Daylight Availability Research Articles

Trees in Daylight Simulation – Measuring and Modelling Realistic Light Transmittance through Trees

ABSTRACT Trees influence daylight availability inside and outside buildings by attenuating, scattering, and transmitting light. They resemble a complex fenestration around buildings that change in form, materiality, and permeability based on species of trees, seasonal variations, and environmental or human interventions. The current practice of modeling trees in daylight simulations ignores this complexity and models tree crowns as cones, spheres, or cylinders with assumed reflectance or transmittance value. In this paper, the authors propose an open-source, low-cost method using photography and image processing to measure the on-site transmittance of a tree crown described as gap percentage. Gap percentage is used to generate a 3D primitive crown model that mimics the distribution of leaves and gaps. When used in daylight simulation platforms such as Radiance, the proposed model predicts vertical light transmittance and creates shadow patterns similar to the measured tree crown. The 3D crown model also predicts luminance and illuminance-based daylight metrics similar to a detailed morphological tree model. An open-source program is created and described to generate trees from measured gap percentage data based on this research.

Optical characterization of historical coloured stained glasses in winter gardens and their modelling in daylight availability simulations

Coloured stained glasses, with their peculiar light transmission properties, affect the perception of indoor spaces especially in winter gardens, where a great amount of coloured glazed surfaces can be easily found. This research aims at advancing the knowledge of coloured stained glasses in architecture and how they can be modelled in daylight simulation software tools. To this aim, the paper first proposes the measurement of light transmittance spectra for a series of coloured glazing tiles installed in a richly decorated Liberty style winter garden in Catania (Southern Italy). The measurements are performed in-place with a portable spectrophotometer, which does not imply dismantling the glazed tiles. A second novelty consists in the identification of the perceived chromaticity for the transmitted daylight, by means of the CIE Colour Space. This analysis reveals that, despite around 75% of the glazed elements are coloured, indoor light is still perceived as colour-neutral because of the wise location of clear panes.Then, the calculated integral transmittance values were used to model the winter garden in the Radiance-based ClimateStudio tool, and the reliability of two different degrees of simplifications in the model was also investigated. The comparison between simulated and measured indoor illuminance values demonstrates that the proposed simplified approach allows very good reliability in daylight modelling, with an average discrepancy below 11%, while also reducing time needed for the preparation of the model. Finally, the validated model is used to assess year-round daylight availability indoors by means of climate based daylight metrics.

Testing Daylight availability for cliff dwellings by adding Clerestory: A case study in Taba, Egypt

The succession of day and night affects human beings’ psychological and health status. Therefore it is essential to transfer the proper amount of daylight. The one-directional daylight source causes the most significant problem in dwellings: the deep gloom sectors. The Clerestory is an old strategy that provides daylight and air inside zones. We develop a strategy to solve daylight problems for earth-sheltered and excavated buildings. The main goal is to measure the enhancement of daylight penetration of excavated mountainous buildings settled in cliffs at various slopes after setting Clerestory. The research presents a simulation study to test Clerestory’s capability to penetrate daylight by using the DIVA plug-in as a tool. The study model is a touristic chalet with a total built-up area of 100sq—meters in Taba, Egypt. The chalet overlooks the Red Sea with a south-oriented facade. The exposed roof’s material and the Clerestory distance inward the facade control daylight penetration and cause a homogeneous daylight distribution.

Optimization of Daylighting Outdoor Availability in Urban Kampung

Liveability interprets as making residents comfortable in their built environment. As daylighting becomes a necessity for human beings, daylight availability can improve the liveability of dwelling habitats, especially in high-density urban areas. Relayouting the building block without reducing the usable floor area can improve daylight availability. Kampung Braga is an example of how a heavy slum area has a low liveability quality and classifies into impoverished slum settlements at the stake of being resettled. The spatial arrangement becomes necessary to enhance the community’s quality of life. This article aims to examine how the intervention through urban layout can affect daylight availability to improve the liveability for kampung Braga. This research uses simulation methods with climate-based daylight modelling (CBDM) software to simulate daylighting with a dynamic approach. Rhinoceros for modelling, Honeybee for vertical sky component (VSC) simulation, and DIVA for daylight availability simulation. Based on the simulation on three alternative urban layouts in line with spatial plan context, it is shown that intervention through urban layout and typology of kampung Braga has shown better VSC and daylight availability values than the existing conditions. It is necessary to pay attention to the context of the building around the site when designing a specific building typology. Modifying configuration, floor height, model, and orientation show a better VSC reception and vertical facade illumination. City stakeholders need to be aware of the low liveability of the urban kampung. Planning the right urban plan design can improve daylighting availability and increase the liveability of the urban kampung.

