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This paper investigates the cost of developing various daylighting strategies for a standard office building in relation to their ability to reduce electric lighting consumption. The reference building design for this study corresponds to a typical configuration that minimises the construction costs and is typical of the French market. We have compared scenarios that entail moving service spaces to the periphery, increasing ceiling height and adding light wells of various shapes. These special features increased the proportion of the indoor area with sufficient daylight by up to 40%, with an increase of construction costs ranging between 1.3% and 15.5% of the cost of the building. The extra cost of adding light wells was estimated at an average of €344 per work place, or €34 m −2 for a standard building with a distance between facades of 18 m. This value has to be compared with typical construction costs of €1500 m −2 . Payback time on investment based only on savings on lighting electricity appeared to be far too long (from 41 years to 540 years depending on the configuration tested) for this alone to justify the investment. However, benefits should be assessed in relation to the occupants’ well-being, safety in case of an electrical black-out, and rental and resell value. [ABSTRACT FROM AUTHOR]

Energy certification of buildings is promoted by the current energy policy of the European Union. The Building Energy Performance Regulation was published in 2002 and since then several studies have been conducted in European countries. The lighting energy requirements of buildings are determined using the methodology described in the European Standard EN 15193 which takes into account the required visual comfort conditions. In Turkey, a new national calculation methodology, Building Energy Performance-Turkey (BEP-TR), has been developed based on Turkey’s particular conditions. In this paper, the BEP-TR lighting module is briefly described. Its use is then demonstrated by the prediction of the lighting energy requirements for a prototype primary school classroom in different locations in Turkey. The paper also performs a sensitivity analysis of the BEP-TR methodology on the developed daylighting and electric lighting design alternatives. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to determine the optimal office lighting use with different types of lighting controls to achieve energy savings and provide visual comfort for individuals. Design/methodology/approach – A case study and field measurements were carried out in 18 single-occupancy offices in Sweden where six different lighting controls were investigated. Occupancy and daylight hours were key issues for determining the lighting use. For each office, occupancy patterns, use of a ceiling luminaire, energy usage and perceptions of office lighting in the spring-summer and autumn-winter were established. Findings – The use of luminaires varied among the occupants and could be habitual. Though the study yielded positive results concerning the potential for manual or daylight dimming with occupancy switch-off controls to increase optimal lighting use, combining dimming controls with manual on/off controls is rather effective if occupants generally sit in their offices most of the day. Research limitations/implications – Precise comparisons of the performances of the different controls were limited due to the offices’ different window orientations; thus, measurements in identical offices are desirable. The small sample size limited analyses of lighting use and the personal perceptions of lighting quality. Practical implications – Apart from the contribution to simulation techniques, the findings imply that office lighting controls should be selected taking individuals’ behavioural patterns and perceived lighting quality into consideration. Originality/value – This paper describes an approach to determine the use of lighting controls and provides a basis for establishing optimal lighting use for individuals with regard to occupancy and daylight availability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Traditional dynamic shading systems are usually driven by electricity for continuously controlling the angle of blind slats to minimize the indoor solar heat gain over times. This paper proposed a novel design of buoyancy driven dynamic shading system, using only minimum amount of electricity. The energy performance and the improved thermal comfort induced by the system were simulated by EnergyPlus for a typical office space under the context of Taiwanese climate. The design processes are composed of three parts: an alterable angle of blind slats that raises the energy performance to be suitable for every orientation, the buoyancy driven transmission mechanism, and a humanized controller that ensures its convenience. The environmental friendly design aspects and control mechanisms to fulfill demands for manufacturing, assembling, maintenance and recycling, etc., were also presented as readily for building application. Besides, the effectiveness of cooling energy saving and thermal comfort enhancing were compared against the cases without exterior blinds and with traditional fixed blinds installed. The results show that the cooling energy is drastically reduced over times and the blind system is effectively enhancing the indoor thermal comfort. [ABSTRACT FROM AUTHOR]

