This paper evaluated the performance of the building integrated solar thermal shading (BISTS) system on building energy consumption and daylight levels through energy and daylighting modeling and simulations. A medium office reference building in Los Angeles defined by the DOE was used in the case studies. The horizontal BISTS louvers on the south windows and vertical BISTS louvers on the east and west windows were modeled and simulated. The final BISTS configuration was achieved by considering the balance between primary energy savings and daylight provision. The results revealed that 1) the BISTS system could effectively improve the daylight condition for a single perimeter room by increasing the useful daylight level and reducing the excessive level. 2) The savings for the building energy consumption were not significant. The final design with the BISTS layouts on three facades could result in 5.3% of total primary energy saving. 3) 90 degrees of slat angle should be avoided for both the horizontal and vertical BISTS louvers. Smaller angles - between 0 degrees and 60 degrees - are preferred. 2015 Elsevier B.V. All rights reserved.