Sunlight is one of the most accessible environmental agents which has been used as primary energy source. In current study, the effect of daylight distribution in interior spaces on human thermal comfort conditions and energy consumption in the residential buildings is investigated based on light shelf using simulation methods and tools. Firstly, a comprehensive parametric study is presented to examine the impact of light shelf design parameters (including angle, depth and number of the light shelves) on two objective functions of building's total energy consumption (including heating, cooling and electrical energy) and predicted percentage of dissatisfied people. Then, employing genetic algorithm, a multi objective optimization is conducted in order to minimize the two objective functions simultaneously. Light shelves are evaluated for three orientations of West, South and East; horizontally and vertically. Results show that the optimum angle, depth and number of light shelves for West orientation are 24.37 degrees, 0.571 m and 5, respectively; for South orientation are 89.62 degrees, 0.295 m and 4, respectively; for East orientation are 36.51 degrees, 0.659 m and 4, respectively. In addition, results indicate that optimum conditions of light shelves decreases the total heating, cooling and electrical energy consumption by 27.819 kWh/m(2), 49.176 kWh/m(2) and 34.853 kWh/m(2), respectively. (c) 2020 Elsevier Ltd. All rights reserved.