Research has shown multiple effects of light correlated color temperature (CCT) on office staff. However, the CCT ranges in previous research were relatively narrow. This study investigated the effects of CCT over a wider range and examined the influence of task type and light exposure duration. A within-subject design involving 4 CCTs (4000, 6000, 8000, and 10,000 K) × 2 task types (computer vs. paper-based task) × 2 test times (5 vs. 90 min) was employed. The results showed that CCT had main effects on perception, mood, and performance. Participants felt more comfortable but also sleepier under the lighting of 4000 K than other CCTs. Positive mood deteriorated, but task performance might improve with a gradual CCT manipulation from 4000 K to 10,000 K. Furthermore, participants rated their mood more positively with computer tasks than with paper-based tasks, but no significant effect of light exposure duration was found in this study. These findings highlight that the optimal CCT level varies for different demands such as comfort, positive mood, alertness and task performance, so selection of office light CCT should be weighed according to the scenario demands. • Effects of office light CCTs were investigated for a wide range of 4000–10000 K. • The influence of task type and light exposure duration were analyzed. • The optimal CCT level varied for comfort, mood, alertness, and performance. • Results showed a more positive mood with computer tasks than paper-based tasks. [ABSTRACT FROM AUTHOR]

The European Union has financed a 3-year research project to establish optimal spectral power distributions of LED light sources for use in offices, commerce and homes. This paper summarizes the general questions relevant to colour preference investigations and introduces the investigations performed in the three laboratories that participated in the research. Subsequent papers will deal with details of the investigations and provide recommendations for optimum spectra in different indoor applications. [ABSTRACT FROM AUTHOR]

In order to determine user acceptance for light-emitting diode (LED) office lighting, a full-scale experiment was conducted in two mock-up office rooms with different light spectra at two different illuminances. Six LED spectra and two fluorescent lamp spectra were used for the study. There were four spectra (three LED spectra and one fluorescent lamp spectrum) at a correlated colour temperature (CCT) of 4000 K and four spectra (three LED spectra and one fluorescent lamp spectrum) at a CCT of 6500 K. Forty observers evaluated the lighting environments under different spectra and rated the lighting environments sitting at a working desk and at a meeting table. The observers preferred the task illuminance of 500 lux to 300 lux and the CCT of 4000 K to 6500 K. The observers preferred the spectral power distributions (SPDs) under which they found the lighting environment to look brighter and more spacious. The observers’ preferences showed that spatial brightness was affected by illuminances and SPDs. The lighting with a SPD having higher values of a reference-based metric (CQS Colour Preference Scale) and an area-based metric (CQS Gamut Area Scale or Gamut Area Index) was preferred most at a CCT of 4000 K. It was also found that the lighting with the fluorescent lamp was least preferred among the other SPDs at the CCT of 4000 K. The observers preferred both the simple and complex SPDs over fluorescent lamps at 4000 K in the office environment. It would be a good option to develop simple LED SPDs while maintaining the criteria of good lighting for an office environment. [ABSTRACT FROM AUTHOR]

Two mock-up office rooms, one with a spectrally tuneable LED lighting system and the other with a fluorescent lamp (FL) lighting system were built for user acceptance studies for office lighting. One room was illuminated with six LED luminaires and the other with six FL luminaires. Each LED luminaire has 480 LEDs (20 different LED types and 24 of each type). Each FL luminaire has eight fluorescent lamps, four with a correlated colour temperature of 4000 K and four of 6500 K. User acceptance studies in the office environments were conducted with 40 observers, each observer having 16 sessions (six LED spectral power distributions (SPDs) + two FL SPDs and two illuminances (500 lux and 300 lux)). The observers performed office-related tasks while being totally immersed in one of these lighting conditions. The objective of this study was to verify previous results obtained in small-scale booth experiments and to further study peoples’ preferences for LED office lighting. The small-scale experiments showed that LEDs with a higher value of reference-based colour metrics (such as colour quality scale (CQS) colour preference scale) and with a higher value of area-based or volume-based metrics (such as CQS gamut area scale or gamut area index) were preferred by the observers. The office room study of the present work validated the findings of the earlier experiments but now in an office lighting environment. Furthermore, the observers preferred 4000 K to 6500 K at a light level of 500 lux and the light level of 500 lux over 300 lux. It was also found that the simplest LED SPD with three peaks has similar colour quality characteristics to complex LED SPDs with several peaks. [ABSTRACT FROM AUTHOR]