Regional applicability of thermochromic windows based on dynamic radiation spectrum

Thermochromic (TC) window has been developed as an effective approach to realize building energy saving by regulating solar transmittance according to temperature stimuli; however, the non-uniform transmission and absorption of the solar spectrum result in a significant color shift and temperature increase. This study investigates the radiometric, photometric and colorimetric performances of four different TC windows with an experiment-verified model. The simulation and calculation are conducted under measured spectrum conditions in Beijing; subsequently, a comprehensive evaluation method for daylight-thermal environment method is conducted. The results show that all selected TC windows possess an energy efficiency between 3.0% and 7.9%, improve daylight availability from 2.8% to 18.8%, and reduce discomfort hours by up to 111 h. Two hydrogel TC windows improve the quality of dynamic transmitted daylight by nearly 7% considering correlated color temperature and color rendering index; the HETS hydrogel TC window is found to be the most suitable for Beijing. Finally, to increase the application potential of TC windows in Beijing, several material properties are desired, including high transition temperature with high solar modulation capability, high and uniform visible light transmittance, and low emissivity. This process for the optimization of climate-responsive material can be further adopted in other areas.

Courtyard configuration to optimize shading, daylight and ventilation in a tropical terrace house using simulation

PurposeThis study aims to identify the optimal configuration to enhance the environmental conditions of a terrace house courtyard space in a hot and humid climate. The use of the courtyard has declined in new housing developments although it is an effective element to bring in light and wind to promote passive ventilation to occupants. To achieve the comfort level, the courtyard needs to be open, but some occupants modify it with enclosures, such as polycarbonate, to increase the useable and shaded area. This affects bringing in daylight but deters the passive ventilation from happening. Thus, this research is important to create a courtyard that brings in daylight and wind as well as shades from the harsh sun of the tropics and to educate the occupants on the role of the courtyard as a passive ventilation system.Design/methodology/approachThe research method employed is a simulation study. A terrace house with a courtyard design in Penang was chosen as a case study of the baseline model. The courtyard configurations of the case study were evaluated, and 4 settings based on the literature review were established for simulation. The effects of the courtyard configurations were tested through daylight and CFD simulations. Daylight and ventilation requirements from Malaysia Standard were used to evaluate and compare the effectiveness of the proposed settings.FindingsThe results suggested that the semi-enclosed courtyard feature with a shading device could provide the optimal environmental conditions of the courtyard space in a terrace house in a hot-humid climate. This paper will benefit the architectural community in which it is intended to implement courtyard design in modern terrace houses and will also contribute to the discovery of the most suitable courtyard typology in a hot-humid climate.Research limitations/implicationsThe study does not include studies on thermal comfort, energy performance, or use behavior of occupants in this courtyard. The study only focuses on the influence of different courtyard configurations in improving the courtyard space's daylight availability and indoor air movement.Practical implicationsThe data from this study reveal that alteration of courtyard design needs to suit comfort level that should not alter the functions of the courtyard as a passive design. The simulation method offers data for microclimatic conditions according to the changes in design. This study attempts to design influence on multiple parameters of shading, daylighting and ventilation to optimize the use of tropical climatic conditions.Social implicationsThe terrace house with courtyard would create a passive design strategy that would naturally ventilate, provide daylight, and will save on energy usage. The courtyard then with its enhanced comfort for the user will be able to function as a useable space to foster family relationships.Originality/valueThe study on courtyard design using the simulation method mostly have been conducted using a single parameter. This study highlights the analysis and process of identifying the optimal configuration for the architectural feature of a courtyard to provide a comfort level for occupants in hot and humid climates using the simulation method using data from two pieces of software.

