Improving the Accuracy of Daylight Calculation with Impact of Sun-shading Devices for the Russian Standard

Abstract

Lighting engineering represents a complex scientific field, which requires the generalization of knowledge in assessing visual comfort, constructive and architectural solutions for the adaptation to the site climate. Global environmental issues and sustainable development require architectural design to serve the modern building achieve maximum energy performance. Especially in hot regions, the specific tasks of designing daylight systems cannot be sufficiently completed without carefully considering the problems of insolation and sunscreens. The present method in Russian regulations is a daylight factor method calculation with high accuracy under the overcast sky and without impact of shading devices. Unfortunately, this method revealed a few possible inaccuracies if considering the impact of shading devices and should be improved with the proposal of two coefficients K_shad and K_ref­, which replace the approximate factor τ₄. The results show that a significant effect from the shading coefficient reduces light entering the room. Light reflection from shading devices is slightly increased by up to 15% when the ground surface has a high reflectance. With this approach, it is possible to complete the method of side-lighting calculation with specific parameters and finishing surfaces of the shading devices. The research shows the potential of increasing light reflection to the room under the real sky with sunlight. Finishing the daylight factor calculation would potentially lead to the development of a method to define the window area in design stage to adequate the daylight requirements, which now processes most in the rule of thumb.