The deep building layouts typical in the U.S. have led to a nearly complete reliance on artificial lighting in standard office buildings. The development of daylight control systems that maximize the penetration and optimize the distribution of natural daylight in buildings has the potential for saving a significant portion of the energy consumed by artificial lighting, but existing systems are either static, costly, or obstruct views towards the outside. We report the Dynamic Daylight Control System (DDCS) that integrates a thin cast transparent polydimethylsiloxane (PDMS)-based deformable array of louvers and waveguides within a millimeter-scale fluidic channel system. This system can be dynamically tuned to the different climates and sun positions to control daylight quality and distribution in the interior space. The series of qualitative and quantitative tests confirmed that DDCS exceeds conventional double glazing system in terms of reducing glare near the window and distributing light to the rear of the space. The system can also be converted to a visually transparent or a translucent glazing by filling the channels with an appropriate fluid. DDCS can be integrated or retrofitted to conventional glazing systems and allow for diffusivity and transmittance control. [ABSTRACT FROM AUTHOR]

Building designs regularly fail to achieve the anticipated levels of in-use energy consumption. The interaction of occupants with building controls is often cited as a key factor behind this discrepancy. This paper examines whether one factor in inadvertent energy consumption might be the appearance of post-completion errors (when an intended action is not taken because a primary goal has already been accomplished) in occupants' interactions with building controls. Post-completion errors have been widely studied in human-computer interaction but the concept has not previously been applied to the interaction of occupants with building controls. Two experiments were carried out to examine the effect of incorporating two different types of simple prompt to reduce post-completion error in the use of light switches in office meeting rooms. Results showed that the prompts were effective and that occupants switched off lights when leaving the room more often when presented with a normative prompt than with a standard injunction. Additionally, an over reliance on PIR sensors to turn off lights after meetings was observed, which reduced their intended energy savings. We conclude that achieving low carbon buildings in practice is not solely a technological issue and that application of user-models from human-computer interaction will encourage appropriate occupant interaction with building controls and help reduce inadvertent energy consumption. [ABSTRACT FROM AUTHOR]

Existing visual comfort metrics are reviewed and critiqued based upon their ability to explain the variability in human subjective responses in a daylit private office laboratory environment. Participants (n= 48) evaluated visual comfort and preference factors, totaling 1488 discreet appraisals, and luminance-based metrics were captured with high dynamic range images and illuminance-based metrics were recorded. Vertical illuminance outperformed all commonly referenced visual comfort metrics including horizontal illuminance, IES luminance ratios, daylight glare probability (DGP), and daylight glare index (DGI). The bounded borderline between comfort and discomfort is introduced, and preliminary visual comfort design criteria are proposed for several existing metrics. Fundamental limitations of glare indices are documented, and the implications of inconsistent application of luminance ratio calculation methods are quantified. Future research is detailed. [ABSTRACT FROM PUBLISHER]

For indoor lighting the glare assessment by Unified Glare Rating (UGR) is widely adopted. However, disagreement exists on how to evaluate glare of non-uniform sources. This recently gained attention with the introduction of small and bright LEDs in general lighting. Earlier studies in a laboratory set-up showed that with equivalent average luminance, discomfort glare from a non-uniform stimulus seems to be greater than that of a uniform stimulus. We investigate the relation between discomfort glare perception of office employees and a set of parameters that is typical for LED luminaires, in a representative office environment. The offered light settings varied in luminance pattern, beam shape and illuminance on the work plane. In agreement with earlier work it can be concluded that point array LED luminaires provoke more discomfort glare in open plan offices than uniform sources and that the currently used UGR is not a good predictor in these cases. The luminance characteristics in the exit window (peak luminance, luminance contrasts, and spatial luminance distribution) play an important role in the design of comfortable (LED) office luminaires. A better understanding of these characteristics and their effects on glare perception, as well as a redefinition of a glare index are essential for a reliable prediction of glare perception. [ABSTRACT FROM AUTHOR]

