Lighting simulation standards recommend default values for opaque material reflectance values, bu... more Lighting simulation standards recommend default values for opaque material reflectance values, but these are varied and not based upon measured data. In response, a database of 1,288 opaque material reflectance measurements collected using spectrally-specific spectrophotometer sensors is presented. The database is analyzed according to object type, material type, and color. Photopic, melanopic, and wavelength-specific median reflectance data is presented alongside interquartile ranges which allow the reader to assess typical reflectance values and the variance of reflected light from surfaces in the built environment. The lighting materials database is included as supplemental material and has been integrated into a searchable website for use by the lighting simulation public.
We demonstrate a case study of Urban Heat Island (UHI) indicators in Toronto, ON, Canada under fi... more We demonstrate a case study of Urban Heat Island (UHI) indicators in Toronto, ON, Canada under five climate change scenarios until 2080. We simulated 48,600 UHI predictions by varying nine urban design parameters: building height, site coverage ratio (SCR), façade-to-site ratio (FSR), green coverage ratio (GCR), tree canopy ratio (TCR), building type, albedo, green roof coverage, and material thermal properties (of the window, roof, and walls). Results show that under future climates, UHI intensity decreases slightly, while our indicator of heat stress (hours above 30 C°) rises significantly. Vegetation, SCR, FSR, and building height are found to have the strongest effect on mediating UHI under climate change, indicating the importance of increasing greenspace and reducing building surface area and density in urban design. Key Innovations • A novel method for modelling representative urban neighborhoods and microclimates using typical weather data modified to include impacts of climate change and Urban Heat Island (UHI). • Reveals how urban microclimates may change under future climate scenarios in a large northern city and what urban design parameters have the most capacity to reduce associated UHI. Practical Implications This study implements a model calculation method using open-source tools and datasets. The analysis evaluates which types of urban design settings have beneficial impacts on urban microclimates under forecasted climate change and UHI scenarios. This process can be applied to other cities and climates without technical or intellectual property limitations. The code used in this research is published as a re-useable repository for other researchers: https://github.com/C38C/UHI_in_Future_Climates
We compare a new, novel lighting design workflow based on human photobiology with existing metric... more We compare a new, novel lighting design workflow based on human photobiology with existing metrics for nonvisual lighting design. There are a variety of light simulation methods and a lineage of circadian system biological models, but they are not connected into a cohesive workflow. We applied this novel workflow to two design variables: window spectral transmittance and surface reflectance. This article reviews and compares existing frameworks of circadian design to our novel workflow in terms of material spectrum sensitivity and the resulting evaluation of architecture in terms of circadian health. Our results highlight how architectural design can directly impact an occupant's circadian health. Our comparative analyses demonstrates how direct photobiology-driven alertness and health metrics differ from previous circadian design metrics. Key Innovations • Novel workflow based upon light's impact on human photobiology-driven alertness and health. • Relationships and visual comparisons between various light simulation methods and design variables • Relationship between circadian health metrics and design variables Practical Implication Lighting simulation methods need to be validated as there are discrepancies in their treatment of the spectral qualities of materials. Circadian design metrics should consider the direct biological symptoms of the circadian system.
We assess the state of the art in non-image forming effects (NIF) of light on human health, alert... more We assess the state of the art in non-image forming effects (NIF) of light on human health, alertness and wellbeing as applied to the design of the built environment. There are many methods of calculating spectral daylighting weighted for its impact on circadian dynamics and alertness; however, all current analysis is based on a saturation effect. We add electric lighting to the calculation methods and implement a collection of photobiological models from medical literature to predict circadian dynamics, alertness, and melatonin levels due to light exposure. The new framework is tested under several different daylight, electric light, and monitor screen use scenarios. Key Innovations We present a method of simulating high resolution timeseries spectral irradiance due to daylight, electric light, and monitor screens. Changes in light exposure due to daylight and electric light control systems can be calculated. Timeseries spectral irradiance is used to drive a photobiological model that predicts NIF effects of light: melatonin dynamics in the bloodstream, alertness, and circadian phase shifting. New metrics for assessment of NIF light are proposed and compared under a variety of design scenarios. Practical Implications A new framework is presented to directly predict the NIF physiological and alerting effects of light. These methods are reproduceable using a new Python library we are sharing with the publication of this paper: https://github.com/C38C/NIF_Photobiology
In this paper we present a post-occupancy study of 326 participants in 10 daylit office buildings... more In this paper we present a post-occupancy study of 326 participants in 10 daylit office buildings in Singapore and correlate the results with climate-based daylighting metrics (CBDM) and electric lighting simulations using calibrated simulation models of the 10 buildings. For the first time, this study tests CBDMs which are used in building design against their impact on occupant perception within buildings. We find significant correlations between CBDMs and reported occupant satisfaction with access to daylight, view interest, perception of 'too low' lighting levels, and visual comfort. Overall, CBDMs which account for lower illuminance thresholds such as continuous daylight autonomy (CDA) and useful daylight illuminance combined (UDIc, 100-3000 lx) correlate more strongly with subjective results than do electric lighting sufficiency metrics such as daylight autonomy (DA) at 300 lx and 500 lx thresholds. Simple descriptive statistical representations of annual daylight distributions, mean and median annual daylight illuminance values, outperform CBDMs in correlation strength and p-value. Based upon these results, new metrics are proposed for occupant satisfaction with daylight access and views. In addition, increased daylight levels are shown to decrease reporting of lighting levels being 'often too low' even when adequate electric lighting is provided, and contrast is likely to be beneficial to space perception at non-glaring thresholds.
