Daylight Quality Assessment of Rooms with Lateral Daylighting by the Room Light Saturation Criterion

Abstract

The availability of daylight for residential and public spaces is extremely important. However, not always enough light to solve visual problems ensures the quality of the light environment in the room. The development of recommendations for improving the quality of daylighting is an important and urgent task, since the quality of human life and work depends on it, as well as energy savings. A criterion of light saturation of a room has been introduced into the norms, the evaluation characteristic of which is cylindrical illuminance only for electrical lighting. The article presents the results of a fullscale psychophysical experiment to assess the qualitative indicator of natural illumination of rooms with side light openings. The analysis of subjective assessments of observers showed the absence of a relationship between high estimates of the saturation of the room with light and the values of the relative horizontal illuminance of the daylight factor Dh, as well as the relative cylindrical illuminance of the Dc. However, there is a correlation between the feeling of comfort of the light environment and the values of the Dc/Dh ratio. The proposals on the normalized value and its values corresponding to the levels of saturation with daylight of the room are formulated. The analysis of the data obtained from the results of the experiment allowed us to establish that the quality of lighting of the workplace and the room as a whole is highly appreciated by the observer in terms of saturation level if the ratio of Dc/Dh in the centre of the room is located in the interval 1–1.3, while the value of the cylindrical illuminance Ec at the point furthest from the light transmission with a high assessment of light saturation by observers is Ec = 120 lx, Dc = 2 %.