Using the daylighting is the best way to reduce energy consumption in buildings and reaching to the zero energy building. Iranian architecture has to reach experiences in the methods of daylighting. In order to recognize the performance of windows, the relation between the area of a window and the area of a room and the sky viewing angel have been investigated. Seventeen rooms from twelve traditional and old houses from Yazd city in Iran was studied. Items which discussed include the geometry and the proportion of each room, the location of a room in the yard, the location of a window in a wall, the lighting surface ratio to from surface, sky viewing angle of each window in each room in front and section view. Data collection method was field observation and data analysis, Numerical analysis and with using the metrics and computational methods which was introduced in the standard books of natural lighting guide. Then the gathered information was analyzed in two levels: which included room’ s features, a geometry of each room and neighbors. In the neighbors, the distance of front view is very important and play a pivotal role in using the skylight in each room. After investigating rooms, research shows that there is a strong role in a traditional house to use daylight and sunlight in buildings. In terms of natural lighting can be considered the design of the room in two levels, first neighborhood situation and Ratio indoors and outdoors, which lets a room to see the sky and use the skylight. It is very important that this ratio can clear the needed sky view for each city. For instance, the ratio of sky view of Tehran is totally different from Yazd. The second level is about the dimension of a room and windows or geometry or form of a plan which can determine brightness levels and how the distribution in a room. Both of these levels are very significant for having daylighting and sky lighting in a room. As a result of the research, the exact relationship between the area of a window and the height of it with the width of a room and the sky view was found. There is a relationship between the surface of windows and the height of it, the depth of the room, and the visibility of the sky, which can be used to find the window proportions and the depth of a room for using the daylighting. This consequence can inspire the contemporary and young architects or designer to find the ratio of proportion windows and rooms in new buildings with an approach to the traditional architecture of Iran to create better space for users and reduce energy consumption. Moreover, this heritage can be presented for other countries to improve the level of our traditional architecture, when it can be examined by the newest standard of daylighting (CIBSE 2015) so its value is proved for the world of architecture. These rules help designers to consider the Features of the site.