Daylight Illuminance Research Articles

Quality of Daylighting in Childcare Facilities: A Comparative Study of Polish Regulations with International Sustainability Rating Systems

This study examines the quality and availability of daylight in childcare facilities, focusing on compliance with Polish Technical Conditions (TCs) and comparing them with international certification systems such as BREEAM, LEED, and WELL. Polish regulations regarding sunlight exposure require revisions to support the sustainable development of buildings, impacting children’s well-being, their health, and the building’s energy efficiency. Daylight’s significance for children’s health and development underpins the investigation, highlighting its impact on the circadian rhythm, cognitive abilities, and well-being. The research utilized computational simulations with Rhinoceros 7 and Ladybug and Honeybee plugins to model a preschool room’s daylight performance under various window configurations and orientations. Quantitative and qualitative analyses were conducted, focusing on parameters such as Daylight Factor (DF), Daylight Autonomy (DA), and Useful Daylight Illuminance (UDI). The findings revealed that while the TCs’ requirements ensure minimum daylight access, they result in nonoptimal lighting quality as defined by international standards. Almost half of the surveyed rooms in the case with a WFR of one-eighth did not meet the condition for having acceptable daylight levels, as defined in the study. In the same study, only about one-third of the analyzed variants achieved the threshold for good daylight quality. At a WFR of one-eighth, no room variant reached the level considered to indicate excellent daylight quality. The results show the need for revised regulations incorporating comprehensive metrics like Climate-Based Daylight Modeling (CBDM). This study suggests that integrating advanced methods of assessing daylight quality could significantly improve daylight conditions in childcare environments. This research is a starting point for discussing the need to modernize the Polish Technical Conditions (TC) to support the sustainable development of childcare facilities in Poland.

Effect of Ventilation Strategies of Center-Mounted Louver Ventilation Window on Building Energy Consumption and Daylighting

An innovative center-mounted louver ventilation window suitable for seasonal ventilation strategies was proposed, combining the regional climate of Qingdao. The sustainable development concept is embodied, which can not only reduce building energy consumption but also consider the quality of daylighting. This research constructed a comprehensive evaluation framework, taking an office building in Qingdao as an example. The framework utilized the parametric design platform Grasshopper and its environmental design plug-in Ladybugtools. It considered the daylighting performance and energy consumption of the building. This study included six different ventilation strategies, with energy use intensity and useful daylight illuminance as evaluation indicators. The results indicated that the seasonal ventilation strategies and parameters of blinds were optimized to significantly improve the energy efficiency of the building without compromising daylighting quality. The optimized solution reduces energy consumption from 83.81 kWh/m2 to 55.0 kWh/m2, achieving a 34.4% reduction while maintaining a high UDI. This energy-saving effect reveals the influence of different ventilation strategies on energy and daylighting. And it provides an important reference for sustainable design in similar climate contexts.

The Circadian Response to Evening Light Spectra in Early Childhood: Preliminary Insights.

Although the sensitivity of the circadian system to the characteristics of light (e.g., biological timing, intensity, duration, spectrum) has been well studied in adults, data in early childhood remain limited. Utilizing a crossover, within-subjects design, we examined differences in the circadian response to evening light exposure at two different correlated color temperatures (CCT) in preschool-aged children. Healthy, good sleeping children (n = 10, 3.0-5.9 years) completed two 10-day protocols. In each protocol, after maintaining a stable sleep schedule for 7 days, a 3-day in-home dim-light circadian assessment was performed. On the first and third evenings of the in-home protocol, dim-light melatonin onset (DLMO) was assessed. On the second evening, children received a 1-h light exposure of 20 lux from either 2700 K (low CCT) or 5000 K (high CCT) (~9 and ~16 melanopic equivalent daylight illuminance (mEDI lux), respectively) centered around their habitual bedtime. Children received the remaining light condition during their second protocol, with the order counterbalanced across participants. Salivary melatonin was collected to compute melatonin suppression and circadian phase shift resulting from each experimental light condition. Melatonin suppression across the 1-h light stimulus was significantly greater during exposure to the high CCT light (M = 56.3%, SD = 19.25%) than during the low CCT light (M = 23.90%, SD = 41.06%). Both light conditions resulted in marked delays of circadian timing, but only a small difference (d = -0.25) was observed in the delay between the 5000 K (M = 35.3 min, SD = 34.3 min) and 2700 K (M = 26.7 min, SD = 15.9 min) conditions. Together, these findings add to a growing literature demonstrating high responsivity of the circadian clock to evening light exposure in early childhood and provide preliminary evidence of melatonin suppression sensitivity to differences in light spectrum in preschool-aged children.

