth International Conference on Ecological Vehicles and Renewable Energies. 2015. Tenth International Conference on Ecological Vehicles and Renewable Energies (EVER) , Monte-Carlo, Monaco , March 31 - April 2, 2015.

In this article is presented the preliminary evaluation of the performance of radiation transmission of glass block, used in support of photovoltaic cells, investigating different internal surface points of the block, which are subject to different shading during daylight hours. The aim is to establish how the edging setting, the only opaque element, can reduce the amount of light radiation during the day, introducing in this way a reduction of efficiency of the entire generation system. The generation system can be based on traditional photovoltaic cells or on the most suitable dye sensitized solar cells. An experimental measurement setup employing a microprocessor-based instrument has been created and a set of measures have been carried out. The measures prove that the shading effect at different irradiation angles do not affect significantly the lighting over the PV cell.

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A unified framework for evaluating non-visual spectral effectiveness of ocular light exposure: key concepts

M. L. Ámundadóttir; S. W. Lockley; M. Andersen

2015. 28th CIE Session , Manchester, UK , June 29 - 4 July, 2015.

The first evidence for a novel type of photoreceptor in humans was published in the form of an action spectrum for melatonin suppression. This action spectrum has very different spectral sensitivities compared to rod and cone photoreceptors. This discovery led scientists to rethink how lighting needs for human health are evaluated. Existing literature provides useful information about how to evaluate and report non-visual spectral sensitivities to light but lacks a unified description. In this paper, key concepts in the existing methods are identified and categorized to formulate a unified framework to assess the non-visual potential of light that is adaptable to a wide range of lighting solutions.

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Assessing robustness regarding weather uncertainties for energy-efficiency-driven building refurbishments

G. Chinazzo; P. Rastogi; M. Andersen

2015. 6th International Building Physics Conference (IBPC 2015) , Torino, Italy , 14-17 June.

Conventionally, building energy performance is evaluated through energy simulations using a single input weather file referring to present weather conditions. However, the analysis shown in this study demonstrates the high sensitivity of calculated energy consumption to weather files chosen for simulation. Thus, we propose that multiple present and future weather files must be incorporated as random instances of an unknown population, i.e. the climate. This paper describes a methodology to assess the robustness of different energy efficient refurbishments over possible climate projections, by taking into account uncertainties in weather files. The innovation consists in the discussion of energy outcomes in terms of ranges instead of single values.

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Embedding Stochasticity in Building Simulation Through Synthetic Weather Files

P. Rastogi; M. Andersen

Proceedings of BS 2015. 2015. 14th International Conference of the International Building Performance Simulation Association , Hyderabad, India , December 7-9, 2015.

This paper presents an attempt to create synthetic weather data for stochastic building simulation. The synthetic data are created entirely from the freely available Typical Meteorological Year (TMY) weather files using time series models and resampling. The generated data turn out to be representative of recorded data for our case study without any prior ‘knowledge’ of the long term distributions of meteorological parameters. The current model does not address spells above or below some temperature of interest (e.g. heat waves), and the authors are working to incorporate that in future work. Another avenue for further exploration is modifying the mean to incorporate the results of Regional Climate Models for future conditions. Correlation of the synthetic data with synthetic solar radiation and humidity has been verified and the authors’ work with this ensemble of weather time series of interest will be presented in future publications.

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A parametric design-based methodology to visualize building performance at the neighborhood scale

G. Peronato; É. Nault; F. Cappelletti; F. Peron; M. Andersen

Building Simulation Applications BSA 2015 2nd IBPSA-Italy conference Bozen-Bolzano, 4th – 6th February 2015. 2015. Building Simulation Applications 2015 - 2nd IBPSA-Italy Conference , Bolzano/Bozen, Italy , February 4-6, 2015. p. 351-358.

This paper focuses on parametric design-­based visualization methods to represent building performance at the neighborhood scale in the perspective of an integrated design-support system. The goal of the developed methodology is to convey the relative effectiveness of different design alternatives according to a wide range of building performance indicators, including the potential for active solar applications, the energy need for space heating/cooling and (spatial) daylight autonomy The proposed methodology is applied to a case study of a typical urban renewal project in Switzerland for which several design variants were analyzed using validated climate-­based simulation engines. For each design variant, simulation results are represented qualitatively using multiple false-­color maps and quantitatively through comprehensive plots. We conclude by showing the applicability of this methodology to a large number of neighborhood-­scale design variants as well as the complementarity of the proposed visualization methods. On the basis of the case study application, a possible implementation as a design-­support tool is finally discussed.

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2014

Solar reflected glare affecting visual performance

L. Brotas; J. Wienold

2014. Windsor Conference 2014: Counting the Cost of Comfort in a Changing World , Windsor Park, United Kingdom , April 2014.

Visual comfort is important to the wellbeing of people and their productivity. However, too much light in the field of view can cause discomfort and disability glare. Under certain conditions it can even cause accidents. This paper addresses the disability glare created by veiling glare and the effect it may have of reducing the visual performance in outdoor spaces. Veiling glare is a particular case when light is reflected off a surface and causes annoyance or impairment of a task to the person in a particular view angle. Two factors that determine the nature and magnitude of veiling reflections are the specularity of the surface being viewed and the geometrical relationship between the observer, the surface and any source of high luminance. Different methods to assess disability glare exist but there is still no clear understanding on criteria to judge an outdoor scenario. A case study where reflected glare form Photovoltaics overlooking a building is of particular concern is presented.

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Concept, Design and Performance of a Shape Variable Mashrabiya as a Shading and Daylighting System for Arid Climates

B. Karamata; M. Andersen

30th PLEA Conference - SUSTAINABLE HABITAT FOR DEVELOPING SOCIETIES. 2014. 30th International Passive and Low Energy Architecture conference (PLEA 2014) , Ahmedabad, India , December 16-18, 2014. p. 344-351.

The design of a solar protection system that can minimize solar gains while maximizing daylight and view to the outside is particularly challenging in arid climates, such as in the Middle-East, where sand, wind and corrosion impose specific constraints. We propose a system that provides a trade-off for three requirements: (i) maximize diffuse sunlight and view to the outside, (ii) efficiently block direct sunlight and (iii) transform a fraction of it into diffuse light for indoor daylighting. Compliance with this last requirement provides a solution for the common problem of insufficient daylighting even in the presence of abundant solar radiation, which often forces occupants to fully close their shading system and use electric lighting. In addition, our design potentially copes well with these extreme environmental conditions and preserves local architectural character (mashrabiya-inspired design). In this paper, we establish quantitative specifications for these three requirements, provide the working principle of our shading and daylighting system and its design, which consists of a shape variable mashrabiya (SVM). We calculate and analyze the annual daylighting performance of our SVM and benchmark it against the performance of Venetian blinds and diffuse sunlight alone. Finally, we provide the minimum reflectance required for the SVM to comply with our third requirement. We built a mock-up of our SVM to investigate the validity of our simulation model.

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Stationary solar concentrator delivering beyond the étendue law with homogeneous illumination

B. Karamata; M. Andersen

2014 OSA Light, Energy and the Environment Congress. 2014. Optics for Solar Energy (SOLAR) in Light, Energy and the Environment Congress , Canberra, Australia , December 2-5, 2014.

We describe a concept for a novel stationary solar concentrator that relies on a new self-adaptive optical valve, non-imaging optics and the integrating sphere principle. Our analytical model reveals that this unique combination theoretically allows reaching a concentration up to around 9.5 suns, which a factor of 4.5x higher than the limit imposed by the fundamental étendue law, and provides perfect illumination homogeneity. These features are ideal to boost the performance of photocatalytic/photochemical reactors.

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A sensitivity analysis on glare detection parameters

M. Sarey Khanie; Y. Jia; J. Wienold; M. Andersen

2014. 13th International Radiance Workshop 2014 , London, UK , September, 1-3, 2014.

Maximizing daylight access while maintaining a glare-free indoor environment is an ongoing challenge for daylighting design. Glare is a discomfort sensation that is produced as a result of greater variation of luminance across the visual field than the one that the eye is adapted to. This type of discomfort sensation is one of the main drivers for building users' interaction with the façcade setting, which consequently can change the building's performance over time. Optimised integration of glare-free daylight solutions thus proves to be crucial for a sustainable building design. The existing methods for glare-free daylighting design rely on analyses on image-based advanced renderings with accurate simulation of light behaviour. These methods are becoming more commonly used for daylighting design using simulated three-dimensional geometrical model of the architectural space and employing tools such as Radaince for rendering the light. As convenient as this approach seems, it has complexities in attempts to define different components of the visual comfort metrics. One of these complexities is detecting the glary image pixels. The existing glare source detection methods consider any image pixel of luminance value that is x-times larger than the average luminance of a visual adaptation region as a potential glare source pixel. The method then searches the image based on a predefined search radius to find and combine all the glary pixels as one glare source. In this method, the value of the threshold multiplier and the search radius are decided intuitively based on the luminous environment of the studied scene. In this study we have made a sensitivity analysis on the threshold and search radius parameters for glare source pixels detection.

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2013

Bioclimatic Design in Casablanca (Morocco): Decision Support through Building Performance Simulation

S. Attia; G. Van Moeseke

2013. SUBTROPICAL CITIES , Fort Lauderdale, Florida , October 17-19, 2013.

In this paper, bioclimatic design strategies in Moroccan architecture have been analyzed for the city of Casablanca. The aim of this study is to enable architects to re-understand the lessons of tradition, because the way towards bioclimatic architecture should start by understanding vernacular architecture. The first part of the paper presents climate analysis and a set of bioclimatic principles addressing orientation, shading, thermal mass, insulation and natural ventilation as a mean for passive cooling. The second part explores the potential of implementing the Passivhaus Standard in Casablanca. Based on a validated building model, the performance of one of an apartment, satisfying the Passivhaus Standard has been determined by means of building performance simulation. The analysis evaluated different bioclimatic strategies and examined the transfer of the Passivhaus concept to hot warm climate, while ensuring thermal comfort during summer. Results showed that the studied building concept, comprising several bioclimatic design strategies can be transferred, with appropriate adaptations, also to hot climates. Finally the study developed significant recommendation that support architects with principles and strategies for bioclimatic design.

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The usability of green building rating systems in hot arid climates: A case study in Siwa, Egypt

S. Attia; M. Dabaieh

2013. SUBTROPICAL CITIES , Fort Lauderdale, Florida , October 17-19, 2013.

In the last three years there has been a proliferation of regional building rating systems across the Middle East. Most those emerging rating systems and labels imitate the British and American rating systems BREEAM and LEED that emerge from an impact reduction paradigm. Thus they are neglecting the local historic, climatic, economic, technological, cultural and social context. This paper presents two case studies of a recently constructed ecolodges in Siwa, Egypt, that performs beyond the existing rating systems requirements. The paper illustrates the environmental and sustainability design strategies adapted to El-Babinshal and Adrère Amellal buildings’ context. In this study, various design strategies are surveyed and their response to climate, occupants and society is evaluated. The paper presents a set of sustainability principles addressing (1) the site, (2) water, (3) energy, (4) resources, (5) comfort, (6) heritage and (7) social responsibility. In addition, the building is examined across the environmental criteria of LEED, Estidama and the Egyptian Green Pyramid Rating System. Results showed that the building failed to comply with the three rating systems despite winning the Egyptian Hassan Fathy Award for environmental design. The paper elaborates on this conflict and presents recommendations to improve the questioned rating systems and support architects with the principles and strategies for sustainable design.

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A review and analysis of parallel goniophotometry

B. Karamata; M. Andersen

LUXEUROPA 2013. 2013. LUXEUROPA 2013 -- the 12th European Lighting conference , Karakow (Poland) , September 17-19, 2013.