Comparative Analysis of the Daylight and Building-Energy Performance of a Double-Skin Facade System with Multisectional Shading Devices of Different Control Strategies

There is a tendency toward larger transparent envelopes in architectural design, which could causes excessive energy consumption and visual discomfort. Using advanced shading systems with control strategies could potentially improve the indoor environmental quality and reduce the building energy consumption. In this research, daylight and thermal performances of a double-skin facade (DSF) system with multisectional shading devices using combinations of roller shades and blinds along with different control strategies were investigated under three representative climatic conditions of China. The performance of DSF systems with and without shading devices were comparatively analyzed by evaluating the annual heating, cooling, and artificial lighting energy consumption, daylight availability, and visual discomfort index using EnergyPlus and Radiance. The results indicated that the DSF with a multisectional shading system and proper control algorithms can save up to 6.8% and 4.8% for annual building energy consumption in Xiamen and Shanghai, respectively, but slightly increased by 2.4% in Beijing, when compared with the baseline without any shading device. For daylight performance, the multisectional shading system with proper control strategy shows a significant contribution to eliminating annual sunlight exposure (ASE) and discomfort glare while maintaining the daylight availability at a similar level compared to the system without shading. Meanwhile, the combination could improve spatial daylight autonomy (sDA) by 11.9%, 16.7%, and 19.1% in Xiamen, Shanghai, and Beijing, respectively, when compared with the individual shading system.

A Study on Daylighting Performance of Split Louver with Simplified Parametric Control

A split louver consists of two sections with their slat angles to be adjusted separately for glare protection and redirection of sunlight, respectively. The upper section works in conjunction with the lower section to enhance daylight availability and uniformity throughout the year. The study aims to improve the daylighting performance of the split louver by applying a simplified parametric control, which predetermines the angle difference between adjacent slats in the upper section for a chosen solar altitude and then keeps this difference fixed during operation. The slats in the upper section can be changed parametrically using the Grasshopper to reflect daylight onto the ceiling and then illuminate the rear zone of a space. The lower section of the split louver can control the daylight in the front space area and may affect the amount of light in the back. The performance indicator in evaluating the proposed split louver design for the chosen typical days is the percentage coverage of the work plane area for the illuminance range of 150~750 lux, which was achieved up to 100% in some cases. The proposed split louver with the simplified parametric control has the potential to provide relatively consistent and distributed daylight coverage of the floor area and a glare-free environment.

Multi-performance optimization of static shading devices for glare, daylight, view and energy consideration

Exterior static shading devices of buildings, if correctly designed, can control sunlight and daylight to reduce glare while guaranteeing interiors' natural illumination and connection to the outside which increase occupants' physiological and psychological wellbeing. The shadings can also control solar radiation, which has strong influence on buildings' energy use. Most of the existing research investigated the effects of static shadings on either energy use, or daylight availability and distribution or glare using single-view assessments. A number of studies integrated the analysis of two or the three performances. Very few analyzed the effects on view out. This research investigates through simulations the potential of exterior static shadings in reducing disturbing glare, and the effects on daylight provision, view out, and energy use in two classrooms in the northern city of Tallinn, Estonia. The novelty resides in the integration of the four performances analysis through a multi-objective optimization workflow, allowed by a spatial glare assessment method. Results showed that, for the building type and location, static shadings reduced visual discomfort by up to 89.8% while reduced primary energy use by up to 29.1% and provided adequate levels of daylight and view out. The most performative shading types and detailed results are presented and discussed.

Balancing daylight in office spaces with respect to the indoor thermal environment through optimization of light shelves design parameters in the tropics

The study aims to investigate the preferred daylighting availability ranges for the best visual and thermal comfort in office workspace through optimal modifications light-shelve parameters, grounded on parametric design and optimization, with a focus on its visual and thermal indices. To identify the final optimal solutions, single and multi-optimization scenarios were used. The findings revealed that optimizing for a single objective might obstruct the attainment of other goals. In other words, the first scenario, optimization only for daylight availability, results in an increase in temperature. While optimizing for indoor thermal performance solely, none of the preset daylight availability acceptance requirements were met. However, multi-objective optimization solutions were the final optimal solutions nearest to the ideal. Final optimum solutions of the best design parameters of light shelves can improve the total average of daylight availability by 56.25%, 50.63%, 57.50% and 71.88%, and the indoor thermal performance was improved by decreasing the average temperature for thermal environmental performance indicators by 4.15%, 3.27%, 3.17% and 4.76%, respectively, in March, June, September and December. The study concludes that daylighting levels of 500 lux to1300 lux provide the best range of optimal daylighting for visual and thermal comfort indicators for office spaces in the tropics.

