Daylit Environment Research Articles

Comparison of questionnaire items for discomfort glare studies in daylit spaces

When studying discomfort glare, researchers tend to rely on a single questionnaire item to obtain user evaluations. It is unclear whether the choice of questionnaire item affects the distribution of user responses and leads to inconsistencies between studies. This study aims to investigate if different glare questionnaire items yield similar distributions of user discomfort in daylit environments. We conducted a comparative study of selected questionnaire items from previous glare experiments, testing them in three independent user studies with different lighting conditions and glare stimuli. We compared the resulting outputs across questionnaire items with 540 data points from 149 participants. Results indicated that ordinal questionnaire outputs show strong correlations (0.68 < ρ < 0.85), high internal reliability (α = 0.93) and captured the same latent construct. Binary questionnaire items reflected different glare thresholds but still correlated well with ordinal items. The construct validity of tested questionnaire items was confirmed through responses to an open-ended question. These findings suggest that the tested questionnaire items may be used for category rating-type discomfort glare evaluations and consistently capture the same construct.

A study about daylighting knowledge and education in Europe. Results from the first phase of the DAYKE project

This paper presents selected results from the first stage of DAYKE (Daylight Knowledge in Europe), a 3-phase project that investigates the knowledge on daylighting in buildings among architecture students and practitioners across Europe. Subjective judgements from 561 students from 8 architecture universities in the EU, collected through two surveys in 2018. The key findings are: (i) the spatial distribution of comfort and mood in the classrooms varied depending on sky conditions and distance from windows; (ii) the average daylight factor DFm showed a good agreement with subjective judgements on the amount of daylight in a space; (iii) experts and non-experts provided similar judgements on the perception of a daylit environment; (iv) a general lack of knowledge about daylighting metrics, regulations, assessment tools and software was highlighted. Furthermore a difficulty in implementing daylighting into the design practice is also identified.

Does interruption of electricity supply for supplementary lighting affect the long-term carbon dioxide exchange of greenhouse tomato crops?

Due to new electricity generation and supply schemes, optimising cost and return in greenhouse production could be achieved with interruptive schemes for supplementary lighting (SL). We analysed the effect of interrupted SL (ISL) on both the cost of electricity and crop yield of tomato cultivation during a winter in Brandenburg, Germany (LAT 52°N). We applied SL for 60 days to a tomato crop (cv. Komeett) with two nighttime regimes of nine hours using high pressure sodium lamps (HPSL; 400 W and 210 μmol m–2 s–1) resulting in equivalent daily light integral (DLI, mol m–2 day–1). CO2 assimilation of the crop stand was measured either continuously in four airtight gas exchange greenhouse compartments (28.8 m2 each) or from a sampling of total dry mass. Measurements were used to evaluate the predictions of an existing deterministic photosynthesis model. Results indicate: 1) continuously measured crop net photosynthesis (Pn) overestimated the total CO2 assimilation when measured as crop dry matter at only 1.7%, and 2) an ISL regime had only a low influence on total dry mass formation, presenting 7.6% higher total dry matter in comparison to the model results. It is concluded that 1) continuous measurements of Pn in a daylit environment can be used as a dry mass increase indicator, 2) ISL can be applied without losses in tomato yield, and 3) the existing tomato crop photosynthesis model was not suitable for ISL control. Thus, price optimised ISL can be applied with no negative effect only by looking at electricity prices.

Influence of indoor temperature and daylight illuminance on visual perception

This paper details the results of an experimental study investigating the combined effect of indoor temperature (19 ℃, 23 ℃ and 27 ℃) and horizontal illuminances (∼140 lx, ∼610 lx and ∼1440 lx) on visual perception, with daylight as the only source of light. The goal is to evaluate the cross-modal effect of temperature and the unimodal effect of daylight illuminances on the visual perception of daylight. A 3 × 3 mixed-design experiment was conducted in an office-like test room with 84 participants. Results show that cross-modal effects of indoor temperature on visual perception occurred: Temperature influenced the perceived warmth of daylight, and temperature interacted with daylight illuminance as the high illuminance was considered more pleasant, was better evaluated and was more often chosen than the low one only in a thermally comfortable condition. In terms of unimodal effects, differences in visual comfort evaluations were substantial only between the low and the other two illuminances, suggesting that visual comfort did not increase with illuminance above an already comfortable threshold. Moreover, perceived brightness under the high daylight illuminance was lower than that reported in past studies under a comparable electric light illuminance, leading to the hypothesis that high illuminances might be more tolerated in a naturally-lit environment compared to a space illuminated with electric light. Findings advance the understanding of occupant perceptions of daylit environments and suggest that, together with visual factors, thermal conditions should be considered in visual perception investigations.

