Utilization Of Daylight Research Articles

Experimental and simulation analysis of daylight glare probability in offices with dynamic window shades

This paper presents an experimental and simulation study to evaluate daylight glare probability (DGP) in office spaces with roller shades. Roller shades can be controlled in various ways and have an openness, transmitting direct and diffuse light even when fully closed. Since DGP combines the overall brightness of the visual field and the perceived contrast of the scene in one metric, the development of glare protection guidelines is complex in this case. Full-scale experiments with an HDR camera in test offices were combined with a validated, integrated daylighting and glare model. Correlations between DGP and design parameters (work plane or vertical illuminance) were developed and the applicability of DGP and DGPs for closed and controlled shades is discussed. The results show that DGPs is not an accurate metric when the sun is within the field of view – even for low openness fabrics – while the DGP equation might need a correction for such cases, due to extreme values of the solar corona's luminance influencing the luminance term. DGP and work plane illuminance are not well correlated, except for the case of perfectly diffuse fabrics. However, for all instances when the sun is not visible by the occupant, DGPs can be used to approximate daylight glare, including cases with sunlight on various surfaces in the space, for any fabric openness and control type. This enables the development of model-based, real-time glare control shading operation, with vertical illuminance being the basic parameter. Simple sunlight protection strategies cannot prevent glare, despite maximizing daylight utilization.

Optimization of Building Performance in Terms of Envelope Elements through Combined Energy Modelling and Generic Optimization

Buildings account for approximately 40% of the global energy consumption and 36% of total carbon dioxide emissions. At present many efforts are underway to reduce energy consumption and carbon footprint of buildings by optimizing their performance. Building envelope elements have a major impact on the performance of buildings. However, the best combination of the building envelope elements for optimizing the performance of buildings is difficult to determine and is not known. Building performance analysis is mostly done through energy modelling by using a whole building simulation tool. However, this is a slow and a tedious process, and generally only a few cases are evaluated in a large range of possible scenarios. By combining a generic optimization scheme with energy modelling, the best combination of building envelope elements can be determined and, thereby, it is possible to optimize the performance of buildings successfully subject to predefined constraints. This paper describes how the performance of an office building located in the suburbs of Colombo, Sri Lanka is optimized in terms of building envelope elements through combined energy modelling and generic optimization. The optimized envelope design with its efficient utilization of daylight, not only reduces the annual energy consumption substantially, but also leads to better thermal comfort for the occupants.

Assessment of climate-based daylight performance in tropical office buildings: a case study

The utilization of daylight can significantly affect building performance, energy efficiency, productivity, as well as occupants' comfort and satisfaction in buildings. This paper aims to assess daylight performance for tropical office buildings in a parametric approach. Thus, four passive design categories are investigated, namely interior surface reflectance, glazing visual transmittance, light shelves and shading control. The approach is exemplified using the case study of two selected offices in Singapore. This study contributed to the assessment of the daylight performance and prediction of the consequences of retrofitting alternatives toward fostering the utilization of daylight in existing buildings in the tropics.

Occurrences of Standard Skies and Luminuos Turbidity Factor in Bratislava

Levels of daylighting in nature continually changing and their daily courses are different day to day. Effectiveness of daylight utilisation in buildings depends on exterior luminous conditions resulting from sunny and sunless situations. Generally, prevailing interiors are illuminated by diffuse skylight during year but sunny orientated rooms can be often exposed by direct sunlight. To describe these conditions the occurrence of sky luminance patterns and light attenuation properties of atmosphere expressed e.g. by luminous turbidity factor are needed. This paper presents the comparison and evaluation of occurrences of ISO/CIE General Standard Sky and luminous turbidity factor in two distant years on the base of measured instantaneous global and diffuse horizontal illuminance, global and diffuse horizontal irradiance and zenith luminance taken during 1995 a 2002 at ICA SAS in Bratislava. The different occurrences of luminous situations described by general standard sky types were found. Results of the luminous turbidity factor calculation show that various atmospheric pollutions during sunny situations can be expected.