Calibrated climate-based lighting simulation models of buildings have the capacity to perform an ... more Calibrated climate-based lighting simulation models of buildings have the capacity to perform an essential role in post-occupancy evaluations, such as annual frequency assessments of daylighting quality and visual discomfort. However, in most post-occupancy case studies the role of lighting analysis is temporally limited by instantaneous measurements or limited in scale by requiring constant monitoring with expensive sensors. It is challenging to build calibrated models based on point-in-time measurements due to the presence of electric lighting, transient use of dynamic shades, limited information on the material specifications, and short durations of accessibility to the spaces being studied. The authors propose and present a calibration process for annual daylighting and electric lighting simulation models based on one-time field measurements of large daylit and electrically-lit spaces exemplified through a data set of 540 individual office desks across 10 office spaces. The calibration process includes measuring lighting, physical and material data during a one-time visit that are used to calibrate high dynamic range images and lighting simulation models using actual weather data. The calibration accuracy is validated based on measured and simulated luminance and illuminance data. Comparing measured and simulated illuminance, relative RMSE values were 25.8% and 45.5% for horizontal and vertical measurements respectively. When tracking errors using log10(illuminance), approximating human perceptual differences, errors of 4.3% and 6.8% were achieved. Vertical illuminance was found to vary more with measured data due to the uncertainty of monitor screen luminances. The authors aim to achieve calibrated lighting models reliable enough to be used in assessing the relationship of annualized lighting metrics to participants long-term perceptions of lighting quality, thereby enabling simulation models to be used in the post-occupancy evaluation process of building lighting. This paper demonstrates that measured data through one-time visits can be utilized to build reliable calibrated lighting simulation models to integrate long-term annual lighting results in post-occupancy evaluations.
This paper presents a post-occupancy study of 543 participants in 10 daylit office buildings in S... more This paper presents a post-occupancy study of 543 participants in 10 daylit office buildings in Singapore. Calibrated daylighting and electric lighting simulation models of each building were created and verified. HDR photographs and vertical and horizontal illuminance measurements were taken at each participant's workspace, and a survey on their long-term and instantaneous subjective evaluations of lighting were collected. For the first time, this study compares climate-based daylighting metrics (CBDM's) to occupant's long-term subjective impressions. The authors find that simulated mean annual horizontal illuminance correlates strongly with occupants' satisfaction with access to daylight. 50% occupant satisfaction with daylight begins at levels as low as 80 lx, far below current lighting sufficiency standards. Vertical illuminance measures did not exhibit strong correlations with reported discomfort. These results are an initial investigation of CBDM's use for more than lighting sufficiency and illustrate the need for further study of overlighting metrics.
This paper presents a novel study comparing advanced annual visual discomfort calculations to typ... more This paper presents a novel study comparing advanced annual visual discomfort calculations to typical illuminance-based overlighting metrics. The Unified Glare Rating (UGR), Daylight Glare Probability (DGP), and simplified Daylight Glare Probability (DGPs) are calculated at an occupant’s eye level and are compared to the Useful Daylight Illuminance Exceeded (UDI-e, % time ≥ 3,000 lx) climate-based daylighting metrics. 720 designs are tested annually comprising 10,121,583 individual visual discomfort calculations. The author finds that UDI-e can predict discomfort correctly or provide extra scrutiny on discomfort analysis in between 93.1% and 98.9% of cases; therefore, it is sometimes a reasonable replacement for more arduous visual discomfort calculations. Prudence is still necessary in using illuminance-based replacements in spaces susceptible to experiencing strong contrast.
Urban settlements require design improvements towards increased comfort and reduced energy consum... more Urban settlements require design improvements towards increased comfort and reduced energy consumption through active and passive means to create liveable cities in the future. This study investigates the impact of 6 urban design criteria—building height, plot ratio, greenery, glazing ratio, shading, and materiality—on discrete environmental metrics for sustainability using Morris sensitivity analysis (SA) method. The authors calculate a series of critical and emerging environmental measures which indicate the suitability of an urban design: Urban Heat Island (UHI), Outdoor Thermal Comfort—using the Universal Thermal Climate Index (UTCI), Urban Energy Use Intensity (EUI), Urban Daylight Autonomy (UDA), and Annual Mean Ventilation. This study identifies essential parameters for comfortable and low-energy urban communities in early-phase urban design processes for tropical climates using Morris sensitivity analysis. The effort is focused on an increased modelling comprehensiveness—including more related and co-dependent sustainability measures compared to previous works—and understanding the impact of parameters investigated on a comprehensive set of environmental measures. The authors find that building height and site coverage ratio most significantly impact many of the studied environmental measures. However, all parameters are significant on at least one environmental measure; therefore, it is difficult to simplify the complex process of urban environmental and sustainable design.
This paper describes a visualisation framework for organising data outputs generated from a compl... more This paper describes a visualisation framework for organising data outputs generated from a complex multi-objective optimisation design space. The three-part visualisation framework is structured to identify solution clusters along the Pareto front, before providing designers with design space navigation control through genotype value displays. These provide smaller focus design spaces which are then supported by spatial displays of a series of solution phenotypes and their respective performance simulations. This visualisation tool aims to provide a diverse range of quantitatively high-performance design solutions determined through building performance simulations, that can further subsequent higher order qualitative design evaluation such as design aesthetics.
When communicating the results of environmental building performance analysis, it is important to... more When communicating the results of environmental building performance analysis, it is important to display resultant information in order (a) to be holistically understood and (b) to guide architectural design decisions. This paper proposes a spatial dashboard of environmental performance data as a means to intuitively relate architectural form and performance and achieve the two goals above. The dashboard visualizes daylighting, natural ventilation, and thermal comfort information spatially localized throughout axonometric representations of buildings. Results can be customized by time of day, adding time as another analytical dimension in addition to space. Environmental data, normally hidden, is visually revealed in relation to architectural form. The dashboard enables intuitive design decisions to be made relative to performance measures across time and space.
This manuscript describes a methodology for organizing and displaying disparate sources of buildi... more This manuscript describes a methodology for organizing and displaying disparate sources of building performance simulation data to form spatial displays of a myriad of building performance outputs and drive design understanding from an architectural point of view. The results are based on annual simulation data, are spatially discrete, and can be displayed and interpreted through a variety statistical methods. A series of simple visualizations to describe the performance of passive and active architectural design strategies are presented in addition to further suggestions for temporally varying data display animations.