A reliable computer simulation of natural and artificial lighting of an indoor environment requires the thorough knowledge of the angular intensity distribution of light scattered or emitted by the various objects involved such as the illuminated surfaces, the trans-illuminated windows or fenestration systems, as well as the luminaires. The angular intensity distribution of light flux reflected, transmitted or emitted as a function of the illumination angle can be measured with an instrument called goniophotometer. Fast measurement, essential in most practical applications, requires the simultaneous detection of all scattering directions with a so-called parallel goniophotometer. In this paper we define and explain the three working principles on which a parallel goniophotometer can rest, namely (i) screen imaging, (ii) dioptric angular mapping, and (iii) catadioptric angular mapping. We provide a state-of-the-art of these instruments and compare their performance and limitations based on a few key parameters.

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Real-world tasks with full control over the visual scene: combining mobile gaze tracking and 4pi light-field measurements

J. Stoll; M. Sarey Khanie; S. Mende; J. Wienold; M. Andersen et al.

Book of abstracts: 17th EUROPEAN CONFERENCE ON EYE MOVEMENTS 11-16 August 2013, Lund, Sweden. 2013. 17th EUROPEAN CONFERENCE ON EYE MOVEMENTS (ECEM) , Lund, Sweden , August 11-16, 2013. p. 264.

Measuring gaze allocation during scene perception typically faces a dilemma: full control over the stimulus requires comparably constrained scenarios, while realistic tasks leave the visual input hard to control. We propose to capture the full (4pi) light-field of an oce space, while participants perform typical oce tasks. Using a wearable eye-tracking device ("EyeSeeCam"), gaze, head and body orientation are measured along with subjective well-being and performance. In the present study, 52 participants performed four oce tasks ("input", "reflection", "output", "interaction"), each with three dierent tools (phone, computer, paper) under varying lighting conditions and outside views. We found that eye and head were fundamentally differently affected by view and that this dependence was modulated by task and tool, unless participants' task was related to reading. Importantly, for some tasks head movements rather than eye movements dominated gaze allocation. Since head and body movements frequently remain unaddressed in eye-tracking studies, our data highlight the importance of unconstrained settings. Beyond assessing the interaction between top-down (task-related) and bottom-up (stimulus-related) factors for deploying gaze and attention under real-world conditions, such data are inevitable for realistic models of optimal workplace lighting and thus for the well-being of an occupant's workplace.

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Tool for Design Decision Making: Zero Energy Residential Buildings in Hot Humid Climate

S. Attia; E. Gratia; A. De Herde; J. Hensen

2013. BS2013: 13th International Conference of the International Building Performance Simulation Association , Chambery, France , August 26-30, 2013.

Informed decision-making is the basis for the design of Net Zero Energy Buildings (NZEBs). This paper investigates the use of building performance simulation tools as a method of informing the design decision of NZEBs. The aim of this study was to develop a design decision making tool, ZEBO, for zero energy residential buildings in hot climates and to evaluate the effect of a simulation-based decision aid, on informed decision-making using sensitivity analysis. An assessment of the role of the BPS tools used in informing the decision-making was ascertained through cases studies, usability testing and several self-reported metrics. The paper provides results that shed light on the effectiveness of sensitivity analysis as an approach for informing the design decisions of NZEBs

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Modeling dynamic aspects of human nonvisual responses to light

M. L. Ámundadóttir; M. A. Hilaire; S. W. Lockley; M. Andersen

2013. SLTBR 2013: 25th annual SLTBR meeting , Geneva, Switzerland , June 21-23, 2013.

Since 2002, when the first reports on the discovery of a novel type of mammalian ocular photoreceptor were published, a new field of study at the intersection of photobiology and architecture started to emerge. These novel non-rod, non-cone photoreceptors in the retinal ganglion cell layer are the primary mediators of nonvisual responses to light in humans, including synchronizing circadian rhythms and directly alerting the brain. This study aims to understand how these nonvisual responses evolve over time with respect to changes in the intensity, spectral composition and exposure duration of light stimuli. The ultimate goal is to incorporate these effects of light into building design. Recent studies in the field of photobiology provide us with information about the human nonvisual responses to light. Researchers have identified intensity, spectrum, duration, history and timing of light exposure as important parameters that influence the responsiveness of the nonvisual system. Experimental research quickly reaches its limitations, because it is infeasible to carry out a complete experiment with respect to all parameter combinations. Mathematical models are the method of choice to enable such analysis. A block-structured model is proposed that combines linear filters, a nonlinear term and a feedback mechanism. The linear filters reflect the temporal processing between the light stimulus and the output response. The nonlinear term is the sigmoid-shaped intensity-response curve that receives input from the feedback mechanism to regulate the system’s response with changes in prior light history and timing of circadian phase. Moreover, the spectral sensitivity of the nonvisual system is modeled as a time-varying function. Based on this model, which takes the intensity, spectrum and duration of light exposure into account, it is possible to compare the nonvisual efficiency of different spectra as a function of duration. Results demonstrate that duration is an important parameter in addition to spectral sensitivity when comparing nonvisual effects of different light sources at low light intensities. This model provides a framework that can inform designers about the effects of lighting on human health and wellbeing in real-life settings. The ultimate goal of this work is not to reveal the underlying functionality of the retina, but rather to predict human nonvisual responses to light using mathematical models and test the predictions experimentally. Modeling dynamic aspects of nonvisual responses to light is important to understand the dynamic relationship between light and human nonvisual responses that occurs in real-world settings.

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Measuring the Usability and Effectiveness of CAAD Tools and Applications

S. Attia; M. Andersen

2013. eCAADe 2013 - Computation and Performance , Delft, The Netherlands , September 18-20, 2013.

Computer Aided Architectural Design (CAAD) decisions and judgments have been at the heart of architectural design practice. Despite the increasing popularity of computer aided design applications, measuring the decision making of designers empirically remains elusive. Past research claiming usefulness of the CAD has relied largely on anecdotal or case studies that are vulnerable to bias. The study reviews results of prior investigations. The relatively few laboratory experiments report hardly any empirical results regarding the measurement of CAD decision making. The study provides an overview of the literature of existing measurement methods that have been used in psychology and neuroscience to assess individual variations in design making, and highlight these different measurement methods’ strengths and weaknesses. We conclude with a comparative evaluation of the different measures and provide suggestions regarding their constructive use in building realistic theories of designer’s decision making measurement.

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Achieving Informed Decision Making Using Building Performance Simulation

S. Attia

2013. eCAADe 2013 - Computation and Performance , Delft, The Netherlands , September 18-20, 2013.

Building performance simulation (BPS) is the basis for informed decision-making of Net Zero Energy Buildings (NZEBs) design. This paper aims to investigate the use of building performance simulation tools as a method of informing the design decision of NZEBs. The aim of this study is to evaluate the effect of a simulationbased decision aid, ZEBO, on informed decision-making using sensitivity analysis. The objective is to assess the effect of ZEBO and other building performance simulation (BPS) tools on three specific outcomes: (i) knowledge and satisfaction when using simulation for NZEB design; (ii) users’ decision-making attitudes and patterns, and (iii) performance robustness based on an energy analysis. The paper utilizes three design case studies comprising a framework to test the use of BPS tools. The paper provides results that shed light on the effectiveness of sensitivity analysis as an approach for informing the design decisions of NZEBs.

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Application of the Cradle to Cradle paradigm to a housing unit in Switzerland: Findings from a prototype design

S. Attia; J. F. Beney; M. Andersen

2013. PLEA 2013 - 29th Conference on Passive-Low Energy Architecture conference - Sustainable Architecture for a Renewable Future , Munich, Germany , September 10-12, 2013.

The Cradle to Cradle (C2C) paradigm is emerging as an important regenerative design approach. C2C is aiming to create a positive footprint of the built environment, beyond carbon neutrality. However, there are very few studies that address the application of the C2C concept in building design. More importantly, there is hardly any documentation processes on methods or tools currently being used to design and evaluate C2C buildings. Therefore, the purpose of this paper is to design, model and assess a C2C building prototype with a focus on energy and materials. The research methodology is based on literature review, case study design and performance (energy/materials) evaluation (DesignBuilder/SimaPro). The paper articulates the values, principles and goals of the C2C paradigm and translates them through the prototype design in the Swiss context. The results of the prototype design point to a 74% independence from non-renewable energy resources, compensating the operating and embodied energy during the building’s life. On the other hand only 8% of the building materials were totally recyclable according to the C2C principles. The design process delivers insights on the application of the C2C concept in the built environment reporting on the limitation and means of improvement.

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Early Decision Support for Net Zero Energy Buildings Design using Performance Simulation

S. Attia

2013. CISBAT 2013 - CleanTech for smartcities and buildings , Lausanne, Switzerland , September 4-6, 2013.

This paper aims to investigate the use of building performance simulation tools as a method of informing the design decision of NZEBs. The aim of this study is to evaluate the effect of a simulation-based decision aid, ZEBO, on informed decision-making using sensitivity analysis. The objective is to assess the effect of ZEBO and other BPS tools on three specific outcomes: (i) knowledge and satisfaction when using simulation for NZEB design; (ii) users’ decision-making attitudes and patterns, and (iii) performance robustness based on an energy analysis. The paper utilizes three design case studies comprising a framework to test the use of BPS tools. Two types of data were collected, mainly preference and performance data. The preference data were used to collect information from participants using self-reported metrics. The performance data were used to collect information on the energy performance of the final design. The energy evaluations were compared with the results of a quantitative assessment of the overall design performance. Finally the results were compared and presented. The paper provides results that shed light on the effectiveness of sensitivity analysis as an approach for informing the design decisions of NZEBs.

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Computational Optimisation for Zero Energy Buildings Design Interviews results with twenty eight International expert

S. Attia; M. Hamdy; W. O’Brien; S. Carlucci

2013. BS2013 - 13th International Conference of the International Building Performance Simulation Association , Chambery, France , August 26-30, 2013.

This paper summarizes a study that was undertaken to reveal potential challenges and opportunities for integrating optimisation tools in Net/Nearly Zero Energy Buildings (NZEB) Design. The paper reviews current trends in simulation-based Building Performance Optimisation (BPO) and outlines major criteria for optimisation tools selection and evaluation. This is based on analyzing users’ needs for tools capabilities and requirement specifications. The review is carried out by means of interviews with 28 optimisation experts. The findings are based on an inter-group comparison between experts. The aim is to assess the gaps and needs for integrating BPO tools in NZEB Design. The findings indicate existing limitations including model uncertainty, computation time, difficulty of implementation and steep learning curve. Future directions anticipated or needed for improvement of current tools are presented.

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Benchmark Models for Air Conditioned Residential Buildings in Hot Humid Climate

S. Attia; A. Evrard

2013. BS2013 - 13th International Conference of the International Building Performance Simulation Association , Chambery, France , August 26-30, 2013.

This study reports the results of a recent field survey for residential apartment buildings in Egypt. The aim of the survey is to create representative building energy models. Two building performance simulation models are created reflecting the average energy consumption characteristics of air-conditioned residential apartments in Alexandria, Cairo and Asyut. Aiming for future evaluation of the cost and energy affects of the new Egyptian energy standard this study established two detailed models describing the energy use profiles for air-conditioners, lighting, DHW and appliances in respect to buildings layout and construction. Using EnergyPlus simulation tool the collected surveyed data was used as input for two building simulation models. The simulation models were verified against the apartment characteristic found in the survey. This paper presents details of the building models including the energy use patterns and profiles created for this study.

