Daylight Penetration Research Articles

LRT Digest 2 Tubular daylight guidance systems

Executive summaryThis Digest concerns passive tubular daylight guidance systems (TDGS), the most commercially successful method of daylight guidance. TDGS were introduced some 20 years ago and thus...

Balcony and Jalousi Effectiveness Review to Promote Daylight in Interior for Tropical Country

City growth will eventually affect its people lifestyle. Higher buildings, which serve higher economic value, will need to be supported with open area for social interaction. The three principal of sustainable design is not only to embrace the economic growth, but also to consider social interaction and ecology in it. Since the colonial era Balconies and jalousies are well known as architectural elements that provide more space for interaction, economically possible to make use of, and provide shading for the space underneath. This research will investigate how these elements efficiency will affect the introduction of daylight into interior space to save energy. This quantitative research was conducted with IES-VE 2012 software with embedded suncast, Flucs-DL, and Radiance software in it to calculate the depth of daylight penetration and glare potential. The simulation was set in tropical country (Singapore).

Performance of a daylight guiding system in an office building

Daylighting systems in commercial buildings can produce various benefits such as maximizing daylight penetration, optimizing visual comfort and reducing energy consumption. Optimizing and balancing the desirable and unpleasant effects of a daylighting system can be a challenge and requires a comprehensive study, with both measurements and simulation. This study examines the effectiveness of installing a controlled semi-silvered reflective louvre system in the clerestory portion of a direct solar (north) facing façade system in a deep cellular office space. On-site measurements were made to evaluate the performance of the system. Simulation and correlation studies have been carried out to identify the daylight contribution of the louvre system. The energy-saving potential and cost benefits of the daylight-guiding system were predicted using energy simulation. Experimental results show that the reflective louvre system can provide up to 70% additional illuminance at the workplane level under clear sky conditions. However, the system failed to produce a reasonable cost saving to the office space and has the drawback of creating contrast and casting light patterns onto the room surfaces at different times of the day.

A double-pane window with enclosed horizontal slats for daylighting in buildings in the tropics

In the tropics, daylighting from a side window requires shading to intercept direct sunlight from the window whilst allowing penetration of daylight from sky. In this paper, daylighting from a double-pane glazed window with enclosed horizontal slats (slat window) was investigated for which it is situated on either north or south wall of a room. Full-scale experiments and simulations were conducted to characterize distribution of the interior daylight from the slat window under a real tropical climate. Performance of the slat window was evaluated in terms of the “useful daylight illuminance” (UDI), interior daylight availability and light power density (LPD) of an integrated dimmable lighting system. Empirical formulas were developed for determining annual average LPD values of the dimmable lighting system over its served area. The LPD value can be used with a reduced form of the energy equation of Thailand's building energy code to evaluate the reduced annual electrical energy consumption for accreditation of the daylight use in a building. The analysis of life cycle cost proved that the daylighting from the slat window integrated with the dimmable lighting system is cost effective.

Automated Micro-controller based room lighting energy management using dimmable CFL ballast considering day-light penetration

Automated Micro-controller based room lighting energy management using dimmable CFL ballast considering day-light penetration

Computational analysis on the enhancement of daylight penetration into dimly lit spaces: Light tube vs. fiber optic dish concentrator

Capturing daylight into an unevenly lit lecture room with north-facing windows has been analyzed with the help of Photopia and Radiance. Two different daylighting systems, a light tube and a fiber-optic solar dish concentrator, are considered as means to lead light rays into an interior space with insufficient illumination from daylight. Photopia is used to photometrically model the daylighting systems as light travels through highly reflective light guiding elements of these systems. The candela power distribution curves (CDCs) generated by Photopia are imported by Radiance to produce photometric data and images of different locations in the lecture room. These results clearly reveal the functional benefits of each system when harvesting daylight for indoor illumination. For solar altitudes of less than 50°, more daylight can be harvested by the solar tracking dish concentrator system. Also, its minimum-to-average (illuminance) uniformity ratio on the work plane remains between 0.55 and 0.72, varying quite less than that of the light tube, ranging from 0.46 to 0.88.