Singapore is one country that is leading the charge in environmental design in the tropics by adv... more Singapore is one country that is leading the charge in environmental design in the tropics by advocating for smart strategies in buildings. The small city-state uses Residential Envelope Transmittance Values (RETV) to quantify heat transfer through residential building façades. This study compares simulated performance metrics of ten Singaporean housing developments to calculated RETV values to evaluate qualitative metrics such as daylight penetration and interior operative temperature (comfort) against physical building features such as shading and window-to-wall ratio. The authors have determined that while RETV is a unique way to quantify thermal transfer through the building envelope, it ignores many of the qualitative characteristics implicit in passive buildings that define building performance.
Trees play a significant role in influencing daylight availability inside and outside buildings. ... more Trees play a significant role in influencing daylight availability inside and outside buildings. They temper, scatter and transmit light subsequently reducing the availability or acting as a passive source of daylight. Current daylighting simulation practices either avoid modelling trees or model them as cones, spheres or cylinders with an assumed reflectance value. Trees are complex in their shape and—depending on crown density and clumping nature—their optical properties change considerably. In order to predict the effect of trees on daylight, researchers need to first measure and quantify this effect. Hence, in this paper the authors propose a low-cost method employing high dynamic range photography and automated image processing to measure two variables of the tree crown: gap percentage and transmittance percentage. These measured variables can be used in daylight simulation platforms such as Radiance to geometrically model the crown of a tree and specify its optical properties
Measuring the luminous environment enables researchers and practitioners to study perception and ... more Measuring the luminous environment enables researchers and practitioners to study perception and visual comfort in existing environments in order to decipher the components that contribute to good or problematic lighting characteristics. High dynamic range photography is commonly used to study visual perception and comfort. This paper presents new findings and specific methods of capturing interior scenes that may include peaks caused by a direct view of the sun and specular reflections. Methods are tested to improve the range of luminance values that can be captured, and new guidelines are proposed to improve the accuracy of computed visual comfort indices.
This paper investigates accuracy in typical High Dynamic Range (HDR) photography techniques used ... more This paper investigates accuracy in typical High Dynamic Range (HDR) photography techniques used by researchers measuring high resolution luminance information for visual comfort studies in daylit spaces. Vignetting effects of circular fisheye lenses are investigated for reproducibility between different lenses of the same model and sharing between researchers. The selection of aperture size is related to vignetting intensity, dynamic range and potential for lens flare. Lighting variability during capture processes is also tracked, and it is recommended to measure vertical illuminance in order to validate the stability of a scene. Finally, luminous overflow—a concept where a HDR photograph cannot measure the true luminous environment—is introduced. Its effect on the glare metrics UGR and DGP is investigated by using neutral density (ND) filters to increase the dynamic range of photographs under direct sunlight. It is recommended to use ND filters in scenes with vertical illuminances greater than 5 000 lx or with direct vision of the sun.
This paper describes the cataloguing of opaque visual material properties in a database structure... more This paper describes the cataloguing of opaque visual material properties in a database structure based on various measurement processes from the simple (illuminance and luminance measurements) to the complex (spectrophotometers and goniophotometers). A standard rendering environment was setup in the Radiance simulation engine in order to enable comparisons of color and specularity via physically-based renderings. All materials are also organized by their surface type (wall, ceiling, floor, etc.), color, location of measurement, reflectance, specularity, roughness, and material type (plastic, metal, etc.). Furthermore, for the first time, a large amount of full-spectral measurements are available in the catalogue at 10 nm measurement increments. This is imperative for understanding circadian stimulation and photosynthetic potential in future simulation practice and architectural design analysis.
A new concept of long term visual comfort is introduced to describe the long-term visual impressi... more A new concept of long term visual comfort is introduced to describe the long-term visual impression of space occupants. This concept, in contrast to instantaneous assessment of visual comfort, aims to describe an overall rating of visual quality. A paired study consisting of occupant surveys and detailed 6-minute timestep comfort simulations was performed for the studio spaces of Gund Hall (Cambridge, MA, USA), which is occupied by over 500 students. Occupants reported four primary ways of experiencing visual discomfort: discomfort glare, insufficient monitor contrast, direct visibility of the sun and direct sunlight on the workplane. Survey results were located spatially and in terms of orientation within Gund Hall, and the simulation model was calibrated based on furniture layout, measured material reflectances and local measured weather data. The results of the study illustrate that it is possible to use current simulation-based visual comfort predictions to predict occupants' long-term visual comfort assessments in a complex daylit space. Between 53.7% and 70.1% percent of polled occupants' evaluations were correctly identified. Through a spatial and temporal presentation of the simulation data, this new methodology can be used as feedback during the process of designing daylit spaces, avoiding visual discomfort and increasing satisfaction with the built environment.
Proceedings of the Transportation Research Board 93rd Annual Meeting, 2014
Disability glare, visual impairment due to extreme brightness or contrast, can be caused by inten... more Disability glare, visual impairment due to extreme brightness or contrast, can be caused by intense reflections from new constructions nearby existing transportation or building infrastructure. A case study analysis is performed of a disability glare hazard at an airport created by the installation of a large array of photovoltaic panels between an air traffic control tower and the aircraft taxiway. The panels reflect blinding quantities of daylight into the control tower, produce temporary after images and dangerously obscure taxiing aircraft. The existing FAA guidelines for installation of solar technologies are discussed relative to their shortcomings in identifying the glare hazard.
High dynamic range photography is used to analyze the glaring situation at the airport, and the authors propose a maximum brightness threshold of 30,000 cd/m2 based on the physiology of human vision and the brightness of tasks necessary for air traffic controllers at the case-study airport. Detailed reflectivity and three-dimensional models of the photovoltaic panels and the airport are created and validated against measured data. Using these models, an annual analysis is performed of the glare hazard. This analysis is displayed temporally using graphs and spatially using images that indicate where the glaring reflections originate. Such information is useful in identifying potential for disability glare before new constructions are built. Finally, the authors use the new method to analyze designs for remediation of the glare hazard.