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Integrating non-visual effects of light into lighting simulation: challenges ahead

M. L. Ámundadóttir; S. W. Lockley; M. Andersen

Proceedings of the 12th European Lighting Conference. 2013. LuxEuropa 2013: 12th European Lighting Conference , Krakow, Poland , September 17-19, 2013. p. 177-182.

Lighting is a major influential factor that affects human health and sense of wellbeing in the built environment. Since 2002, when the first reports on the discovery of a novel type of photoreceptor were published, a new field of study started to emerge at the intersection of photobiology and architecture. This novel photoreceptor is considered the primary mediator of non-visual responses to light in humans while the classical photoreceptors, rods and cones, are responsible for vision. Daily changes in the light spectrum and intensity impact a range of circadian, physiological and behavioral functions, including sleep quality, mood, alertness and cognitive performance. This new understanding on how light affects human physiology has sparked a growing interest in the role of lighting design on health and wellbeing. This paper discusses the challenges ahead in integrating non-visual effects of light – mediated by the novel photoreceptor – into a computer-based lighting simulation framework.

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Simulation-based evaluation of non-visual responses to daylight: proof-of-concept study of healthcare re-design

M. L. Ámundadóttir; S. W. Lockley; M. Andersen

2013. BS 2013: 13th International Conference of the International Building Performance Simulation Association , Chambery, France , August 26-30, 2013.

The discovery of a novel non-rod, non-cone photoreceptor in the human eye that mediates a number of effects on the brain has sparked a growing interest in incorporating these non-visual effects of light into the design process of buildings. Appropriately–timed light exposure has the potential to stabilize and improve circadian rhythms, including sleep, and has direct stimulating effects on alertness and performance. The novel photoreceptors are more sensitive to blue light than the rods and cones used for vision, and respond differently to light intensity, duration, history and timing of a light exposure. The dynamic behavior of the non–visual system provides new challenges in evaluating lighting performance of buildings. In this proof–of–concept study, a novel model that predicts the non–visual responses to light is introduced. The model is used as a part of simulation–based framework for the evaluation of daylighting performance. The evaluation includes four different light pattern generation methods used to investigate the influence of occupants’ movements and activities on simulation results. The framework is applied to the re–design of a healthcare facility. The results lead to new ideas and suggestions for future re–design.

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Revisiting parallel catadioptric goniophotometers

B. Karamata; M. Andersen

SPIE Optical Metrology 2013. 2013. SPIE Optical Metrology - Optical Measurement Systems For Industrial Inspection Viii , Münich, Germany , April 13-16, 2013.

DOI : 10.1117/12.2020561.

A thorough knowledge of the angular distribution of light scattered by an illuminated surface under different angles is essential in numerous industrial and research applications. Traditionally, the angular distribution of a reflected or transmitted light flux as function of the illumination angle, described by the Bidirectional Scattering Distribution Function (BSDF), is measured with a point-by-point scanning goniophotometer yielding impractically long acquisition times. Significantly faster measurements can be achieved by a device capable of simultaneously imaging the far-field distribution of light scattered by a sample onto a two-dimensional sensor array. Such an angular-to-spatial mapping function can be realized with a parallel catadioptric mapping goniophotometer (CMG). In this contribution, we formally establish the design requirement for a reliable CMG. Based on heuristic considerations we show that, to avoid degrading the angular-to-spatial function, the acceptance angle of the lens system inherent to a CMG must be smaller than 60 degrees. By means of a parametric study, we investigate the practical design limitations of a CMG caused by the constraints imposed by the properties of a real lens system. Our study reveals that the values of the key design parameters of a CMG fall within a relatively small range. This imposes the shape of the ellipsoidal reflector and drastically restricts the room for a design trade-off between the sample size and the angular resolution. We provide a quantitative analysis for the key parameters of a CMG for two relevant cases.

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Beyond illumination: An interactive simulation framework for non-visual and perceptual aspects of daylighting performance

M. Andersen; A. Guillemin; M. L. Ámundadóttir; S. F. Rockcastle

2013. BS2013 - 13th International Conference of the International Building Performance Simulation Association , Chambéry, France , August 26-30, 2013.

This paper presents a proof-of-concept for a goal-based simulation structure that could offer design support for daylighting performance aspects beyond conventional ones such as illumination, glare or solar gains. The framework uses a previously established visualization platform that simultaneously and interactively displays time-based daylighting performance alongside renderings, and relies on a goal-based approach. Two novel performance aspects are investigated in the present paper: health and delight. For the first aspect, drawing from the latest findings in photobiology in terms of effects on sleep, health and well-being, the goal is to integrate time-dependencies of non-visual responses to light into a dynamic light-response model for the non-visual system that can be part of a design process. For the second, the goal is to deepen our understanding of the perceptual qualities of daylight through a dynamic analysis of spatial contrast and its variability over time. The two approaches discussed in this paper introduce a new framework for the Lightsolve simulation environment that includes a Radiance calculation engine combined with an interactive visualization platform for temporal and spatial ‘distribution’ of performance.

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Lightsolve - a full-year goal-based tool for daylighting performance evaluation

M. Andersen; A. Guillemin; L. Cantelli

2013. CISBAT 2013 - CleanTech for smartcities and buildings , Lausanne, Switzerland , September 4-6, 2013.

Lightsolve is an innovative tool that offers architects and lighting engineers a goal-based simulation platform for daylighting performance evaluation in early stages of building design. Users can import their own 3D model and define their own design goals for a comprehensive spectrum of daylighting performance perspectives regarding task illumination, visual comfort, overheating risks, health effects and visual interest of a space. The tool provides key information to the designer that is easy and intuitive to grasp thanks to a combination of unique, visual and interactive graphical display formats. Available visualization options include photo-realistic renderings, full-year temporal performance representation as color maps, and spatial performance distribution through false-color renderings. Both model orientation and localization can be user-defined, and weather data (e.g. TMY) can be used to get climate-specific results. Accuracy is ensured by the usage of the ubiquitous and extensively validated Radiance simulation tool.

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Daylight dynamics to guide early stage design: a user-driven goal-based approach to “good” lighting

M. Andersen; A. Guillemin

2013. PLEA 2013 - 29th Conference on Passive-Low Energy Architecture conference - Sustainable Architecture for a Renewable Future , Munich, Germany , September 10-12, 2013.

More and more refined methods are currently being developed that aim to inform designers about daylighting management in a comprehensive way, many of which try to investigate annual daylighting potential through climate-based modeling. In this paper, we propose to address the issue of dealing with very different quantities all relevant to ‘good’ daylighting performance (illumination potential, glare risks, aesthetics, physiological effects of light) by resorting to a goal-based approach, so that such quantities or metrics can all be evaluated on a relative basis within a single simulation framework and a unique, intuitive and visual format. Specifically, the paper proposes to build upon the goal-based approach adopted by the Lightsolve simulation framework to bring together physical, physiological and perceptual aspects of light around the temporal variability of their effects. A prototype interface is presented that proposes an interactive, highly visual simulation environment in which to integrate these goal-based concepts. The paper also describes the premices of an expert system aiming to guide the user towards improved design solutions. The objective is to support early stage design regarding both conventional aspects of daylight performance such as workplane illuminance, glare and associated solar gains, and unconventional ones such as perceptual or non-visual effects of daylight, all considered in combination within a unified framework of analysis.

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Human-Driven Daylighting: research perspectives and outlook

M. Andersen

2013. 8th ENERGY FORUM on Advanced Building Skins , Bressanone, Italy , November 5-6, 2013.

Daylighting opens up a range of topics of investigation at the interface between architecture and building technology, especially when focusing on the integration of building performance in design. While it 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, which makes it both a challenging and essential aspect of how “performative” a space can be considered. This paper aims to provide an overview of research perspectives regarding how architectural design, building engineering and other domains of science could be more strongly bridged to address the need for meaningful metrics in architectural design and propose approaches to integrate the complexity of human needs in buildings into effective design and decision-making support.

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Identifying and modeling the integrated design process of net Zero Energy buildings

S. Attia; E. Walter; M. Andersen

2013. High Performance Buildings - Design and Evaluation Methodologies , Brussels, Belgium , June, 24-26, 2013.

High Performance Buildings (HPB), including Net Zero Energy Buildings (NZEBs) and nearly Zero Energy Buildings (nZEB) are emerging as an important market in Europe and around the world. However, there are very few studies that aim to model the process of HPBs and define key design processes, decisions and competencies of design teams. More importantly, there is hardly any documentation processes on tools currently being used to design high performance building. Therefore, the purpose of this paper is to identify, model and propose a generic integrated process maps for HPB. The generic process map focuses on the design phases steps, roles and tools used. The research methodology is based on literature review and a case study. With the help of a process modelling software (TIBCO), a Swiss office building (Green Office) is used to validate the produced process maps. The visual maps delivers insights on the integrated design process reporting on the means of improving the delivery of HPBs.

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Uncovering relationships between view direction patterns and glare perception in a daylit workspace

M. Sarey Khanie; J. Stoll; S. Mende; J. Wienold; W. Einhäuser et al.

2013. LUXEUROPA , Krakow, Poland , September 17-19,2013.

This paper presents the results of an experimental study that aims to provide objective insights as to how luminance distribution in an office setting modulates our view direction (VD) in a daylit workspace while performing office tasks. Using the office-like test facility at Fraunhofer ISE (Freiburg, Germany) to create a range of controlled daylighting conditions, and a wearable mobile eye-tracker to measure eye and head orientation, we assessed VD distributions for subjects performing a standardized sequence of typical office tasks relative to two different daylight conditions: low contrast condition with no direct sunlight as compared to high contrast condition with direct sunlight coming into the room. Our results show that while the participants look more outside the window during a non-cognitive and non-visual office task, this effect is lower under the high contrast lighting conditions. Moreover, the focus of the VDs is on the task area when the participants are performing a task involving visual and cognitive activities.

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Toward Assessing the Sensitivity of Buildings to Changes in Climate

P. Rastogi; S. F. Horn; M. Andersen

2013. PLEA 2013: 29th Passive and Low Energy Architecture Conference , Munich, Germany , 10-12 September, 2013.

Substantial numbers of existing and new buildings are expected to survive long enough to experience perceptible shifts in climate ‘normals’ (averages). To predict a building's response to changes in typical weather, two inputs are required: weather data representing this change, and suitable metrics to compare building performance across different climate normals. This paper presents initial work on a proposed method for assessing the sensitivity of new or existing buildings to climate change. This method begins with a selection of weather files to represent climate change, then quantities a building's passive performance in those climates using an enthalpy-based metric, and ends with a graphical analysis of the performance of the building in different climates to assess its robustness. In this paper, we propose an objective performance metric based on the extent to which a building creates indoor conditions passively, i.e. without auxiliary systems. Initial work suggests that the performance assessment carried out here is reproducible and applicable for indoor environment design and evaluation in different ranges of climate change. This approach enables a comparison of building performance without the bias introduced by inherent differences in climatic conditions.

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Early design phase evaluation of urban solar potential: Insights from the analysis of six projects

É. Nault; E. Rey; M. Andersen

2013. IBPSA 2013 - 13th International Conference of the International Building Performance Simulation Association , Chambéry, France , August 25-28, 2013.

This paper presents the outcome of a study based on the early-stage analysis of six virtual urban-scale designs located in Bern, Switzerland. A preliminary solar potential evaluation methodology is devised, inspired by previous studies, to allow the comparison of the projects’ potential for exploiting solar energy through passive (e.g. daylight) and active (e.g. photovoltaic) measures. The workflow employed distinguishes itself by integrating and confronting conflicting performance indicators and geometrical parameters. Findings show diversity in the performance among the different designs, while also highlighting the need to review the definition of urban solar potential and refine its assessment.