Crucial impact of spectrum calculation on energy and daylighting performance of glazing windows

The rapid advancement of spectrally selective materials has enabled the development of smart windows that can regulate different bands of solar radiation. However, existing methods for calculating spectral properties vary, leading to inconsistent results when evaluating their light-electricity-heat-color performance. Therefore, this paper presents five methods for calculating window spectral properties, intending to compare and identify the most effective approach for assessing building thermal performance, energy efficiency, and daylighting. The methods focus primarily on the solar spectrum input and the glazing spectrum response. The solar spectrum inputs include the Beijing local solar spectrum, ASTM G173-03, and ISO 9845 (methods S1 to S3), and the glazing spectrum response methods differ based on whether they account for spectral selectivity and the choice of spectral weighting functions (methods S3 to S5). The findings reveal that variations in solar spectrum input have a minimal effect on window performance, while differences in glazing spectral response calculations significantly impact results. It is particularly evident in thermochromic windows, where discrepancies in energy efficiency, specifically in lighting load, can reach up to 67.21 %, and variations in dynamic daylighting performance, specifically in Useful Daylight Illuminance (UDI) below 500 lx, can be as high as 28.27 %. To provide more accurate assessment results of glazing windows, this study recommends using the spectral calculation method S1, which incorporates the local solar spectrum and applies the standard luminous efficiency function to the glazing spectrum response. This paper highlights that further refinement of spectral calculation methods will enhance their utility for performance evaluation and guide the reverse design of innovative window features.

Useful daylight illuminance for ornamental plants in buildings – The method to design the green interior

Useful daylight illuminance for ornamental plants in buildings – The method to design the green interior

Design and Development of a Low-Cost Educational Platform for Investigating Human-Centric Lighting (HCL) Settings

The design of reliable and accurate indoor lighting control systems for LEDs’ (light-emitting diodes) color temperature and brightness, in an effort to affect human circadian rhythms, has been emerging in the last few years. However, this is quite challenging since parameters, such as the melanopic equivalent daylight illuminance (mEDI), have to be evaluated in real time, using illuminance values and the spectrum of incident light. In this work, to address these issues, a prototype platform has been built based on the low-cost and low-power Arduino UNO R4 Wi-Fi BLE (Bluetooth Low Energy) board, which facilitates experiments with a new control approach for LEDs’ correlated color temperature (CCT). Together with the aforementioned platform, the methodology for mEDI calculation using an 11-channel multi-spectral sensor is presented. With proper calibration of the sensor, the visible spectrum can be reconstructed with a resolution of 1 nm, making the estimation of mEDI more accurate.