In this paper we present, demonstrate and validate a method for predicting city-wide electricity ... more In this paper we present, demonstrate and validate a method for predicting city-wide electricity gains from photovoltaic panels based on detailed 3D urban massing models combined with Daysim-based hourly irradiation simulations, typical meteorological year climactic data and hourly calculated rooftop temperatures. The resulting data can be combined with online mapping technologies and search engines as well as a financial module that provides building owners interested in installing a photovoltaic system on their rooftop with meaningful data regarding spatial placement, system size, installation costs and financial payback. As a proof of concept, a photovoltaic potential map for the city of Cambridge, Massachusetts, USA, consisting of over 17,000 rooftops has been implemented as of September 2012.
The new method constitutes the first linking of increasingly available GIS and LiDAR urban datasets with the validated building performance simulation engine Daysim, thus-far used primarily at the scale of individual buildings or small urban neighborhoods. A comparison of the new method with its predecessors reveals significant benefits as it produces hourly point irradiation data, supports better geometric accuracy, considers reflections from neareby urban context and uses predicted rooftop temperatures to calculate hourly PV efficiency. A validation study of measured and simulated electricity yields from two rooftop PV installations in Cambridge shows that the new method is able to predict annual electricity gains within 3.6 to 5.3% of measured production when calibrating for actual weather data and detailed PV panel geometry. This predicted annual error using the new method is shown to be less than the variance which can be expected from climactic variation between years. Furthermore, because the new method generates hourly data, it can be applied to peak load mitigation studies at the urban level. This study also compares predicted monthly energy yields using the new method to those of preceding methods for the two validated test installations and on an annual basis for ten buildings selected randomly from the Cambridge dataset.
Lighting simulation standards recommend default values for opaque material reflectance values, bu... more Lighting simulation standards recommend default values for opaque material reflectance values, but these are varied and not based upon measured data. In response, a database of 1,288 opaque material reflectance measurements collected using spectrally-specific spectrophotometer sensors is presented. The database is analyzed according to object type, material type, and color. Photopic, melanopic, and wavelength-specific median reflectance data is presented alongside interquartile ranges which allow the reader to assess typical reflectance values and the variance of reflected light from surfaces in the built environment. The lighting materials database is included as supplemental material and has been integrated into a searchable website for use by the lighting simulation public.
We demonstrate a case study of Urban Heat Island (UHI) indicators in Toronto, ON, Canada under fi... more We demonstrate a case study of Urban Heat Island (UHI) indicators in Toronto, ON, Canada under five climate change scenarios until 2080. We simulated 48,600 UHI predictions by varying nine urban design parameters: building height, site coverage ratio (SCR), façade-to-site ratio (FSR), green coverage ratio (GCR), tree canopy ratio (TCR), building type, albedo, green roof coverage, and material thermal properties (of the window, roof, and walls). Results show that under future climates, UHI intensity decreases slightly, while our indicator of heat stress (hours above 30 C°) rises significantly. Vegetation, SCR, FSR, and building height are found to have the strongest effect on mediating UHI under climate change, indicating the importance of increasing greenspace and reducing building surface area and density in urban design. Key Innovations • A novel method for modelling representative urban neighborhoods and microclimates using typical weather data modified to include impacts of climate change and Urban Heat Island (UHI). • Reveals how urban microclimates may change under future climate scenarios in a large northern city and what urban design parameters have the most capacity to reduce associated UHI. Practical Implications This study implements a model calculation method using open-source tools and datasets. The analysis evaluates which types of urban design settings have beneficial impacts on urban microclimates under forecasted climate change and UHI scenarios. This process can be applied to other cities and climates without technical or intellectual property limitations. The code used in this research is published as a re-useable repository for other researchers: https://github.com/C38C/UHI_in_Future_Climates
We compare a new, novel lighting design workflow based on human photobiology with existing metric... more We compare a new, novel lighting design workflow based on human photobiology with existing metrics for nonvisual lighting design. There are a variety of light simulation methods and a lineage of circadian system biological models, but they are not connected into a cohesive workflow. We applied this novel workflow to two design variables: window spectral transmittance and surface reflectance. This article reviews and compares existing frameworks of circadian design to our novel workflow in terms of material spectrum sensitivity and the resulting evaluation of architecture in terms of circadian health. Our results highlight how architectural design can directly impact an occupant's circadian health. Our comparative analyses demonstrates how direct photobiology-driven alertness and health metrics differ from previous circadian design metrics. Key Innovations • Novel workflow based upon light's impact on human photobiology-driven alertness and health. • Relationships and visual comparisons between various light simulation methods and design variables • Relationship between circadian health metrics and design variables Practical Implication Lighting simulation methods need to be validated as there are discrepancies in their treatment of the spectral qualities of materials. Circadian design metrics should consider the direct biological symptoms of the circadian system.
We assess the state of the art in non-image forming effects (NIF) of light on human health, alert... more We assess the state of the art in non-image forming effects (NIF) of light on human health, alertness and wellbeing as applied to the design of the built environment. There are many methods of calculating spectral daylighting weighted for its impact on circadian dynamics and alertness; however, all current analysis is based on a saturation effect. We add electric lighting to the calculation methods and implement a collection of photobiological models from medical literature to predict circadian dynamics, alertness, and melatonin levels due to light exposure. The new framework is tested under several different daylight, electric light, and monitor screen use scenarios. Key Innovations We present a method of simulating high resolution timeseries spectral irradiance due to daylight, electric light, and monitor screens. Changes in light exposure due to daylight and electric light control systems can be calculated. Timeseries spectral irradiance is used to drive a photobiological model that predicts NIF effects of light: melatonin dynamics in the bloodstream, alertness, and circadian phase shifting. New metrics for assessment of NIF light are proposed and compared under a variety of design scenarios. Practical Implications A new framework is presented to directly predict the NIF physiological and alerting effects of light. These methods are reproduceable using a new Python library we are sharing with the publication of this paper: https://github.com/C38C/NIF_Photobiology
In this paper we present a post-occupancy study of 326 participants in 10 daylit office buildings... more In this paper we present a post-occupancy study of 326 participants in 10 daylit office buildings in Singapore and correlate the results with climate-based daylighting metrics (CBDM) and electric lighting simulations using calibrated simulation models of the 10 buildings. For the first time, this study tests CBDMs which are used in building design against their impact on occupant perception within buildings. We find significant correlations between CBDMs and reported occupant satisfaction with access to daylight, view interest, perception of 'too low' lighting levels, and visual comfort. Overall, CBDMs which account for lower illuminance thresholds such as continuous daylight autonomy (CDA) and useful daylight illuminance combined (UDIc, 100-3000 lx) correlate more strongly with subjective results than do electric lighting sufficiency metrics such as daylight autonomy (DA) at 300 lx and 500 lx thresholds. Simple descriptive statistical representations of annual daylight distributions, mean and median annual daylight illuminance values, outperform CBDMs in correlation strength and p-value. Based upon these results, new metrics are proposed for occupant satisfaction with daylight access and views. In addition, increased daylight levels are shown to decrease reporting of lighting levels being 'often too low' even when adequate electric lighting is provided, and contrast is likely to be beneficial to space perception at non-glaring thresholds.
