Abstarct: In this study, first, the desired office building was simulated in the basic mode in Design Builder software and then considering that one of the ways to improve energy consumption in buildings is to reduce the heat loss of various components of the building, including walls, roof, and windows in accordance with the requirements and principles set forth in the regulations, the use of various types of building insulation on the roof and exterior walls, and replacement of windows baxsed on the requirements of Article 19 of the National Building Code were investigated and compared. By evaluating the economy and calculating the return of investment, required measures to reduce energy consumption were prioritized. Also, a suitable photovoltaic system was designed using the Design Builder software. According to the results of the simulation, after various studies, the optimal scenario, which included changing the window to double-glazed, using glass wool insulation of 8 cm thickness on the exterior walls of the building, and using glass wool insulation of 6 cm thickness for the roof of the building, was selected. So, its energy consumption improved by 50.8% compared to the baxse building, its return of investment is 0.7 years, and the carbon dioxide emissions of this scenario decreased by 54.2% compared to the baxse building. The results of the simulated photovoltaic system on the roof of the building shows the electricity production is up to 307.5834 KWh in a year.