Evaluation of Daylight Perception Assessment Methods.

Daylight is an important component in maintaining human health and wellbeing and plays a key role in physiological, psychological, and behavioural regulation. Understanding the complexity of daylight perception is vital since the degree of satisfaction with daylight conditions could greatly impact individual mood, behaviour and cognitive performance. This paper aims at (1) presenting an overview of current knowledge on methods for assessing daylight perception and (2) establishing a methodology for assessing daylight perception in the context of cultural background. An experiment was conducted with 50 students who were instructed to select the best and worst seats, describe the best desks’ daylight conditions and draw boundary lines between perceived daylit and non-daylit spaces in a library. The study showed that subjective rating and seat preference methods were consistent with actual daylight levels. However, participants’ boundary lines did not represent the actual daylight availability in the space. The study suggests that individual daylight perception in the context of cultural background can be assessed using the subjective rating and seat preference methods.

Predicting annual illuminance and operative temperature in residential buildings using artificial neural networks

Simulation-based multi-objective optimizations is proving to be an effective approach for supporting the building design and finding a balance between daylight availability, thermal comfort and energy performance. This article investigates the potential for applying ANNs to predict both annual daylight illuminance and operative temperature, in order to reduce the overall simulation time. The main findings from deploying a simulation model is the importance of multi sensor-node calculations including long- and shortwave radiation for operative temperature. Operative temperature is usually calculated for the room center, in contrast to daylight where illuminance is calculated for a grid of sensor-nodes. The results show a significant difference in operative temperature at different locations in the room where shortwave radiation has greatest impact on the results. It is therefore important to address operative temperature in the same way as daylight illuminance, using a grid of sensor-nodes when exploring multi-objective optimization performance. However, these calculations are computational demanding and increase simulation time by 2000%. A fully connected neural network is developed with five hidden layers and five different neuron structures. In general, the ANN models are showing promising results which may be integrated in a multi-objective design workflow. The results show significant time saving potential by implementing ANNs. The overall time is reduced by 96% by using ANN models for predicting annual temperature and illuminance values.

TROPICAL DAYLIGHT AVAILABILITY AND SKY TYPOLOGIES FOR DAYLIGHTING EVALUATION AND DESIGN

Daylighting in buildings is a critical functional requirement in the tropical climate. It has numerous benefits, whereas poor implementation is bound to create high energy consumption and user's discomfort, unlike in the temperate region. Daylight data for design is fundamental toward achieving optimal daylighting due to variations for different locations. Like most regions in the tropics, Nigeria has limited data in this regard. Therefore, this study investigated the availability of daylight and skies using daylight modelling methods. The global illuminance and irradiance data were input to model the outdoor daylight and sky types. The modelled, measured, and RadianceIES outdoor illuminance data were comparatively analysed relative to the design time and date. The results show that the sky is predominantly intermediate. More so, the monthly mean outdoor illumination varies from 47 to 67 klux at noon and as low as 9 klux during the morning and late afternoon. The study concluded that the mean outdoor illuminance for design is 30.7klux, 60.0klux, and 46.0klux at 0900, 1200, and1500 hours, respectively. In architecture, the use and applications of these data are to improve thermal, visual comfort, low-energy and task illuminance design in buildings, thus resulting in enhanced performance, cost savings, and user satisfaction.