Calibrated climate-based lighting simulation models of buildings have the capacity to perform an ... more Calibrated climate-based lighting simulation models of buildings have the capacity to perform an essential role in post-occupancy evaluations, such as annual frequency assessments of daylighting quality and visual discomfort. However, in most post-occupancy case studies the role of lighting analysis is temporally limited by instantaneous measurements or limited in scale by requiring constant monitoring with expensive sensors. It is challenging to build calibrated models based on point-in-time measurements due to the presence of electric lighting, transient use of dynamic shades, limited information on the material specifications, and short durations of accessibility to the spaces being studied. The authors propose and present a calibration process for annual daylighting and electric lighting simulation models based on one-time field measurements of large daylit and electrically-lit spaces exemplified through a data set of 540 individual office desks across 10 office spaces. The calibration process includes measuring lighting, physical and material data during a one-time visit that are used to calibrate high dynamic range images and lighting simulation models using actual weather data. The calibration accuracy is validated based on measured and simulated luminance and illuminance data. Comparing measured and simulated illuminance, relative RMSE values were 25.8% and 45.5% for horizontal and vertical measurements respectively. When tracking errors using log10(illuminance), approximating human perceptual differences, errors of 4.3% and 6.8% were achieved. Vertical illuminance was found to vary more with measured data due to the uncertainty of monitor screen luminances. The authors aim to achieve calibrated lighting models reliable enough to be used in assessing the relationship of annualized lighting metrics to participants long-term perceptions of lighting quality, thereby enabling simulation models to be used in the post-occupancy evaluation process of building lighting. This paper demonstrates that measured data through one-time visits can be utilized to build reliable calibrated lighting simulation models to integrate long-term annual lighting results in post-occupancy evaluations.
This paper presents a post-occupancy study of 543 participants in 10 daylit office buildings in S... more This paper presents a post-occupancy study of 543 participants in 10 daylit office buildings in Singapore. Calibrated daylighting and electric lighting simulation models of each building were created and verified. HDR photographs and vertical and horizontal illuminance measurements were taken at each participant's workspace, and a survey on their long-term and instantaneous subjective evaluations of lighting were collected. For the first time, this study compares climate-based daylighting metrics (CBDM's) to occupant's long-term subjective impressions. The authors find that simulated mean annual horizontal illuminance correlates strongly with occupants' satisfaction with access to daylight. 50% occupant satisfaction with daylight begins at levels as low as 80 lx, far below current lighting sufficiency standards. Vertical illuminance measures did not exhibit strong correlations with reported discomfort. These results are an initial investigation of CBDM's use for more than lighting sufficiency and illustrate the need for further study of overlighting metrics.
This paper presents a novel study comparing advanced annual visual discomfort calculations to typ... more This paper presents a novel study comparing advanced annual visual discomfort calculations to typical illuminance-based overlighting metrics. The Unified Glare Rating (UGR), Daylight Glare Probability (DGP), and simplified Daylight Glare Probability (DGPs) are calculated at an occupant’s eye level and are compared to the Useful Daylight Illuminance Exceeded (UDI-e, % time ≥ 3,000 lx) climate-based daylighting metrics. 720 designs are tested annually comprising 10,121,583 individual visual discomfort calculations. The author finds that UDI-e can predict discomfort correctly or provide extra scrutiny on discomfort analysis in between 93.1% and 98.9% of cases; therefore, it is sometimes a reasonable replacement for more arduous visual discomfort calculations. Prudence is still necessary in using illuminance-based replacements in spaces susceptible to experiencing strong contrast.
Urban settlements require design improvements towards increased comfort and reduced energy consum... more Urban settlements require design improvements towards increased comfort and reduced energy consumption through active and passive means to create liveable cities in the future. This study investigates the impact of 6 urban design criteria—building height, plot ratio, greenery, glazing ratio, shading, and materiality—on discrete environmental metrics for sustainability using Morris sensitivity analysis (SA) method. The authors calculate a series of critical and emerging environmental measures which indicate the suitability of an urban design: Urban Heat Island (UHI), Outdoor Thermal Comfort—using the Universal Thermal Climate Index (UTCI), Urban Energy Use Intensity (EUI), Urban Daylight Autonomy (UDA), and Annual Mean Ventilation. This study identifies essential parameters for comfortable and low-energy urban communities in early-phase urban design processes for tropical climates using Morris sensitivity analysis. The effort is focused on an increased modelling comprehensiveness—including more related and co-dependent sustainability measures compared to previous works—and understanding the impact of parameters investigated on a comprehensive set of environmental measures. The authors find that building height and site coverage ratio most significantly impact many of the studied environmental measures. However, all parameters are significant on at least one environmental measure; therefore, it is difficult to simplify the complex process of urban environmental and sustainable design.
This paper describes a visualisation framework for organising data outputs generated from a compl... more This paper describes a visualisation framework for organising data outputs generated from a complex multi-objective optimisation design space. The three-part visualisation framework is structured to identify solution clusters along the Pareto front, before providing designers with design space navigation control through genotype value displays. These provide smaller focus design spaces which are then supported by spatial displays of a series of solution phenotypes and their respective performance simulations. This visualisation tool aims to provide a diverse range of quantitatively high-performance design solutions determined through building performance simulations, that can further subsequent higher order qualitative design evaluation such as design aesthetics.
