Investigation of effect of window size on natural lighting and energy use in residential complexes in hot dry climate of Iran

Windows are the most basic component of the building in providing natural light. two of window features that affects quantity and quality of natural lighting conditions of the building are dimensions and proportions of the window. Furthermore, window size affects building energy use (artificial lighting, cooling and heating energy). So, this article was allocated with the purpose of optimizing daylighting and energy use in residential building and as regard extreme sunlight in hot and dry climate of Iran, Isfahan City was selected for this study. For investigation of window size, an integrated of light and energy simulation using Diva and Honeybee software and Energy plus engine was used. First, considering different percentages of window to south wall, the optimized of window percentage was determined. Then, the role of shape and proportion of the window in natural lighting was investigated. The purpose of this research is providing guidelines for architects to determine best size and proportion of windows in residential buildings. Results show that increasing window size does not increase daylight as much as. So, however increasing window size decreases electrical lighting use, excessive increasing window size will not affect remarkable saving electrical lighting use. So, furthermore as regard forced cooling use with artificial light, it is not expected very small windows decrease cooling use. Also as regard as losing energy from windows, it is not expected very large windows decrease heating use. It is resulted from this research that the window to wall ratio (WWR) 30% is optimized for the south window. However, the acquired size depends on conditions of building design such as building plan, surrounding buildings and other design factors and for each building must be determined separately.Keywords: Spatial Daylight Autonomy (sDA), Annual Sunlight Exposure (ASE), Electrical lighting use, Cooling use, Heating use.