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Celebrating Contrast and Daylight Variability in Contemporary Architectural Design: A Typological Approach

S. F. Rockcastle; M. Andersen

2013. LUX EUROPA , Krakow, Poland , September 17-19, 2013.

The perceptual performance of architecture can be greatly altered by the ephemeral quality of daylight. Unlike artificial light sources, which can be adjusted to meet performance criteria regardless of geographic location and time of day, daylight is a variable source of illumination. When used to illuminate the static environment of a building, sunlight can dramatically alter our perception of interior architecture. Despite a wide range of daylight design strategies, neither high nor low levels of contrast and variability are synonymous with performance: it is the specific conditions that must be engaged appropriately within the context of each architectural work. While there have been several attempts at quantifying brightness and luminance diversity in daylit architecture (through the use of digital images), we have yet to see a method that can measure the spatial and temporal diversity of light within the visual field. In order to establish the importance of luminous composition within interior architecture, this paper presents a survey of contemporary architecture from around the world to develop a more effective vocabulary about contrast and temporal variability under daylight conditions. This survey allows us to grasp the broad range of design strategies employed within contemporary architecture and develop a matrix of contrast typologies against which each space could be compared on a relative scale from high to low. This matrix allows us to develop a precise language about the composition of perceptual luminosity within each space and helps architects to contextualize and compare the perceptual impacts of daylight within space.

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Generation of Weather Files Using Resampling Techniques: An Exploratory Study

P. Rastogi; M. Andersen

2013. Building Simulation 2013: 13th International Conference of the International Building Performance Simulation Association , Chambéry, France , August 25-28, 2013.

Simulating a building to predict its performance over the course of a full year requires an accurate representation of the stable and representative weather patterns of a location, i.e. a weather file. While weather file providers give due consideration to the stochastic nature of weather data, simulation is currently deterministic in the sense that using one weather file always generates one performance outcome (for a given set of building parameters). Using a single time series or aggregated number makes further analysis and decision-making simpler, but this overstates the certainty of the result of a simulation. In this paper, we investigate the advantages and disadvantages of incorporating resampling in the overall simulation workflow by comparing commonly used weather files with synthetic files created by resampling the temperature time series from the same weather files. While previous studies have quantified uncertainty in building simulation by looking at the calculation itself, this paper proposes a way of generating multiple synthetic weather files to obtain better estimates of expected performance. As case studies, we examined the performance of the ‘original’ and synthetic files for each of a sample of world climates.

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Investigation of gaze patterns in daylit workplaces: using eye-tracking methods to objectify view direction as a function of lighting conditions

M. Sarey Khanie; J. Stoll; S. Mende; J. Wienold; W. Einhäuser et al.

Proceedings of CIE Centenary Conference "Towards a New Century of Light". 2013. CIE Centenary Conference "Towards a New Century of Light" , Paris, France , 2013. p. 250-259.

Despite numerous efforts in developing glare indices through human assessment studies, predicting visual comfort in indoor environments still poses important challenges in design. A major limitation in discomfort glare indices is that they all ignore its dependencies on view direction. In this study we adopted eye-tracking methods in a series of human assessment experiments in order to record actual visual response when experiencing discomfort glare. We set up an experiment where the view directions distributions were monitored as the participants were working in a side-lit office with three different task-supports - monitor, paper and phone - on a standardized office task sequence. The participants were allocated randomly to two groups where they were exposed to two different views from the window. The results show that the “view outside the window” is the main determinant of view direction bias whenever the participant is not focused on any cognitive or visual office task procedure.

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Modeling non-visual responses to light: unifying spectral sensitivity and temporal characteristics in a single model structure

M. L. Ámundadóttir; M. A. Hilaire; S. W. Lockley; M. Andersen

2013. CIE Centenary Conference "Towards a New Century of Light" , Paris, France , April 15-16, 2013.

The discovery of a novel type of photoreceptor that mediates non-visual light responses in humans has sparked a growing interest in the role of lighting design on human health and wellbeing. Researchers have identified intensity, spectrum, duration/pattern, history, and timing of light exposure as important variables that control the responsiveness of the non- visual system. All of these variables need to be considered when developing a model of non- visual light responses. Currently, there is no mathematical model that incorporates all five variables to predict the non-visual effects of light on humans. In this paper, a modular model structure is proposed towards this end. The model is represented by a sequence of different blocks or elements. Based on a part of this model, which takes into account the intensity, spectrum, and duration of light exposure, it is possible to compare the spectra of different light sources in terms of non-visual driven efficiency. This model provides a framework that can inform designers about how lighting improves human health.

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Towards climate-based irradiation recommendations for optimal solar design: insights from a parametric study

É. Nault; E. Rey; M. Andersen

2013. sb13 - Sustainable Buildings: Implementing Sustainability, Barriers and Chances , Munich, Germany , April 24-26, 2013.

In the early phases of the building design process, decisions are made on certain geometrical parameters, which strongly dictate the future performance of the building. To support decision- making, an understanding of the relation between design parameters and performance is essential. This paper presents the results of two parametric studies conducted to investigate the impact of specific design parameters on three performance indicators related to solar potential and thermal and visual comfort. Results indicate which parameter has the strongest impact on each indicator and provide useful and potentially non-intuitive insights into the dynamics of building performance.

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2012

Limits and artefacts of reflective imaging goniophotometers for complex solar façade systems

B. Karamata; M. Andersen

EuroSun 2012. 2012. EuroSun 2012 - ISES Europe Solar Conference , Rijeka, Croatia , September 18-20, 2012.

The design of systems for solar light collection, modulation and/or distribution requires a thorough knowledge of their optical properties. The angular distribution of the scattered incident light flux, described by the Bidirectional Scattering Distribution Function (BSDF), can be measured with a step-by-step scanning goniophotometer but requires considerable time, especially when aiming at high angular resolution over a wide range and numerous incidence angles like in typical solar applications. Considerably faster measurements can be achieved with a so-called imaging goniophotometer, which simultaneously measures light fluxes in all scattered directions by dispatching them over different portions of a two-dimensional sensor array. In this contribution, we revisit the widely accepted principle of a reflective imaging goniophotometer (RIG), which is based on a hemispherical (or ellipsoidal) mirror and a fisheye camera. Specifically developed ray-tracing tools allowed us to obtain accurate figures relative to the influence of key design parameters on angular resolution. Our calculations reveal that the measurement accuracy is too low for samples larger than a few tens of millimeters. Most importantly, we found significant limitations and artefacts in the angular-to-spatial mapping function inherent to the RIG principle, which generally severely bias BSDF measurements.

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Prescribing for Daylight: Can We Account for the Disparate Measures Within A Unified Framework?

J. Mardaljevic; M. Andersen

Proceedings of Experiencing Light 2012 conference. 2012. Experiencing Light 2012 conference , Eindhoven, The Netherlands , November 12-13, 2012.

The potential for a building design to provide daylight for general illumination was, until very recently, evaluated using only the daylight factor, i.e. a ratio of internal to external illumination under a single standardised overcast sky. Other known effects of daylight, such as the occurrence of visual discomfort which is more likely to occur during non-overcast conditions, were assessed or estimated by other means, often relying more on the skill of the experienced lighting designer than by use of a repeatable set procedure. In the last few decades there has been a gradual increase in awareness of the non-visual effects of daylight/light received by the eye Webb (2006). The quality and nature of the internal daylit environment is believed to have a significant effect on human health in addition to general well-being and worker productivity. Demonstrating compliance with various guidelines at the design stage is an ever increasing concern. For daylight this is invariably carried out nowadays using simulation rather than scale models. After many decades of reliance on the daylight factor as the sole quantitative daylight metric, there has been an explosion of activity in daylight modelling research which has delivered numerous new techniques, approaches and metrics. This paper describes various end-user requirements - both current and emerging - for daylight modelling and discusses how these might be accommodated within a single modelling framework.

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User-based evaluation of an interactive expert system for full-year daylighting design support

J. M. L. Gagne; M. Andersen

Proceedings of the Building Simulation and Optimization Conference BSO12. 2012. Building Simulation and Optimization Conference BSO12 , Loughborough, UK , September 10-11, 2012.

This paper presents the results of an original design process-oriented user study conducted on an interactive expert system specifically developed for full year, climate-based daylighting design support. The aim of the study was to determine how well its decision-making algorithm would work when independent human interactions and decisions were included into the process through a two-step process, first based on design heuristics then using the expert system. The results of this evaluation demonstrate that the expert system is generally successful as a performance-driven design tool and as a method for influencing and educating designers in ways that they can improve the daylighting performance of their designs. It also demonstrates the relevance of the proposed user study to validate design support tools that account for the unpredictability of the inherently ill-defined architectural design process itself.

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Daylighting Metrics: Is there a relation between Useful Daylight Illuminance and Daylight Glare Probabilty?

J. Mardaljevic; M. Andersen; N. Roy; J. Christoffersen

Proceedings of the Building Simulation and Optimization Conference BSO12. 2012. Building Simulation and Optimization Conference BSO12 , Loughborough, UK , September 10-11, 2012.

The establishment of climate-based daylight modeling within research and practice has led to a fundamental reassessment of both the basis and purpose of daylight metrics. Whilst there is no consensus yet on the precise nature of the metric(s) that should replace the daylight factor, it is generally agreed that these should be founded on climate-based daylight modeling (CBDM). In this paper we examine the relation between the predicted annual occurrence of glare and one of the candidate CBDM metrics that has been proposed, called useful daylight illuminance (UDI). The purpose is to determine if one or more of the UDI metrics (predicted for the horizontal workplane) could serve as a proxy for the probability of daylight glare (i.e. a measure of vertical illuminance received at the eye). For glare we use the simplified daylight glare probability model. The setting is a residential building which we use as a ‘virtual laboratory’ in two design configurations, each evaluated under all 32 combinations of 8 European climates and 4 building orientations.

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Dynamic Annual Metrics for Contrast in Daylit Architecture

S. Rockcastle; M. Andersen

Proceedings of SimAUD 2012 - Symposium on Simulation for Architecture and Urban Design. 2012. SimAUD 2012 - Symposium on Simulation for Architecture and Urban Design , Orlando, Florida, USA , March 26-30, 2012.

Daylight is a dynamic source of illumination in architectural space, creating diverse and ephemeral configurations of light and shadow within the built environment. It can generate contrasting levels of brightness between distinct geometries or it can highlight smooth gradients of texture and color within the visual field. Although there are a growing number of studies that seek to define the relationship between brightness, contrast, and lighting quality, the dynamic role of daylight within the visual field is underrepresented by existing metrics. This study proposes a new family of metrics that quantify the magnitude of contrast-based visual effects and time-based variation within daylit space through the use of time-segmented daylight renderings. This paper will introduce two new annual metrics; Annual Spatial Contrast and Annual Luminance Variability. These metrics will be applied to a series of abstract case studies to evaluate their effectiveness in comparing annual contrast-based visual effects.

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Practical and Policy-Relevant Performance Metrics for Complex Fenestration Systems

S. Dave; M. Andersen

Proceedings of the 2012 ASHRAE Winter Conference. 2012. 2012 ASHRAE Winter Conference , Chicago, Illinois, USA , January 21-25, 2012.