During the first stages of building design, issues such as local climate, surrounding buildings and orientation are determining factors. The impact of these boundary conditions on daylight illuminances in an open-plan office space is studied in terms of daylight factor, daylight autonomy and useful daylight illuminances. Climate conditions in the location determine the characteristics of the daylight source, such as the ratio between diffuse lighting and global lighting. However, surrounding buildings and elements which may block daylight in the space hold more weight than the orientation of glazed façades, but are not always taken into consideration in daylighting studies. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Daylighting systems using a parabolic trough and linear Fresnel lens. [•] Uniform illumination into the optical fibers and to large-scale building interiors. [•] Hybrid system combining daylight and LED light improves illumination quality. [ABSTRACT FROM AUTHOR]

One of the main objectives of EU climate and energy policy is to reduce energy dependency and "decarbonise" the economy. These policies have a considerable influence on the building sector, and where Directive 2010/31/EU on the energy performance of buildings establishes that all new buildings in the EU shall have to consume 'nearly zero-energy' as from 2021 and that all public authority owned or rented buildings apply these measures as from 2019. The analysis presented in this paper -focusing on the case of office buildings due to their far greater energy demands with respect to residential buildings- forms part of a study that attempts to examine the technical characteristics and economic feasibility of these "nearly zero-energy" buildings. [ABSTRACT FROM AUTHOR]

Highlights: [•] Energy efficiency of an office building lighting system in Dubai is examined. [•] Effects of daylight and artificial lighting on the HVAC system are assessed. [•] VELUX and DIALux tools are used for daylight and lighting simulations. [•] Lighting control logic algorithm is developed using FX tools and discussed. [•] Integration of lighting control and space cooling systems is presented. [Copyright &y& Elsevier]

This study estimated daylight illuminance and classified its effectiveness in an office with a movable blind system. First, measurements were carried out to validate and apply a simulation model using DIALux. Second, the simulation model was constructed utilizing physical properties similar to those of the case office. Third, the simulation model provided the daylighting calculations in terms of the slat angles of the movable blind system. A fuzzy model was later employed using the Mamdani fuzzy inference system. Four inputs, namely, hour, angle, distance and location, were fuzzified in this model. The daylight illuminance at specific points was successfully estimated by implementing fuzzy rules, resulting in a prediction power of 87%. To test the distribution of daylight illuminance inside the office, effectiveness classes of uniformity were constructed by this model in accordance with daylighting standards and design norms. Regarding the movable blind system, slat angles of 30° and 45° provided more uniformly distributed daylight than other angles throughout standard working hours. Thus, according to the degree of match between the simulated and fuzzy models, the majority of the uniformity outcomes of the fuzzy model fully fit the simulation outcomes. Because the fuzzy model successfully estimated the daylight illuminance and its distribution (uniformity), it could be easily employed to examine early architectural design schemes. [ABSTRACT FROM AUTHOR]

The lighting research often requires human surveys for defining subjective qualities rating new settings, new test scenarios is usually a time and resource-consuming task. The article deals with designing internal artificial lighting as part of the working environment, which is subject to certain rules, derived from the nature of lighting. Good lighting exerts an impact on visual comfort which contributes to overall psychological well-being and indirectly also to the quality and productivity of performance to reliability of the visual performance, which must be maintained, especially for visual demanding operations and in adverse conditions to ensure quality of work and safety. Modeling and simulation technologies are tools to streamline the presentation and assess the risks for the implementation. [ABSTRACT FROM AUTHOR]

We developed a web application to investigate online-based experiments for the psychovisual assessment of luminous environments. We reproduced online a laboratory experiment conducted in a virtual environment, in which the luminous environment of an office room lit by different combinations of ambient/task lighting was assessed by observers. A control panel of 30 observers performed both experiments. Statistical analyses revealed no statistically significant differences between data collected in the laboratory and online. In addition, an online-based experiment involving 1114 observers was conducted to study the uncontrolled experimental conditions that may impact results. We show that, by increasing the panel size, bias, mainly related to the perceived contrast and brightness of the display and the brightness of the surrounding area is removed. Findings suggest that 100 observers are enough to remove bias. [ABSTRACT FROM AUTHOR]

