Optimal Window Position for Hot and Arid Environments: A Practice in Tehran based on Annual Daylight

The task of designing exterior window openings presents two main issues, namely the building energy envelope and natural daylighting. The inclusion of large windows in a building can result in significant energy loss. Hence, it is ideal to aim for an optimal opening area. This research endeavors to provide constructors with solutions and guidelines to achieve the most efficient windows, with the optimal window-to-wall ratio for hot and arid climates, by utilizing spatial Annual Daylight calculations through DesignBuilder's EnergyPlus software. The research model is based on an ASHRAE Standard 140 building located in Tehran, with 24 window layouts and four orientations. The findings reveal that the most efficient window layouts for maximizing annual daylight while minimizing the window-to-wall ratio are those with a sill height of 120 cm or higher and a window height exceeding 60 cm. However, considering these setups, a height of 120 cm is sufficient for up to 6 meters of space depth, and it is recommended to allocate the remaining window area to its width. Furthermore, in order to achieve a more balanced distribution of annual daylight with an optimal window-to-wall ratio, avoiding window widths of less than 25% of the room's width is recommended.