The selection of a fenestration system for a building is critical, as it impacts energy performance, occupant comfort, and ambiance of a space. Complex Fenestration Systems (CFS) address these criteria using a wide variety of novel technologies but are difficult to define or be characterized. Existing metrics for fenestration systems are unable to reveal the dynamics or degree of variety over climate conditions or time of year that define CFS because they rely on a single and arbitrarily-defined set of environmental conditions to calculate. Although the optical characteristics of a CFS can be predicted using its Bi-Directional Transmission Distribution Function (BTDF) – a mathematical dataset that describes the angular distribution of light flux as it passes through a material – this information is too abstract to be meaningful to the building industry. A set of metrics that uses the BTDF in an intuitive way could allow the performance and physical characteristics of these technologies to become more accessible, ultimately allowing the various benefits of daylighting to be realized. The proposed approach offers a solution to this problem by using an annual climate-based methodology to provide a comprehensive evaluation of a system by incorporating three of the most relevant performance aspects: energy efficiency, occupant visual comfort, and ability to view through. Three metrics, the Relative Energy Impact (REI), the Extent of Comfortable Daylight (ECD), and the View Through Potential (VTP), were derived from these three criteria to express, in relative terms, a façade’s contribution to building energy use, the fraction of time and space for which it achieves comfortable daylight conditions, and the degree of transparency as it relates to an occupant’s view through the façade, respectively. These metrics are intended to exist as a mechanism by which manufacturers can evaluate and compare façade systems, provide high-level intuition of relative performance for designers and contractors, and enable the balance of performance objectives based on user preference. In order to successfully implement these metrics, a simple and repeatable calculation process was identified first through a series of sensitivity analyses compromising on relevance or accuracy, and then by defining input conditions that are able to reduce calculation or simulation time substantially. Using both approaches, each of these metrics was further and applied to five sample façades that cover a broad range of Complex Fenestration System types, including a validation study for the VTP metric. A visual representation of this information in a condensed format was then investigated so as to allow straightforward comparisons amongst systems and a synthetic understanding of their performance. A graphical, label-like structure could indeed provide an initial suggestion for the use of these metrics in the rating and standard-setting environments.

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2011

Daylighting Metrics for Residential Buildings

J. Mardaljevic; M. Andersen; N. Roy; J. Christoffersen

Proceedings of the 27th Session of the CIE. 2011. 27th Session of the CIE , Sun City, South Africa , July 11-15, 2011.

It is now widely accepted that the standard method for daylighting evaluation - the daylight factor – is due for replacement with metrics founded on absolute values for luminous quantities predicted over the course of a full year using sun and sky conditions derived from standardised climate files. The move to more realistic measures of daylighting introduces significant levels of additional complexity in both the simulation of the luminous quantities and the reduction of the simulation data to readily intelligible metrics. The simulation component, at least for buildings with standard glazing materials, is reasonably well understood. There is no consensus however on the composition of the metrics, and their formulation is an ongoing area of active research. Additionally, non-domestic and residential buildings present very different evaluation scenarios and it is not yet clear if a single metric would be applicable to both. This study uses a domestic dwelling as the setting to investigate and explore the applicability of daylighting metrics for residential buildings. In addition to daylighting provision for task and disclosing the potential for reducing electric lighting usage, we also investigate the formulation of metrics for non-visual effects such as entrainment of the circadian system.

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Informing well-balanced daylight design using Lightsolve

M. Andersen; J. L. Gagne; S. Kleindienst

2011. CISBAT 11 - CleanTech for Sustainable Buildings - From Nano to Urban Scale , Lausanne, Switzerland , September 14-15, 2011.

Designing spaces that are able to balance illumination, glare and solar gains over a whole year is a real challenge, yet a problem faced every day by building envelope designers. To assist them in this search, a full year, climate-based daylighting simulation method was developed, called Lightsolve, meant to be used early on in the design process when façade and space details have not yet been defined. It focuses on the variation of daylight performance over the day and the year, combining temporal performance visualization with spatial renderings, and including an expert system to support a guided search process. This paper describes the foundations and set of innovative simulation resources that Lightsolve offers as a whole, and puts its different components - including a time reduction method, a set of three goal-based metrics and an expert system - back to Lightsolve’s overall context aiming to an early stage, comprehensive, prospective support for daylighting design.

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Integration of Eye-tracking Methods in Visual Comfort Assessments

M. Sarey Khanie; M. Andersen; B. M. 't Hart; J. Stoll; W. Einhäuser

2011. CISBAT 11: CleanTech for Sustainable Buildings - From Nano to Urban Scale , Lausanne, Switzerland , September 14-15, 2011.

Discomfort glare, among different aspects of visual discomfort is a phenomenon which is little understood and hard to quantify. As this phenomenon is dependent on the building occupant’s view direction and on the relative position of the glare source, a deeper knowledge of one’s visual behavior within a space could provide pertinent insights into better understanding glare. To address this need, we set up an experiment to investigate dependencies of view direction distribution to a selected range of brightness and contrast distributions in a standard office scenario. The participants were asked to perform a series of tasks including reading, thinking, filling in a questionnaire and waiting. The direction of their view was monitored by recording participants’ eye movements using eye-tracking methods. Preliminary results show that different facade configurations have different effects on the eye movement patterns, with a strong dependency on the performed task. This pilot study will serve as a first step to integrate eye-tracking methods into visual comfort assessments and lead to a better understanding of the impact of discomfort glare on visual behavior.

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Streamlining Access to Informative Performance Metrics for Complex Fenestration Systems

S. Dave; M. Andersen

Proceedings of CISBAT 11: CleanTech for Sustainable Buildings - From Nano to Urban Scale. 2011. CISBAT 11: CleanTech for Sustainable Buildings - From Nano to Urban Scale , Lausanne, Switzerland , September 14-15, 2011.

A mechanism to accurately assess the performance of complex fenestration systems (CFS) is crucial for driving the appropriate adoption of these technologies to improve user comfort and energy use in both new construction and retrofit design. Typically, CFS are not provided sufficient consideration because user intuition is lacking: existing metrics, while valid for conventional systems, fail to reveal the dynamic nature of the performance of CFS. Conducting and reporting elaborate simulation results is neither feasible nor useful for manufacturers and users and thus a comprehensive rating system based on novel performance metrics has been identified as a means to describe CFS. This paper describes the methodology used to determine the simplified calculation procedure for three metrics defined in a previous paper, and the rational for the ultimate decision. The three metrics, the Relative Energy Impact (REI), the Extent of Comfortable Daylight (ECD), and the View-Through Potential (VTP) aim to provide context in three important areas of daylighting technology performance, namely energy efficiency, occupant visual comfort, and view through the facade respectively, such that the user can select systems to address his or her own priorities. Conducting and reporting full resolution calculations for all input conditions would be unfeasible and unwieldy because of the quantity of data that would have to be managed and the effort that would be spent on such en enterprise for every system. A method to eliminate redundancies and minimize the number of input parameters and calculations thus becomes necessary. This paper proposes an approach based on trends, sensitivity analysis, and error minimization techniques and presents the iterative simplifications required to produce the same relative ranking performance of the sample systems as a benchmark analysis would.

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Climate-based Daylight Performance: Balancing Visual and Non-visual Aspects of Light Input

M. Andersen; J. Mardaljevic; N. Roy; J. Christoffersen

2011. CISBAT 11 - CleanTech for Sustainable Buildings - From Nano to Urban Scale , EPFL, Lausanne, Switzerland , September 14-15, 2011.

This study uses a domestic dwelling as the setting to investigate and explore the applicability of daylighting metrics for residential buildings, including the formulation of metrics for nonvisual effects. The simulation approach used to generate the performance data from which the metrics are derived is called climate-based daylight modelling (CBDM). This approach delivers predictions of various luminous quantities using sun and sky conditions that are derived from standardised annual meteorological datasets. Although there are uncertainties regarding the precise calibration, there is now sufficient empirical data to parameterise models that also simulate the non-visual aspects of daylight, e.g. for circadian entrainment and a general sense of "alertness". For these non-visual aspects, vertical illuminance at the eye was predicted using a modified climate-based daylight modelling approach. In the paper, we consider what relation there might be between the three aspects of daylight provision and if these relations appear to be complementary or conflicting in nature: for task; to reduce electric lighting usage; and, for non-visual effects. The implications for future building guidelines for daylighting are also discussed.

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A Novel Louver System for Increasing Daylight Usage in Buildings

K. Thuot; M. Andersen

Proceedings of PLEA. 2011. PLEA 2011 - Architecture and Sustainable Development , Louvain-la-Neuve, Belgium , July 13-15, 2011.

Advanced daylighting systems can be effective in increasing light levels in building spaces and reducing energy consumption due to electric lighting. However, a recurring issue found in most existing daylighting systems is the necessity of coupling the light-redirecting technology with a separate light shade to reduce glare risks. A different approach is proposed here, based on the use of a louver system which scatters incoming light onto a reflective ceiling, where it is redirected deep into the space. This type of system is effective for both diffuse daylight and direct sunlight without causing glare and without the need for a shading system. Annual simulations of workplane illuminance were conducted with Radiance using Tokyo weather data and a generic south-facing deep-plan office space. Glare was evaluated through testing of a physical prototype of the system. The new system was compared to a base case consisting of an unshaded window of equal area to the louver system. The results show that the novel louver system enables a significant decrease in electric lighting usage and outperforms the uncovered window, while adequately controlling direct sunlight to prevent glare.

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An Interactive Performance-Based Expert System for Daylighting Design

J. L. Gagne; M. Andersen

Proceedings of PLEA. 2011. PLEA 2011 - Architecture and Sustainable Development , Louvain-la-Neuve, Belgium , July 13-15, 2011.

Architects are increasingly using digital tools during the design process, particularly as they approach complex problems such as designing for successful daylighting performance. However, while simulation tools may provide the designer with valuable information, they do not necessarily guide the user towards design changes which will improve performance. This paper proposes an interactive, goal-based expert system for daylighting design, intended for use during the early design phase. The expert system consists of two major components: a daylighting knowledge-base which contains information regarding the effects of a variety of design conditions on resultant daylighting performance, and a fuzzy rule-based decision-making logic which is used to determine those design changes most likely to improve performance for a given design. The system gives the user the ability to input an initial model and a set of daylighting performance goals in the form of illuminance and daylighting-specific glare metrics. The system acts as a “virtual daylighting consultant,” guiding the user towards improved performance while maintaining the integrity of the original design and of the design process itself.

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A comprehensive method to determine performance metrics for complex fenestration systems

S. Dave; M. Andersen

Proceedings of PLEA. 2011. PLEA 2011 - Architecture and Sustainable Development , Louvain-la-Neuve, Belgium , July 13-15, 2011.

The ability to accurately and concisely describe the performance of complex fenestration systems (CFS) is essential to their effective implementation into the building industry. CFS are a diverse category of daylighting technologies that manipulate the light that is permitted to enter a building space. The variety and degree of dynamics that exist in the range of such technologies require a robust and flexible set of metrics that can communicate performance simply and informatively. This paper presents an approach for processing their detailed optical properties - expressed as Bi-Directional Transmission Functions (BTDF) - into a comprehensible set of metrics that can convey useful information about a system’s adherence to visual comfort and energy-efficiency objectives. These metrics can then inform non-technical members of the building industry about the performance capabilities of a façade. This paper describes the novel method by which performance is evaluated, accounting for spatial and temporal variation in environmental condition.

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2010

Solar Heat Surplus and Solar Heat Scarcity: the Inclusion of Solar Heat Gain in a Dynamic and Holistic Daylight Analysis

S. Kleindienst; M. Andersen

Proceedings of SimBuild 2010 - 4th National Conference of IBPSA-USA. 2010. SimBuild 2010 - 4th National Conference of IBPSA-USA , New York , August 11-13, 2010.