Facade design principles for nearly zero energy buildings in a cold climate

Cost optimal and as energy efficient as possible façade solutions, including window properties, external wall insulation, window-to-wall ratio and external shading were determined with energy and daylight simulations in the cold climate of Estonia. Heating dominated in the energy balance and therefore windows with higher number of panes and low emissivity coatings improved energy performance. The window sizes resulting in best energy performance for double and triple glazing were as small as daylight requirements allow, 22–24% respectively. For quadruple and hypothetical quintuple glazing the optimal window-to-wall ratios were larger, about 40% and 60% respectively, because of daylight utilization and good solar factor naturally provided by so many panes. The cost optimal façade solution was highly transparent triple low emissivity glazing with window-to-wall ratios of about 25% and external wall insulation thickness of 200mm (U=0.16). Dynamic external shading gave positive effect on energy performance only in case of large window sizes whereas due to high investment cost it was not financially feasible. Limited number of simulations with Central European climate showed that triple glazing with double low emissivity coating and window-to-wall ratio of about 40%, i.e. slightly larger and with external shading compared to Estonian cost optimal one, clearly outperformed conventional design.

Daylight Factor for Energy Saving in Retrofitting Institutional Building

In Malaysia, lighting is the second electric power consumption after air conditioning and it is increasing every year. Most of the lighting design standard for building in Malaysia is based on MS1525, and this being taken without further measure on daylight consideration. Movement from inefficient and unsustainable energy practice to more energy efficient initiatives is vital for building. Universiti Teknologi Malaysia as one of the major institutional building is consuming 9 to 16 million kWh per year. Thus, about 20% of energy consumed was from artificial lighting. This paper aim to highlights the cost benefit study of lighting retrofit, which integrates the utilization of daylight into existing building. Data for this study was obtained through illumination in-situ measurement on two types of artificial lighting with the inclusive of day lighting before and after lighting retrofit. The measurement was conducted in a typical building in Block C09 of Universiti Teknologi Malaysia (UTM). Annual saving and payback period were analysed from the collected data. It is estimated that total energy consumption decreasing around 47.7% over a year from 84,232kWh to 44,014kWh by retrofitted the fluorescent T8, 36W with fluorescent T5, 25W. The estimated total annual electricity bill saving is at RM11,073 (USD3500.00). The return in retrofitting cost is at 2.5 years payback period. The payback analysis portray that lighting design is best integrated with daylight. The significant amount of saving in energy consumption and the cost of retrofit is obtained by integrating daylight as a source of lighting for interior space.

Possibilities for characterization of a PCM window system using large scale measurements

The introduction of dynamic envelope components and systems can have a significant reduction effect on heating and cooling demands. In addition, it can contribute to reduce the energy demand for artificial lighting by better utilization of daylight. One of these promising technologies is Phase Change Materials (PCM). Here, the latent heat storage potential of the transition between solid and liquid state of a material is exploited to increase the thermal mass of the component. A PCM layer incorporated in a transparent component can increase the possibilities to harvest energy from solar radiation by reducing the heating/cooling demand and still allowing the utilization of daylight. Measurements have been performed on a state-of-the-art, commercially available window that integrates PCM using a large scale climate simulator. The glazing unit consists of a four-pane glazing with an integrated layer that dynamically controls the solar transmittance (prismatic glass) in the outer glazing cavity. The innermost cavity is filled with a PCM, contained in transparent plastic containers. When dynamic components are incorporated in the building envelope, it makes the characterization of static performance (e.g. the thermal transmittance, U-value; the solar heat gain coefficient) insufficient in giving the full picture regarding the performance of the component in question. This article presents a series of preliminary measurements, and the related methodologies, carried out on a window with incorporated PCM. The tests have been carried out using several test cycles comprised of temperature and solar radiation cycling, where the aim has been to delve deeper into the possibilities for the characterization of dynamic building envelope components by full scale testing in a climate simulator, showing potentials and limitations of this approach and measurement facility. It was found that even for temperatures similar to a warm day in Nordic climate, the potential latent heat storage capacity of the PCM was fully activated. Long periods of sun combined with high exterior temperatures are needed.

