Assessing Daylight Access Requirements in Iranian National Building Code (Case Study in Qazvin)

Nowadays most people spend majority of their life indoors. Since accessing to a good view and enough daylight links to the relief of boredom and stress, more social interaction, better visual performance, higher productivity, improve general well-being, and even reduce discomfort glare, they should be considered as one of the main driving forces in the design process. However in this paper, our main focus is on daylight access and we skip the view. So, when are any spaces eligible for being defined as daylight? In general a daylight room is a space, only or predominantly, dependent on natural light mostly throughout the year. Now the question is how building designers can be sure about their designed space to be ranked as daylight. One way is to propose and create a daylight chapter in buildings regulations or recommendations and ask architects and engineers to follow it. At the moment there are some rules directly or indirectly connected to assure enough daylight access. Therefore how much existing Iranian building regulations can help us to insure the sufficient access to daylight for regularly occupied spaces of buildings is the main goal of this paper. To insure enough natural light access for a building, the existing building rules divides the interior spaces to two different areas; the first one is those rooms that have only access to daylight indirectly through a patio, atrium, or other similar spaces, while the second is the spaces directly connected to the outside through their windows or skylights. Then regarding to the regulation for the former rooms, based on the total building property area, it defines the patio area for each one, while for the latter rooms the minimum windows area are calculated based on the rooms’ floor area and their depth. So none of them discuss about other parameters or elements like the materials reflectance, architectural layout configurations, building orientations, buildings functions, shading devices, occupancy schedules, surrounding obstructions, etc. that affect directly or indirectly on daylight quality and quantity of indoor spaces. For doing such assessments, the starting point is to define which type of daylight analysis metrics is needed to achieve acceptable results. As a dynamic daylight metric considers different climate conditions throughout a year, it gives us much more reliable results than other daylight metrics. It usually uses a relevant weather data file representing the prevailing conditions measured at the site. Between all different types of dynamic daylight metrics we choose Daylight Autonomy. The daylight autonomy in a building is defined as the percentage of occupied hours per year, when the minimum illuminate level can be maintained by daylight alone. To make any computer simulations, we need a 3D model. So for this project, we created it in Revit software and then imported it into Ecotect software. We used Ecotect to adjust the model for exporting to Daysim software. Daysim is a validated Radiance based computer program and we used it to calculate Daylight Autonomy. The next step is to define our case study. So we chose a 4-story apartment in the city of Qazvin located in 150 km northwest of Tehran. Here, all analyzes were done only for the rooms located in the northern side of building with access to natural light just through an atrium. Since Qazvin climate is similar to many other cities in Iran, we can generalize the findings of this paper to some other cities in the country. To evaluate the daylight condition of this case study, different atrium shapes with different surrounding materials were chosen and analyzed. Based on the findings of this paper, for increasing the natural light access of those rooms that are indirectly connected to outside through a medium like patio, atrium or courtyard, the best way is applying transparent or translucent materials on the exterior wall of that intermediate space. So more daylight can come into the rooms and larger area of sky dome can be seen from each window in the room. In this case, it is recommended to orient the atrium in a way that its longer axes are parallel to the building exterior northern wall. Otherwise, in case of having no possibility to apply a transparent or translucent material on the patio wall facing outside, we should limit the number of apartment stories to the maximum of three. In this case it is better to make the patio shape more square-like rather than rectangular. Moreover, it is clear that applying higher reflectance material for each of architectural elements like walls, floors, ceiling, etc. and also higher glass transmission for the windows make the rooms lighter and brighter. Although all different cases comply with the existing Iranian building regulations and designed based on their recommendations and rules, the annual daylight conditions of the interiors were different. It means that the existing rules are not enough to ascertain enough access of indoor areas to daylight. So we can conclude that we should revise or reconsider the existing building regulations in accordance with the latest progress in daylight analysis and day lighting design of the buildings.