Solar heat gain is one of the tradeoffs associated with using natural light, and should be considered in any complete daylighting analysis. Because the non-spatial aspect of solar heat gain makes it more difficult to analyze along side illuminance or glare, this paper uses time-variant graphics as a basis of comparison. This paper also introduces a new goal-based solar heat gain metric, Solar Heat Scarcity and Surplus, which was inspired by the balance point analysis method. Although dynamic energy analyses should ultimately be used in determining energy loads, balance point can be as useful indicator in the earliest stages of design. The applicability of this metric to inform design through a validation with the recently released 16 DOE Benchmark Commercial Buildings is discussed, and as a proof of concept, the Solar Heat Scarcity and Surplus metric is applied to a simple options analysis. Scarcity and Surplus metric is applied to a simple options analysis.

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Multi-Objective Façade Optimization for Daylighting Design Using a Genetic Algorithm

J. M. L. Gagne; M. Andersen

Proceedings of SimBuild 2010 - 4th National Conference of IBPSA-USA. 2010. SimBuild 2010 - 4th National Conference of IBPSA-USA , New York , August 11-13, 2010.

A building’s facade design has significant impact on the daylighting performance of interior spaces. This paper presents a tool based on a genetic algorithm (GA) which facilitates exploration of facade designs generated based on illuminance and/or glare objectives. The method allows a user to input an original 3d massing model and performance goals. The method assumes that the overall building form remains the same while the facade elements may change. Ten facade parameters are considered, including glazing materials and geometric characteristics of apertures and shading devices. A simple building information model (BIM) is used to automatically generate a 3d model of each individual. Results from single and multi-objective case studies are presented to demonstrate a successful goal-driven design exploration process.

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2009

Sustainability through Light: A Contemporary Approach to Articulate Design and Technology

R. Urbano-Gutiérrez; M. Andersen

Proceedings of Lux Europa 2009 – 11th European Lighting Conference. 2009. Lux Europa 2009 – 11th European Lighting Conference , Istanbul, Turkey , September 9-11, 2009.

This paper describes the concept, design and development process of an interactive and immersive exhibition on state-of-the-art façade technologies for advanced daylighting control. Its aim is to propose an effective, informative and interactive experience that increases the awareness and understanding of designers and the general public about advanced daylighting strategies. This exhibition will focus on revealing their performance while emphasizing their key role in integrating sustainability in architecture. It will use tactic installations of these materials and assemblies to get architects to explore the fascinating spatial design opportunities enabled by their capabilities to control daylight and solar radiation. Visitors will interact with these technologies by walking through the space and getting to understand the basic principles of daylighting and the potential of these technologies through custom installations and case studies, using digital and analog media. The exhibition presents an opportunity to use a real space as a case study and a laboratory for new applications of these materials. The ultimate goal of this research project is to serve as an efficient didactic instrument to connect design, technology and industry at national and international levels.

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The Adaptation of Daylight Glare Probability to Dynamic Metrics in a Computational Setting

S. Kleindienst; M. Andersen

Proceedings of Lux Europa 2009 – 11th European Lighting Conference. 2009. Lux Europa 2009 – 11th European Lighting Conference , Istanbul, Turkey , September 9-11, 2009.

Because nearly all existing glare equations depend on source size, relative position, and luminance, predicting glare in daylighting software generally requires the pixel-processing of a rendered image meant to reproduce a human’s view. When considering multiple positions, views, and times of day and year, making an annual assessment of glare becomes prohibitively time consuming using traditional methods. Using the recently developed metric Daylight Glare Probability as a reference, this paper builds upon an existing approximation method for DGP based on vertical illuminance. The existing method performs well for glare situations based on high vertical illuminance but is less accurate for luminance contrast-based glare. The approach that is presented here suggests a way to overcome these weaknesses by using geometric information and illuminance data generated from the computer model.

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User Assessment of a New Interactive Graphical Visualization for Annual Daylighting Analysis

S. Kleindienst; M. Andersen

Proceedings of CISBAT 2009 - Renewables in a Changing Climate: From Nano to Urban Scale. 2009. CISBAT 2009 - Renewables in a Changing Climate: From Nano to Urban Scale , Lausanne, Switzerland , Sept 2-3, 2009.

Despite the abundance of daylighting design software, there are few tools which focus on annually comprehensive and climate-realistic data, and fewer which give performance as a function of time. Lightsolve, a tool under development, emphasizes the importance of full year, climate specific data in early stage daylight design. It performs a representative group of annual simulations based on TMY2 data and graphically displays the results using both temporal maps and spatial renderings. With any new method, it is critical to determine if the intended audience finds it more useful than existing methods. Therefore, two user surveys were given. The first was given to practitioners and students attending a daylighting design workshop at MIT in January of 2009. Participants were taught to use both Lightsolve and Ecotect (with exports to Radiance and Daysim). The aim of this survey was to help validate the usefulness of Lightsolve’s temporal approach and the intuitive nature of the temporal maps, and to observe architects’ interaction with the software. Because of the limited number of responses, a different stand-alone survey comparing spatial and temporal daylighting data was given, mostly to student architects, in May of 2009. The aim was to judge how intuitive temporal data was to the inexperienced architect. This paper presents the findings of both surveys.

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Circadian Effects of Daylighting in a Residential Environment

S. J. Gochenour; M. Andersen

Proceedings of Lux Europa. 2009. Lux Europa 2009 – 11th European Lighting Conference , Istanbul , September 9-11, 2009.

This paper examines the effects of housing design upon the amount of natural light available for cuing of the human circadian system. It further assesses whether the conditions present in historic Boston row houses, when considered in the context of human moving around, can be adapted to provide sufficient light to maintain occupants' circadian rhythms. While software has been developed to simulate the amount of light in lux or lumens being received on a sensor point, these programs have generally been used to calculate the light received on a static, horizontal surface, such as a desk or other workspace. For the sake of determining a room's circadian potential, however, the sensor used must be vertical, as is the human eye during the day, and must be able to both rotate and translate – i.e. it must move forward and backward in a room and turn to face different viewpoints, as a human user does. Based on a series of simulations which take into account these factors it is possible to offer suggestions for both restoration and future design.

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A Simulation-Based Expert System for Daylighting Design

J. M. Lee; M. Andersen

Proceedings of Lux Europa. 2009. Lux Europa 2009 – 11th European Lighting Conference , Istanbul , September 9-11, 2009.

In this paper, we propose an expert system for daylighting in architecture which is used to guide a goal-oriented, user-interactive design process. This system is supported by a knowledge-base which has been populated using a set of previously completed simulations using the Design of Experiments methodology. The knowledge-base contains information regarding the effects of a variety of design conditions on resultant daylighting performance. Eighty different design conditions are considered, encompassing two different values of ten design variables on four facades. Daylighting effects are considered for three times of day, for three seasons, and for five zones. The use of the knowledge-base as both a stand-alone resource and as a component of the expert system is considered. Within the expert system, the knowledge-base provides customized information based on user inputs and guides an iterative process which improves daylighting performance of the user’s original design.

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Goal-Based Daylighting Design Using an Interactive Simulation Method

J. Lee; M. Andersen; Y. Sheng; B. Cutler

Proceedings of IBPSA 2009 - 11th International Building Performance Simulation Association Conference. 2009. IBPSA 2009 - 11th International Building Performance Simulation Association Conference , Glasgow , July 27-30, 2009.

This paper proposes an interactive goal-based method for designing day lit buildings. The lighting simulation tool which supports this process is a hybrid global illumination rendering method which efficiently computes annual daylighting metrics. The goal-based method uses a knowledge base populated using a set of previously completed simulations that quantify the effects of various façade design modifications. The knowledge base guides a simple algorithm over an iterative design process. The current knowledge base includes information about window size, shape, location on the façade, and simple shading devices. Three case studies are given in which this iterative optimization method was applied; all resulted in improved daylighting performance.

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A first application of the Lightsolve approach: Pre-design of the new Belgian VELUX headquarters

M. Bodart; C. Cauwerts; M. Andersen

Proceedings of PLEA 2009 - Architecture Energy and the Occupant's Perspective. 2009. PLEA 2009 - Architecture Energy and the Occupant's Perspective , Québec City, Canada , June 22-24, 2009.

This study presents the application of the “Lightsolve” method on the pre-design of a new sustainable building in order to optimize its daylighting. At the time of the project, this method combined climate-based illuminance and glare evaluations with visual renderings. Illuminances were presented according to a goal-oriented approach and glare was evaluated through the DGP. Both were displayed on temporal maps. The Lightsolve method was used to size lateral and zenithal openings and shading devices. A first conclusion of the study is that it is necessary to couple daylight metrics with a solar gain metric. Comparison between Lightsolve and daylight methods used in rating systems showed that these ones do not give enough accurate information for optimizing the daylighting design. Designer’s satisfaction evaluation showed that the goal-oriented approach and the temporal map representation were appreciated although this latter was rather difficult to understand. It also showed that an expert tool should be proposed in order to help designers to analyse their results. Finally, it was pointed out that the quality of daylight should be evaluated in Lightsolve, which will be done through a PhD work.

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2008

Application of the Lightsolve methodology for the pre-design of the new Belgian VELUX headquarters

M. Bodart; C. Cauwerts; M. Andersen

Proceedings of Building Physics Symposium. 2008. Building Physics Symposium , Leuven, Belgium , Oct 29-31, 2008.

Through the example of the VELUXBelgium building, this paper presents a real case application of a new methodology that is being developed to favor an interactive and intuitive approach of daylighting in buildings in the schematic design phase. The Lightsolve method, under development, is based on an interactive goal-oriented approach, and provides visual representations of annual, climate-based data that rely on a combination of sky distributions using the ASRC-CIE model. This paper focuses on the use of graphical representation of climate-based daylight performance metrics (illuminance and glare metrics) combined with luminance renderings for evaluating the design options occurring during the pre-design stage of the building.

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Prospective evaluation of the Circadian Efficacy of (Day)Light in Rooms

C. Pechacek; M. Andersen; S. W. Lockley

Proceedings of the IESNA 2008 conference. 2008. IESNA 2008 conference , Savannah GA , Nov 9-11, 2008.

Recent studies have attempted to link environmental cues, such as lighting, with human performance and health, and initial findings seem to indicate a positive correlation between the two. Light is the major environmental time cue that resets the human circadian pacemaker, an endogenous clock in the hypothalamus that controls the timing of many 24-hour rhythms in physiology and behavior. Insufficient or inappropriate light exposure can disrupt normal circadian rhythms which may result in adverse consequences for human performance, health and safety. This paper addresses the problem of prospective analysis of building architecture for circadian stimulus potential based on the state of the art in photobiology. Three variables were considered in this analysis: lighting intensity, timing, and spectrum. Intensity is a standard design tool frequently used in illuminating engineering. Timing and spectrum are not commonplace considerations, so the analysis that follows proposes tools to quantitatively address these additional requirements. Outcomes of photobiology research were used in this paper to define threshold values for illumination in terms of spectrum, intensity, and timing of light at the human eye, and were translated into goals for simulation – and ultimately for building design. In particular, the climate-based Daylight Autonomy (DA) metric was chosen to simulate the probabilistic and temporal potential of daylight for human health needs. The developed method was applied to study the impact of key architectural decisions on achieving prescribed stimulus of the circadian system in a hospital patient room design; studied variables included orientation, window size, and glazing material. A healthcare setting was specifically chosen with the intent of follow-on research to validate our findings with actual patient outcome data.

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Assessing Solar Bidirectional Light Distribution with the Heliodome

M. Andersen; E. Stokes; N. Gayeski

2008. IESNA 2008 - Illuminating Engineering Society Of North America Annual Conference , Savannah GA , November 9-11, 2008.