Design Methodology for Street-Oriented Block Housing Considering Daylight and Natural Ventilation

This study presents a design methodology for street-oriented block housing, as a model for gradual small-scale block-unit development, that can secure two hours of continuous access to daylight on the winter solstice at azimuth angles of 0° and 60° in Seoul, South Korea, and, in addition, developed a methodology for wind path planning for existing types of developed housing. The results of this study have confirmed the feasibility of a housing design that can secure two hours of continuous access to daylight along with no less than 200 percent of development density, achieved through the elimination of self-shadows by using distances between residential buildings and shadow characteristics according to azimuth angles. In addition, the study identified an air flow stagnation section by assessing the air flow of the exterior space of street-oriented block housing in consideration of day-lit environments, and examined a planning model that can enhance natural ventilation potential by activating the air flow of the exterior space. Wind path planning was conducted for 24 alternatives that were produced based on the developed design methodology, and the wind velocity ratio of street-oriented block housing ranged from 0.34 to 0.59. In terms of disadvantages of street-oriented block housing in securing wind paths, this study confirmed that air flow could be strengthened by adjusting the form of the lower-part opening, which is open in the direction of incoming wind, designing a staggered mass layout in high-rise masses, and combining building floor heights. The above findings of this study suggest that a performance-based approach is necessary for the improvement of environmental performance in street-oriented block housing, in consideration of azimuth angles and the prevailing wind direction from the initial phase of planning.

住宅空間における昼光環境の動的変動に関する研究(2) 模型空間によるシミュレーション

住宅空間における昼光環境の動的変動に関する研究(2) 模型空間によるシミュレーション

Adequacy of Immersive Virtual Reality for the Perception of Daylit Spaces: Comparison of Real and Virtual Environments

ABSTRACTThis article presents a novel experimental method that uses a virtual reality (VR) headset, aiming to provide an alternative environment for the conduction of subjective assessments of daylit spaces. This method can overcome the difficulty of controlling the variation of luminous conditions, one of the main challenges in experimental studies using daylight, and its novelty lies in the implementation of physically based renderings into an immersive virtual environment. The present work investigates the adequacy of the proposed method to evaluate five aspects of subjective perception of daylit spaces: the perceived pleasantness, interest, excitement, complexity, and satisfaction with the amount of view in the space. To this end, experiments with 29 participants were conducted to compare users’ perceptions of a real daylit environment and its equivalent representation in VR and test the effect of the display method on the participants’ perceptual evaluations, reported physical symptoms, and perceived presence in the virtual space. The results indicate a high level of perceptual accuracy, showing no significant differences between the real and virtual environments on the studied evaluations. In addition, there was a high level of perceived presence in the virtual environment and no significant effects on the participants’ physical symptoms after the use of the VR headset. Following these findings, the presented experimental method in VR seems very promising for use as a surrogate to real environments in investigating the aforementioned five dimensions of perception in daylit spaces.

A Review of Light Shelf Designs for Daylit Environments

Light shelves have been discussed in numerous studies as suitable solutions for controlling daylight in side-lit spaces. It is a system that can be easily modified, offering a range of design solutions. It can be easily mounted on the exterior and/or the interior of a vertical opening, it can come in various shapes from static flat forms to curved reflective surfaces, or it can even be actively controlled. A light shelf can offer shading and at the same time can redirect a significant part of the incoming light flux towards the ceiling improving daylight uniformity. Due to the aforesaid functions, light shelves are among the most popular system design solutions when it comes to daylight exploitation. The purpose of this paper is twofold. Firstly, to present the main research findings in relation to light shelves as daylighting systems and secondly to analyze the results, trying to establish a common basis for some efficient and practical design rules. The present paper is a review of the research realized in the last three decades concerning these systems together with their associated implications in a building’s daylight performance as well as in its energy balance in a few cases. In addition, the critical review of their design principles is included, which makes the presented information useful for design teams trying to select the optimal available system for any specific project.

A Design Methodology for Perimeter Block Housing Considering Day-lit Environments and Energy Performance

Perimeter block housing was introduced from the 2000s as an alternative means of urban construction that has been polarized between the large-scale development of high-density high-rise buildings and the development of small plots of land. The results of this paper allow the possibility of forming building types that satisfy the standard of two consecutive daylight hours for all households by using the properties and principles of shadows in perimeter block housing. It also provides the possibility of the combination of building forms without daylight interference from the south mass by manipulating the distances between adjacent buildings at different azimuth angles. Furthermore, comparing the energy load of residential buildings as suggested from the results of the study, it was possible to confirm whether residential buildings optimized for the day-lit environment have an effect in terms of energy usage performance, and further suggested planning directions through the analysis of daylight, sunray, and energy load. The study suggests a rational methodology for the layout of residential buildings that is optimized for the day-lit environment and also considers the issue of energy performance.