Performance of a daylight-redirecting glass-shading system

This paper evaluates the daylighting performance of a prototype external dynamic shading and daylight-redirecting system, and the main focus is on the performance simulation. The demonstration project was carried out on a building with an open-plan office. Part of the original façade was replaced with the prototype façade. This layout allowed the use of the same orientation and surroundings for both façades. The working plane illuminance was measured over several months and the measurements were accompanied with annual daylight simulations. The prototype system improved the daylighting conditions compared to the original system. The visual comfort was evaluated by glare analysis and the redirected daylight did not cause an additional discomfort glare. The higher utilization of daylight can save 20% of the lighting energy. The thermal insulation of the fenestration was maintained, with slightly increased solar gains, but without producing an excessive overheating.

Utilization of Natural Daylight in Office Buildings

Daylight utilization in office buildings for creating natural indoor working condition and saving lighting consumption was reported in this paper. An office model was developed for the simulation on the influence of glazing transmittance, sill height and Window-to-wall Area Ratio (WAR) on indoor illuminance distribution and lighting saving. The equations expressing the relationship between the illuminance and the affecting factors were presented. The simulation results indicated that the lighting saving was a quadratic function of glazing transmittance. The increase of sill height by 0.1m produced an increased lighting saving of 0.219 W/m 2 in sunny day as well as 0.225 W/m 2 in cloudy day. The increase of WAR by 0.1 produced an increased lighting saving of 2.719 W/m 2 in sunny day as well as 1.687 W/m 2 in cloudy day.

Internal Shading for Efficient Tropical Daylighting in Malaysian Contemporary High-Rise Open Plan Office

In tropical climate, there is actually abundant quantity of daylight but yet to be utilised. The excessively high and unpredictable external illuminance could cause non-uniform indoor illuminance distribution and visual discomfort. In order to improve daylighting quality in contemporary high-rise open plan offices, proper design of internal shading should be investigated. A base model was derived from previous case studies for simulation using Radiance. Various venetian blinds, vertical blinds and light shelves were configured for the experiment. Daylight factor (DF) was evaluated for quantitative performance; work plane illuminance (WPI) distribution and vertical plane luminance ratio were investigated for qualitative performance. The findings demonstrated that generally blinds were not a good potential for daylight utilisation but good in reducing luminance contrast. Light shelves improved performances in DF and WPI distribution but increased the luminance contrast. Hence, integrations of light shelves and partial venetian blind (45° closed) were proposed as the effective designs for all orientations. The highest improvements of 31.8% in WPI distribution and 66.7% in luminance ratio were achieved for south and east orientations, respectively. This paper demonstrates that with proper internal shading design, effective daylighting depth can be significantly improved from typically used 2.5 H rule of thumb to 3.6 H.

Investigating Daylight Quality Using Self-Shading Strategy in Energy Commission Building in Malaysia

There are a lot of office buildings without strategies for daylight utilization. Different strategies are suggested for better use of daylight. Self-shading strategy has been suggested to eliminate direct solar radiation to minimise energy use for cooling in offices but, the amount of daylight penetrating into the building can be reduced. In this research, the effectiveness of self-shading strategy on daylight is investigated through experimental method. Daylight parameters are measured in two individual office rooms in Energy Commission Building as a model of self-shading buildings. The objective is to investigate daylight quality in individual office room based on different criteria such as work plane illuminance, relative daylight ratio, surface luminance have been compared with recommended values. Finding of this research demonstrates that by employing self-shading strategy, the amount of daylight that enters the space could reduce but by applying other strategies like light shelves and venetian blinds, with self-shading strategy, acceptable performance in terms of daylight quality can be achieved. These strategies can be employed for future design of office buildings to reduce energy consumption for lighting as well as to comply with the goal of sustainable architecture.

Availability of luminous flux below a bended light-pipe: Design modelling under optimal daylight conditions

To quantify an averaged directionality of light beams transmitted by hollow light guides the asymmetry parameter has been introduced which is computed from the luminous intensity solid or curve. In many situations, the light guides with upper part elbowed toward the Southern sky are able to collect more light than a corresponding straight pipe. However, under different sunlight and skylight conditions the internal reflections are more complex, resulting in a large variety of light-pipe efficiency. A more realistic prediction of the luminous intensity solid under manifold exterior daylight conditions is significant for the optimal design and installation of passive illumination systems using bended light guides. Here, the orientation of the elbow is crucial for an efficient utilization of daylight, especially during a clear day. This study documents that the maximum efficiency of the bended light-pipe is reached when its upper part is pointed nearby the sun position but directly towards the sun.

