Daylighting plays a key role in occupants' thermal and visual comfort as well as developing a sustainable environment. Windows size, shape, and the relevant room dimensions are three major factors that affect the quality and quantity of daylighting. Window to Floor Ratio (WFR) is a key parameter is being used to assess the quantity of daylighting and affects the quality of interior design of buildings. Determining Daylight Factor (DF) is a complicated analysis related to obtaining sufficient natural light and simultaneously avoiding overheat. In this paper, DF was applied to measure and assess the validity of current standard WFR suggested by Iran's National Building Daylight Regulation. In addition, Uniformity Ratio was assessed to discover and control the quality of daylighting. 24 alternatives were analysed based on window shape, size, and space dimensions to assess DF and uniformity. The results show the current WFR is not accurate therefore, based on Daylight Credit (LEED), BREEAM, and Green Star standards; an optimal range of WFR, 15–24%, was presented which also controls glare and overheat. The study also indicated how window shape and size affected the average DF and uniformity simultaneously.
