The effect of internal light shelf on quality of daylight distribution in space and lighting energy consumption reduction

Document Type : Original Article


1 Department of architectural engineering, Khorasan Institute of Higher Education, Mashhad, Iran.

2 Young Researchers and Elite Club, Mashhad Branch, Islamic Azad University, Mashhad, Iran.


The optimal use of daylight in interior spaces of residential buildings leads to increase in space quality, comfort condition and optimal energy consumption. Present study investigates the daylight distribution aiming to reach the people’s comfort condition and optimal electrical energy consumption of artificial lighting. For this reason, a zone from each orientation of Yas residential building (located at Mashhad city of Iran) was selected and light analysis was conducted in the interior environment for the baseline condition as well as 7 proposed light shelves (vertical light shelf for East and West orientations, horizontal light shelf for North and South orientations). Measurement criterion for daylight quality is Daylight Autonomy (DA) which a DA of 50% provides the amount of 300 lux light in the interior environment. Then, the amount of saving in lighting electrical energy, which consumes by the lamps during the day, was calculated considering the optimal light shelves. Results show that light shelf No. 3 provides the optimal comfort condition in zone A (west) and light shelf No. 2, No. 4 and No. 6 provide the optimal comfort condition in zone C (North) while the light shelf No. 5 is able to control some the light entering the zone D (East). In addition, considering the light shelves in the studied zones, the electrical energy consumption of the lamps reduced by 576.048 kWh/year.