Optimization Potential of Side-Lit Windows for Energy and Daylight Performance of University Classrooms in Shanghai

University classrooms have an urgent need for energy saving and environmental optimization due to the energy consumption characteristics and the demand for a daylight environment. Classrooms in hot summer and cold winter (HSCW) areas in China are typically designed with a south-facing layout, but the indoor environment of the classrooms in actual use is not as satisfactory as it should be. This research examines the impacts of side-lit window design parameters and shading forms on the energy and daylight performance by using measurements and simulation. It is found that there is significant seasonal variation in the energy consumption of teaching buildings in HSCW areas, with cooling energy consumption being the primary focus of energy conservation. Additionally, appropriate shading measures can not only compensate for the energy deficiencies of the orientation and window-to-wall ratio (WWR), but also considerably enhance the indoor daylight conditions. The results indicate that the most effective way to optimize energy and daylight performance in classrooms is to adopt a north-facing layout with 400 mm shading louvers. The illuminance level of the working plane can be made more uniform and the useful daylight illuminance (UDI) can be increased to over 60%. Therefore, classroom designs in HSCW areas can be more flexible in terms of optimizing energy efficiency and daylight conditions by integrating various design parameters and shading measures.

Daylighting in modernist educational architecture in the United Kingdom

The consideration of environmental quality in buildings became prominent in the Modernist movement in the UK and on the international scene, after the Second World War, including the emphasis on daylight access, particularly in educational buildings. The Marylebone building of the University of Westminster (1970s), in central London, is an example of this architectural trend. With rooflights, tilted ceilings, double height spaces and other features, this is a late modernist example of optimised daylighting design in educational buildings in the United Kingdom. However, the north-south symmetrical approach to the rooflights and the distribution of internal spaces raise questions about the efficiency of daylight. Hence, the aim of this technical study was to assess the daylight performance of the Marylebone building, considering its original and current layouts, with the use of Climate-Based Daylight Modelling (CBDM). Performance criteria included Useful Daylight Illuminance (UDI), Daylight Factor (DF), Illuminance levels and Glare Probability. Among the main results, it was found the achievement of the minimum threshold of 300 lux for most of the year (equivalent to 2% DF). Risks of glare were identified closer to windows and under the rooflights on the south side. It is concluded that the daylight strategies of the project were attuned to the activities and furniture layout of the atelier studio of the 1970s but not fully suitable for the use of personal computers that replaced the drawing boards in the 1990s, due to the excessive illuminance levels and penetration of direct solar radiation, leading to the recent insertion of internal blinds.

Indoor Daylighting Quality Optimization Methods of a Novel Linear Transmissive Concentrator-Photovoltaic/Daylighting System in Overcast Conditions

This study proposes a control method for improving the efficiency of natural daylighting in linear transmission-type concentrator-photovoltaic/ daylighting (LTC-PV/D) systems. The study focuses on tackling the low capacity efficiency and shading of light in LTC-PV/D systems under overcast environments. The light-harvesting performance of a proposed new dynamic trackable transmissive concentrating integrated window in an overcast environment is investigated in this study. The results indicate that, in terms of light harvesting efficiency, the percentage value of the daylight factor value of the LTC-PV/D system being more than 2% is 78.8%. Further, the maximum illuminance uniformity result reaches 0.43, which is in line with the standard of indoor illuminance demand and superior to the common results of the photovoltaic window (66.06% and 0.31), indicate a good day-lighting performance in overcast environments. For the regulation method of LTC-PV/D systems in overcast environments, the recommended control angle is 90° for using the daylight factor and uniform daylight factor indices as evaluation criteria. The trend of the indoor useful daylight illuminance is affected by different levels of outdoor diffuse radiation. For an outdoor diffuse radiation less than 280 W/m2, the optimal control angle is 90°. For outdoor diffusion radiation levels of 320, 360, and 400 W/m2, the corresponding optimal regulation angles are 55°, 35°, and 25°, respectively. This study presents a control method for the transmissive concentrating photovoltaic louver under overcast conditions, which aims to optimize and enhance the indoor natural lighting environment of buildings. The proposed method increases the maximum useful daylight illuminance by 37.3%.

