Abstarct: The issue of using daylight and the importance of it is one of the important issues that has a great importance in architectural design because of the today's energy crisis and its usage reduction. Light, particularly natural daylight, plays a vital role in the visual perception of objects and environments. Daylight is one of the most fundamental aspects of creating a high quality indoor environment that is considered as a favorable factor because of the reaching to two important human needs, such as the ability to see better and creating some environmental stimuli. In this study, a comprehensive and detailed study on the windows of buildings as the major component of sunlight has been done. The Studies has been done on various items related to Windows, including the proper orientation of the building to get the maximum amount of sunlight in Mashhad climate, good size of windows in both north and south sides (noting that the east-west stretch is considered the most appropriate direction for Mashhad climate), examining the effects of single and double windows in energy efficiency, the impact of crushing the windows in the four main directions on the energy savings, investigating the function of window Sheds and determining the best length for this region and comparing coolers and air conditioners as cooling devices in this region and the results have been separately drawn in tables and charts for faster understanding. Scientific studies of this research are done by using physical models as well as computer models. This study has been done in Mashhad climate and on a cube with the size of 4*8 *8, and in accordance with Section 19 of National Building Regulations. To ensure the accuracy of the results, some of the above- mentioned items has been done on the buildings in Mashhad and the figures obtained were compared with the price of electricity and gas of residential units. Modeling and energy calculations were done using design Builder software. Another part of the study is about the family economy and the impact of energy saving rate with proposed solutions in Rls. In each of the cases mentioned above, the economic calculation is done and finally, what is more appropriate in terms of energy efficiency and what is more appropriate in terms of Rial has been discussed. The reason for this difference in terms of energy and in terms of Rial is due to the considerable difference in the price of gas and the price of electricity in our country. In Iran, the price of electricity is much higher than gas prices.