When communicating the results of environmental building performance analysis, it is important to... more When communicating the results of environmental building performance analysis, it is important to display resultant information in order (a) to be holistically understood and (b) to guide architectural design decisions. This paper proposes a spatial dashboard of environmental performance data as a means to intuitively relate architectural form and performance and achieve the two goals above. The dashboard visualizes daylighting, natural ventilation, and thermal comfort information spatially localized throughout axonometric representations of buildings. Results can be customized by time of day, adding time as another analytical dimension in addition to space. Environmental data, normally hidden, is visually revealed in relation to architectural form. The dashboard enables intuitive design decisions to be made relative to performance measures across time and space.
This manuscript describes a methodology for organizing and displaying disparate sources of buildi... more This manuscript describes a methodology for organizing and displaying disparate sources of building performance simulation data to form spatial displays of a myriad of building performance outputs and drive design understanding from an architectural point of view. The results are based on annual simulation data, are spatially discrete, and can be displayed and interpreted through a variety statistical methods. A series of simple visualizations to describe the performance of passive and active architectural design strategies are presented in addition to further suggestions for temporally varying data display animations.
Singapore is one country that is leading the charge in environmental design in the tropics by adv... more Singapore is one country that is leading the charge in environmental design in the tropics by advocating for smart strategies in buildings. The small city-state uses Residential Envelope Transmittance Values (RETV) to quantify heat transfer through residential building façades. This study compares simulated performance metrics of ten Singaporean housing developments to calculated RETV values to evaluate qualitative metrics such as daylight penetration and interior operative temperature (comfort) against physical building features such as shading and window-to-wall ratio. The authors have determined that while RETV is a unique way to quantify thermal transfer through the building envelope, it ignores many of the qualitative characteristics implicit in passive buildings that define building performance.
Trees play a significant role in influencing daylight availability inside and outside buildings. ... more Trees play a significant role in influencing daylight availability inside and outside buildings. They temper, scatter and transmit light subsequently reducing the availability or acting as a passive source of daylight. Current daylighting simulation practices either avoid modelling trees or model them as cones, spheres or cylinders with an assumed reflectance value. Trees are complex in their shape and—depending on crown density and clumping nature—their optical properties change considerably. In order to predict the effect of trees on daylight, researchers need to first measure and quantify this effect. Hence, in this paper the authors propose a low-cost method employing high dynamic range photography and automated image processing to measure two variables of the tree crown: gap percentage and transmittance percentage. These measured variables can be used in daylight simulation platforms such as Radiance to geometrically model the crown of a tree and specify its optical properties
Measuring the luminous environment enables researchers and practitioners to study perception and ... more Measuring the luminous environment enables researchers and practitioners to study perception and visual comfort in existing environments in order to decipher the components that contribute to good or problematic lighting characteristics. High dynamic range photography is commonly used to study visual perception and comfort. This paper presents new findings and specific methods of capturing interior scenes that may include peaks caused by a direct view of the sun and specular reflections. Methods are tested to improve the range of luminance values that can be captured, and new guidelines are proposed to improve the accuracy of computed visual comfort indices.
This paper investigates accuracy in typical High Dynamic Range (HDR) photography techniques used ... more This paper investigates accuracy in typical High Dynamic Range (HDR) photography techniques used by researchers measuring high resolution luminance information for visual comfort studies in daylit spaces. Vignetting effects of circular fisheye lenses are investigated for reproducibility between different lenses of the same model and sharing between researchers. The selection of aperture size is related to vignetting intensity, dynamic range and potential for lens flare. Lighting variability during capture processes is also tracked, and it is recommended to measure vertical illuminance in order to validate the stability of a scene. Finally, luminous overflow—a concept where a HDR photograph cannot measure the true luminous environment—is introduced. Its effect on the glare metrics UGR and DGP is investigated by using neutral density (ND) filters to increase the dynamic range of photographs under direct sunlight. It is recommended to use ND filters in scenes with vertical illuminances greater than 5 000 lx or with direct vision of the sun.
This paper describes the cataloguing of opaque visual material properties in a database structure... more This paper describes the cataloguing of opaque visual material properties in a database structure based on various measurement processes from the simple (illuminance and luminance measurements) to the complex (spectrophotometers and goniophotometers). A standard rendering environment was setup in the Radiance simulation engine in order to enable comparisons of color and specularity via physically-based renderings. All materials are also organized by their surface type (wall, ceiling, floor, etc.), color, location of measurement, reflectance, specularity, roughness, and material type (plastic, metal, etc.). Furthermore, for the first time, a large amount of full-spectral measurements are available in the catalogue at 10 nm measurement increments. This is imperative for understanding circadian stimulation and photosynthetic potential in future simulation practice and architectural design analysis.
A new concept of long term visual comfort is introduced to describe the long-term visual impressi... more A new concept of long term visual comfort is introduced to describe the long-term visual impression of space occupants. This concept, in contrast to instantaneous assessment of visual comfort, aims to describe an overall rating of visual quality. A paired study consisting of occupant surveys and detailed 6-minute timestep comfort simulations was performed for the studio spaces of Gund Hall (Cambridge, MA, USA), which is occupied by over 500 students. Occupants reported four primary ways of experiencing visual discomfort: discomfort glare, insufficient monitor contrast, direct visibility of the sun and direct sunlight on the workplane. Survey results were located spatially and in terms of orientation within Gund Hall, and the simulation model was calibrated based on furniture layout, measured material reflectances and local measured weather data. The results of the study illustrate that it is possible to use current simulation-based visual comfort predictions to predict occupants' long-term visual comfort assessments in a complex daylit space. Between 53.7% and 70.1% percent of polled occupants' evaluations were correctly identified. Through a spatial and temporal presentation of the simulation data, this new methodology can be used as feedback during the process of designing daylit spaces, avoiding visual discomfort and increasing satisfaction with the built environment.