Der Beitrag behandelt die Erweiterung des Energieausweises durch eine ökonomische und ökologische Bewertung. Das prototypische Excel-Tool wird 'EnergieausweisPlus' genannt. Anhand eines Beispiels an einem Referenzgebäude wird gezeigt, welche unterschiedlichen Auswirkungen die untersuchten Fassadenaufbauten im Lebenszyklus haben. Es werden die Ergebnisse von sechs verschiedenen Fassadentypen diskutiert. Damit wird auch aufgezeigt, dass bereits in einer sehr frühen Planungsphase Aspekte der Energieeffizienz ebenso wie ökologische und ökonomische Aspekte berücksichtigt werden können. Evalution of various façade constructions with regard to environmental impact and life cycle assessment LCA and office building case study. The paper discusses the extension of the energy performance certificate through an economic and ecological assessment. The prototypical Excel-Tool is called 'Energy Performance Certificate Plus'. Based on an example of a reference building the different effects in the life cycle of each studied façade construction is shown. The results of the six different façade types are discussed. In an early phase of planning a building it is possible to estimate aspects of energy as well as ecological and economical influences. [ABSTRACT FROM AUTHOR]

Highlights: [•] Developed a comprehensive methodology for assessing performance of a daylight guiding system. [•] The formula for predicting indoor illuminance under clear sky condition has high level of accuracy. [•] The formula for predicting indoor illuminance under overcast sky conditions is within 30% error. [•] The louvre system can provide up to 70% more illuminance under clear sky conditions. [•] Energy simulation shows that the system has failed to achieve a reasonable cost saving. [Copyright &y& Elsevier]

Abstract: This study examines the Energy-Saving Performance Contract (ESPC) of an office building by applying IPMVP Option D in combination with the energy analysis model established for the building by eQUEST simulation software to calibrate energy consumption simulation results using actual electricity billing data. The rates of error between actual values and energy consumption simulation results from the calibrated and uncalibrated models are then explored to confirm the accuracy of the calibrated model. Finally, the calibrated model is used to examine the impact of energy consumption parameter changes on the overall energy consumption in a building. The results indicate that, compared to actual energy consumption, the mean bias error (MBE) and root mean square error (RMSE) for uncalibrated simulation results are 24.48% and 125,050, whereas the MBE and RMSE for calibrated simulation is 0.37% and 34,197. When lighting power density increases or decreases by 50%, overall energy consumption decreases by 30.78% or increases by 31.19%, respectively. Therefore, illumination density has the greatest impact on energy consumption. This study also recommends that accurate parameter settings be confirmed when using IPMVP Option D simulation verification to ensure a highly accurate building energy consumption model, thereby facilitating the Measurement and Verification (M&V) of energy savings. [Copyright &y& Elsevier]

A multi-objective methodology is proposed to optimise lighting solutions by taking into account not only energy objectives but also subjective ones such as visual preferences. The originality of this method lies in the integration of subjective data obtained from psycho-visual tests conducted with panels of observers potentially representative of end users, into a multi-objective optimisation framework. This method makes it possible to identify all the best tradeoffs and the direct correspondence between power demand and user visual preferences, to handle constraints, to handle inter-individual differences and to optimise preferences on various visual attributes at the same time. The methodology was developed through a pilot study of office lighting optimisation. The findings are consistent with previous work and provide additional application knowledge about the case study. [ABSTRACT FROM AUTHOR]

