Connectivity of the Window to Floor Area Ratio and the Daylighting Assessment Criteria

Abstract

In most of standards and design codes, the selection of parameters or size of the openings/windows plays an important role. It influences the thermal and daylight distribution in the room, which provide thermal and visual comfort, define energy efficiency criteria. Offering a rational window size, which is largely known as the Window to Floor ratio (WFR) will help builders and architects in the design process. Mostly, this ratio can be approximately determined by the rule of thumb. In the Russian Standard documents, daylighting assessment criteria for side lit space of the public and office buildings are represented by the minimum Daylight Factor (DF_M). The Window to Floor Ratio could be calculated based on this value. In recent studies, to provide at least 50% of floor area in occupied spaces that have a target illuminance for 50% of daylight time, the daylighting assessment has been based on the target Daylight Factor (DF_T), which is defined by the median value and the new target minimum Daylight Factor (DF_TM). This means the WFR should be recalibrated to satisfy the DF_T and DF_TM instead of DF_M. Focusing on this aim, it is necessary to find out the relationship between the DF_T and the DF_M in a space. In other words, the uniform of Daylight Factor standing on the rule of daylight distribution in spaces should be analysed using the method of experiments and modelling. The results show that in the typical spaces, the DF_M^—which is used to calculate WFR could be accepted by the value of $\frac{{1}}{{3}}$ of the DF_T, the WFR is not only proportional to the DF_T but also depends on the character of daylit space, which described by the ratio of the room depth to the window height in a proportional relation.