Neutral daylight illumination with variable transmission glass: Theory and validation

The dynamic control of daylight is seen as key for the effective exploitation of natural illumination in buildings. Traditional control solutions are invariably used in a sub-optimal manner: blinds/shades are left down for long periods and lights are left switched on. A glazing with a transmissivity that varies continuously between clear and dark extremes, and which can be controlled automatically, could be much more effective in providing a ‘well-tempered’ daylit environment that meets occupants needs. Amongst the different types of variable transmission glazing that have undergone extensive research and development in the last few decades, those based on electrochromism appear to have the best performance characteristics and the greatest market potential. Electrochromic (EC) glazing generally exhibits a shift in spectral transmission as the glass darkens, e.g. causing it to appear blue as it tints. Occupants, however, are believed to prefer a neutral spectrum of daylight illumination without any pronounced hue. In this paper, the authors show that it is possible to maintain a neutral spectrum of illumination with electrochromic (EC) glazing under normal operation provided that just a small proportion of the EC glazing is kept in the clear state. A theoretical model to predict the daylight spectrum resulting from any arbitrary combination of clear and tinted glazing is described. Predictions from the model are compared with measurements of the daylight spectra in an office with EC glazing under various states of tint. The predicted spectra show excellent agreement with the measurements. The model is applicable to any combination of clear and/or tinted glass panels irrespective of the glazing type(s). The paper concludes with a discussion of design considerations for the effective deployment of EC glazing.

Visual Comfort Analysis of Innovative Interior and Exterior Shading Systems for Commercial Buildings using High Resolution Luminance Images

The objective of this study was to explore how calibrated high dynamic range (HDR) images (luminance maps) acquired in real world daylit environments can be used to characterize, evaluate, and compare visual comfort conditions of innovative facade shading and light-redirecting systems. Detailed (1536 × 1536 pixel) luminance maps were time-lapse acquired from two view positions in an unoccupied full scale testbed facility. These maps were analyzed using existing visual comfort metrics to quantify how innovative interior and exterior shading systems compare to conventional systems under real sun and sky conditions over a solstice-to-solstice test interval. The results provide a case study in the challenges and potential of methods of visualizing, evaluating and summarizing daily and seasonal variation of visual comfort conditions computed from large sets of image data.

Iluminação natural: a contribuição de suas reflexões no interior do ambiente construído

This article tackles the impact of internal reflections in day-lit built environments. This study shows how the inner space geometry, surface properties, openings percentage, position and distribution affect the values and distribution attributed to the internally reflected component. Such knowledge enables us to establish parameters and relations among the above variables so as to fill a gap in the existing biography. The simplified methods provided and used by existing legislation to assess the day-lit environment do not take into account light's basic components, which affect the internal spaces. Therefore, this fact has a negative influence on the prediction of light's behavior. Daylighting contribution in an environment depends directly on the sky component, on the light reflected on external surfaces, and also on the light reflected on internal surfaces among other aspects; this knowledge is crucial for a good understanding of the day-lit environment. The findings of this study should enable the manipulation of variable values and parameters, which affect the reflected light in order to ensure both the quantity and mainly the quality of the day-lit environment.

A study on subjective preference to daylit residential indoor environment using conjoint analysis

This paper reports a study of the subjective preference to daylit indoor environment of a residential room using conjoint analysis, which is a highly reputable method used to analyze the mutual relationships among different attributes. Seven influential attributes were selected in the view of daylight performance assessment. They include ‘general brightness’, ‘desktop brightness’, ‘perceived glare’, ‘sunlight penetration’, ‘quality of view’, ‘user friendliness of shading control’ and ‘impact on energy’. Each of them has two levels. A total of eight combinations (profiles) of attributes with various levels were established by adopting fractional factorial design. Subjects were asked to rank-order the eight profiles according to their preference in terms of daylit environment of a residential room. The study aims at finding out the relative impact of the seven selected attributes to the overall daylight performance and seeking an organized assessment method for a residential daylit environment. Conjoint analysis found that the seven attributes have importance level in the order of ‘quality of view’, ‘general brightness’, ‘impact on energy’, ‘user friendliness of shading control’, ‘perceived glare’, ‘desktop brightness’ and ‘sunlight penetration’.