Abstract: Double-skin façade (DSF) buildings have been developed and used in both new and renovated buildings to increase human comfort and decrease energy consumption. Daylighting in DSF buildings has received less attention compared ventilation strategies. This paper aims to evaluate the daylighting characteristics of 12 existing DSF systems that are exposed to different climates by using the IES simulation software. The protocol was applied to south-facing models under overcast sky conditions and was implemented under different outdoor illuminance. Different designs of DSF systems significantly affect the indoor illuminance values inside the office. At the office entrance, the indoor illuminance values are free of glare. All DSF models fail to meet the standard indoor illuminance requirement of at least 200lx within 75% of the office space. Among all the DSF models, the percentage of the office space covered with at least 200lx are found in the range of 40–68%, 13–52%, and 5–30% at an outdoor illuminance of (19,000, 12,000, and 6000)lx, respectively. At an outdoor illuminance of 19,000lx, the studied DSF systems from subtropical climates show the best daylighting characteristics and are potential subjects for further optimization. Based on the assumptions of this case study, daylighting analysis shows that the existing 12 DSF systems do not follow daylighting strategies. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: The present study aims to define and validate an analytical procedure for determining the optimal movement profile for dynamic shading system based on the horizontal mobile blinds for high level of illumination and visual comfort in indoor environments. The algorithm is developed to design a dynamic solar shading system for an office building (Ergo Tower) situated in Milan, Italy. The calculations take into account variables such as geographic location, date, time, surface orientations and geometrical and functional characteristics of shading system. In the first step the solar coordinates and the variation of solar incidence angle on the building surfaces have been defined. Using the equations of solar geometry the typical solar path (sun position e.g. solar altitude, azimuth etc.) corresponding to the specific location for the entire year and also the variation of the incidence angle with which the direct radiation affect the building surfaces are described. Based on the geometry of shading system, the optimal values of inclination of the profiles can be calculated. Finally, due to the technical limitations of the systems, the feasible configuration has been determined corresponding to an angle close to the optimal values of inclination for ensuring appropriate shading. This test system allows the definition of the movement of dynamic solar shading systems based on a specific location and geometrical/mechanical characteristics of a certain technical solution. [Copyright &y& Elsevier]

As a demonstration, our proposed system has been introduced into actual offices in Tokyo. It consists of fluorescent lighting fixtures, light control units, microprocessors, illuminance sensors, and distributed optimization software. The lower control limit of a fluorescent light fixture is between 20% and 30%. We measured the relationship between the color temperature and the dimming range for the illuminance. The experimental results showed that the dimming range for the illuniinance was narrow. To provide each worker's desired illuminance and color teiliperature, an LED ceiling light which can control the luminance between 0% and 100% is preferable. However, LED ceiling lights for office use have not been developed so far. The two leading light equipnient niakers have prototyped LED ceiling lights. We developed an intelligent lighting system using these lights and verified its effectiveness. The experimental results showed that the proposed systeni could provide the required illuminance and color temperature, and could achieve an energy savings of 60 to 80%. The intelligent system has a high affinity for LED lights. From the point of view of effective utilization of energy, the intelligent lighting system using LED ceiling lights showed good performance. [ABSTRACT FROM AUTHOR]

There are many factors that drive the energy consumption and demand in high-rise commercial office buildings. Understanding the effects of individual building parameters and two-factor interactions can be very useful for directing building audits and developing energy simulation models. A fractional factorial analysis was conducted to evaluate a large number of building parameters in an effort to quantify their effect on building energy consumption and demand. The analysis utilized building data collected from 22 building audits of high-rise commercial office buildings located in the downtown Chicago Loop area. Simulation results for three of the buildings show the effects of each factor and two-factor interactions on energy consumption and demand over a set of climate zones. The factors of primary importance include lighting and equipment power density, chiller efficiency, window U-value, the mass of interior furnishings and supply fan static pressure. [ABSTRACT FROM AUTHOR]

Abstract -- This paper addresses the lighting design strategies and advanced technologies used in the design of the Masdar Headquarters, an office building set within Abu Dhabi, the United Arab Emirates. The building, which is now under construction, is expected to have 103% net-positive energy use. The work emphasizes design goals centered on human visual needs and investigates lighting conditions related to sustainable and climatically responsive architecture. The optimization of the daylighting design strategies is presented, including a shading trellis with integrated photovoltaic cells, the conical courtyards, and the sawtooth facade. The study highlights electric lighting concepts predicated on available daylight and advanced lighting controls that incorporate digital dimming ballasts, programmed and user operable controls, daylight harvesting, and occupancy monitoring. Simulation was utilized to investigate parameters such as daylight factor, daily radiant energy including photosynthetically active radiation (PAR) and average daily total (ADT), and sunlight patterns. These analyses informed the daylighting design, electric lighting design, and the specific lighting controls. Such lighting components supplemented by other design strategies contribute to the energy-use goals while providing high quality luminous environments that meet end-users' visual needs. [ABSTRACT FROM AUTHOR]