자연채광 유도공간에의한 전시공간내 채광에 관한 연구

In recent years, it clearly shows the tendency toward the utilization of daylight in many exhibitory buildings such as museum since the expectation of visitors for whom high illuminance levels are preferable to perceive the details of the works of art. Shading devices and special glazings are often used as the tool to control the amount of light and heat which should be avoided for the presentation of high-light sensitive art works such as paintings. Another way of controling the light is to provide the space for inducing and attenuating light in the exhibitory building. This study aims to investigate the illuminance on the exhibitory space when the space for inducing and attenuating light is applied. Interaction between the daylight and the space was simulated by Lumen Micro program with variation of the size of the exhibitory space, the length of inner wall, surface reflectivity, area of windows to obtain the illumination of the wall surface. This study shows that those variables affect the illumination on the wall surfaces. By comparing the results with suggestive illumination of KS and ICOM, available wall for display on natural lighting are suggested for the seasons and time.

Daylight utilisation in perimeter office rooms at high latitudes: Investigation by computer simulation

A simulation study of daylight autonomy in perimeter office rooms at high latitudes is presented where the following variables are studied: Glazing-to-wall ratios (GWR), climate, orientation, inner surface reflectance, glazing visual transmittance, Venetian blind management and electric lighting dimming and switching systems. Based on daylight utilisation alone, the results indicate an optimal GWR ranging between 20% and 40%, with a North orientation requiring a larger GWR (40%), a South orientation a smaller GWR (20%) and an East/West orientation an intermediate GWR (30%). The reflectance of inner surfaces has a significant effect on daylight autonomy and the use of low transmittance glazing demands a larger GWR (60%) to achieve the same daylight autonomy as 20% GWR with high transmittance glazing. Also, the results indicate that the choice of electric lighting dimming and switching systems has a more significant impact on electricity use than the GWR, orientation and the other variables examined.

An open-loop venetian blind control to avoid direct sunlight and enhance daylight utilization

Abstract Shading devices, such as venetian blinds, are widely used to eliminate glare and maintain a comfortable working environment for occupants. This paper proposes an open-loop control of blind height and slat angle based on an analytic model of solar position, and geometry of venetian blinds and the windows. The algorithm enables completely blocking direct sunlight from entering the room beyond a certain user specified interior distance from the window while enhancing daylight utilization. We derive closed-form solutions for blind height and angle which are easily implemented in practice. Moreover, the proposed blind control algorithm is simulated with favorable performance. The algorithm has also been implemented and verified in real-time test-beds.

Effect of adjacent shading on the thermal performance of residential buildings in a subtropical region

There are various architectural features of a residential building that can influence its indoor climate and electricity consumption, such as thermal insulation, window size, glazing material, albedo of building façade and orientation. In addition to these architectural features, shading effects (either by external objects or by the building itself) can also affect the thermal performance of a building. External shading effects are mainly caused by nearby trees or buildings, while shading effect imposed by the building itself usually depends on the layout design of the building, i.e. building shape and layout arrangement of the flats on each floor. Some flats in a building may receive a shading effect from adjacent flats located in the same building block. When architects or building designers conduct the layout design of a building, a number of factors such as building regulations, site limitations, scenic view, noise control, natural ventilation and daylight utilization will be considered. The thermal performance of a building is one of the major issues that should be taken into account. The objective of this study is to assess the thermal performance of residential buildings under the effect of adjacent shading in subtropical Hong Kong. A literature survey was carried out to identify typical layout designs of residential buildings from the past two decades. Building energy simulations were conducted for residential building blocks with different layout designs. It is found that adjacent shading effect has a substantial impact on the thermal performance of residential buildings. The findings are reported in this paper.