All Sky Model as a standard sky for the simulation of daylit environment

It is important to apply natural light effectively for low energy consuming daylighting design. A reliable standard sky that expresses real sky luminance distributions is required for the simulation and evaluation of daylit environment. Any applicable standard sky, however, has never found that shows accurately actual states of daylight. In order to establish a suitable sky model that can represent all the sky luminance distributions from clear sky to overcast sky continuously, the authors propose a sky luminance distribution model named “All Sky Model”. The detailed descriptions about All Sky Model for the simulation and evaluation of daylit environment are explained in this paper.

絶対値で表す天頂輝度と天空輝度分布 : 天空輝度分布の分類法の研究(その4)

A numerical equation has been proposed by the authors in the previous papers. It gives the relative values of the sky luminance distribution for all sky conditions. Though the numerical equations for the zenith luminance in absolute value on the various standard skies have been proposed by several researchers to get the sky luminance distribution in absolute value, they do not bring the suitable value for the new equation. A numerical equation on the zenith luminance using the same indices as those of the newly proposed equation has been composed. It has made it possible for the sky luminance distribution in absolute value to be estimated by one of the easiest measurable values, the global illuminance. The result of this research work convinced the authors of its contribution to the progress and development of the prediction technique in the daylit environment. The new equation of the zenith luminance in absolute value is introduced, the process of composing it is explained in detail and the examples of the sky luminance distribution for all sky conditions in absolute values are illustrated in this paper.

日射量による昼光照度の推定方法に関する研究

The solar irradiance and illuminance are important as meteorological data to predict indoor environment. However, the data concerning the daylight are not measured at the ordinary meteorological stations. The horizontal global irradiance is normally measured in the meteorological stations in Japan. The luminous efficacy, by which the irradiance can be converted into the illuminance, is essential for obtaining fundamental daylight data for the prediction of the daylit environment. The luminous efficacy has been investigated for a long time in the world. Several considerations have been put forward. But the sufficient theories on the luminous efficacy have not established yet. The relations between the diffuse irradiance and the diffuse illuminance, the direct normal irradiance and the direct normal illuminance, and the horizontal global irradiance and the horizontal global illuminance were examined and discussed based on the data acquired at the measurement of the IDMP station operated by the authors. The results of the examination are stated and the equations newly proposed by the authors on the luminous efficacies are introduced in this paper.

新しい直接照射型人工天空の開発

Daylighting is fundamental and essential in constructing a comfortable interior environment in architectural space.Research work on daylight and daylighting designs are often carried out applying scale models which is an important technique for the prediction of daylit interior spaces.Artificial skies can be used to reproduce sky luminance distribution through artificial light sources. They are the most effective and useful in the evaluation of daylit environments with scale models. As a result, a number of artificial skies have been constructed at various research organizations throughout the world in the last half a century.A new artificial sky was intended to be developed and constructed by the authors. The artificial skies already constructed throughout the world are being surveyed, for the planning of the new facility. These artificial skies can be roughly classified into four categories as follows: 1. Mirror type, 2. Reflection type, 3. Translucent type, and 4. Direct type.After a survey and comparison of the performance of these types of artificial skies, the concept of a new artificial sky will be established.

居住空間における昼光環境の動的変動に関する研究

居住空間における昼光環境の動的変動に関する研究

オフィス空間を想定した模型室における昼光環境の動的変動に関する研究

オフィス空間を想定した模型室における昼光環境の動的変動に関する研究

The influence of elevated C02on growth and age-related changes in leaf gas exchange

Rumex obtusifolius plants were grown for several months in daylit environment chambers (Solardomes) force-ventilated with air containing 350 or 600 µ;mol mol–1 C02. Elevated CO2 was found to accelerate the natural ontogenic decline in photosynthesis, but did not reduce leaf duration. In both CO2 treatments photosynthetic rates declined progressively with increasing leaf age, the decline being greater for plants grown in elevated C02 such that rates became lower than in ambient CO2. The degree of CO2-induced photosynthetic down-regulation as determined by A/C1 analysis was found to be dependent on leaf age. The major contribution to the decline in photosynthesis was likely to be a reduction in Rubisco activity as changes in stomataland mesophyll limitations were small. Instantaneous water use efficiency (WUE1) was greater for plants in elevated CO2, but these values declined rapidly with leaf age, whereas in ambient CO2 values were always lower, but were maintained for longer. Growth analysis indicated an increased root:-shoot ratio for plants grown in elevated CO2, this occurring almost entirely as a result of increased root growth. Greater root proliferation and increased WUE1, are characteristics which should give this persistent and troublesome weed an increased competitive advantage under projected conditions of climate change