A large variety of angularly selective fenestration systems has been developed in the past two decades and shows great potential in improving visual comfort while reducing energy consumption, especially when combined with spectrally selective properties. Such systems include light-redirecting glazing, shading, film coatings, reflectors and others. To assess the potential of these systems accurately and reliably, one needs to be able to predict in detail how they modify the energy, direction, and spectral make-up of solar radiation. For this assessment, spectral (wavelength-dependent) Bidirectional Transmission or Reflection Distribution Functions are used, usually referred to as BTDFs or BRDFs, or more generally BSDFs for Scattering Functions. To enable a faster, cheaper, and continuous investigation of these properties over most of the solar spectrum (400 to 1700 nm), an innovative goniospectrometric instrument has been created, relying on digital imaging, on light collection by an ellipsoidal half-transparent mirror, and on a filtering method in the visible range to generate spectral radiometric BSDFs. This so-called Heliodome instrument is described in this paper. It enables the performance of new fenestration technologies to be assessed in terms of lighting and solar gains management potential. Its major innovations compared to other devices are to enable an analysis of both the visible and the near-infrared portions of the solar spectrum, to provide spectral as well as photometric light distribution data, and to ensure a continuous investigation of the transmitted or reflected light in a time-efficient way.

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D-LITE: a new perspective for searching and selecting light-control technologies as a designer

R. Urbano Gutiérrez; M. Andersen

Proceedings of the PLEA 2008 conference. 2008. PLEA 2008 conference , Dublin , Oct 22-24, 2008.

Even though a large variety of innovative façade technologies has been developed to refine the control of solar radiation and increase the amount of useful natural illumination, their effective implementation in buildings is still uncommon. Increasing the awareness of designers to their existence and facilitating an understanding of their potential thus appears as a priority. An important step in that direction is to make the search and selection process more intuitive. This paper proposes a way to address this issue with a new database format. It focuses on the generation of visual strategies to express technical aspects and performance data with a more intuitive and architecturally based language, adapted to a designer’s needs and respectful of a realistic design process. The project takes shape as a freely accessible online database of light-interacting technologies for envelopes, available at www.d-lite.org, that provides an efficient meeting space for professionals in the field.

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Informing daylighting design with the Lightsolve approach: why and how

M. Andersen; S. Kleindienst; L. Yi; J. Lee; M. Bodart et al.

2008. PLEA 2008 - 25th Passive and Low Energy Architecture International Conference , Dublin , October 22-24, 2008.

To efficiently and appropriately integrate daylighting strategies in their projects, building designers need reliable methods to address issues such as daily and seasonal variations or the balance between sufficient illumination with visual and thermal comfort aspects. This integration must also happen early in the design process to have a significant impact on energy savings and ultimate building performance. This paper proposes to address this need by fulfilling three major objectives: support the design process using a goal-oriented approach based on iterative design improvement suggestions; provide climate-based annual metrics in a visual and synthesized form; and relate quantitative and qualitative performance criteria thanks to a novel interface for browsing daylighting analysis data in various forms. A methodology to achieve these objectives is described here as the Lightsolve approach.

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Combining annual daylight simulation with photobiology data to assess the relative circadian efficacy of interior spaces

C. S. Pechacek; M. Andersen; S. W. Lockley

Proceedings of eSim 2008 - 5th National Conference of IBPSA-Canada. 2008. eSim 2008 - 5th National Conference of IBPSA-Canada , Quebec City, Canada , May 20-22, 2008.

Recent studies have attempted to link environmental cues, such as lighting, with human performance and health, and initial findings seem to indicate a positive correlation between the two. The technical question this paper addresses is the use of Daylight Autonomy (DA) to simulate the probabilistic and temporal potential of daylight for human health needs. It will isolate one topic: human circadian rhythm organization as a proxy for human health. We use outcomes of photobiology research to define threshold values for lighting, which will be used as goals in simulations. These goals will consist of spectrum, intensity, and timing of light at the human eye. The variability of key architectural decisions in hospital room design- orientation, window size, and glazing material—are studied for their impact on achieving the goals. We chose healthcare settings as our case study, with the intent to validate and pursue this research in the future using patient outcomes and data collected in hospitals.

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Graphical display for annual climate-based daylight simulation

S. Kleindienst; M. Bodart; M. Andersen

Proceedings of eSim 2008 - 5th National Conference of IBPSA-Canada. 2008. eSim 2008 - 5th National Conference of IBPSA-Canada , Quebec City, Canada , May 20-22, 2008.

Due to daylight variability, a design cannot be thoroughly assessed using single-moment simulations, which is why we need dynamic performance metrics like Daylight Autonomy and Useful Daylight Illuminance. Going one step further, the annual variation in performance (condensed to a percentage by DA and UDI) is also valuable information, as is the ability to link this data to spatial visualizations and renderings. The challenge, therefore, is to provide the information necessary to early design decision-making in a manageable form, while retaining both the continuity of annual data. This paper introduces a simplification method based on splitting the year into weather averaged periods, which are simulated using Perez’s ASRC-CIE sky model while sun penetration data is provided at greater resolution. The graphical output, in “Temporal Map” format, is shown to be visually and numerically comparable to reference case maps created using detailed illuminance data generated by Daysim.

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2007

The Heliodome project: an innovative approach in assessing solar-optical properties of light-redirecting materials in combination with sun course simulations

M. Andersen; N. Gayeski; E. Stokes; R. Osser; C. Browne

2007. CISBAT 2007 - Renewables in a changing climate: Innovation in the Built Environment (plenary session) , Lausanne , September 4-5, 2007.

The Heliodome is a new type of video-based goniophotometer to measure materials and coatings intended to be used for advanced fenestration technologies or energy-efficient luminaires. Using calibrated digital cameras combined with a light projecting surface (ellipsoidal mirror), the spectral, bi-directional transmission or reflection properties of these materials can be assessed to a reasonable degree of accuracy. Its major innovations compared to other devices are to enable an analysis of both the visible and the near-infrared portions of the solar spectrum, to provide spectral as well as photometric light distribution data, and to ensure a continuous investigation of the transmitted or reflected light in a time-efficient way. The rotating table also serves as a heliodon, an architectural design tool for visualizing sunlight distribution inside a scale model and performing analyses on appropriate sun control strategies. This automated setup is complemented by a portable, manual outdoor heliodon that uses the real sky and sun as light sources. The paper details current progress in the development of this dual use device, called the “Heliodome”, that includes an original methodology for using a Charge Coupled Device (CCD) camera and a near-infrared Indium Gallium Arsenide (InGaAs) camera to measure arbitrary spectra.

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New Methods for Assessing Spectral, Bi-directional Transmission and Reflection by Complex Fenestration Systems

N. Gayeski; M. Andersen

Proceedings of SOLAR 2007: Sustainable Energy Puts America to Work. 2007. SOLAR 2007: Sustainable Energy Puts America to Work , Cleveland , July 7-12, 2007.

Advanced fenestration systems are increasingly being used to distribute solar radiation purposefully in buildings. Distribution of visible light and near infrared radiation can be optimized for daylighting and to reduce thermal loads. This can be achieved by fenestration systems that are spectrally and angularly selective. To study these systems, a device that measures the spectral, bi-directional transmission and reflection distribution functions of complex fenestration system components is under development. This device incorporates spectroradiometrically calibrated digital cameras and absorption filters to gather quasi-spectral information. The cameras could also be used to study the distribution of solar radiation in rooms.

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Development of Two Heliodon Systems and Recommendations for their Use

R. Osser; M. Andersen; L. Norford

Proceedings of SOLAR 2007: Sustainable Energy Puts America to Work. 2007. SOLAR 2007: Sustainable Energy Puts America to Work , Cleveland , July 7-12, 2007.

Heliodons aid the building design process by allowing the simulation of different solar angles with respect to physical scale models. At MIT, two different variations of this setup are being developed. The first one consists of a small, portable heliodon that is manually operated, and meant for use outdoors with the real sun and sky. The second is a larger indoor setup that consists of a computer-controlled moving table exposed to a stationary light source. A computer interface allows the designer to automatically take useful sets of model photos from a camera positioned next to or inside a model. Both approaches are presented in this paper and their limitations, causes of inaccuracy and potentialities are discussed based on experimental verification and through Radiance simulations. The results of a usability study with student volunteers and a case study on an existing research space on the MIT campus are also presented.

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2006

Improving Daylighting in Existing Buildings: Characterizing the Effect of Anidolic Systems

S. Kleindienst; M. Andersen

Proceedings of SOLAR 2006. 2006. SOLAR 2006: Renewable Energy - Key to Climate Recovery , Denver, USA , July 7-13, 2006.

Because of the longevity of the built environment, it is important not only to study methods of daylighting in new buildings, but to consider daylighting in existing buildings as well. Technologies exist which could benefit these buildings, but predicting the impact of these technologies on a daylit space remains difficult, and the highly computational modeling process probably discourages many people from even considering such devices. The aim of this study, therefore, is to produce an intuitive set of guidelines and recommendations for the applicability of a certain daylighting technology to a given space. The device on which this study focuses is the zenithal anidolic collector, and data is gathered using the software RADIANCE.

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2005

Experimental validation of daylighting simulation methods for complex fenestration systems

F. Maamari; M. Andersen; J. de Boer; W. L. Carroll; D. Dumortier et al.

Proceedings of Lux Europa 2005 - Lighting for Humans. 2005. Lux Europa 2005 - Lighting for Humans , Berlin , September 19-21, 2005. p. 245-248.

The objective of this paper is to assess the capability of existing lighting simulation methods to predict the performance of complex fenestration systems, which are becoming a commonly used component in buildings construction domain. A specific experimental protocol was conducted to collect reliable reference data based on illuminance measurements inside a black box with (and without) one complex glazing sample facing a measured external luminance distribution. Two types of simulation methods were tested and compared: The first is based on modeling the glazing sample in a ray-tracing simulation program and the second is based on use of the samples' BTDF data. The BTDF data sets were combined with the external luminance distribution to predict the flux distribution inside the room and the resulting illuminance values at the reference points. The comparison between the experimental reference data and the simulation results showed that the influence of the CFS could be predicted with good accuracy.

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Experimental and simulation-based approaches to assess bidirectional properties of complex fenestration systems

M. Andersen; J. de Boer

2005. Lux Europa 2005 - Lighting for Humans , Berlin, Germany , September 19-21, 2005.

A serious effort has been made in developing accurate and efficient bidirectional goniophotometric devices for detailed studies of Complex Fenestration Systems, capable of measuring BTDFs and/or BRDFs in an appropriate way. The existing instruments are almost all based on a scanning process, i.e. on relative individual movements of the detector and of the sample and/or the source to monitor all incoming and outgoing light flux directions for which BT(R)DF data are needed, except for two that rely on a flux-based investigation combining the use of digital imaging for detection with the collection of the light emerging from the sample on a projection surface (diffusing screen or mirrored ellipsoid). The second part of the paper focuses on virtual goniophotometers that have been developed, mainly based on commercial forward ray-tracing simulation tools and allowing one to complement experimental assessment in a very efficient way.

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Combining time-efficient goniophotometry with scale model studies in a unique instrument

M. Andersen; D. Ljubicic; C. Browne; S. Kleindienst; M. Culpepper

2005. Lux Europa 2005 - Lighting for Humans , Berlin, Germany , September 19-21, 2005.

A new measurement device for the in-depth investigation of the light distribution within buildings is being developed, whose aim is on one hand to assess the sunlight distribution inside scale models of buildings or rooms, and on the other hand to achieve truly time-efficient bidirectional goniophotometric measurements of coatings or materials. The types of materials expected to benefit from this detailed characterization are typically the ones used for complex fenestration systems such as novel solar blinds, new glazing or coating materials, sunlight and daylight-redirecting devices, as well as the many types of reflectors used in luminaires.

