To determine building envelope alternatives providing optimum conditions in terms of visual, thermal, acoustical comfort in offices, a research project supported by Yildiz Technical University Research Fund has been run. The part related to the visual comfort of the project is summarised as research method, determination of basic data, calculations, comparison of outcomes and presentation of suitable building envelope alternatives in this article. In order to exemplify the situations, three rooms with different dimensions in the ground floor, two different glass types and two transparency ratios are chosen. There is one window on the facade of the office rooms and investigations have been realised for cardinal directions, obstructed and unobstructed cases. The daylight illuminances are calculated according to average sky model using statistical meteorological data of Istanbul. The illuminance distributions in the rooms are evaluated in terms of necessary illumination level on the working plane. The findings show that, the day, facade direction, obstruction and transparency ratio are the basic parameters to be considered to hold the required daylight illumination, whereas glass type and thickness of the wall do not affect the visual comfort significantly for the examined cases. (C) 2002 Elsevier Science B.V All rights reserved.