Experimental Evaluation Study of the Comfort and Energy Performance of Suspended Particle Device Smart Windows in a Residential Building: Achieving Optimal Control during the Cooling Season

In contrast to traditional windows, smart windows dynamically affect indoor visual and thermal environments through Visible light transmittance (VT) and Solar heat gain coefficient (SHGC) changes. Therefore, for enhancing smart window application effects, it is necessary to analyze comprehensively the impacts of smart window tinting on indoor visual and thermal environments, and to establish appropriate tinting control methods. This study aimed to determine optimal smart window control strategies for residential buildings during the cooling season by evaluating visual and thermal comfort and energy performance in an actual building equipped with SPD smart windows. An experimental building was located in Sejong, South Korea (36.5°N latitude, 127.3°E longitude; temperate climate zone), and the measurements were conducted from July to August 2023 to compare glare, indoor daylight illuminance, thermal comfort, and cooling and lighting energy between typical and smart windows. And, optimal control methods were proposed from general comfort and energy performance perspectives. The measurements indicated that it was difficult to satisfy all aspects of the visual and thermal environment, and comprehensively it was recommended to employing “always tinting” on summer. However, on a clear day, jointly applying smart windows and lighting dimming control and controlling automatically based on indoor daylight illuminance levels were found to be the most effective as it not only secured visual comfort performance but also reduced lighting energy consumption.

Multi-objective optimization of horizontal louver systems with flat, single-curvature, and double-curvature profiles to enhance daylighting, glare control, and energy consumption in office buildings

Identifying the most optimal slat shape significantly influences the performance of louver systems in terms of daylighting, glare control, and energy consumption. This is particularly crucial in climates with high levels of solar irradiance, where thermal gain and daylight illumination highly affect buildings and occupants. This study aims to identify the optimal slat shapes for various profile types—flat, single-curvature, and double-curvature—that simultaneously reduce annual energy consumption and enhance annual daylighting and visual comfort performance in fully glazed office buildings. This goal is achieved by employing a multi-objective optimization (MOO) algorithm, NSGA-II, applied to a control-point-based algorithm designed to generate diverse slat shapes for each profile type. The main objective functions include the maximization of spatial useful daylight illuminance (sUDI) and spatial glare autonomy (sGA), as well as the minimization of energy use intensity (EUI). The MOO process results in a diverse set of Pareto optimal slat shapes for each profile type, which are subsequently ranked by a fitness function. Findings suggest that the Pareto optimal solutions within each type significantly improve the overall performance of the space compared to the base case. Specifically, among these solutions, flat profiles with the highest fitness scores enhance daylighting levels of the space to a greater extent (9.028% to 14.583%) compared to single (−2.778% to 12.5%) and double-curvature profiles (−5.556% to 9.722%) with the highest scores. Regarding glare, double-curvature profiles with the highest fitness scores provide a more visually comfortable environment for users by improving the sGA value by 19.879% to 33.247% compared to the base case. However, those with a concave-convex shape produce excessive illumination in the perimeter zone, whereas those with a convex-concave shape present challenges in providing sufficient daylight in the rear zone of the space. Additionally, applying any of the Pareto optimal solutions to the louver system reduces the annual energy consumption of the office space compared to the base model. While the improvements are almost comparable, flat profiles with the highest fitness scores marginally reduces energy consumption to a greater extent (62.906% to 68.161%).

Energy saving potential of advanced dual-band electrochromic smart windows for office integration

Integrating dynamic transparent technologies into building envelopes is becoming crucial for tackling the challenges posed by climate change, improving energy efficiency, and enhancing occupant comfort. Nowadays, a range of dynamic glazing technologies exists, among which electrochromic glazing is notably effective in contributing to sustainability objectives in building design. This paper presents a comprehensive simulation analysis of the energy efficiency and interior comfort impacts of a novel class of spectrally selective dual-band electrochromic windows, also referred to as “Plasmochromic”. A simplified office model, oriented both south and west, was used to compare the performance of dual-band electrochromic glazing, using experimental data collected from a window-scale prototype, with that of commercially available advanced glazing systems. The comparison was conducted under two different control strategies: a rule-based and a model-based control algorithm. Five European climate zones have been considered to cover most of the continent’s climatic conditions and provide a comprehensive evaluation of the glazing performances. The simulations demonstrate the superior capability of dual-band electrochromic windows, when coupled with an intelligent control strategy, in reducing total annual energy consumption for heating, cooling, and lighting by up to 27% compared to the best-performing static solar control glazing systems. Additionally, they achieve a reduction of up to 32% in visual discomfort, measured by the cumulative value of useful daylight illuminance.