Daylight has the potential to positively impact occupants and reduce energy consumption in buildings if utilized correctly (). However, unintended negative outcomes can arise from unsuccessful daylighting schemes. Common issues, such as glare and heat gain, are important architectural considerations in design of the building envelope, but less studied are corresponding interior design considerations ( such as furniture layout and access to controls) and associated occupant interactions and appraisals. The purpose of the current study is to expose some of the key issues related to the occupant use of daylight and daylight control in perimeter offices, to discuss the contributing design process factors, and to suggest possible improvements to the design process including an increased role for interior designers. The research methodology followed a case study approach and included post-occupancy evaluation (POE) questionnaires, interviews, and observations of a single higher education building with intentionally daylit perimeter offices. We discovered that the building in question was passed between three separate design teams throughout the design process, which may have contributed to the lack of integration between the architectural daylight design and the interior furniture and daylighting control fit-out. More than 50% of total respondents ( n = 35) reported obstructed blind controls due to poor furniture design and layout. Of these, nearly 60% of occupants modified their office environment to gain access to blind controls. Ultimately, findings of this study demonstrate the importance of an integrated, multidisciplinary approach to daylighting design, one that considers both the specific building context and the human response. [ABSTRACT FROM AUTHOR]

Lighting represents a significant component of commercial buildings, particularly office buildings. Fluorescent lighting is invariably used in all commercial, industrial and residential areas. A significant amount of lighting energy is wasted every day by leaving the lights on and not utilizing daylight energy. However, if daylight illuminance can be harnessed, this will reduce the electricity consumption of fluorescent lamps and save energy. This paper explains possible significant savings in lighting energy consumption and hence in costs, without reducing the performance and visual satisfaction in office or industrial buildings. It is proposed to obtain energy saving by reducing the supply voltage without degradation in lighting performance. Experimental results confirm that as much as 20% of electrical energy can be saved by reducing about 9% of the supply voltage, without noticeably affecting light output while complying with lighting standard limits. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the possibility of using daylight as the main source of light for learning and teaching activities in a classroom building of the Universidade Tecnológica Federal do Paraná, in Curitiba, Brazil. Beginning with a survey on light bulb and luminaire types used in the building and on the potential of daylighting in such environments, six different classroom types with different solar orientations were selected for analysis. The research methods included the estimation of daylighting potential from obtained daylight coefficients (DCs) for periods of the year and sky conditions, other than those of the onsite measurements; the evaluation of conformity of the lighting system to the Brazilian RTQ Code (Regulamento Técnico de Qualidade), an energy consumption rating system, aimed at reducing electric energy consumption in office buildings; the estimation of electric energy demand for a combined use of daylighting and lighting system; the proposal of an efficient lighting system; and cost assessment using payback analysis. Results suggest energy savings of up to 94% when integrating daylight with the artificial lighting system, a payback within the range of 22-60 months for a complete substitution of the existing lighting system for a more efficient one. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated the effect of moving from small offices to a landscape environment for 19 Visual Display Unit (VDU) operators at Alcatel Denmark AS. The operators reported significantly improved lighting condition and glare situation. Further, visual discomfort was also significantly reduced on a Visual Analogue Scale (VAS). There was no significant correlation between lighting condition and visual discomfort neither in the small offices nor in the office landscape. However, visual discomfort correlated significantly with glare in small offices i.e. more glare is related to more visual discomfort. This correlation disappeared after the lighting system in the office landscape had been improved. There was also a significant correlation between glare and itching of the eyes as well as blurred vision in the small offices, i.e. more glare more visual symptoms. Experience of pain was found to reduce the subjective assessment of work capacity during VDU tasks. There was a significant correlation between visual discomfort and reduced work capacity in small offices and in the office landscape. When moving from the small offices to the office landscape, there was a significant reduction in headache as well as back pain. No significant changes in pain intensity in the neck, shoulder, forearm, and wrist/hand were observed. The pain levels in different body areas were significantly correlated with subjective assessment of reduced work capacity in small offices and in the office landscape. By careful design and construction of an office landscape with regard to lighting and visual conditions, transfer from small offices may be acceptable from a visual-ergonomic point of view. [Copyright &y& Elsevier]