Daylighting in atrium building: a study of the influence of atrium façade design

Atrium spaces have the potential to make vital contribution to the sustainable strategy and consequently ecodynamics of a building. The environmental benefi ts in terms of daylight, natural ventilation, and heating that an atrium offers are widely recognised. Daylight availability in an atrium space is generally high; however, this may not necessarily be true for the adjoining spaces. Previous studies indicate that the daylight performance of the adjoining spaces can be improved through the design of atrium facades, whereby there is a progressive increase in the fenestration from the upper to the lower fl oors. Therefore, this paper seeks to systematically investigate the effects of different atrium facades design characterised by varied distribution of fenestrations on daylight (DFs) in an atrium and horizontal penetration of daylight in its adjoining spaces under overcast sky conditions for a four sided, top-lit, square atrium building of Well Index (WI) 1.25. Studies were undertaken using computer simulation software programs ECOTECT and RADIANCE with the objective of understanding the infl uence of facades and providing guidelines for facade design to create optimal daylighting conditions in the adjoining spaces. Three main curves were developed, each of which included fi ve options of 20%, 30%, 40%, 50% and 60% openings on top fl oor with a progressive increase in openings and 100% opening on the ground fl oor. Results demonstrate that facade compositions have a very limited infl uence on daylight in the adjoining spaces offering very little benefi ts to the lower fl oors, where daylight is critical. But increase in opening on the top fl oor may increase DFs signifi cantly on the top two fl oors. For this study, the option of 60% opening on top fl oor with progressive increase to 100% opening on ground fl oor provided the best results.

Active Control of Daylighting Features in Buildings

: Due to increasing awareness of the importance of energy efficiency, daylighting features such as light shelves are becoming more and more popular. A light shelf is a horizontal or inclined projection with a high reflectivity meant to increase the depth of daylight penetration into a room. Currently, a light shelf is treated as a passive design element. It is designed to maximize the average distribution of daylight during the operating hours of a building and its geometry is not adapted to the changing conditions during the day. This article discusses a methodology for the active control of light shelves. A light shelf system whose geometry can be adapted is presented. The control of this system is treated as a global optimization problem. Geometrical parameters of light shelves are computed in real time to minimize the energy required for artificial lighting. An example of an office building is taken to illustrate the hourly energy savings possible through active control. It is demonstrated that building automation and control have considerable potential for energy savings.

Daylighting Strategy for Sustainable Schools: Case Study of Prototype Classrooms in Libya

Over the last few years, topics related to sustainable development and energy saving in Western countries led to several research projects aiming to promote the amount of natural daylight used in school buildings. The same issues arise now in Libya, especially those concerning the use of natural daylight. The promotion of natural daylight in the classrooms saves electrical energy and improves the working conditions for both teachers and students. The extreme solar heat in Libya has always been an imperative factor in relation to building heat. Especially during the period from June to August great care is given to avoid overheating while still preserving the use of natural daylight. The present research aims to propose and to test several architectural devices that can be integrated into educational building designs, allowing the penetration of natural daylight while respecting the traditional aestheticism and creating a comfortable school environment.

Performance Prediction by Modelling of a Light-pipe System used under the Climate Conditions of Korea

A light-pipe system can introduce daylight into the deeper building interiors, thus potentially displacing the requirement for electrical lighting. For the light-pipe system to be widely used in Korea, it is important to quantify its daylighting performance with due consideration regarding the effects imposed by the local climate conditions. This paper reports the development of a model to predict the daylighting performance of a light-pipe system used in Korea. This model study was based on the monitoring data obtained from a window-less space in which the light-pipe system was installed. The model can predict indoor illuminance distributions and daylight penetration factors as a function of outdoor illuminance, solar altitude and the amount of cloud present. Comparisons were made between the predicted and the monitored data obtained from the study; and also between predictions given by the developed model and other existing predictive models. The comparisons have provided validation of the newly developed model and that the predicted results were robust and reliable.