Assessment of Climate Change Impact in Tropical Buildings: Sensitivity Analysis of Light Shelf and Building Design Parameters for Daylighting and Thermal Balance

Climate change may lead to more intense sunlight in tropical regions, potentially increasing the daylight available for buildings. While this can enhance natural lighting inside buildings, it may also exacerbate issues such as glare and overheating if not properly managed through shading devices and glazing treatments. Nevertheless, common strategies to mitigate heat gain and glare such as shades and blinds often obstruct natural light, necessitating increased reliance on artificial lighting. The conflicting interplay between daylighting and thermal performance can undermine building performance if not carefully considered. Existing research on the influence of key design parameters in tropical climates tends to focus predominantly on heat gain mitigation, neglecting other aspects. This study addresses these gaps by examining the holistic daylighting and thermal energy performance of buildings to develop optimised façade and resilient designs against climate change. The investigation encompasses an analysis of 11 design parameters of light shelves and building characteristics that are critical during the initial design stage. Global sensitivity analysis (GSA) is employed to identify the most influential design parameters affecting useful daylight illuminance, uniformity ratio, cooling energy, and solar gain energy. A case study involving double-story terrace houses in Malaysia is employed, with analyses conducted for the present and future climates of three Malaysian cities (Kuala Lumpur, Bayan Lepas, and Kota Bahru). The findings reveal that, across all three cities, glazing transmittance is the most influential parameter for daylighting performance, while room depth assumes primary significance for thermal performance. Although the relative ranking of parameters remains consistent between present and future climates, their magnitudes differ. In summary, this paper gives designers insights into the critical design parameters essential for achieving a balanced and resilient daylight-thermal design in tropical climates at the initial stages of the design process.

Multi-objective optimization prediction model for building parameters of photovoltaic windows based on NSGA II-BP

This article simulates the indoor useful daylight illuminance (UDI), energy consumption, and power generation of photovoltaic (PV) window buildings using EnergyPlus simulation software. Extensive data on these simulation parameters are obtained using parametric simulation software and combined with actual meteorological data. The factors significantly influencing PV window building performance are determined based on ANOVA. A model is developed to predict energy consumption, power generation, and UDI of PV window buildings using a back propagation neural network. For better lighting quality, lower energy consumption, and greater power generation, NSGA-II is introduced to optimize the windows' performance with multi-objective parameters. Moreover, the resulting energy saving rate, annual average power generation growth rate, and UDI growth rate are compared with the initial values to evaluate the effectiveness of the optimal solution. The results demonstrate that the energy saving rate of the building is 18.23 %, and the growth rates of the useful daylight illuminance and power generation reach 41.6 % and 5.12 %, respectively, compared to the initial values.

Seasonal optimization of envelope and shading devices oriented towards low-carbon emission for premodern historic residential buildings of China