Investigating Daylight Quality in Malaysian Government Office Buildings Through Daylight Factor and Surface Luminance

In recent years, there has been an increasing interest in using daylight to save energy in buildings. In tropical regions, daylighting is always an energy saver. On the other hand, daylight provides visual comfort. According to standards, it shows that many criteria should be taken into consideration in order to have daylight utilization and visual comfort. The current standard in Malaysia, MS 1525 does not provide sufficient guideline. Hence, more research is needed on daylight performance. If architects do not consider daylight design, it not only causes inconvenience in working spaces but also causes more energy consumption as well as environmental pollution. This research had surveyed daylight performance in 5 selected office buildings from different area of Malaysian through experimental method. Several parameters of daylight quality such as daylight factor, surface luminance and surface luminance ratio were measured in different rooms in each building. The result of this research demonstrated that most of the buildings were not designed for daylight utilization. Therefore, it is very important that architects follow the daylight design recommendation to reduce consumption of electric power for artificial lighting while the sufficient quality of daylight is available. Keywords—Daylight factor, Field measurement, Daylighting quality, Tropical

Post Occupancy Evaluation of Day lighting in Lecture Halls at the New Buildings in the University Of Mosul (College Of Electronic Engineering as a Case Study)

The University of Mosul has recently witnessed a construction of several departments, administrative buildings and lecture halls which may suffer after occupation some environmental or functional problems that require deep studies and researches to diagnose those problems, Hence comes the importance of post occupancy evaluation studies of those buildings as an integral part of the planning , design and construction processes to explore what is positive and negative in the design process , and get benefit from such researches to adopt the positives to enrich the design process and stand on the negatives and their causes to find an appropriate solutions and avoid repeating them in the design of future buildings. The problems stemming from the indoor environmental quality in the lecture halls comes at the front of these negatives and in particular the daylight and the use of it to enriches the indoor environment and it is supportive impact on students and lecturers performance and psychological health on one hand and the rational consumption of energy expended on artificial lighting on the other. This study focuses on the post occupancy evaluation of daylighting in the lecture halls at the new buildings of the University of Mosul, and the college of Electronic Engineering has been chosen as a case study because the adoption of one typical design to all of its four departments and replicated in other locations. The study reveals a deficiency of utilization of daylight as a design factor to provide visual comfort for the occupants of these buildings through the cognitive and realistic measurements adopted for this study.

Genetic algorithms for ceiling form optimization in response to daylight levels

Utilization of daylight in indoor spaces creates opportunities for energy savings and is linked to increasing productivity in the workplace. This sensitive aspect in environmentally aware architectural design depends on many interfacing factors. In this research, ceiling geometry is investigated as an element that can provide control to natural light, achieved through reflection and diffusion of the external and internal reflected components of daylight. This paper presents a generic optimization procedure for architects that aids in generation and finding of curvilinear and mesh ceiling forms. The objective was to maximize daylight uniformity ratios. A genetic algorithm was developed and coded in LUA, a versatile scripting language. Radiance simulation software was employed as the backend daylighting performance calculation engine, and Ecotect as the front end form input and visualization tool. Conclusions about the optimum ceiling geometry and form for a designed example case were drawn. The presented method provided architects with a variety of choices for designs which are weighed through daylighting performance. Results showed that this approach offers a robust and yet precise form finding method.

Application of RELUX Software in Simulation and Analysis of Energy Efficient Lighting Scheme

a building with maximum utilization of daylight and use of energy efficient luminaires will reduce the cost of energy use. In the present study, by means of computer simulations using RELUX software, the interaction between natural and artificial light and the related illumination conditions expected in a commercial office building in Mumbai, India have been simulated and analysed. In this way, it was possible to evaluate the relevant loads for artificial illumination that has been considered not as the principal but a complementary light source. The main goal of this study is to show the potential of drastically reducing the electrical energy consumptions for illumination, by adopting day lighting harvesting solutions. Comparison were done using two different lighting schemes one with Fluorescent Luminaires and without daylight harvesting and other one with LED fixtures with daylight harvesting using combined occupancy and daylight dimming sensors. With the latter scheme a saving of 80% can be achieved on energy and operating costs for a period over 25 years.