Determining the Most Efficient Window-to-Wall Ratio in Southern Façade of Educational Buildings in Kerman

The energy consumption of the buildings is highly dependent on the specifications of its envelope. Windows have a significant effect on the thermal specification of the building envelope, because of their high thermal conductivity and direct solar transmittance. Hence, specifying the best window-to-wall ratio (WWR) is very important in all climates. This study aims to specify the effective variables on optimizing the window-to-wall ratio for the southern façade in Kerman, based on the thermal specifications of the building envelope. The research method is a combination of field surveys and software simulations. In the field survey method, window to south façade ratio of 26 single-spaces in 16 traditional residential and educational buildings in Kerman were measured, drawn, and analyzed. The results showed that the window-to-wall ratio of 5% to 15% had the most frequency in the surveyed samples. In the software simulation method, window and wall heat transfer coefficients were analyzed rather than SHGC (solar heat gain coefficient), and their effects on annual load were determined. Finally, the 30% ratio was specified as the most efficient window-to-wall ratio for the southern façade in Kerman. According to the results, it can be concluded that if the only thermal analysis is considered, the optimum window-to-wall ratio in the southern façade in Kerman is 15% while using the single glazed window; and it is 30% while using the double glazed window if the SHGC is not less than 0.4. The results also revealed a high dependency on the buildings’ annual thermal load to windows’ SHGC. So, finally, modifications were proposed in the 9th appendix of Code 19, to include the SHGC factor.