The renovation of historic residential buildings is required to balance the daylighting and thermal comfort of the building space with the conservation of the architectural features. However, there is a lack of dynamic optimization in the dimension of seasons for the historic residential buildings, while conservation factors are not considered in the design strategies. Therefore, in this study, a seasonal multi-optimization method for the historic residential buildings was introduced to improve the daylighting and thermal comfort while reducing carbon emissions. At first, the field and network investigation were conducted and a prototypical model was developed based on the second-order cluster analysis method. Furthermore, the envelope (internal insulation materials, internal insulation thickness, window types) and shading devices (inclination angle of shutters and shutter depth for different seasons and orientations) were optimized based on the Grasshopper platform. Finally, the best renovation solution orientated by low-carbon emission was proposed. The results show that the optimal material for the internal insulation of the wall is polyurethane, which has a thickness of 0.10 m. The window type is 6 mm high transmission reflective glass. The greatest inclination angle of shutters in summer is the window facing southeast. Conversely, in spring and autumn, the southwest windows have the greatest inclination angle of shutters. In winter, the inclination angle of shutters for the northeast windows is a maximum of 26°. The inclination angle of shutters for southwest windows in autumn is the most needed for design, and the angle is upward reversed 47°. The maximum shutter depth of 0.19 m in the southeastern windows is a 72.71 % improvement relative to the minimum shutter depth. Compared with the prototypical model, the useful daylight illuminance of the building model is improved by 12.41 %, the thermal discomfort hours percentage is reduced 3.09 %, and the life cycle carbon emissions is reduced by 14.6 %. The optimal design strategies for the building envelope and shading devices considering conservation principles can improve the daylighting and thermal comfort of the historic residential buildings.

The Optimization of Transparent Domes With Bionic Architecture Approach and Emphasizing on Providing Optimal Daylighting Using Crab Eye Structures

Statement of the problem. The hypothesis of this research is that it is possible to use the eye structure of aquatic animals, which performs well in low light conditions, to improve, optimize and introduce new daylighting systems. The intended transparent dome in this study is a double glass skin dome with placed modules between the two layers of dome to control daylighting. According to the natural structure investigated in this research, these modules are dynamic and variable in two fully open condition to receive maximum daylight in low dim light conditions (e.g., in the cloudy sky) and semi-closed in the completely sunny sky with intense radiation. Results and conclusions. What is intended as an independent variable in this research are: the opening width, and the shape of modules (square, hexagonal and triangular), the height of the modules and the rotation angle of the light reflecting panels of the modules. The dependent variables (appropriate illuminance and appropriate lighting distribution pattern) are investigated by Useful Daylight Illuminance (UDI). Radiance software have been used as daylight simulators. The results of this research include the optimal physical characteristics of the modules and the performance of variables on the illumination under the dome.

Parametric Optimization Approach to Evaluate Dynamic Shading Within Double-Skin Insulated Glazed Units for Multi-Criteria Daylighting Performance in Tropics

This research aims to support the choice of an appropriate dynamic louver shading system (DL-SS) within double-skin facade insulated glazed units (DSF-IGUs) as a high-performance integrated window system (DSF-IGUs/DL-SS) that meets both thermal and energy performance via daylight availability under a tropical climate. The research framework has developed a multi-objective optimization method to achieve research objectives via optimizing two different scenarios of the proposed system. The first scenario was optimized for daylighting availability, meanwhile, the second scenario was optimized for energy and thermal performance. For each scenario, the best solutions are selected from respective Pareto fronts according to energy efficiency criteria, thermal comfort via enhancing daylighting availability. Based on the best options resulting from both optimizations, the final step involved comparing the results of all performance indicators in the best cases to select the best solution. Overall, based on the optimizing objectives, the ranking of the best cases varied based on giving priority to the improvement objective in the optimization process. For each scenario, the best solutions are selected from the respective Pareto fronts. Overall, ranking of the best cases varied based on giving priority to the improvement objectives. Optimizing DL-SS within DSF-IGUs while giving priority to improving energy and thermal comfort while maintaining daylighting at acceptable levels is more reasonable. Thus, the DSF-IGUs/DL-SS best-case resulting from the second optimization scenario was overcome all best cases and ranked first in energy and thermal comfort. Compared to the base case, the differences of total Predicted mean vote and percentage of dissatisfied for better thermal comfort achieved were -0.35% and -1.48% with an average decreased by 22.99% and 28.72%, respectively. The differences of total energy and cooling load for better energy performance reduced by -96.84 kwh/m2. and -86.88 kwh with an average decreased by 25.33% and 26.20%, respectively. Meanwhile, the total satisfied of spatial Daylight Autonomy for better daylighting distribution and better daylighting availability of useful daylighting illuminance improvement were improved by -5.54% and +24.76% with an average percentage variation increased by 6.25% and 36.87%, respectively.

