طراحی فرآیندی جهت نیل به روشنایی طبیعی مناسب برای یک فضای کاری اداری در شهر تهران از طریق محاسبه ابعاد بهینه ی پنجره، سایبان و عمق مفید اتاق

By having daylighting in mind through a building design process rather than end of it, achieving a more sustainable space is much easier and feasible. Since many people spend an important amount of their lives at their working spaces, accessing enough natural light together with satisfying view are essential for their physiological and psychological health. Moreover as a daylighted space has a good potential to increase employees’ performance and productivity, it can benefit both its owner and its occupants. Now, the question is what factors constitutes a well daylighted space. To balance occupant comfort and energy consumption, daylight availability in such spaces should neither be too low nor excessive. The conventional definition for a well daylighted space is based on the IES recommendations (Andersen M, et. al. 2012, p. 3). Any spaces that comply with it should have yearly enough access to daylight. To evaluate any space, this guideline asks to calculate both Special Daylight Autonomy (sDA300/50%) and Annual Sunlight Exposure (ASE1000/250h). However, in this paper, we create another new definition for a daylighted space which is called useful daylighting. It is applicable when we want to see if the space has enough access to useful daylight in a year or not. As its name is suggested based on calculating sUDI100-2000/50%. In both daylighted definitions, to define any areas as daylighted, at least 75% of all the regularly occupied space of it should have minimum UDI100-2000 or DA300 of 50%. Additionally for a well daylighted space, the maximum acceptable value for ASE1000/250h is 10%. In this paper, at first we define a working space that its dimension and windows to wall ratios (WWR) are taken from the reference office definition recommended by Christoph Reinhart and his colleagues in 2013 (Reinhart, et. al 2013). Then, to solve the issues of excessive sunlight entering the interiors, two methods are suggested. The former is to use horizontal or vertical + horizontal outside shading systems, while the latter is to exclude part of task area facing too much sunlight during a year. Therefore by analyzing ASE1000/250h ≤ 10% for four main geographical room orientations (East, West, North and South) and for each WWR we can define an effective type and size of a shading system or an efficient distance that task area should be away from the window walls. Then by calculating Special Useful Daylight Illuminance (sUDI100-2000/50% ≥ 75%) for each WWRs and room orientations we can find out the optimum WWR when we want to define the room to have useful daylighting. After that, regarding recommendations for a well daylighted space, we need to find the efficient and acceptable depth for rooms. To do so, a new metrics that is called Average Daylight Autonomy is created here. It is defined as the average of DA300 for all points on the task surface grid having the same distance from the window wall. In the next step by calculating aDA300 of each distance from the window wall, we can find the border line between aDA300 ≥ 50% and aDA300 < 50% or in other word between daylit and not-daylit space. The distance of this border line from the window wall is the efficient depth of the room. However as it is already discussed any daylighted space needs to have DA300/50% more than 75%, therefore to find the acceptable depth for rooms we can multiply the efficient depth of room by 1.3333 (=100/75). So in the end of this part for each room, we can define the optimum WWR and room’s length. Thereafter, to make the final decision about which solution (using shadings or excluding task areas) is the best, we can calculate the number of hours per year that the shading system restricts entering sunlight into the space. Hence, the solution that has less number of closing hours is the winner. In the end, it is worth to say that considering enough access to natural light is just one of the requirements to design a successful and high quality space, while other concerns like aesthetics of the space, improving health, happiness and comfort of their occupants, reduction in energy consuming and excessive heating or cooling loads, decreasing noise problems, occupants behaviors, etc. should be taken into account. Finally, as a conclusion, the main and final goal of this paper is to define a good method for finding the efficient dimension of different rooms, types and sizes of shading systems, and interior layouts for any types of buildings.