Daylight Metrics Research Articles

Daylight Design of Office Buildings: Optimisation of External Solar Shadings by Using Combined Simulation Methods

Integrating daylight and energy performance with optimization into the design process has always been a challenge for designers. Most of the building environmental performance simulation tools require a considerable amount of time and iterations for achieving accurate results. Moreover the combination of daylight and energy performances has always been an issue, as different software packages are needed to perform detailed calculations. A simplified method to overcome both issues using recent advances in software integration is explored here. As a case study; the optimization of external shadings in a typical office space in Australia is presented. Results are compared against common solutions adopted as industry standard practices. Visual comfort and energy efficiency are analysed in an integrated approach. The DIVA (Design, Iterate, Validate and Adapt) plug-in for Rhinoceros/Grasshopper software is used as the main tool, given its ability to effectively calculate daylight metrics (using the Radiance/Daysim engine) and energy consumption (using the EnergyPlus engine). The optimization process is carried out parametrically controlling the shadings’ geometries. Genetic Algorithms (GA) embedded in the evolutionary solver Galapagos are adopted in order to achieve close to optimum results by controlling iteration parameters. The optimized result, in comparison with conventional design techniques, reveals significant enhancement of comfort levels and energy efficiency. Benefits and drawbacks of the proposed strategy are then discussed.

A systematic method for selecting roller shade properties for glare protection

Currently, there is no methodical procedure for selecting solar-optical properties of roller shades, which affect the energy and indoor environmental performance of perimeter building zones. This paper presents a new systematic methodology for identifying the range of shading properties (openness factor and visible transmittance) that can significantly reduce the risk of glare. A model that calculates angular beam–beam and beam–diffuse shading optical properties using minimum inputs is used within a hybrid ray-tracing and radiosity daylighting model, validated with full-scale experiments. The temporal variation of beam and total vertical illuminance is used to define the annual visual discomfort frequency and establish a process for selecting the range of acceptable shading properties for each set of external parameters (location, orientation, glazing visible transmittance, and buffer zone). The combined impact of visible transmittance and openness factor on discomfort frequency and daylight metrics is non-linear and complex. Recommendations for openness factors and visible transmittance values are made for different scenarios. Selecting the upper limits of suggested ranges can provide more daylight into the space and reduce the probability of high contrast. These guidelines may be used for selection of shading products, followed by considerations about energy savings and provision of outside view.

Evaluation of Illuminance of Rooms Oriented to Different Cardinal Points

Daylighting levels in interiors are changed every day since sunrise to sunset in dependence on luminous exterior conditions. Indoors are illuminated by diffuse skylight prevailing time of the year in Central European counties while a lot of sunny situations occur mainly during transitional and summer periods. The later can produce overheating as well as glare or disturbing luminance due to excessive sunlight in the space close to windows. If interiors are designed with screened work places the influence of direct sunlight during working time has to be evaluated.The article will present results of computer daylight simulations in a side-lit office room oriented to cardinal points. The study is focused on daylighting evaluation of the room orientation influence on levels under clear sky conditions and compared with results achieved for the CIE overcast sky model. The calculations were run in software Daylight Visualizer 2.6.7. The daylight simulation show that applying the clear sky model for illumination of oriented rooms, the substantial different illuminances can be resulted compared to outputs from the common overcast sky daylight metrics.

Light versus Energy Performance of Office Rooms with Curtain Walls: A Parametric Study

A parametric study aimed at identifying the best performing solution in terms of lighting, heating and cooling demand minimization for an office room is presented. Different orientations, room and façade lay-outs, glazing and lighting control systems have been combined and 192 configurations have been analysed through a two-step process: daylight factor and dynamic daylighting metrics and the corresponding energy demand for lighting were calculated in step 1 using Daysim; the energy demand for heating and cooling was determined in step 2 using a quasi-steady state approach, to verify whether the best configurations obtained in step 1 also resulted in the lowest global energy demand.