Monitoring and Evaluation of a Light-pipe System used in Korea

The use of natural lighting has the potential for improving both the energy efficiency and indoor environmental quality in buildings. A light-pipe system can bring natural light to spaces that would otherwise not be able to benefit from the advantages of daylight penetration. This paper presents the monitoring results of a light-pipe system that was installed in a window-less space of a building located in Korea. Indoor illuminance distributions and concurrent outdoor illuminance were monitored at a 1 s interval over a period from April 2009 to May 2009. The results demonstrated the effects caused by the amount of clouds, solar altitudes and external total illuminances; on both the daylighting performance of the light-pipe system and the indoor illuminance distributions of the space. The findings of this study indicated that the light-pipe system could be an effective tool particularly for introducing daylight indoors, even under overcast sky conditions in Korea.

Automated blind control to maximize the benefits of daylight in buildings

Venetian blinds are a common type of shading device and are increasingly operated automatically to overcome the limitations of manual operation. Automated blinds need to be controlled to maximize benefits of daylight in the point of occupant comfort and energy consumption. However, the previous control methods are focused on minimizing negative impacts of daylight, so they might fail to maximize positive impacts of daylight. They may often overpredict a blind's position, resulting in the undesirable blockage of daylight. In this paper, we propose a new control method for automated venetian blinds to maximize occupant comfort. The proposed control method can not only protect occupants from direct solar glare but also maximize daylight penetration into buildings based on occupants' preferences on daylight. The proposed control method is designed to allow the occupants to define the zone they want protected from direct sunlight. It can control the blinds to protect only the defined zone; therefore, more daylight can be introduced to the other areas, excluding the predetermined zone. A control method for the case of one blind with one zone was developed and then extended for the case of multiple blinds with multiple zones.

User attitudes toward tubular daylight guidance systems

The study reports quantity and quality of daylight delivered by tubular daylight guidance systems in large open plan offices. The daylight contribution was of the order of 25% of total design workstation illuminance giving daylight penetration factors of between 0.5% and 1.3%. User views suggest that tubular daylight guidance systems were inferior to windows in delivery of both quantity and quality of daylight although satisfaction with some aspects improves with increased daylight penetration

Determining photosensor settings for optimum energy saving of suspended lighting systems in a small double-skinned office

SUMMARY A photoelectric dimming control system applied to a suspended direct/indirect and indirect lighting system was analyzed to determine effective control options in a small office with double-skin envelope. Computer simulations were performed for photosensors positioned at three different locations with three specific configurations under three Commission Internationale de l'Elairage standard sky types. Optimum ideal dimming level was determined for each combination of room orientation, photosensor configurations and positions. In general, fully shielded photosensors achieved better control performance among other configurations used for the photosensors on the ceiling and the back wall. The effect of photosensor configurations on dimming system performance was as significant as the photosensor positions. As the penetration of daylight decreased due to the shaded area on the internal envelope, the control system performance deteriorated. The correlation between the photosensor signals and the desktop illuminance levels due to daylight was not significantly meaningful under the lighting systems. Lighting energy savings were determined for the best and good system control performance. Copyright r 2009 John Wiley & Sons, Ltd.

An Examination of Visual Comfort in Transitional Spaces

This study investigated the issue of visual comfort at building entrances as the user moves from darker interior spaces to the brighter exterior. The effects on visual comfort of several design features such as overhead trellises, solid overhangs, vertical fins, and solid sidewalls were assessed. These features were tested individually and in various combinations. Visual comfort was expressed in terms of the luminance ratios at equidistant station points along the user's path in the transition entry zone. Discomfort sensations resulting from the difference in luminance ratios according to various design combinations ranged from “dramatic” (high visual discomfort or shock) to “subtle” (little visual discomfort). It was found that several design features significantly affect visual comfort. In particular, a deep canopy with combined transmittance characteristics (partially and entirely blocking daylight penetration) extending over the entrance of the building leads to the greatest visual comfort, but a simple 4.8m overhang was also found to be adequate, leading to reasonable visual comfort.