Seasonal Effects of Daylight Conditions on Occupant Perception and Skin Temperature

Current research on the relationship between daylight and well-being has shown that access to daylight plays a relevant role both in terms of light perception and with respect to physiological mechanisms not directly related to vision. The aim of this paper is to analyze changes in reported light perception and in physiological responses, represented in this case by the skin temperature of research participants (n = 16) across three seasons (winter, spring and summer seasons) in a temperate, mid-latitude location, Karlsruhe, in southern Germany (49°N, 8.5°E). Sessions have been held in thermally stable rooms of a climate chamber, with daylight exposure to two opposing solar orientations of the glazed façade, namely equatorial and non-equatorial orientations, over 5-h morning sessions. Differences in light perception as well as changes in physiology have been observed. Results showed an increased sensitivity of the individuals in terms of light perception to changes in daylight in winter while such sensitivity dropped in spring and summer, with greater daylight availability and diminished lighting variability during sessions. Due to the intrinsic relationship between light perception and circadian entrainment, the same was verified for changes in skin temperature, which were also found to be significantly related to daylight availability. Seasonal influence suggests that variability of brightness and correlated color temperature (CCT) of natural light can affect both psychological and physiological patterns in humans.

Predicting Daylight Illuminance for 15 CIE Standard Skies Using a Simple Software Tool

Estimation of internal daylight availability is the key step in evaluating various daylighting schemes. Interior daylight is often expressed as daylight factor under the traditional International Commission on Illumination (CIE) overcast sky. Nonetheless, such approach may be inflexible to estimate the kinetic situations as the solar locations vary under cloudless skies. Recently, the CIE adopted 15 standard skies covering the usual skies found in the world. The interior daylight illuminance is influenced by the sky conditions in terms of luminance levels and distributions with respect to the window-facing orientation at any given period. The daylight coefficient concept considering the variations of the sky luminance patterns can be employed to accurately compute the indoor daylight level. A full-scale computer simulation can be costly in modeling the building geometry with a long simulation time. Moreover, additional times and advanced skills are required for preparation and post-processing. Simple design programs would be convenient and helpful in preliminary design phase when various designs and schemes are being studied and analyzed. This paper adopts a simple computer program for computing the interior daylight under the 15 CIE standard skies. The capability of the suggested software was assessed against the simulated results using a computer program, namely, RADIANCE, and the field measurement readings. The running time based on the simple program was far less than that using RADIANCE. The findings showed that the internal daylight simulated by the proposed simple software were in good agreement with the simulated results by RADIANCE and measured readings. The peak daylight factor discrepancy was <2%, and the RMSE was 14.5% of the corresponding measured average values.

Solar energy density as a benchmark to improve daylight availability and energy performance in buildings: A single metric for a single-objective optimization

Different simulation engines are currently required to perform daylight and energy evaluations of complex fenestration systems: Radiance has been validated to evaluate complex geometries but EnergyPlus cannot deal with them, making infeasible the thermal evaluations. The Shading Coefficient method adds an extra step to overcome that limitation: it runs irradiance simulations to create shading schedules that are shared between the simulation engines. This work supports the premise that Solar Energy Density (SED) can be used as a benchmark to evaluate the dual performance of perforated screens (PS). Therefore, only irradiance calculations will be required in evaluations – instead of running three different simulations. Orthogonal Arrays and Principal Component Analysis were the statistical techniques used to select the PS sample and weight the simulation results. The resultant SED thresholds concurrently fostered the accomplishment of daylighting and energy goals, at five different orientations: they maximised the daylit area and minimised the overlit area and total energy use. This work also presents an application example of the single-metric approach to test its effectiveness to perform single-objective optimization of PS design by using Evolutionary Algorithms. The SED approach has the advantage of reducing considerably the simulation time needed to perform the parametric optimization of PS.

Effect of Roller Shades on Chromaticity and Colour Rendering Performance of Transmitted Daylight

Several studies have focused on the performance of roller shades in terms of glare, outdoor vision, daylight availability and energy performance. Currently, other parameters linked to visual amenity, such as chromaticity and colour rendition, are becoming relevant. When solar radiation passes through a window, it changes its spectral composition due to the presence of the solar shading system and the glazing. Against this background, the present study focuses on the spectral transmittance of eleven woven screen fabrics and its influence on the chromaticity and colour rendition. Results show that dark-coloured woven screen shades provide higher correlated colour temperature (CCT) values (range 6470 K - 6479 K) and therefore would produce “cooler” visual environments, while light-coloured woven screen shades provide lower CCT values (range 5210 K - 5644 K) creating “warmer” visual environments. Regarding colour rendering metrics, the light transmitted through all the studied woven shades shows excellent colour rendition. Finally, it is concluded that the combined analysis of optical properties, spectral data and its impact on parameters that determine the quality of lighting in an interior space enables an understanding of woven screens performance, which results in the possibility of taking appropriate decisions when selecting woven shades.

