Determining the Optimal Inclination Angle for Atrium Daylighting in Tehran Based on Sun Angles and Climatic Features

Daylight has a positive effect on people's health, employee productivity and property value. However, with the growth of high-rise buildings in populated cities, access to natural light for the lower floors are challenging. Atrium is one of the strategies for bringing daylight to these floors. Atrium’s daylight performance can be evaluated before construction thanks to computer simulations. Until now, daylight simulation has been limited to one cloudy sky condition. With the help of new methods of computer simulation of daylight, it is possible to study the effects of sun angles and sky conditions throughout the entire hours of a year. This development has made it possible to apply the direct sunlight component to the simulation and study its impacts of architectural features that are related to it. This study focuses on the effect of the angle of inclination of the inner walls of the atrium on the daylight performance of adjacent rooms.

 Different angles of the atrium in the north and south direction have been studied by the method of "Climate-based daylight modeling" for the city of Tehran. (sDA), (ASE) and (UDI) are daylight metrics which have been used in computer simulations.

The inclination of the inner walls of the atrium at an angle of 20 degrees to the south improves all three criteria mentioned in the lower floors of it. However, the inclination of the atrium walls to the north, not only reduces the daylight in the lower parts, but also increases the glare in the upper floors.

Although the effect of inclination angle on daylight performance of atrium is not as prominent as other factors, the designer can maximize this effect in the early stages of design, with the correct arrangement and prioritization of spaces to benefit from daylight.