Simulations of accidental coal immersion

Coal is currently becoming an increasingly interesting fossil energy resource and that is the reason why its maritime transport, and hence the risk of collier accidents, increase. In this work, the environmental impact of an accidental coal immersion at sea is studied: the physicochemical effects are estimated using innovative experimental setups – a laboratory seawater canal called “polludrome” is used to evaluate the behaviour of coal particles submitted to a seawater flow, and a specifically designed tub is used to study the physicochemical consequences induced when coal is introduced into continuously renewed seawater. When coal is introduced into seawater, the most easily visible consequences are physical: fine coal particles reduce the daylight penetration up to 100% and move along with the flow, and coal chunks accumulate on the floor. Chemical effects are also measured: humic matters are dissolved from coal into seawater (up to 2 mg L −1), but no release of polycyclic aromatic hydrocarbons is evidenced. Some inorganic compounds are dissolved, among which manganese, whose concentrations can reach 1 μg L −1. Fortunately, the results show that the environmental impact of this type of accident would remain limited.

Estimating depth of daylight zone and PSALI for side lit office spaces using the CIE Standard General Sky

The use of daylight has energy saving implications. But to harness daylight in buildings requires detailed analysis into its penetration. The paper predicts the depth of daylight zone and Permanent Supplementary Artificial Lighting of Interiors (PSALI) in a generalized high-rise office space in Kuala Lumpur, Malaysia. Using CIE Standard General Skies, two experiments are conducted to find the probable upper and lower limits of daylight penetration throughout the year. As CIE Standard General Skies are not widely incorporated into simulation software, therefore, a combination of Daylight Coefficient method and Waldram Diagrams is used for daylight calculation. The lowest daylight penetration is taken as the depth of daylight zone while the difference between the lowest and highest daylight penetration is considered for the depth of PSALI zone.

Evaluating visual comfort and performance of three natural lighting systems for deep office buildings in highly luminous climates

This work, part of a wider study, presents a qualitative and quantitative approach to evaluate daylighting systems for use in office buildings located in latitudes where natural luminous conditions throughout the year are of high solar radiation, as in Israel. Their widespread application in this kind of climate, where the excessive penetration of direct radiation can be a problem, is possible. They can produce a consequent improvement of working conditions and energy savings, yet this is not the case now. Three different systems that affect penetration of daylight in a sidelit office space were analysed: a single window without any external protection, a horizontal lightshelf and a basic anidolic concentrator, mounted on the view window, together with improved reflectances of the surface's finishes making office space. These were simulated through Radiance in a prototype that responds to a deep office space typology for different seasons of the year and hours of the day. The systems are compared for illuminance and glare performance.

Analytical tests for investigating the accuracy of lighting programs

To help potential users test and compare lighting computer programs, this paper defines some basic reference test cases with analytical solutions. These can be used to verify the accuracy and the capacity of lighting programs to correctly simulate different aspects of lighting calculations; daylight entry inside buildings, influence of incidence angle on glass transmittance, light distribution from luminaires having photometric files, inter-reflections between diffuse surfaces with influence of surface transmittance and finally daylight factor calculations under CIE overcast sky. To illustrate the use of these tests they were conducted with a software package available on the market, and the results compared with the analytical solutions. The tests demonstrate the software capabilities and limitations with regard to inter-reflection calculations, to simulation of luminaries and to daylight penetration through unglazed or glazed apertures.

A computer model for predicting the daylight performance of complex parallel shading systems

In tropical areas where the exclusion of solar heat from buildings is a paramount consideration, shading systems consisting of adjustable parallel multiple slats have evolved which exclude direct solar radiation whilst permitting some daylight penetration. The modelling of daylight illuminance from these systems is not easy using conventional graphical or computational quantitative techniques. This paper sets out a computer-based model for the analysis of the general case of parallel shading systems. The model is illustrated by reference to the Rowshan shading system used in the Hedjazi architecture of Saudi Arabia.