Research On Natural Lighting In College Classrooms Based On Visual Comfort

Daylighting in college classrooms is a key role in creating a comfortable classroom environment.Recently,green building and healthy building concepts and corresponding evaluation standards are formulated to regulate the requirements of building daylighting from design to operation.However,the light climate environment in different regions,and architectural features between regions are significant due to vast area in China.There are also significant differences in human behavior habits.Taking Nanning as an example,the light climate is characterized by sufficient natural lighting,light and transparent architectural features,and it is easy to cause the indoor lighting level to meet the requirements,but it is prone to produce glare and uneven luminance distribution.Therefore,this dissertation concerns the optimization of natural lighting in college classrooms as the starting point,analyzes the current situation of college classrooms based on the perspective of visual comfort,and conducts research on natural lighting in college classrooms from two aspects of lighting evaluation and optimization methods.Firstly,the formation principle of natural light climate and the evaluation system of natural light are introduced from the theoretical approach,the evaluation of dynamic daylighting and the theory of uncomfortable glare are reviewed.The main factors affecting visual comfort are summarized.The second is a summary of the current situation of classroom lighting in Nanning.The field-work investigated the lighting characteristics of some college classrooms in Nanning,and summarized them from the aspects of building plans,window forms,shading facilities,and use functions.A questionnaire survey was conducted on the satisfaction rate of light environment,comfortable illumination range,lighting expectation and behavior pattern in college classrooms.The results show that the classroom windows in this area are generally large,and the window-to-ground ratio changes between 0.2-0.4,which may easily lead to visual discomfort problems such as glare;students are generally satisfied with the light environment of the classroom,and the statistical comfortable illumination interval is 300-2000 lx.The third is to select a teaching building of Guangxi University in Nanning as the main research object and carry out the actual measurement of the light environment.The indoor brightness and illuminance changes of the whole cloudy day and sunny day(Typical meteorological day)were tested.Calculate the daylight factor,daylight uniformity,and glare index according to the measured results.Analyze the causes of indoor glare,the distribution of glare in the room and the change of glare over time.The measured illuminance level of the classroom in all cloudy and sunny days is relatively high.Compared with the DGI indicator,the DGP indicator is more in line with the actual glare experience.The fourth is to use Rhino software to model,and use Ladybug and Honeybee software to conduct lighting simulation analysis on the research objects on Grasshopper platform.The results of daylight factor and dynamic daylighting evaluation index were analyzed,and the definition of “classroom comfortable daylighting depth” was proposed based on the perspective of visual comfort,and suggests that the setting of glare point in classroom should consider the Angle changes of vertical and horizontal directions comprehensively.In this paper,based on the requirements of the comfortable daylight environment,combined with research and test data,a theoretical analysis of the lighting influence law of the high-light-to-ground ratio lighting classroom is carried out.Based on the influence factors such as the form of building daylighting port,shading facilities,orientation and optical properties of surface materials,the optimization of classroom light environment in colleges and universities is studied.The study found that in a double-sided window classroom with a high window-to-ground ratio,adjusting the window transmittance and arranging the sunshade can effectively improve the indoor visual comfort,and it is not appropriate to use the east-west direction when choosing the orientation.In addition,the proposed " classroom comfortable daylighting depth " is of guiding significance for the construction of classroom daylight environment in colleges and universities.