natural lighting

The main purpose of lighting in offices is to provide effective and comfortable working environments. Mental comfort and health in turn guarantee an increase in user motivation and lead to better performance and efficiency. Providing sufficient and appropriate light in the workplace increases the willingness to work in employees, the operational accuracy and efficiency, and output. It also results on ocular health, better protected eyes and less fatigued nerves work better, and eventually fewer workspace accidents.The purpose of this research is to investigate lighting from the perspective of operational satisfaction and well-being using the case of Shiraz National Documentation Center.In this research, it is assumed that in the space occupied by the users; while using artificial light in the space, they are not satisfied with the amount of natural light and its effective factors. 

In this regard, after using library resources, in the topic of space lighting, field data collection with a photometer and in the topic of employee satisfaction and well-being, a phenomenological and psychoanalytical approach to analyze the unconscious behavior of humans through questionnaires and software analysis in SPSS; Because the brightness of the space alone does not have the ability to express the pleasantness and desirability of the ambient lighting from the users’ point of view. 

According to the results, employees have an average of 50% or higher in terms of satisfaction, well-being and visual comfort. But it does not mean that those who are working in the space without natural light are satisfied with the conditions. According to field observations, these spaces do not even have substitutes for visual compositions and nature themes. In terms of satisfaction, well-being and visual comfort in the female group, the average values are higher than the male group; In the post-graduate class, it is more than other classes and the working position of expert is higher than other working positions.

The accurate prediction of the visual comfort zone in an indoor environment is difficult as it depends on so many parameters such as individual and environmental variables. It is important in large compact urban areas in which the density and shadow from neighboring buildings can limit the accessible daylighting in indoor spaces. Lighting is one of the most important environmental parameters in office spaces. The employees spend most of their hours in office spaces during the day, and most of their activities are based on receiving visual information from the surroundings. Besides, being satisfied with lighting conditions is one of the main elements that significantly affects the environment’s overall comfort level. Currently, in Iran, the visual comfort zone and the preferred illumination level are not defined for office spaces, and experts refer to the findings achieved in other countries. To assess the lighting in architectural spaces and define the conditions for conformity in many standards, the authors have used some metrics as the physical measures. Generally, there are static and dynamic metrics to evaluate various aspects of daylight. Static metrics, such as illuminance-based daylighting metrics and Daylight Factor (DF), are typically evaluated based on illuminance and have been used in building regulations for a long time. In most standards and codes, the minimum recommended illumination level for working planes in a regular office is 500 lx. Due to climatic and cultural differences, the findings of other countries may not be appropriate for Iran. On the other hand, many studies have been conducted to find an acceptable lighting level in offices; however, the results show the acceptable range for illuminance in different countries is not the same. So, this paper tries to investigate the satisfaction range with the illumination level in office spaces which architects and researchers could use. Therefore, a field measurement was conducted to evaluate the illumination levels, and to examine the effect of lighting conditions on employee level of satisfaction and perception of lighting level with actual illuminance levels in office spaces in Tehran, using both questionnaire and physical illuminance measurements.

The focus is on six office buildings in the metropolis of Tehran, Iran. The buildings were selected to consider different spaces in old and new buildings, one-story and high-rise buildings, open plan, and cubicle offices with varying orientations. The selected rooms were one, two- or multi-user offices, located on different floors, with various window orientations and an optional atrium/outside window. Fluorescent interior artificial lighting was used in all spaces with a color temperature between 4000K and 5000K. The survey involved 509 questionnaires (280 were filled out in summer and 229 in winter).

Most of the participants have spent at least three months in their offices and have been adapted to the environment. All participants were Iranians (to avoid the impact of occupants’ culture on lighting perception). Most of them reported that they spend more than 8 hours or between 6 to 8 hours in their offices during the day. Field measurement includes illuminance, temperature, and relative humidity. The questionnaires were filled out in 146 and 109 rooms in summer and winter, respectively. At the same time, while users completed the questionnaire, the physical parameters were measured. The Spearman rank correlation coefficient was applied for quantitative variables. By using a monotonic function, the Spearman rank correlation coefficient is a non-parametric measure that assesses statistical dependence between two variables to describe their relationship.