Efficient venetian blind control strategies considering daylight utilization and glare protection

This paper presents the development of new venetian blind control strategies considering daylight provision, lighting energy use and visual comfort. A hybrid ray-tracing and radiosity method is used to calculate transmission through the window-blind system and interior illuminance distributions taking into account specular and diffuse material properties. Work plane illuminances are used to extract daylighting metrics, while directional light distribution and respective luminance values are used to calculate glare potential. Four types of control strategies were evaluated – a cut-off angle control, a daylight-redirecting control, and two glare protection control modes. Using the common “cut-off” angle may result in a strong second reflection that might significantly affect visual discomfort depending on view direction and profile angle. Proper rotation of the tilt angle and consideration of specular characteristics can minimize this effect and redistribute daylight deeper into the space, although glare problems cannot be eliminated in some cases. Moreover, two additional control strategies were developed based on glare probability and sky conditions: the first is a model-based control derived from real time glare simulation results. The second is a “simplified” control that uses pre-calculated correlations between glare probability and transmitted illuminance to establish binary set points that can be used in model-predictive control algorithms.A detailed daylighting analysis was performed in order to evaluate set points for blind control actions, annual daylighting metrics, lighting energy use and daylight glare probability and duration. Different room sizes, glazing properties, blind material characteristics and orientations were studied. The results showed that diffuse blinds do not reduce the risk of glare when light redirection is desired; double-sided slats with a diffuse top and a specular bottom surface are better in this regard. Fixed angles at 60° or higher provide satisfactory results for most cases, although there is a penalty in daylighting efficiency. The two glare protection control algorithms proved to be efficient in providing high daylight autonomy values without the risk of glare for all studied cases.

The daylighting dashboard – A simulation-based design analysis for daylit spaces

This paper presents a vision of how state-of-the-art computer-based analysis techniques can be effectively used during the design of daylit spaces. Following a review of recent advances in dynamic daylight computation capabilities, climate-based daylighting metrics, occupant behavior and glare analysis, a fully integrated design analysis method is introduced that simultaneously considers annual daylight availability, visual comfort and energy use: Annual daylight glare probability profiles are combined with an occupant behavior model in order to determine annual shading profiles and visual comfort conditions throughout a space. The shading profiles are then used to calculate daylight autonomy plots, energy loads, operational energy costs and green house gas emissions. The paper then shows how simulation results for a sidelit space can be visually presented to simulation non-experts using the concept of a daylighting dashboard. The paper ends with a discussion of how the daylighting dashboard could be practically implemented using technologies that are available today.

Daylight metrics and energy savings

The drive towards sustainable, low-energy buildings has increased the need for simple, yet accurate methods to evaluate whether a ‘daylit’ building meets minimum standards for energy and human comfort performance. Current metrics do not account for the temporal and spatial aspects of daylight, nor of occupants comfort or interventions. This paper reviews the historical basis of current compliance methods for achieving daylit buildings, proposes a technical basis for development of better metrics, and provides two case study examples to stimulate dialogue on how metrics can be applied in a practical, real-world context.

