In the present paper, daylight factor model (DFM) has been developed for daylight aperture which has been experimentally validated for east oriented wall window under clear sky condition. The correlation coefficient (r) and the root mean square percentage error (e) are in the range of 0.96-0.99 and 5.1-7.9%, respectively. It has been seen that there is a close agreement between modeled and measured values. The annual average daylight factor (DF), sky component (SC) and internally reflected component (IRC) values for the room were determined to be 1.8%, 1.2% and 0.6%, respectively. It is observed that the south oriented window has maximum DF while it is minimum for north oriented window. It is also concluded that the window in the upper position allows higher illuminance of the rooms compared to a wall window toward the bottom of the room. (C) 2015 Elsevier Ltd. All rights reserved.