The results revealed that occupants were more satisfied with higher levels of illuminance. The measured illuminance is categorized into certain levels to investigate the acceptable range for the lighting level. For this purpose, the measured lighting level was classified into 14 ranges. The values of less than 300 lx are in the first category, higher than 900 lx are in the last category, and the values between these mentioned ranges are classified into 50 lx intervals. The highest satisfaction from the environmental lighting level is provided in the illuminance range between 600 to 649 lx. The illumination level above this range results in more satisfaction compared to illumination levels less than 550 lx. Thus, there is an optimal range of satisfaction with lighting level, and the preferred lighting comfort range for the investigated office spaces is between 600 to 649 lx. While the illumination level higher than 550 lx is acceptable for most of the occupants.

Light, as the most pervasive natural element, plays an important role in an individual’s experience of space. The important place of this phenomenon in various sciences, religions, philosophies, and, above all, its role in perceiving the visual, and environmental effects of architectural spaces is significant. The presence of light and aesthetic perception of space in magnificent Iranian architectural spaces reflect the knowledge and skills of their architects in the use of light. In fact, the wise use of light is one of the significant characteristics of Iranian historical architectural spaces. In addition to providing lighting, in traditional Persian architecture, the use of daylight has met the climatic, physical, psychological, and aesthetic needs. In this regard, Iranian architects have been successful in creative use of light in interior spaces. Various combinations of light entrances confirm this claim. The present study attempts to examine the qualitative and quantitative role of light in a certain type of Safavid architecture, i.e.  Rasteh and Charsooq of the Grand (Qeysarriyeh) Bazaar of Isfahan by scrutinizing the relationship of light and its origins with its functional purposes. The Grand Bazaar is an example of a certain type of architecture that stimulates human senses through its spatial arrangement and architectural components. It is comprised of massive arches that provoke the imagination by a sequence of lights and shadows in curved hallways, and create a kind of expectation in people dragging them to the bazaar intersection rich in light entered from the dome aperture. The present study aims at investigating the quantity and quality of daylight, and different functions of light in apertures according to the behavior and use of daylight in a public-commercial space where using different types of apertures is limited due to the specific functions. Part of this study is performed using a descriptive-analytical method and another part is conducted through software analysis in which natural light is simulated in specific dates and at given times throughout a year. Therefore, the quantitative indicators of daylight are assessed using Honeybee and Ladybug plugins, and Radiance engine. Proper lighting quality means a state in which efficiency, legibility, and optimal energy consumption are enhanced and the space attractiveness and youthfulness, as well as residents’ wellbeing is improved. First, to achieve a constant pattern to simulate the changes of daylight in a building, the software was programmed for two specific days of the year when the sun is at its highest and lowest altitudes; i.e. June 21 and December 21. To analyze the pattern of changes in daylight, simulations are performed at three times of the day, including 9 a.m., 12 p.m., and 3 p.m. Evaluation of daylight can be studied in two types of static and dynamic characteristics. Since the quantity and quality of daylight vary at each moment, there are limitations for static evaluations, and today, the dynamic simulation is more widely used by users. Therefore, the Useful Daylight Illuminance (UDI100-2000)unit, which is one of the dynamic indicators, was considered a good option. This indicator shows how long the natural light in the building is useful during occupancy hours (between 100 and 2000 lux). Results show that there is a specific pattern for using and keeping the daylight in space. The combination of walls and ceiling apertures helps to provide suitable lighting during the working hours in Rasteh of the Grand (Qeysarriyeh) Bazaar in Isfahan throughout the year and during all seasons. As a result, the share of daylight intervals throughout the year are almost constant, and no significant difference is observed in the share of daylight received with the change in season. Also, the amount of daylight received in more than 70% of Rasteh area during 50% of the working hours is between 100 and 2000 lux, indicating a good level of natural lighting in space. The Grand Bazaar is one of the places where the concept of time is perceived. Lighting analyses show that the rhythm and the angle of sunrays along the paths is the most important factor for guiding people who are not visually connected to the outside to understand the time and space direction. Despite the limitations that the Grand Bazaar and its specific functions face in applying various types of light apertures, the results of this study show that the designers have considered the light quantity and quality of bazaar since the early stages of design and they have purposefully and practically designed and programmed the use of natural light in the Grand (Qeysarriyeh) Bazaar. The ideas used in this building can be modernized and architects can use them in designing public spaces.