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An automated device to assess light redirecting properties of materials and perform sun course simulations: the Heliodome project

M. Andersen; D. Ljubicic; C. Browne; S. Kleindienst; M. Culpepper

2005. ISES Solar World Congress 2005 - Bringing Water to the World , Orlando , August 6-12, 2005.

In this paper, the development of an original and time-efficient measurement device is proposed for the detailed investigation of the daylight distribution within buildings. It is meant to be used for two kinds of applications: - to assess the sunlight distribution inside scale models in an automated way so as to serve as a design and educational tool for architects and students and help them find solutions to improve the sunlight distribution within their building projects. - to achieve time-efficient bidirectional goniophotometric measurements of materials, typically used for innovative fenestration systems such as solar blinds, advanced glazing or coatings and daylight-redirecting devices, as well as energy-efficient artificial lighting components like luminaires reflectors e.g. The functioning principle of the device in both configurations is explained here and its early stages of development are presented: design and construction of the mechanical platform, command interface prototype and characteristics of the light detection system.

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2004

Extension of the sky component calculation method to tilted windows

M. Andersen

2004. IESNA 2004 Annual conference of the Illuminating Engineering Society of North America , Tampa, Florida, USA , July 25-28, 2004.

To assess the daylighting performances of a building, one of the most commonly used quantities is the Daylight factor, which is defined for a given surface element inside the analysed room as the ratio of the inside and outside illuminances under a CIE overcast sky. The Daylight factor consists of three components: the sky component, due to light flux reaching the surface element directly from the sky, the externally and the internally reflected components, respectively due to light flux reflected on external and internal surfaces. To estimate the direct sky component (also called sky factor), analytical methods can be used, based on the luminance distribution of the sky and the window’s geometric properties (dimensions and position in regard to the considered surface element). However, such methods have always been restricted to vertical (lateral) and horizontal (zenithal) windows, requiring heavy approximations to be applied whenever a tilted rectangular opening was considered. In this paper, a generalized method for assessing the sky component is proposed, extending it to rectangular windows of any tilt angle. As a purely analytical approach was found to be inapplicable, it is based on an optimised combination of vertical and horizontal windows situations. To validate the developed methodology, scale model measurements were performed with a sky simulator for two rectangular openings of varying tilt angle (every 15° from vertical to horizontal): the experimental results proved to be in very good agreement with the calculation-based approach.

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Innovative bidirectional video-goniophotometer combining transmission and reflection measurements

M. Andersen; C. Roecker; J.-L. Scartezzini

2004. EuroSun 2004 , Freiburg in Brisgau, Germany , June 20-23, 2004.

To assess the daylighting performances of a building, one of the most commonly used quantities is the Daylight factor, which is defined for a given surface element inside the analysed room as the ratio of the inside and outside illuminances under a CIE overcast sky. The Daylight factor consists of three components: the sky component, due to light flux reaching the surface element directly from the sky, the externally and the internally reflected components, respectively due to light flux reflected on external and internal surfaces. To estimate the direct sky component (also called sky factor), analytical methods can be used, based on the luminance distribution of the sky and the window’s geometric properties (dimensions and position in regard to the considered surface element). However, such methods have always been restricted to vertical (lateral) and horizontal (zenithal) windows, requiring heavy approximations to be applied whenever a tilted rectangular opening was considered. In this paper, a generalized method for assessing the sky component is proposed, extending it to rectangular windows of any tilt angle. As a purely analytical approach was found to be inapplicable, it is based on an optimised combination of vertical and horizontal windows situations. To validate the developed methodology, scale model measurements were performed with a sky simulator for two rectangular openings of varying tilt angle (every 15° from vertical to horizontal): the experimental results proved to be in very good agreement with the calculation-based approach.

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Analysing sources of error in building daylighting performance assessment by comparison of test modules and scale models

A. Thanachareonkit; M. Andersen; J.-L. Scartezzini

Proceedings of EuroSun 2004. 2004. EuroSun 2004 , Freiburg in Brisgau, Germany , June 20-23, 2004. p. 454-462.

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2003

Including of specular component in a BTDF or BRDF assessment based on digital imaging

M. Andersen; J.-L. Scartezzini

2003. CISBAT 2003 - Innovation in building envelopes and environmental systems , EPFL, Lausanne , October 8-9, 2003.

Bi-directional Transmission (or Reflection) Distribution Functions, commonly named BTDFs (and BRDFs), are essential quantities to describe any complex fenestration system in details. They are defined as the ratio of the luminance diffused from a surface element in a given direction (after transmission or reflection), and the illuminance incident on the sample. However, these functions are capable of describing the regular (specular) as well as the diffuse components of emerging light, and their mutual knowledge is necessary to assess a glazing or shading system’s optical performances properly. Although the analytical expression of a BT(R)DF differs whether it is related to regular (specular) or diffuse light, a simultaneous assessment of the two components can be achieved under certain conditions, presented in this paper. They are thereafter analyzed for the particular data acquisition procedure developed for a novel type of bi-directional photogoniometer, based on digital imaging.

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Comparing daylighting performances assessment of building within scale models and test modules

A. Thanachareonkit; M. Andersen; J.-L. Scartezzini

Proceedings of CISBAT 2003: Innovation in building envelopes and environmental systems. 2003. CISBAT 2003: Innovation in building envelopes and environmental systems , EPFL, Lausanne, Switzerland , Oct 8-9, 2003. p. 289-294.

Physical models are commonly used to assess daylighting performance of buildings using sky simulators for purpose of research as well as practice. Recent studies have pointed out the general tendency of scale model assessments to overestimate the performance, usually expressed through work plane illuminance and daylight factor profiles, when compared to the real buildings. The cause of the discrepancy between buildings and scale models is due to several sources of experimental errors, such as modelling of building details, mocking-up of surface reflectances and glazing transmittance, as well as photometer features. To analyse the main sources of errors, a comparison of a full scale test module designed for experimentation of daylighting systems and its 1:10 scale model, placed within identical outdoor daylighting conditions, was undertaken. Several physical parameters were studied in order to determine their impact on the daylighting performance assessment. These include the accurate mocking-up of surface reflectances, the scale model location, as well as the photometric sensor properties. The experimental study shows that large discrepancies can occur between the performance figures. They lead, on average, to a relative divergence of + 60 % to + 105 % in favor of the scale model for different points located in the side lit room. Some of these discrepancies were caused by slight differences in surface reflectances and photometer cosine responses. These discrepancies were reduced to a + 30 % to + 35 % relative divergence, by putting in the effort to carefully mock up the geometrical and photometrical features of the test module. This included a sound calibration of photometric sensors, whose cosine-response appeared at the end to be responsible for the remaining relative divergence observed between the daylighting performance figures.

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Bi-directional light transmission properties assessment for venetian blinds : Computer simulations compared to photogoniometer measurements

M. Andersen; J.-L. Scartezzini; M. D. Rubin; R. C. Powles

2003. ISES Solar World Congress 2003 - Solar Energy for a Sustainable Future , Göteborg, Sweden , June 14-19, 2003.

An accurate evaluation of daylight distribution through advanced fenestration systems (complex glazing, solar shading systems) requires the knowledge of their Bi-directional light Transmission Distribution Function (BTDF). An innovative equipment for the experimental assessment of these bi-directional functions has been developed, based on a digital imaging detection system. An extensive set of BTDF measurements was performed with this photogoniometer on venetian blinds presenting curved slats with a mirror coating on the upper side. In this paper, the measured data are compared with ray-tracing results achieved with a virtual copy of the device, that was constructed with a commercial ray-tracing software. The model of the blind was created by implementing the measured reflection properties of the slats coatings in the ray-tracing calculations. These comparisons represent an original and objective validation methodology for detailed bi-directional properties for a complex system; the good agreement between the two methods, yet presenting very different parameters and assessment methodologies, places reliance both on the digital-imaging detection system and calibration, and on the potentiality of a flexible calculation method combining ray-tracing simulations with simple components measurements.

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2001

Use of Matrices for the Adaptation of Video-based Photogoniometric Measurements to a Variable Referential

M. Andersen

2001. CISBAT'01 - Solar Energy in Buildings , EPFL, Lausanne, Switzerland , October 3 - 4, 2001.

Digital video based luminance mapping systems require the establishment of a precise relation between the considered spatial referential and the associated pixel coordinates on the image, that may vary with the measurement conditions. In this paper, an adaptation of the image calibration according to the referential variations is proposed, based on the use of a set of matrices individually associated to each spatial coordinate. This approach is given through an application example on a recent digital imaging-based bi-directional photogoniometric device.

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2000

Photogoniomètre bidirectionnel pour l’évaluation des performances lumineuses de systèmes de fenêtres

M. Andersen; L. Michel; C. Roecker; J.-L. Scartezzini

2000. Schweizerisches Status-Seminar 2000 - Energie- und Umweltforschung im Bauwesen , EMPA ZEN, Zürich , September 14-15, 2000.

Les applications en lumière naturelle exigent une connaissance objective et systématique des propriétés de transmission lumineuse des systèmes de fenêtres. Ces caractéristiques photométriques sont décrites par une fonction de distribution bidirectionnelle de transmission (BTDF), dont l‘évaluation expérimentale nécessite un équipement approprié. Un nouveau type de photogoniomètre bidirectionnel, basé sur des techniques d’imagerie numérique, a été développé dans ce but. Ses principaux avantages résident dans la réduction significative du temps de mesure et dans la possibilité de déterminer une fonction BTDF quasi continue. Ces résultats ne peuvent être atteints que grâce à des procédures de calibrage spécifiques et précises du photogoniomètre bidirectionnel, présentées dans cet article, avec un traitement approprié des images et des données.

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1999

Réalisation d’un photo-uranotomographe à imagerie numérique

L. Michel; M. Andersen

Proceedings of CISBAT'99 - International Conference on Solar Energy in Buildings. 1999. CISBAT'99 - International Conference on Solar Energy in Buildings , EPFL, Lausanne , September 22-23, 1999. p. 289-294.

La connaissance approfondie du gisement lumineux extérieur est un élément essential pour l'évaluation des performances lumineuses de bâtiments, ainsi que le développement de nouveaux systèmes d'éclairage naturel. La mesure de la distribution de luminances sur la voûte céleste se pratique grâce à un photo-uranotomographe. De tels scanners de ciel sont commercialisés et souffrent des défauts suivants: - Durée de la mesure importante: 30s à plusieurs minutes - Manque de souplesse de la mesure: ils ne permettent de balayer l'hémisphère que selon une seule répartition (145 zones de Tregenza/CIE) - Faible dynamique de mesure: la zone circumsolaire est exclue de la mesure Un nouveau type de photo-uranotomographe basé sur la technique d'imagerie numérique a été développé afin de contourner les défauts des dispositifs existants. L'objet de cette contribution est de présenter le développement d'un photo-uranotomographe à imagerie numérique et d'un illustrer sa mise en service.

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Measurement of bi-directional photometric properties of advanced glazing based on digital imaging techniques

M. Andersen; L. Michel; C. Roecker; J.-L. Scartezzini

1999. CISBAT'99 - International Conference on Solar Energy in Buildings , EPFL, Lausanne , September 22-23, 1999.

Many daylighting applications require a precise knowledge of the transmission properties of fenestration materials, called bi-directional transmission distribution functions (BTDF), which necessitate systematic and accurate measurements. A new type of bi-directional photogoniometer, based on advanced imaging techniques, has been developed to this end; its mechanical concept, the calibration procedures and the first results are presented here.

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