Proceedings of the Transportation Research Board 93rd Annual Meeting, 2014
Disability glare, visual impairment due to extreme brightness or contrast, can be caused by inten... more Disability glare, visual impairment due to extreme brightness or contrast, can be caused by intense reflections from new constructions nearby existing transportation or building infrastructure. A case study analysis is performed of a disability glare hazard at an airport created by the installation of a large array of photovoltaic panels between an air traffic control tower and the aircraft taxiway. The panels reflect blinding quantities of daylight into the control tower, produce temporary after images and dangerously obscure taxiing aircraft. The existing FAA guidelines for installation of solar technologies are discussed relative to their shortcomings in identifying the glare hazard.
High dynamic range photography is used to analyze the glaring situation at the airport, and the authors propose a maximum brightness threshold of 30,000 cd/m2 based on the physiology of human vision and the brightness of tasks necessary for air traffic controllers at the case-study airport. Detailed reflectivity and three-dimensional models of the photovoltaic panels and the airport are created and validated against measured data. Using these models, an annual analysis is performed of the glare hazard. This analysis is displayed temporally using graphs and spatially using images that indicate where the glaring reflections originate. Such information is useful in identifying potential for disability glare before new constructions are built. Finally, the authors use the new method to analyze designs for remediation of the glare hazard.
In this paper we present, demonstrate and validate a method for predicting city-wide electricity ... more In this paper we present, demonstrate and validate a method for predicting city-wide electricity gains from photovoltaic panels based on detailed 3D urban massing models combined with Daysim-based hourly irradiation simulations, typical meteorological year climactic data and hourly calculated rooftop temperatures. The resulting data can be combined with online mapping technologies and search engines as well as a financial module that provides building owners interested in installing a photovoltaic system on their rooftop with meaningful data regarding spatial placement, system size, installation costs and financial payback. As a proof of concept, a photovoltaic potential map for the city of Cambridge, Massachusetts, USA, consisting of over 17,000 rooftops has been implemented as of September 2012.
The new method constitutes the first linking of increasingly available GIS and LiDAR urban datasets with the validated building performance simulation engine Daysim, thus-far used primarily at the scale of individual buildings or small urban neighborhoods. A comparison of the new method with its predecessors reveals significant benefits as it produces hourly point irradiation data, supports better geometric accuracy, considers reflections from neareby urban context and uses predicted rooftop temperatures to calculate hourly PV efficiency. A validation study of measured and simulated electricity yields from two rooftop PV installations in Cambridge shows that the new method is able to predict annual electricity gains within 3.6 to 5.3% of measured production when calibrating for actual weather data and detailed PV panel geometry. This predicted annual error using the new method is shown to be less than the variance which can be expected from climactic variation between years. Furthermore, because the new method generates hourly data, it can be applied to peak load mitigation studies at the urban level. This study also compares predicted monthly energy yields using the new method to those of preceding methods for the two validated test installations and on an annual basis for ten buildings selected randomly from the Cambridge dataset.
Predicting the urban microclimate using simulation tools can help designers to increase outdoor t... more Predicting the urban microclimate using simulation tools can help designers to increase outdoor thermal comfort. This study discusses 4 prediction tools from an urban designer's view regarding their capabilities, limitations, ease of use, and accuracy. ENVI-met, RayMan, SOLWEIG, and STEVE are urban microclimate prediction tools investigated in this study. Measured and simulated air temperature, mean radiant temperature and thermal comfort indices are compared across multiple sites and weather conditions. The novelty is evaluating 4 tools' ability to help drive design decisions and the predictive accuracy of the tools that may influence those decisions from the view of an urban designer.
Calibrated climate-based lighting simulation models of buildings perform an essential role in pos... more Calibrated climate-based lighting simulation models of buildings perform an essential role in post-occupancy evaluations (POE), such as annual frequency assessments of daylighting quality and visual discomfort. However, the role of lighting analysis is temporally limited by instantaneous measurements or limited in scale by requiring constant monitoring of occupied spaces with expensive sensors. Building calibrated models is thus challenging due to limited information , short durations of access, the concurrent presence of electric lighting and daylighting, and transient usage of dynamic shades of occupied spaces. In this paper, the authors present a calibration process to build annual daylighting and electric lighting simulation models based on one-time field measurements, exemplified through a dataset of 540 individual office desks across 10 office spaces. The authors calibrated lighting models to be reliable enough for assessing the relationship of annualized climate-based daylight-ing metrics (CBDMs) to participants long-term perceptions of lighting quality. The proposed process to build calibrated climate-based models for POE's based on one-time field measurements at each building is validated through comparing measured and simulated illuminance data at every work desk and results are sufficiently positive with logarithmic relative RMSE values of 4.3% and 6.8% and relative RMSE values of 25.8% and 45.5% for horizontal and vertical illuminances respectively. Vertical illuminance was found to vary more with measured data due to the uncertainty of monitor screen luminances. This paper demonstrates that measured data through one-time visits can be utilized to build reliable calibrated lighting simulation models to integrate long-term annual lighting results in post-occupancy evaluations.
This paper presents a post-occupancy daylighting study within 17 residences in Singapore consisti... more This paper presents a post-occupancy daylighting study within 17 residences in Singapore consisting of 35 participants. Each residence was visited, and a calibrated daylighting model was constructed and validated based upon 100's of individual illuminance measurements. A survey on subjective lighting quality was administered to each participant. The authors find that simulated annual climate-based daylight measures can be used to predict subjective lighting evaluations such as satisfaction with access to daylight, whether a space is perceived as dim or bright, and when overall daylighting levels are too low. Using the mean annual daylight level per sensor, at a spatial median illuminance threshold of 175 lx, more than 80% of people are predicted to be satisfied with access to daylight in kitchens; however, in bedrooms and living rooms, satisfaction with daylight was high even at low lighting levels. Kitchens can be identified as dim or bright and all residential space types can be identified as often underlit or not based upon median spatial values of annual sensor mean illuminance. Finally, the authors share reported reasons for dynamic window shading use in the residences studied-desire for privacy was found to be of similar importance to the direct sunlight, a difference from dynamic shading use in commercial spaces.