INTRODUCTION OF NEW DAYLIGHTING METRICS FOR HEALTH, WELLBEING, AND FEASIBILITY: A STUDY OF THE INDOOR BUILDING ENVIRONMENT

ABSTRACT This study investigates the applicability of a new daylighting metric based on human health, an emerging framework for evaluating the effect of daylight on building occupants. Procedures based on modeling annual daylight availability are used to determine the mapping of daylight distribution on a daily, seasonal, and yearly basis. Literature review and experimental studies were performed to propose the new day-lighting metrics for health and wellbeing. The proposed metrics have two broad criteria, including daylighting level, timing, and duration. The two details are as follows: (1) 400 lux for 5 hours (2K lux·h) in the daytime; and (2) 500 lux for 1 hour (0.5K lux·h) in the early morning, 8AM–9AM. To verify the applicability of the proposed daylighting metrics to current buildings, sample buildings were selected and daily, spatial and seasonal differences were simulated through computer visualization techniques. Moreover, we evaluated the application of the daylighting metric on the building layout and compared the new daylighting metric for health and wellbeing with conventional daylighting metrics.

INTRODUCTION OF NEW DAYLIGHTING METRICS FOR HEALTH, WELLBEING, AND FEASIBILITY: A STUDY OF THE INDOOR BUILDING ENVIRONMENT

ABSTRACT This study investigates the applicability of a new daylighting metric based on human health, an emerging framework for evaluating the effect of daylight on building occupants. Procedures based on modeling annual daylight availability are used to determine the mapping of daylight distribution on a daily, seasonal, and yearly basis. Literature review and experimental studies were performed to propose the new day-lighting metrics for health and wellbeing. The proposed metrics have two broad criteria, including daylighting level, timing, and duration. The two details are as follows: (1) 400 lux for 5 hours (2K lux·h) in the daytime; and (2) 500 lux for 1 hour (0.5K lux·h) in the early morning, 8AM–9AM. To verify the applicability of the proposed daylighting metrics to current buildings, sample buildings were selected and daily, spatial and seasonal differences were simulated through computer visualization techniques. Moreover, we evaluated the application of the daylighting metric on the building layout and compared the new daylighting metric for health and wellbeing with conventional daylighting metrics.

Subdivided venetian blind control strategies considering visual satisfaction of occupants, daylight metrics, and energy analyses

Thermal and lighting performance in buildings depend on their facade characteristics, and are important factors to achieve environmental sustainability. Application of an integrated model that balances these two performance indices would help optimise window and shading configurations by considering the comfort of occupants. As occupants infrequently operate shadings in shared spaces, the energy efficiency and visual comfort could be improved by planning appropriate shading strategies in initial design process. Thus, this paper presents a multi-stage study on the control strategies of venetian blinds by considering visual comfort and daylight metrics, and through energy analyses. First, the case study was performed in a south-oriented daylit office room. 30 people were interviewed via a survey about working on a laptop considering three different times of a day, five blind types, and three positions. The impact of daylight on their visual comfort was surveyed at different illuminance levels which were measured by daylight loggers. The useful daylight illuminance (UDI), Daylight Availability (DAv), spatial daylight autonomy (sDA), annual sunlight exposure (ASE), and simplified daylight glare probability (DGPs) were used to evaluate the results. Finally, the window and blinds were modelled for different window to wall ratios (WWRs) for long-term energy and daylight analysis, by considering bi-directional scattering distribution function (BSDF) materials and using the five-phase matrix method.Therefore, the positions of the occupants and their activities were determined to be important parameters in deciding the most suitable blind strategy. According to occupants’ working place and daytime, subdivided shadings are recommended, particularly in 90% WWR considering both energy efficiency (40% savings) and satisfaction of occupants.