Visual Comfort Assessment Using High Dynamic Range Images under Daylight Condition in the Main Library Building of Institut Teknologi Bandung

Abstract

The use of daylight in buildings should consider the aspect of visual comfort, since productivity of building occupants is affected by visual comfort. This research focuses on studying visual comfort under daylight condition in a reading hall of the Main Library Building of Institut Teknologi Bandung. An assessment was conducted with measuring daylight physical variables and glare indices and comparing the results with earlier experiments on daylighting visual comfort. Data were collected with applying High Dynamic Range (HDR) image technique, which concept is to combine various exposures of photograph images to obtain an image that has accurate and sufficient information of scene luminance. The HDR images were employed as input for Evalglare software to obtain luminance value from each pixel of the image. The obtained value was then used to calculate the daylight physical variables and glare indices, such as Daylight Glare Probability (DGP) and Daylight Glare Index (DGI).There were 81 measuring points on this assessment, each representing a sitting point of the occupants. Based on criteria proposed by Wienold, the daylighting glare situation the reading hall can be categorised into the comfortable range, since all obtained DGP values were under 0.35, which is the upper threshold of imperceptible range. Meanwhile, based on comparison of measured data to result of research by Hirning et al., it is found that based on DGP, there are 27 points (33%) categorised into comfortable range and 14 points (17%) into uncomfortable range. Based on DGI, 4 (5%) and 63 (78%) points are categorised into comfortable and uncomfortable ranges, respectively. Based on mean luminance of the scenes, 5 (6%) and 63 (78%) points fall into comfortable and uncomfortable ranges, respectively. The remaining points of each group of data fall into a neutral area between comfortable and uncomfortable ranges, since their values are between the upper threshold of the former and the lower threshold of the latter.