This study evaluated the energy impacts and cost differences of multiple lighting control strategies for a controls-only retrofit of a theoretical 1970’s or 1980’s office building, analyzed in Boston and Los Angeles. The minimum control requirements of ASHRAE 90.1–2007 established an energy baseline, and six control systems were assessed. Life-cycle costs were evaluated using equipment and installation cost estimates, provided by an independent contractor, and commissioning cost estimates, provided by an independent commissioning agent. Results suggest that advanced systems can achieve nearly 50 percent energy savings compared to code compliant controls, and that the approach to space-planning can significantly influence the lighting energy density. The cost analysis shows that wireless lighting controls required lower investment to achieve a high level of functionality for retrofit applications. The cost of commissioning was found to generally be offset by the utility rebates available in both locations. This all combines to illustrate that advanced networked lighting control systems can lead to a lower lifetime cost of ownership compared to more traditional systems. [ABSTRACT FROM AUTHOR]

This paper presents an energy-efficient lighting control system for open-plan offices with two novel features: A versatile ‘plug-and-play’ wireless-networked sensing and actuation system, and a control method incorporating multiple management strategies to provide occupant-specific lighting. Workstation-based wireless photosensors are employed to measure task illuminance, and individual addressability of wireless-enabled dimmable luminaires increases the freedom of the lighting system to fulfil various lighting requirements. Daylight harvesting, occupancy control and light level tuning strategies are formulated into an optimisation problem that generates light outputs for each luminaire to produce the desired lighting at each workstation with minimal energy usage. A pilot study of the wireless-networked lighting system implemented in a small open-plan office has shown more than 60% energy savings potential compared to conventional practice without any control. [ABSTRACT FROM AUTHOR]

Abstract: During the study presented in this article, we compared two highly energy-efficient lighting scenarios for evening office lighting (i.e. electric lighting that is typically used for approxiamately 2 h in the evening). The first of these lighting scenarios (referred to as “Reference”-scenario, Lighting Power Density or LPD of 4.5 W/m2) has been successfully in use in many office rooms of the Solar Energy and Building Physics Laboratory’s experimental building, located on the campus of the Swiss Federal Institute of Technology in Lausanne, for several years. The second lighting scenario (referred to as “Test”-scenario, Lighting Power Density of 3.9 W/m2) is more energy-efficient, creates higher workplane illuminances but leads to an increased risk of discomfort glare. The aim of this study was to meticulously compare the two lighting scenarios in order to find a lighting solution for evening office lighting that offers an optimal trade-off between energy-efficiency, visual comfort and visual performance. For this purpose, objective visual performance tests (computer-based and paper-based) and subjective visual comfort assessments with 20 human subjects were carried out. The main hypothesis of our study was that the study participants would not perform worse under the more energy-efficient “Test” -scenario than under the “Reference”-scenario (which is extremely well accepted by the buidling’s occupants). We found that the two tested scenarios are comparable to usual lighting scenarios in other office rooms in terms of subjective visual comfort. The study participants preferred the “Test”-scenario to the “Reference”-scenario. Their performance in a paper-based task was significantly better under the “Test”-scenario than under the “Reference”-scenario. No significant differences in the performance during two computer-based tasks were found. We conclude that energy-efficient lighting with Lighting Power Densities of less than 5 W/m2 is already achievable in today’s office rooms without jeopardizing visual comfort and performance. Less powerfull electric lighting systems do not necessarily mean a decrease in visual comfort and/or performance; our results even show that better visual comfort and better visual performance can be achieved with less connected lighting power. [Copyright &y& Elsevier]

The external building envelope as the outermost part of the building plays the main role in creation the comfort conditions (visual, sound and thermal comfort) for their users. The thermal performance as a main function of the external envelope is very important in high energy consumption buildings. The development of tall buildings in the past decade uses a wide range of energy sources because of high user density in a limited area. Therefore, external envelopes of tall buildings should be designed for appropriate thermal performance and reduction of the total energy demand. In the first part of this paper, the external envelope types, functions and its thermal performance has been evaluated. Then the main components of the envelope that are affective on the thermal preference of external envelope are expressed in order of priority. In the next part, tall building, the need for its use and its role in terms of energy consumption has been introduced shortly. This paper has tried to analyze the tall building envelope structure and represent the envelope specifications as a design pattern to provide a low energy tall building with an appropriate thermal performance. [ABSTRACT FROM AUTHOR]