Enhancing energy efficiency in shipping container house: A novel approach using hybrid louver systems

Reusing shipping containers for residential purposes offers a promising approach to address global energy consumption challenges from economic and environmental perspectives. This study parametrically designed hybrid louver shadings by combining fixed vertical triangular slats with variable-depth horizontal rectangular slats, offering a novel approach to shading prefabricated buildings. The energy consumption, daylighting performance, and visual comfort were assessed for various shading configurations. Results indicated that implementing the proposed hybrid louvers, featuring fixed vertical triangular slats and variable-depth horizontal rectangular slats, significantly reduced Energy Use Intensity (EUI) to 133.95 kWh/m2. Moreover, Useful daylight illuminance (UDI), Daylight Autonomy (DA), and Glare Autonomy (GA) values improved to 95.38%, 89.97%, and 91.16%, respectively. The study highlighted the potential of the proposed shading system to significantly reduce overall energy consumption across various ASHRAE climate zones, including Miami (1A), Guangzhou (2A), Melbourne (3C), Esperance (3C), San Diego (3A), and Milan (4A). Notably, energy reductions of up to 50.2% were projected for climates such as Miami (1A) and San Diego (3A). Furthermore, container buildings in warm climate zones exhibited a significantly lower EUI range of 76.58 to 91.95 kWh/m². This study underscores the transformative potential of hybrid louver systems in promoting the widespread adoption of sustainable residential architecture, contributing to global sustainability efforts.

Wearable Light Loggers in Field Conditions: Corneal Light Characteristics, User Compliance, and Acceptance.

Understanding user challenges with light dosimeters is crucial for designing more acceptable devices and advancing light exposure research. We systematically evaluated the usability and acceptability of a light dosimeter (lido) with 29 participants who wore the dosimeter near the corneal plane of the eye for 5 days. Common reasons for not wearing the dosimeter included exercise, recharging, wet environments, public places, and discomfort. Despite these issues, participants adhered to using the dosimeter with high compliance (89% of recording time). Our findings revealed a significant discrepancy between mean (300 lxmEDI) and median (51 lxmEDI) melanopic equivalent daylight illuminance. This discrepancy indicates that the participants were exposed to significantly lower light levels most of the time. Specifically, participants were exposed to light levels above 250 lxmEDI for only 14% of their wearing time. This highlights the need for increased exposure to recommended light levels. In the evening, participants were exposed to less than the recommended 10 lxmEDI for 58% of their wearing time, which is in line with the guidelines for reducing light exposure before sleep. This study highlights the urgent need for strategies to increase daily light exposure that are more in line with circadian health recommendations.

The Non-Image-Forming Effects of Daylight: An Analysis for Design Practice Purposes

Daylight plays a crucial role in human health, and as research into its effects expands, it is essential for designers to estimate the non-image-forming impacts of various daylighting and lighting strategies. This allows them to create indoor environments that are both pleasant and comfortable. To support this, daylight measurements were taken in five Chinese cities, focusing on spectral power distribution, correlated color temperature, and illuminance. The study calculated the non-image-forming effects of daylight exposure using metrics like melanopic Equivalent Daylight Illuminance and Circadian Light. A key finding was the development of the action factor SAI, which estimates the potential non-image-forming effects of light in built environments. This factor serves as a proxy for understanding how non-image-forming effects relate to correlated color temperatures. Additionally, the research suggests the possibility of creating a time-variational daylighting and lighting strategy with four distinct periods of non-image-forming effects throughout a 24 h day. These insights could be valuable for architects and designers in optimizing indoor lighting systems.