An intuitive daylighting performance analysis and optimization approach

The effective integration of daylighting considerations into the design process requires many issues to be considered simultaneously, such as daily and seasonal variations, illumination, and thermal comfort. To address the need for early integration into the design process, a new approach called Lightsolve has been developed. Its key objectives are to support the design process using a goal-oriented approach based on iterative design improvement suggestions; to provide climate-based annual metrics in a visual and synthesized format; and to relate quantitative and qualitative performance criteria using daylighting analysis data in various forms. This methodology includes the development of a time-segmentation process to represent weather and time in a condensed form, the adaptation of daylight metrics that encompass temporal and spatial considerations, and the creation of an interactive analysis interface to explore design options and design iterations. This system relies on optimization techniques to generate these suggestions. Lightsolve allows the designer to explore other design alternatives that may better fulfil the objectives and to learn about appropriate strategies to resolve daylight or sunlight penetration issues. It offers architects and building engineers support for daylighting design that can be employed interactively within the existing design process. L'intégration des aspects relatifs à l'éclairage naturel dans un projet d'architecture exige l'étude simultanée de nombreuses questions comme ses variations quotidiennes et saisonnières ou l'équilibre entre le niveau d'éclairement et le confort thermique. Afin de répondre à la nécessité d'une intégration rapide dans le processus de conception architecturale, une nouvelle approche baptisée Lightsolve a été mise au point. Ses principaux objectifs sont les suivants: guider le processus par une approche inverse s'appuyant sur des suggestions itératives d'amélioration du projet; fournir des paramètres annuels basés sur le climat sous forme visuelle et synthétique; mettre en relation les critères de performance quantitatifs et qualitatifs en utilisant diverses formes de données d'analyse d'éclairage naturel. Cette méthodologie inclut le développement d'un processus de segmentation temporelle permettant de représenter les conditions météorologiques ainsi que la date ou l'heure sous forme condensée; elle permet également d'englober des considérations temporelles et spatiales pour l'éclairage naturel et comprend la création d'une interface d'analyse interactive pour explorer les options et les itérations du projet dans sa phase conceptuelle. Ce système repose sur des techniques d'optimisation qui génèrent des suggestions de modifications. La méthode Lightsolve permet ainsi au concepteur d'explorer d'autres alternatives pour son projet, susceptibles de mieux atteindre les objectifs visés et de s'informer sur des stratégies appropriées permettant de résoudre des problèmes d'éclairage naturel et de penetration de la lumière directe du soleil. Elle offre aux architectes et aux ingénieurs en bâtiments une aide à la conception en éclairage naturel qui peut être utilisée de manière interactive, afin de ne pas perturber le processus de conception architecturale. Mots clés: éclairage natural, processus de conception architecturale, aide à la conception, énergie, optimisation interactive, simulation, visualisation

Scoping Study for Daylight Metrics from Luminance Maps

Metrics of the quantity and quality of daylight are essential for assessing whether buildings provide good (or even adequate) daylighting for the purposes of human health and wellbeing, visual comfort, and energy saving.At present there are only a few metrics of daylight that are used by designers and researchers. Most of these are very simple, they are based on illuminance and they do not have a proven record in research or usage.Luminance maps offer a richer source of data, and the potential to create new types of metric that will more accurately quantify the quantity and quality of daylight. Recent advantages in camera technology make luminance quick and convenient to measure and to record, opening the way to the development of new luminance-based metrics.This report investigates several potential luminance-based daylight metrics, using real data from surveyed spaces. The metrics are assessed for their stability over time, their ease, accuracy and repeatability of measurement, and their variation between spaces. Several luminance metrics are proposed as being suitable for further investigation and field trials, and eventual incorporation into design guidance.

95/04067 R502/R22 — substitute refrigerant R507 in industrial cooling

Currently, there is no methodical procedure for selecting solar-optical properties of roller shades, which affect the energy and indoor environmental performance of perimeter building zones. This paper presents a new systematic methodology for identifying the range of shading properties (openness factor and visible transmittance) that can significantly reduce the risk of glare. A model that calculates angular beam–beam and beam–diffuse shading optical properties using minimum inputs is used within a hybrid ray-tracing and radiosity daylighting model, validated with full-scale experiments. The temporal variation of beam and total vertical illuminance is used to define the annual visual discomfort frequency and establish a process for selecting the range of acceptable shading properties for each set of external parameters (location, orientation, glazing visible transmittance, and buffer zone). The combined impact of visible transmittance and openness factor on discomfort frequency and daylight metrics is non-linear and complex. Recommendations for openness factors and visible transmittance values are made for different scenarios. Selecting the upper limits of suggested ranges can provide more daylight into the space and reduce the probability of high contrast. These guidelines may be used for selection of shading products, followed by considerations about energy savings and provision of outside view.