Colours that surround us are not just the result of surface properties, rather the interplay betw... more Colours that surround us are not just the result of surface properties, rather the interplay between the spectral distribution of illuminating light and spectrally specific surface reflectance. Despite the temporal and spatial variation of daylight spectral distribution, daylight simulation platforms most commonly use lu-minance based sky models (CIE or all-weather Perez skies) that lack spectral and colorimetric information. LARK and ALFA are the two currently available spectral daylight simulation platforms that use spectral data of skies and materials to produce daylight renderings. The authors measure and perform visual, spectral and colour difference comparisons of complex urban scenes with different materiality-plaster facades, vegetation, reflective facades-in LARK, ALFA and standard non-spectral daylight simulations. The comparisons present the challenges, applications and limitations of using the currently evolving multi-spectral daylight simulations.
The research community has worked on optimizing the design, performance, and operation of radiant... more The research community has worked on optimizing the design, performance, and operation of radiant system technologies; however, the holistic interactions between architectural design decisions and radiant cooling systems design in the tropics have been left unexplored. Morris sensitivity analysis is used to analyze the design performance impact, interactions, variability and non-linear effects of 13 building and systems design parameters on energy, system and comfort performances for 3 radiant systems typologies applied to a parametric office building in the tropical climate of Singapore. It is found that window solar heat gain coefficient, window-to-wall ratio, and system set-point temperature play a key role to ensure building's high multi-objective performance and have an almost monotonic behavior with respective values falling below or equal to 54% and 57% and high room dry bulb air temperatures between 24.8 °C and 27 °C.
This paper presents a study that explores instantaneous and long-term lighting design metrics bas... more This paper presents a study that explores instantaneous and long-term lighting design metrics based on subjective evaluations within higher educational buildings in a tropical weather. Three types of classrooms-computer labs, collaborative spaces, and lecture halls-were studied. Lighting simulation models were calibrated and validated using measurements taken onsite and utilized to generate both instantaneous and annual climate-based lighting predictors. Four hundred and thirty-nine participants' responses to online questionnaires were collected. From an analysis of this data, the authors recommend instantaneous horizontal illuminance of 150 lx and vertical illuminances of 200 lx as the lighting thresholds for classrooms access to daylight, which result in 80% of occupants reporting imperceptible or noticeable daylight glare, as well as 53% of occupants comfortable with daylighting environments. Annual mean vertical illuminance of 200 lx during the daytime leads to 85% of occupants satisfied with annual access to daylight. Daylight falling on monitors should be controlled around 100 lx or lower to satisfy at least 70% of occupants and reduce reflections in monitors. For classrooms under electric lighting, horizontal illuminance of 200 lx and vertical illuminance of 250 lx are recommended to achieve visual comfort for 60% of occupants and visual discomfort for 7% of occupants.
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Papers by J. Alstan Jakubiec
High dynamic range photography is used to analyze the glaring situation at the airport, and the authors propose a maximum brightness threshold of 30,000 cd/m2 based on the physiology of human vision and the brightness of tasks necessary for air traffic controllers at the case-study airport. Detailed reflectivity and three-dimensional models of the photovoltaic panels and the airport are created and validated against measured data. Using these models, an annual analysis is performed of the glare hazard. This analysis is displayed temporally using graphs and spatially using images that indicate where the glaring reflections originate. Such information is useful in identifying potential for disability glare before new constructions are built. Finally, the authors use the new method to analyze designs for remediation of the glare hazard.
The new method constitutes the first linking of increasingly available GIS and LiDAR urban datasets with the validated building performance simulation engine Daysim, thus-far used primarily at the scale of individual buildings or small urban neighborhoods. A comparison of the new method with its predecessors reveals significant benefits as it produces hourly point irradiation data, supports better geometric accuracy, considers reflections from neareby urban context and uses predicted rooftop temperatures to calculate hourly PV efficiency. A validation study of measured and simulated electricity yields from two rooftop PV installations in Cambridge shows that the new method is able to predict annual electricity gains within 3.6 to 5.3% of measured production when calibrating for actual weather data and detailed PV panel geometry. This predicted annual error using the new method is shown to be less than the variance which can be expected from climactic variation between years. Furthermore, because the new method generates hourly data, it can be applied to peak load mitigation studies at the urban level. This study also compares predicted monthly energy yields using the new method to those of preceding methods for the two validated test installations and on an annual basis for ten buildings selected randomly from the Cambridge dataset.
High dynamic range photography is used to analyze the glaring situation at the airport, and the authors propose a maximum brightness threshold of 30,000 cd/m2 based on the physiology of human vision and the brightness of tasks necessary for air traffic controllers at the case-study airport. Detailed reflectivity and three-dimensional models of the photovoltaic panels and the airport are created and validated against measured data. Using these models, an annual analysis is performed of the glare hazard. This analysis is displayed temporally using graphs and spatially using images that indicate where the glaring reflections originate. Such information is useful in identifying potential for disability glare before new constructions are built. Finally, the authors use the new method to analyze designs for remediation of the glare hazard.
The new method constitutes the first linking of increasingly available GIS and LiDAR urban datasets with the validated building performance simulation engine Daysim, thus-far used primarily at the scale of individual buildings or small urban neighborhoods. A comparison of the new method with its predecessors reveals significant benefits as it produces hourly point irradiation data, supports better geometric accuracy, considers reflections from neareby urban context and uses predicted rooftop temperatures to calculate hourly PV efficiency. A validation study of measured and simulated electricity yields from two rooftop PV installations in Cambridge shows that the new method is able to predict annual electricity gains within 3.6 to 5.3% of measured production when calibrating for actual weather data and detailed PV panel geometry. This predicted annual error using the new method is shown to be less than the variance which can be expected from climactic variation between years. Furthermore, because the new method generates hourly data, it can be applied to peak load mitigation studies at the urban level. This study also compares predicted monthly energy yields using the new method to those of preceding methods for the two validated test installations and on an annual basis for ten buildings selected randomly from the Cambridge dataset.